This description covers characteristics that may be relevant to fire ecology and is not meant for identification. Keys for identification are available (for example, [120,137,167,169,192,237]).
Gray alder is a tree or shrub, growing from 15 feet to 82 feet (4.6-25 m) tall. [120]. Bark is smooth and thin [155,348], often with conspicuous lenticels [106] (see photo in Fire Effects and Management). The wood is soft [171]. Leaves are oblong and serrated at the margins [208,355]. The inflorescences are small, naked [131] catkins. Male catkins grow in clusters of 2 to 4. They are 0.8 to 3 inches (2-8 cm) long and pendulous at maturity. Female catkins are woody and resemble cones, growing in clusters of 2 to 6 [106,120,237]. The "cones" are 0.4 to 0.8 inch (1-2 cm) long at maturity [155]. The fruits are described as either irregular samaras [120] or nutlets with small, narrow wings [106,154,171,179,242,345]. They hold 1 to 4 seeds/cone scale [137,155,318]. The seeds lack endosperms, so the cotyledons are relatively small [154]. The root system is shallow and spreading [171]. Roots are typically infected with nitrogen-fixing, actinomycete bacteria [171,205,215,261]. A review reported that thinleaf alder fixes more nitrogen than Sitka alder (Alnus crispa subsp. sinuata) and quantities similar to those of red alder [143].
Gray alder is adapted to periodic flooding in spring or other run-off periods [23,204,267], although it cannot tolerate long periods of inundation. In the laboratory, speckled alder growth and root development were "severely reduced" when water levels were at or above the root crown for 30 days or more (P<0.05) [196,267]. A review ranked gray alder more flood tolerant than cottonwoods, birches, and elms but less tolerant than willows [130].
Morphological characteristics of the gray alder subspecies overlap (review by [143]). Thinleaf alder is typically more tree-like than speckled alder. The subspecies also differ in bark, leaf shape, and leaf margin characteristics [120,127,318].
Speckled alder is a spreading shrub [120] or small tree [131], growing up to 30 feet (9 m) tall [120] and 4.7 inches (12 cm) in diameter. Typically multistemmed with crooked branches, it is "very crooked" in form as a small tree [106], and only assumes tree form on high-quality sites [171]. Its common name refers to the lenticels that give a characteristic "speckled" look to the bark [81]. In a speckled alder community by a small stream in upstate New York, speckled alder stems averaged 14 years old, ranging from 7 to 31 years old. Stem density averaged 7,850 stems/ha [331]. In central New York, age of mature stems ranged from 10 to 25 years. Based on stem sprouting vs. stem mortality rates, the author estimated maximum age of speckled alder clones at about 100 years [176].
Thinleaf alder is an open, spreading shrubby tree or shrub, growing from 15 to 39 feet (4.6-12 m) tall [120,345] and usually less than 4 inches (10 cm) in stem diameter [215]. It often forms thickets along streams [179,231,242,345], although on upland sites it usually grows in discrete, shrubby clumps [208]. Thinleaf alder stems on sandbars of the Tanana River, central Alaska, averaged 14 years old [339]. Morris and others [259] provide a key for identifying thinleaf alder and other western shrubs in winter.
Gray alder occurs in North America and Europe [120,192,296]. It occurs in the northeastern and central regions of Europe, extending locally into the southern mountains [296].
States and provinces (as of 2011 [335]):
United States: AK, AZ, CA, CO, CT, IA, ID, IL, IN, MA, MD, ME, MI, MN, MT, ND, NH, NJ, NM, NV, NY, OH, OR, PA, RI, UT, VA, VT, WA, WI, WV, WY
Canada: AB, BC, LB, MB, NB, NF, NS, NT, ON, PE, QC, SK, YT
States and provinces (as of 2011 [335]):
United States: CT, IA, IL, IN, MA, MD, ME, MI, MN, ND, NH, NJ, NY, OH, PA, RI, VA, VT, WI, WV
Canada: AB, BC, NT, SK, YT
States and provinces (as of 2011 [335]):
United States: AK, AZ, CA, CO, ID, MT, NM, NV, OR, UT, WA, WY
Canada: LB, MB, NB, NF, NS, ON, PE, QC, SK
Early postfire environments generally favor gray alder establishment and growth. As a nitrogen fixer, gray alder can have important ecological effects on postfire plant and soil fauna succession. In riparian areas, sprouting gray alders help stabilize burned banks and shores. Gray alder may provide little protection in riparian areas burned by fire severe enough to kill the roots. Dead and decaying thinleaf alder roots seldom provide substantial protection from erosion during heavy spring run-off [200]. To date (2011), research on using prescribed fire in wetland communities with gray alder was limited, and further research is needed before guidelines for burning in gray alder riparian and wetland zones can be made. Speckled alder: Prescribed fire may help control speckled alder on silvicultural sites and on open mires. Related prescribed fire studies and management recommendations available are summarized here.
In the Great Lakes states, frequent prescribed fires (no return interval given) can help control speckled alder, beaked hazelnut, and American hazelnut in the understories of red pine plantations. Summer fires best prepare a mineral soil seedbed necessary for natural red pine regeneration, and the generally drier fuels results in severer fires and better shrub control than spring prescribed fires [46].
On plantations, interference of postfire speckled alder regeneration with conifer regeneration and growth may be minimal on moist lowland sites where fire has prepared a mineral seedbed for conifers. Speckled alder and mountain alder "grew well" on such sites 10 years after clearcutting and 8 years after a late spring (2 June 1970) prescribed fire on a jack pine/black spruce plantation in southeastern Manitoba. Chrosciewicz [69] concluded that even though "plant competition was generally much more severe" on moist lowland sites than on dry or fresh upland sites, the alders and other postfire regeneration "had no detrimental effect on regeneration of commercial tree species, including pine" on moist lowland sites. Postfire conifer establishment was poor on the upland sites, which the author attributed to lower than normal precipitation and consequently, drier than normal soils, during the first 2 postfire growing seasons [69]. Another study by Chrosciewicz [68], near Winnipeg, Manitoba, had similar results. Five years after low- and moderate-severity spring (late May) prescribed fires, shrub cover, including speckled alder, averaged 15% to 20% in regenerating black spruce stands. This "rather luxuriant vegetation" "seemed to provide valuable shelter to the spruce seedlings in their early development" [68]. See the Research Project Summary on Chrosciewicz's [68] research for information on the fire prescriptions, fire behavior, and for details of black spruce's postfire response.
Early spring burning—after snowmelt but before soil thaw—may help control speckled alder and other woody invaders in wetlands. Researchers found that early spring prescribed burning was more cost-effective than early and late summer cutting or late manual torching for reducing woody encroachment in a tussock sedge-bluejoint grass wetland meadow in Wisconsin. Additionally, it caused the least disturbance to groundlayer vegetation and to the soil. The researchers warned that due to sprouting of woody species (which occurred after all fire and cutting treatments), prescribed fire must be viewed as an ongoing treatment strategy. Speckled alder was a component of the woody vegetation, although Sandberg's birch (Betula × sandbergii) and red-osier dogwood had the most cover. Fire effects on speckled alder alone were not measured [294].
Managers of the Lac St-Francois National Wildlife Area in Quebec found that neither a single wildfire nor mechanical treatment (double-cutting shoots) controlled speckled alder invasion on an acidic, water sedge-hairy sedge fen in the short term, while stump applications of herbicide reduced speckled alder but also reduced nontarget plants. The wildfire had burned part of the fen prior to the study, and plots were established on sections of the burn that were "highly invaded by small to medium-sized individual alder shrubs". Speckled alder root crowns were located at or below the water table. All of 40 speckled alder individuals on study plots survived the fire and were sprouting "vigorously" in postfire year 1. For the double-cut treatment, stems were cut to the root crown in mid-June, with a 2nd cutting of new sprouts in early August. The next year, 80% of cut plants were sprouting "vigorously". While conceding that another cut would increase speckled alder mortality, the authors found cutting too ineffective and costly to justify further cuttings. Foliar applications of glyphosate in July gave 100% control of speckled alder but also killed more nontarget plants than considered acceptable (no limits given). For cut-stump glyphosate treatments, either August or March application gave good control (79% and 93%, respectively). The March treatment was preferred, because it was more effective and accessibility was greater on the frozen winter ground than on the wet summer ground [38]. The authors noted that based on other research [46,161], very frequent prescribed fires (1 or 2 fires annually over 5 years) may control speckled alder but would "carry very high operation costs" and possibly be detrimental to the fen. However, they considered prescribed fire a viable option for long-term control of speckled alder [38].
Thinleaf alder: Recommendations for prescribed fire use in thinleaf alder communities are few and sometimes contradictory. Prescribed fire in these communities may increase plant community productivity or conversely, be used as a tool to control thinleaf alder. Olason and Agee [268] note that although fires were probably historically frequent in riparian Douglas-fir forests of the Pacific Northwest, it may be necessary to "totally protect" riparian forests in areas where favorable salmonid habitat is limited. They suggest treating upslope forests with prescribed fire or fire-surrogate treatments, speculating that such treatments would make wildfires less likely to burn into moist portions of riparian zones [268].
Others suggest that excluding fire from riparian zones may be harmful in the long term. On the Payette National Forest, Idaho, a low-severity May prescribed fire in an upland subalpine fir-Engelmann spruce community burned only slightly into an alder (Alnus spp.)-dominated riparian zone. Comparing these results to late summer wildfires in the same communities, the authors found that with wildfires, the area burned in riparian communities was proportionate to that burned in the upland communities. While fire severity was generally lower in the riparian than the upland communities, portions of the riparian zones burned at high severity. The authors concluded that in riparian zones, spring prescribed fire is not an ecological surrogate for fall wildfire and that a "prescribed fire regime" of repeatedly burning upland communities while excluding fire from riparian forests may eliminate important natural disturbances from riparian and stream habitats [8]. Besides wildfire itself, these disturbances may include postfire erosion, altered stream channels, altered stream temperatures, and altered species composition of the aquatic animal communities [8,107].
Effects of prescribed fires in riparian and wetland zones may be difficult to predict. Prescribed fire may help control thinleaf alder and other woody invasives in freshwater wetlands [42]. Jacobson and others' study [182] provides management recommendations for reducing woody encroachment on open fens. However, in forests, thinleaf alder may increase after overstory removal by prescribed fire and/or cutting, especially on wet sites. Researchers in British Columbia report that although moderate to severe fires are needed to "set back the growth" of thinleaf alder, such fires rarely carry in the wet to moist sites where thinleaf alder usually grows [71].
Thinleaf alder-dominated communities may recover more quickly than adjacent upland communities. Six years after the Diamond Peak Wildfire Complex on the Payette National Forest, woody plant cover in thinleaf alder-dominated riparian communities was greatest on sites where fire severity was greatest (P=0.05). Across 6 riparian sites burned at varying severities, total woody cover ranged from a low of 8% in postfire year 2 to 30% in postfire year 6. The authors found that in postfire year 6, "little recovery had taken place in the upland (ponderosa pine) community" [287].
A May wildfire in a quaking aspen-balsam poplar/thinleaf alder-red alder community reduced nesting and hiding cover for ruffed grouse in the short term. Alders (thinleaf and red alder combined) averaged 8.0 feet (2.4 m) tall 1 year before and 3.5 feet (1.1 m) tall 1 year after the fire. Along a 2,000-foot (600 m) transect, alders <3 feet (2 m) tall averaged 35.8 stems/transect before fire and 3.8 stems/transect 1 year after fire. On drumming sites used by male ruffed grouse, alders <3 feet tall averaged 28.7 stems/transect before fire and 2.9 stems/transect after fire. In postfire years 1 and 2, estimated ruffed grouse numbers in burned areas averaged 50% of ruffed grouse numbers 1 year before fire. By postfire year 3, density of males in unburned drumming areas was almost 3 times that of males in burned drumming areas [99]. See the FEIS review of ruffed grouse for details.Gray alder experiences a wide variety of FIRE REGIMES across its broad distribution in North America. For example, ponderosa pine woodlands in the Pacific Northwest and California historically experienced mostly low-severity surface fires with an average return interval of 13 years [210], while mixed-hardwood-spruce forests of the Northeast historically experienced mostly stand-replacement fires at intervals of 400 years or more [212]. As an early-successional species that sprouts after fire, gray alder is likely to flourish in wetland plant communities where fire is frequent or severe enough to maintain or create open conditions. This is likely true across the species' worldwide distribution. Scots pine-Norway spruce (Pinus sylvestris-Picea excelsa) forests of Scandinavia, where European gray alder is an important component of the vegetation, historically experienced frequent, low-severity surface fires and mixed-severity fires under a fire regime similar to that of ponderosa pine and mixed-conifer forests of the western United States. Frequent understory fires helped maintain European gray alder in the understory (review by [10]). Speckled alder: Little information was available on fire frequency and fire behavior in riparian and wetland plant communities where speckled alder is an important to dominant member of the plant community. One study, near Thunder Bay in Ontario, found wildfire did not carry well once it reached a speckled alder community. A stand-replacement wildfire burned a mixed hardwood-coniferous forest, but the fire slowed or stopped in riparian zones dominated by speckled alder. Speckled alder showed scorching and damage to top branches but was otherwise unharmed, and "little damage was evident in the riparian zone" [209]. Research is needed on FIRE REGIMES of riparian and wetland plant communities in the eastern United States.
Summaries of several fire studies in plant communities where speckled alder was important or dominant follow.
Red-white-jack pine ecosystems of the Great Lakes states historically experienced frequent, low-severity surface fires. Frequent fires prevented development of late-successional tree species such as white spruce and red maple, and also inhibited spread of understory shrubs including speckled alder, mountain alder (A. viridis subsp. crispa), beaked hazelnut, and American hazelnut. Heinselman [165] reported that in these ecosystems, both the late-successional tree and the shrub layers are maturing and expanding under fire exclusion. A fire history study on Pictured Rocks National Lakeshore, Michigan, found red-white-jack pine shoreline forests with speckled alder had a mean fire-return interval of 21.8 years before European settlement, with fire-return intervals lengthening after the early 18th century. At the time of study (1985), the area had not experienced fire for the past 84 years [232].
A study of fire scarring in red and jack pines near Lake of the Clouds in northern Minnesota found fire-return intervals ranging from 16 to 62 years between 1691 and 1818. Speckled alder was a dominant shrub in the area. Over the previous 1,000 years, lake sediment analyses showed a mean fire-return interval of about 70 years; speckled alder pollen was present in most sediment cores sampled across the 1,000 years [323]. A similar lake sediment study in Boundary Waters Canoe Area also found a mean fire-return interval of about 70 years over the past 1,000 years; speckled alder pollen was present in all cores sampled across that time. The extant plant community was a quaking aspen-paper birch/speckled alder forest [324].
Red spruce-balsam fir-white spruce forests of the Northeast historically experienced infrequent, stand-replacement fires at 150- to 300+-year intervals. Surface fires were "extremely uncommon". Speckled alder is an early-successional species in these forests [211].
The black spruce/speckled alder forest cover type of boreal North America is reportedly a stable type that regenerates into forests of similar composition after fire [87]. Information on FIRE REGIMES for this type was not found in the literature. In general, boreal black spruce forests experience stand-replacement fires at intervals of 50 to 150 years [165].
A study by Jacobson and others [182] suggests that historically, infrequent fires may have reduced encroachment of speckled alder and other woody species into open mires in the Northeast. Frequent fires, however, may favor sprouting woody taxa such as speckled alder. A study at Crystal Fen in northern Maine suggested that frequent fires combined with high drainage favored encroachment of speckled alder and other woody species. Charcoal analysis of the fen showed fire was uncommon before a railroad was constructed in the area. Fire frequency increased after 1937, when a drainage ditch was excavated next to a railbed, drying out vegetation, and sparks from diesel-powered trains ignited fires frequently. A survey of tree ages showed that "many" speckled alder, northern white-cedar, and other woody species established between 1937 and 1950. Fire frequency dropped after 1950, when diesel engines replaced steam engines, ignition sources became uncommon, and for undescribed reasons, the fen began flooding again. Increased moisture and no fire, however, did not open the fen: Woody species continued establishing on areas of the fens that, based on pollen and charcoal records, historically had few to no woody plants. The authors recommended restoring the historical drainage pattern, cutting woody species, and/or introducing prescribed fire to restore the open fen [182].
As of 2011, almost no literature was available on FIRE REGIMES of pine or hardwood ecosystems of the Southeast where speckled alder formed a substantial component of the vegetation. A review reported that pond pine and bay (Magnolia and Persea spp.) shrubland bogs, of which speckled alder is a component, burn at irregular, 5- to 50-year intervals. Nearby bog communities with low shrub diversity tend to have less frequent fire-return intervals than the bog communities with high shrub diversity [356].
See the Fire Regime Table for speckled alder for further information on FIRE REGIMES of vegetation communities in which speckled alder may occur. Find further fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find FIRE REGIMES".
Thinleaf alder: Historical FIRE REGIMES for riparian zones of the western United States are not well studied [307,311], although more is known of FIRE REGIMES in riparian and wetland areas of the West than those of the East. Historically, thinleaf alder glades and thickets in the Northern Rocky Mountains probably burned less frequently than surrounding coniferous forests, but at "higher intensity" than surrounding vegetation. Davis and others [92] speculated that thinleaf alder thickets may be maintained by infrequent fire. In most years, thinleaf alder thickets in riparian zones do not burn [92]. Similarly, thinleaf alder stands growing on seeps and springs may burn rarely [200].
In general, fires are less frequent in riparian and wetland areas of the West than in drier areas [12]. At low- to midelevations in the southern Cascade Range and Klamath Mountain regions of California, fire-return intervals in riparian areas overall are about twice those of surrounding areas, but fire intensity is generally greater when the riparian areas burn [307]. Fire-return intervals near intermittent and ephemeral streams are likely similar to those of surrounding areas [311]. In most years, perennial stream communities may serve as firebreaks (review by [311]). A fire management plan for Craters of the Moon National Monument, Idaho, states "there is no evidence that fire is necessary to maintain the (riparian) vegetation type in this area". However, the authors speculated that infrequent, periodic fire would probably improve the health and productivity of shrubs and that most shrubs, including thinleaf alder, would survive fires that were "not too frequent" [17]. Arno and Harrington [12] suggest that prior to 1900, riparian ponderosa pine communities in the western United States burned 2 to 5 times per century. Fire-return intervals in riparian and wetland communities may vary across time and space, however.
In riparian zones where thinleaf alder is known or likely to occur, fires tend to have longer return intervals, and burn at higher severity, than in upland sites ([115,268,310]), Arno 2001 personal communication [11]). This trend is not strong or consistent in all areas, however. Fire frequency and severity have been lower in some riparian areas compared to adjacent upland areas; other sites have similar fire histories on riparian and upland zones. Factors affecting fire-return intervals in riparian zones include soil and plant moisture, fire exclusion, livestock grazing, logging, damming and other water-flow regulation, and presence of invasive species that alter fuel characteristics [111]. Coniferous riparian forests may have historically been too moist to burn in some years; consequently, low- and moderate-severity fires in upland areas would often extinguish at the riparian zone. In an Alberta study of upland and riparian lodgepole pine, subalpine fir-Engelmann spruce, white spruce, and balsam poplar communities on the Jumping Creek Watershed, landform was the primary driver of fire frequencies. Using time-since-fire distributions, the authors found that riparian zones and the larger, entire-watershed area had similar mean fire frequencies. At a fine scale, however, fires were less frequent near stream channels with gravel- or sandbars, whereas terraces above straight streams without bars tended to burn at same frequency as the overall watershed. From 1851 to 1890, fire-return intervals averaged 71 years in riparian and 48 years in entire-watershed zones, respectively. After 1891, fire-return intervals lengthened to 208 and 178 years, respectively. The authors concluded that on the Jumping Creek Watershed, except for bars, areas adjacent to streams were just as likely to burn as upland areas [66]. Understory vegetation was not surveyed in the study, but thinleaf alder is known to occur in the area.
Two studies suggest a trend of longer fire-return interval in riparian Douglas-fir than upland Douglas-fir forests. In Douglas-fir forests on the Steamboat Creek Watershed in southwestern Oregon, mean fire-return intervals were longer in riparian than upland sites (37 vs. 31.5 years), but the difference was not significant. Fire-return intervals ranged from 4 to 167 years on riparian and 2 to 110 years on upland sites. The authors speculated that fires were historically common, of mixed severity, and patchy on their study sites, with a high likelihood of fire in both riparian and upland zones. They suggested that historically, many riparian forests burned when upslope fires backed into riparian zones [268]. On eastside riparian Douglas-fir forests in the Cascade Range of Washington, fire-scarred trees were consistently fewer in riparian than on upland sites. The authors concede that fewer fire scars does not necessarily mean fewer fires; fires in the riparian zone could have been mostly low-severity surface fires that caused less scarring than fires in upland areas, or fires could have been more severe, stand-replacement fires that left fewer standing live, fire-scarred trees than in upland zones. Plant association groups in riparian forests had 25% to 42% fewer wildfires than similar plant associations on sideslopes. Fire-return intervals ranged from 11 to 46 years in riparian forests and from 7 to 39 years on sideslopes. On sideslopes, stands on south-, east-, and west-facing slopes in riparian zones were older than those in nonriparian zones (P≤0.1); differences in stand ages between riparian and nonriparian sites on north-facing slopes were not significant [115].
On the Shasta-Trinity National Forest in the Klamath Mountains of California, fire-return intervals in riparian and upland mixed-conifer forests were compared. Intervals between fires were consistently longer in riparian vs. upland sites [310]:
Fire-return intervals of riparian and upland mixed-conifer sites in the Klamath Mountains [310] Site Mean fire-return interval (range) Time period Number of stumps sampled Root Creek,In a fire history study of Jeffrey pine, white fir, and mixed-conifer forests of the Sierra Nevada in which thinleaf alder was "highly abundant", fire-return intervals were usually similar on riparian and upland sites. On 36 paired riparian and upland sites on the Lassen and Tahoe National Forests, only 9 paired sites had significantly different fire-return intervals (P≤0.1). Fire-return intervals ranged from 15.3 to 86.5 years on riparian sites and from 10.0 to 56.3 years on upland sites. They averaged 30.0 and 27.8 years on riparian and upland sites, respectively. Most fire scarring (88% on riparian and 79% on upland sites) happened in late summer and early fall, after tree-ring growth had stopped [340].
Fires in the spruce-birch and aspen ecosystems of interior Alaska are usually stand-replacing and often extensive [234,344], burning "for days with high intensities, covering vast acreages" [357]. Fire frequency is poorly known but probably ranges from 75 to 150 years. In quaking aspen/thinleaf alder stands on Ester Dome, fire kill was the primary cause of tree mortality [206].
Near Rainbow Lake in Wood Buffalo National Park, Alberta, a fire history study found charcoal evidence of at least 12 local fires in 840 years, with a mean return interval of 69 years. In some cases, thinleaf alder pollen counts (a surrogate for thinleaf alder density) peaked about 35 years after a fire; however, thinleaf alder pollen counts declined after 6 of the local fires. The extant plant community is mixed hardwood-conifer. Thinleaf alder is most common at the lake margins, along with scattered black spruce and tamarack [216].
See the Fire Regime Table for thinleaf alder for further information on FIRE REGIMES of vegetation communities in which thinleaf alder may occur. Find further fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find FIRE REGIMES".
Fire adaptations: Gray alder has many adaptations that can aid its postfire recovery. It sprouts from the root crown and/or roots after top-kill. Root crown sprouting is most common (see Vegetative regeneration), while root sprouting may occur when fire is severe enough to kill the root crown. Gray alder may also establish from seed; this may include seed dispersed from on-site, crown-stored "cones" ([256], review by [35]), wind- or water-dispersed seed originating from off-site parents, or seed in the transient soil seed bank . Some of gray alder's adaptations to riparian environments, including tolerance of high light and the ability to sprout after repeated top-kill, may also benefit gray alder in early postfire environments [209]. Plant response to fire: Speckled alder
Speckled alder sprouts from the root crown after top-kill by fire. Its postfire sprouting response is likely strongest on sites that are moist during the growing season [51]. In a review of fire responses of plant taxa in northern coniferous forests, Heinselman [164] classified speckled alder as fire-tolerant.
A prescribed April fire top-killed most speckled alders in a study site on the Allegheny River floodplain of Pennsylvania. Open areas with individual trees burned well, but dense stands of speckled alder carried fire mostly on the edges. The fire top-killed 55% of speckled alder stems. By postfire month 9, most burned speckled alders were sprouting at or within 2 inches (5 cm) of the soil surface, from near the bottoms of the stems or from the root crowns. However, sprouting in speckled alder was not related to fire; it occurred on burned and unburned stems at approximately the same rate, 90%. Sampled stems produced an average of 8 to 10 sprouts, with basal diameters ranging from 0.1 to 0.5 inch (3-12 mm) and heights ranging from 9 to 47 inches (22-120 cm). Twelve percent of speckled alder stems were browsed, probably by white-tailed deer and cottontails [49]. See the Research Project Summary of this paper for information on the burning conditions and effects of the fire on hawthorns (Crataegus sp.) in the same area.
A few studies show speckled alder may be more common in early than late postfire succession. In a fire chronosequence study in black spruce-jack pine ecosystems of northern Ontario, speckled alder was most common on wet peatlands burned 1 to 3 years prior (P=0.05). Burn ages ranged from 0 to 57 years [308]. Speckled alder reached greatest postfire abundance in postfire year 10 in red pine-black spruce forests of Saskatchewan [306]. In a chronosequence of 9 burned black spruce/mountain-laurel (Kalmia latifolia) forests in Terra Nova National Park, Newfoundland, speckled alder was present only on a 20-year-old burn, with 2% mean cover. Burn ages ranged from 1 to 38 years [30]. In quaking aspen, jack pine, and black spruce swamp communities of Itasca County, Michigan, speckled alder occurred in 7 of 9 burns surveyed. The burns were from 1 to about 58 years old [135]. A review of fire succession in balsam fir forests of the Northeast reported that speckled alder thickets may replace balsam fir after fire and that those thickets may persist for decades before trees establish [128].
Frequent fire likely favors speckled alder over conifers. Speckled alder thickets may form after stand-replacing fire in northern white-cedar communities [186]. In a northern white-cedar swamp in Michigan, speckled alder was most abundant in an area that burned 3 times in 30 years. The authors reported that dense growth of speckled alder and willows now occur on sites where the northern white-cedars experienced the greatest fire kill [110].
Speckled alder increased over 10 postfire years on a hybrid spruce clearcut that was slashburned at low to moderate severity. The site was on the Mackenzie Forest District in subboreal British Columbia. Speckled alder was the dominant shrub before and after the fire, with abundance at postfire year 10 exceeding its prefire cover and frequency. Speckled alder's prefire cover and frequency were 4.6% and 50%, respectively. At postfire year 10, it had 8.9% cover and 67% frequency. Overall, shrub height was more in postfire year 10 than before fire, primarily due to the rapid postfire growth of speckled alder and Rocky Mountain maple. See the Research Paper of Hamilton's [146] study for details on the fire prescription, fire behavior, and postfire responses of other species in the plant community.
Two studies suggest that speckled alder responds similarly to fire and logging. Pooled across plant communities and stand ages, there was no significant difference in speckled alder frequency between wildfire-burned (37.0%) and logged (31.4%) stands in Minnesota. Surveys were conducted in naturally regenerated quaking aspen, jack pine, and black spruce communities that were 25 to 100 years old [292]. In a black spruce forest in west-central Quebec, there was no significant difference in speckled alder cover on the edges of burns and clearcuts. Burns were 3 to 4 years old, and clearcuts were 2 to 5 years old [152].
Both wildfire and clearcutting apparently favored speckled alder; its average frequency was higher than that of any other deciduous shrub after both disturbances in surveys in northeastern Ontario [57]. Speckled alder was more frequent after clearcutting than after wildfire, but a longer period of postdisturbance succession on burned vs. clearcut stands makes direct comparisons difficult. Time since fire averaged 89.6 years, while time since logging averaged 22.9 years: Given speckled alder's role in early succession in this area, greater abundance in the younger, logged communities seemed likely. On clearcut stands (n=131), speckled alder averaged 6.9% frequency in the canopy and 18.47% cover in the subcanopy. Both wildfire and clearcutting apparently favored speckled alder; its average frequency was higher than that of any other deciduous shrub after both disturbances [57].
Thinleaf alder
Thinleaf alder sprouts from the root crown after top-kill by fire ([38,164,346], reviews by [35,92,312], observations reported in [119]). Stem density may increase after fire due to multiple sprouts arising from single root crowns (review by [312]). A review of fire responses of British Columbian shrubs states that thinleaf alder is "set back by moderate or severe fires" [159]. An anecdotal account from central Oregon reports that in thinleaf alder-dominated riparian communities, thinleaf alder withstands low-severity surface fires but is killed by more severe fires [200]. Root sprouting is possible, however, and further investigations are needed to ascertain thinleaf alder's response to moderate and severe fires.
Thinleaf alder establishes on burns from on- or off-site, wind- or water-dispersed seed (reviews by [35,312]). Wind may disperse seed onto burns from "considerable distances" [312]. Seedlings may also establish from seed in crown-stored "cones" after late summer fires (reviews by [35,312]). Viereck and Schandelmeier [346] reported that fire usually kills crown-stored seed in Alaskan alders such as thinleaf alder, but alder seeds are typically blown onto burns from off-site parents. Alders in lightly burned areas may produce "large numbers" of seeds in early postfire years [346]. Thinleaf alder may establish in early postfire years after stand-replacement fires in lodgepole pine. In the Bitterroot Mountains of northern Idaho, thinleaf alder often establishes from wind-blown seed around postfire year 3 [217]. Establishment from soil-stored seed may also occur (see Seedling establishment).
In a greenhouse study using soil from a wildfire-burned area near Slave Lake in Alberta, thinleaf alder sprouted from the roots but did not emerge from the seed bank. Soil samples were collected a week after the fire (cut in blocks 27.4² inches (177 cm²) across and least 4 inches (10 cm) deep). Thinleaf alder sprouted from soil blocks where fire had been "intense", averaging 23% cover after 2 years in the greenhouse. Thinleaf alder did not sprout from soil blocks collected from lightly burned or unburned sites. The plant community was mixed hardwood-conifer dominated by quaking aspen [224].
After summer wildfires on the Plumas National Forest, California, fewer thinleaf alders sprouted on upland sites—where fire crowned—than on gravelbars, where fire was less severe. Postfire response of vegetation on 2 streams, Third Water and Fourth Water creeks, was evaluated in postfire year 1. On the 1st and 2nd terraces above the creeks' gravelbars, the plant community was an incense-cedar-white fir/Eastwood manzanita-huckleberry oak (Arctostaphylos glandulosa-Quercus vaccinifolia) forest. Thinleaf alder dominated the gravelbars [197].
For each topographic position, mean relative density of thinleaf alder and percent of burned thinleaf alders that sprouted along Third and Fourth Water creeks in postfire year 1 [197] Topographic position Gravelbar 1st terrace 2nd terrace Riparian-zone slope Site % of total % sprouting % of total % sprouting % of total % sprouting % of total % sprouting Third Water CreekOn hybrid spruce-Engelmann spruce plantations in subboreal British Columbia, thinleaf alder abundance was similar on clearcuts prepared for planting by either prescribed burning or mechanical treatment (blading). Across treatments, mean thinleaf alder cover ranged from 17% to 25% on plantations <7 years old [147].
In a study of disturbed forests near the Peace River in northern Alberta, thinleaf alder was strongly positively associated (P<0.001) with frequently flooded sites (~1-10 years) but not with recent burns (5- to 20-year-old) or older burns (>20 years). Most (48%) of the white spruce and hardwood forests originated after flooding; fewer regenerated after logging (32%) or stand-replacing fire (19%). Thinleaf alder was recorded only on flooded sites. It was typically present in the earliest seral stages after flooding, establishing on gravelbars, levees, and the lowest stream terraces [332].
Thinleaf alder may occur in late postfire succession. On 12 white fir sites in Sierra County, California, that had experienced stand-replacing wildfires, thinleaf alder occurred only on study plots that had burned 80 years or more prior to the study. Time since fire ranged from 5 to 277 years [72].
In sagebrush ecosystems of the West, mesic thinleaf and other alder shrublands may establish after fire, or they may be self-sustaining [322].
Because gray alder adds nitrogen to soils and typically grows in moist soils, gray alder communities are usually highly productive [132]; hence, their fuel loads can be large. Gray alder may produce a "dense" litter layer [353]. However, because gray alder prefers moist sites, in most years gray alder communities may act as firebreaks. Riparian zones with gray alder are often buffer zones where upland fires decrease in severity or stop [285]. Speckled alder and thinleaf alder communities are placed in fuel model 0 [282] and fire group 0 [312], respectively; these plant communities do not burn readily [282,312]. Communities in fuel model 0 are described as vegetation types in which fire will not carry due to saturated ground or standing water, discontinuous fuels, and/or lack of ladder fuels [282]. However, with dry weather and the accumulation of dry fuel, riparian areas can become corridors for fire spread [285].
Speckled alder: A prescribed burning guideline for Ontario reports that speckled alder communities do not burn well under conditions needed for prescribed fires. McRae [248] found that in boreal black spruce-white spruce-quaking aspen forests of Ontario, prescribed fires did not typically spread into drainageways dominated by speckled alder. Because there was no combustible slash, these drainages acted as fire barriers [248]. An extension publication recommends speckled alder as an ornamental due to its low flammability [7].Several publications provide help for estimating fuel loads in speckled alder habitats. See these publications: [314,329] for information on models to estimate speckled alder biomass in the northern United States and Canada. Buech and Rugg [47,48] provide equations to predict aboveground biomass of speckled alder. Their model was developed in northern Minnesota [47,48]. A photoseries for assessing fuels in coniferous forests of northern Ontario provides size class breakdowns and photos for live and woody surface fuels in black spruce, black spruce-tamarack, black spruce-jack pine, black spruce-poplar (Populus spp.), balsam fir-black spruce, paper birch-white spruce, and poplar-white birch stands [321], all of which may include speckled alder as a component of the vegetation (see Site Characteristics and Plant Communities).
In the laboratory, speckled alder's heat of combustion and total heat release were about average for shrubs of the Northeast [94].
Several studies provide what may be representative examples of fuel loads in speckled alder habitats. In a speckled alder/goldenrod (Solidago spp.) community in upstate New York, speckled alder production averaged 730 g/m²/year. Leaves and twigs comprised 42% of total production; 25% was in the boles; 21% in branches; and 12% in fruits. Herbaceous production averaged 241 g/m², yielding a total aboveground production of 971 g/m² for the speckled alder community [331]. A New York study found total speckled alder production averaged 2,225 g/m², 21% of which was roots [349].
In commercial forests in Michigan, speckled alder biomass was least in oak-hickory and greatest in tamarack stands [273]. In a similar study across commercial forests in the Northern Great Lakes (northern Minnesota, northern Wisconsin, and the Upper Peninsula of Michigan), speckled alder biomass was least in jack pine and greatest in balsam fir stands [313]. No information on stand ages was available.
Speckled alder biomass by forest type Forest type Michigan [273] Northern Great Lakes [313] Biomass (lbs/acre) oak-hickory 13 no data maple-birch 35 239 elm-ash-maple 607 2,584 aspen 134 1,989 paper birch 283 552 red pine 24 383 jack pine 71 153 eastern white pine 118 3,368 white spruce 260 1,758 northern white-cedar 433 4,221 balsam fir 644 5,482 black spruce 1,703 4,090 tamarack 2,607 3,037In Nova Scotia, speckled alder biomass averaged 83 kg/ha in dense mixed-conifer, 140 kg/ha in dense mixed-hardwood, and 1,150 kg/ha in open mixed-conifer forests [328].
Thinleaf alder: Thinleaf alder thickets are somewhat fire-resistant because the duff is usually cool and moist, and the undergrowth is sparse [92]. The generally moist conditions in thinleaf alder stands usually inhibit fire spread (review by [312]). Even when fires are severe in upland areas, riparian zones may remain unburned or burn with lower severity. However, fires may burn severely in riparian areas in drought years [315]. A fire management plan for Lassen National Park, California, reported that natural fires seldom ignite in black cottonwood-thinleaf alder woodlands; instead, those woodlands are generally firebreaks. However, old stands with diseased and downed trees may be "quite flammable", especially if white fir or red fir has formed ladder fuels in the understory [181].
In many forested riparian areas, live and dead fuel structure and loads have altered due to fire exclusion. Arno and Harrington [12] report that in riparian ponderosa pine communities of the West, where thinleaf alder is known to occur, most sites are dominated by dense, shade-tolerant trees such as grand fir, and the shrub and ground layers are sparse.
On 3 thinleaf alder wetland communities in west-central Montana, total aboveground plant productivity ranged from 3,320 to 4,820 lbs/acre. Of that total, shrubs averaged 316 lbs/acre, forbs averaged 1,200 lbs/acre, and graminoids averaged 2,713 lbs/acre [286].
Several studies described below provide what may be representative examples of fuel loads in thinleaf alder habitats by the Tanana River in Alaska. Yarie and Mead [363] present models to estimate twig and leaf biomass of thinleaf alder and other species of the Tanana River Basin.
On sandbars of the Tanana River, total production in 5-year-old thinleaf alder thickets averaged 20,000 kg biomass/ha (including root biomass). Production peaked in 15-year-old thickets at an average of 65,000 kg/ha, while 20-year-old thickets averaged 95 kg/ha [339]. On thinleaf alder-dominated floodplains of the Tanana River, thinleaf alder biomass was almost 5 times greater in 20- vs. 5-year-old stands. Codominant willows and horsetails comprised much smaller portions of the total plant community biomass (3.2-8.7%) [339].
Distribution of biomass (kg/ha) in thinleaf alder-dominated stands of different ages [339] Sample 5 years 15 years 20 years Thinleaf alder biomass* 8,751 27,810 42,741 % of total plant community biomass 42.9 43.5 45.1 Total down woody fuel biomass not available 10,464 16,389 Total litter biomass 4,340 4,134 4,390 Total biomass 20,388 63,876 94,689 *Above- & belowground biomass mass was measured for live plants.After late February logging, a prescribed broadcast burn in July reduced fuels in a white spruce/thinleaf alder/feathermoss (Hylocomium sp.) forest on the Tanana River floodplain. The fire "substantially" decreased organic material on the soil surface and exposed mineral soil. Down and dead woody fuels were reduced an average of 67%, mean depth of the forest floor was reduced 43%, and the soil organic layer was reduced 2.9%. See Zasada and Norum [367] for information on the fire prescription and fire weather conditions.
Gray alder seeds are usually nondormant ([27,300], review by [19]) and, under favorable conditions, may germinate immediately after dispersal (review by [143]). However, some seed lots may require a stratification period, from a few days to over winter (review by [154]). Moist soil ([71], review by [143]) and temperatures from approximately 50 to 77 °F (10-25 °C) [154] are required for germination.
Gray alder seed viability is generally low (review by [143]), but preliminary studies suggest that light enhances germination ([93], review by [154]). Some laboratory studies found only 5% viability in thinleaf alder seeds (review by [143]). In greenhouse trials, speckled alder showed low seed viability (4-42%). Germination of filled seed varied from 0 to 50%, with presoaking and light increasing germination rates [27]. For thinleaf alder seeds collected near Fairbanks, germination averaged 90% for seeds cold-stratified in light and 5% for seeds cold-stratified in dark. Unstratified seed showed 100% germination in light and ≤13% germination in dark [93]. Gray alder seed may germinate without light, however. In a laboratory study, speckled alder showed no significant difference in time to germination and germination rate in dark vs. light, averaging 10 days to germination, and 36% germination, in both light and dark [246].
Gray alder provides winter browse, although wildlife may not prefer it (review by [143]). This preference may be unexpected because the foliage is high in nitrogen (for example, [180,235]). However, gray alder may be a secondary source of wildlife browse due to its wide distribution and local abundance [334]. Gray alder utilization is generally highest from late fall to early spring [334]. Songbirds eat gray alder seeds [215], and squirrels consume the catkins (review by [143]).
White-tailed deer and lagomorphs browse speckled alder [176]. It provides winter forage (review by [141]), but browsing wildlife are likely to avoid speckled alder if more palatable species are available. In a winter deer yard in Quebec, white-tailed deer browsed red-osier dogwood and pussy willow more than expected, and speckled alder less than expected, based on availability [41].
In cafeteria feeding trials in Wisconsin, captive ruffed grouse avoided speckled alder catkins, preferring those of quaking aspen and willows. The authors speculated that secondary metabolites in speckled alder catkins rendered the speckled alder catkins unpalatable [140].
Mule deer browse thinleaf alder sparingly [261,348], although thinleaf alder may be more important in winter [261]. Mountain goats also use thinleaf alder [240], and livestock may browse thinleaf alder heavily in riparian areas [256]
Arthropods and mollusks consume gray alder. Millipedes browse fresh speckled alder leaf litter [235]. Landsnails (Cepaea nemoralis) also browse speckled alder leaf litter [360]. Speckled alder is a host of alder aphids (Prociphilus), which feed only on alders (Alnus) [368]. Alder aphids are a larval food of the harvester butterfly (Feniseca tarquinius) [305].
Palatability and/or nutritional value: Gray alder's palatability is rated poor to fair for big game animals. Sprouts and young plants are preferred over older browse ([334], review by [141]). Its palatability for livestock is rated from poor in the Southwest to fair in the Pacific Northwest and California. Gray alder is generally more palatable to cattle than to domestic sheep and goats [334].
Songbirds, grouse, and American woodcocks eat gray alder buds, seeds, and catkins (reviews by [142,160]). See Grodzinski and Sawicka-Kapusta [139] for information on the nutritional value of gray alder seeds.
Speckled alder is not a preferred browse taxon; it is used primarily as winter forage. It was ranked very low in palatability among woody taxa (22nd among 23) that white-tailed deer used as forage [265]. On the Apostle Islands of Wisconsin, speckled alder was 1 of 4 taxa that white-tailed deer chose last as browse; 28 taxa were tested [21]. A habitat suitability model, developed for coniferous and aspen-birch ecosystems of the Great Lakes region, lists speckled alder as low-preference browse for moose during the growing season [5]. A study on Isle Royal, Michigan, found moose used speckled alder less than expected based on speckled alder's availability and nutritional content (P≤0.05) [25]. American beavers, however, used speckled alder as much as expected (P<0.05) [26].
Speckled alder is high in protein. See these sources: [25,235] for nutritional information on speckled alder browse. See this source: [140] for nutritional information on speckled alder catkins.
Thinleaf alder is generally unpalatable to wild ungulates [151,223], cattle, and horses. It is fairly palatable to domestic sheep [32]. Wild ungulates browse new thinleaf alder growth but generally avoid mature thinleaf alder [151] except as emergency winter forage. On summer rangelands in Tehama County, California, mule deer browsed thinleaf alder less than expected based on availability [223].
In Alaska, feltleaf willow and balsam poplar were more palatable to browsing mammals when grown in the shade of thinleaf alder than when grown in the open (Rohleder 1985 cited in [45]).
Cover value: Gray alder provides shade and hiding cover for many vertebrate species.
Speckled alder: In a Quebec study, speckled alder was the dominant streamside shrub in an ecosystem supporting brook trout, American mink, and Appalachian brook crayfish (Cambarus bartoni), the American mink's primary prey species in that stream [50]. The federally endangered bog turtle [336] is positively associated with speckled alder wetlands (review by [50]). In Alberta, white spruce/gray alder/horsetail/moss (Equisetum/Hypnum and Polytichum spp.) riparian communities provide shade and reduce water temperatures in trout streams [77].
Speckled alder is critical for American beavers. They use speckled alder for den and dam construction more than they use it as browse [103,222]. In Algonquin Provincial Park, Ontario, the number of speckled alder stems found in American beaver dams (403 stems) was over twice that of speckled alder stems found in their food caches (176 stems). Speckled alder was selected for dam construction about 4 times as often as spruces, which were the next most preferred [103]. In another Algonquin Provincial Park study, American beavers used speckled alder more than expected. Although speckled alder composed 25.6% of the standing vegetation, 49.2% of stems that American beavers felled were speckled alder. Speckled alder cover and basal area increased significantly with distance from American beaver dens (P<0.009) [101,102].
Speckled alder provides important cover for American woodcocks, ruffed grouse [99,266], and other birds. Speckled alder thickets provide critical feeding, nesting, molting, and premigratory staging habitat for American woodcocks ([252,258,266,291], Sheldon 1967 cited in [49]). In Michigan, ruffed grouse used speckled alder for cover in drumming sites (review by [160]). A study in eastern hemlock-red maple/speckled alder-mountain-laurel riparian corridors of Pennsylvania found the number of obligate wetland bird species, such as kinglets and flycatchers, was significantly higher in undisturbed speckled alder riparian corridors than in speckled alder-dominated riparian corridors disturbed by residential or agricultural development [83]. Niemi and Pfannmuller [266] provide a list of bird species using speckled alder-dominated wetlands as breeding and nesting habitat in Minnesota and Michigan.
Thinleaf alder: Thinleaf alder provides cover for snowshoe hares [353] and big game animals [261]. Mule deer, white-tailed deer, and elk use thinleaf alder communities for thermal and hiding cover [151]. American beavers use thinleaf alder to make their dens (review by [160].
Thinleaf alder provides forage and nesting sites for songbirds, upland game birds, and wetland birds (reviews by [143,149]).
Thinleaf alder provides cover for aquatic organisms. Dense thinleaf alder thickets provide thermal and shade cover for fish. Thinleaf alder and associated shrubs stabilize stream channels, and overhanging banks reduce erosion [32,151]. In Oregon, thinleaf alder on streambanks provide cover, food, and shade for salmonids [200]. In the Trout Creek Mountains, thinleaf alder-Wood's rose overstories shaded over 70% of the stream channels of 4 streams, while the more open thinleaf alder/woolly sedge communities shaded about 50% of the stream channels. Dense woolly sedge that grew over the streambank enhanced trout habitat [114].
Cattle loaf in thinleaf alder stands, although dense thinleaf alder thickets may impair access. Heavy cattle trampling may degrade thinleaf alder habitats by creating dish-shaped stream channels and reducing cover of palatable herbs [32,151].
Gray alder may compete with timber species, sometimes occupying highly productive sites [142]. When speckled alder is in the understory, clearcutting may result in dense speckled alder stands [160]. Dense stands may prevent or impede conifer regeneration, although scattered individuals present little threat to planted conifers (review by [143]). In northwestern Ontario, speckled alder occurred on wet to moist, nutrient-poor to nutrient-medium sites. It was implicated in competing with conifers for light and moisture but credited with fixing atmospheric nitrogen [51]. On the Tanana River floodplain in central Alaska, thinleaf alder inhibited growth of understory white spruce seedlings by shading and root competition. Thinleaf alder's dense litter layer may also inhibit conifer establishment [353].
When using mechanical treatment to control gray alder, the root crown must be destroyed to prevent sprouting. Stems in contact with soil may layer; layering is common after logging [51]. These sources: [38,51] provide information on controlling speckled alder with herbicides.
Gray alder wood has little commercial value due to the species' small stature. It is used for firewood [171] and for smoking salmon [345].
American Indians used gray alder medicinally (Moerman 1986 cited in [120]). They used the bark to make red dye [157,190,203,215,348].
Gray alder's catkins are formed the previous growing season and are exposed in buds during winter. In spring, gray alder flowers before leaf-out and stem elongation [120,171,176]. Male catkins drop in late spring, shortly after pollination [176,261]. There is "considerable" leaf drop in summer and fall [106]. Seeds disperse in fall or winter, although female catkins remain on the plant [171,176,261]. Both male and female catkins form the year prior to opening, so in fall, gray alders usually display immature male and female flower clusters, immature fruits, and old female catkins [171,176,261]. Phenology of speckled and thinleaf alder is as follows:
Speckled alder
Area Event Season Illinois flowers May-June [255] Atlantic coast flowers March-April [105] central New York flowers April seed disperses winter; often over snow [176] Adirondack Mountains sheds pollen late March-April [205] flowers late April-May [64] Blue Ridge Mountains flowers May-June [359] Northeast flowers March-May [237] Canada flowers March-May [154] Quebec, Gaspe Peninsula flowers March-May fruit ripe August-October seed disperses fall-winter [257] Thinleaf alder Area Event Season Alaska flowers May-June [345] California seeds ripe August-September [254] Colorado, South Platte River Basin seeds disperse 2 pulses: early June & late August [253] Idaho flowers March-April fruit ripens August-September [154] Montana flowers March-April fruit ripens August-September [154] New Mexico flowers April-June [241] Nevada flowers April-June [193] Oregon flowers March-April fruit ripens August-September [154] Great Basin flowers February or later [261] Northern Great Plains flowers May fruits August-September [219] North-central Great Plains flowers late April fruits September [318] Great Plains flowers April-June [137]Gray alder is monoecious [171,318]. The flowers are wind-pollinated [81,261], so most plants are cross-pollinated. However, thinleaf alder self-pollinates rarely (review by [154]).
Genetic differences among populations are generally small in species with wind-dispersed pollen and seeds (for example, [168]), such as gray alder. Allozyme studies of speckled alder in central Quebec showed high rates of gene flow and weak genetic differentiation among 4 populations [34].
Spatially, the genetic make-up of individuals in speckled alder thickets may be random. Studies of 4 speckled alder thickets in New York showed clones were randomly distributed, and clumps of single genotypes were not aggregated. Thus, the author concluded that although speckled alder regenerates vegetatively, sexual regeneration was driving the genetic structure of these 4 populations [175].
Wind and water disperse thinleaf alder seeds ([81,93], reviews by [35,312]). In waterways of Alaska, thinleaf alder seeds stayed afloat for "long periods of time" (Densmore 1976 personal observation [93]). On a floodplain of Little Otter Creek in Vermont, speckled alder seed was found in floodwaters but not in seed rain deposited on soil. The surrounding plant community was a red maple-sugar maple (Acer saccharum) forest [178].
Thinleaf alder may establish from seed in crown-stored "cones" after disturbances such as fire ([256], review by [35]), road construction, logging, and mining [256].
Gray alder seedling establishment may be rare except in primary succession or on disturbed, open sites. In central New York, 4 populations of speckled alder showed no seedling establishment over 3 years [176]. In a Freeman maple-white ash swamp in New York, speckled alder establishment averaged 10 seedlings/100 m². One-year-old seedlings averaged 5.2 inches (13.1 cm) tall; 2-year-old seedlings averaged 13.5 inches (34.3 cm) tall [29].
Soil disturbance and/or exposed mineral soil favor gray alder establishment ([71], review by [143]). In Michigan, the margins of American beaver ponds were favorable sites for speckled alder germination and establishment [222]. In a Swedish field experiment, European gray alder seedling survival was higher in mineral soil (34%) than in humus (9%) [300].
Gray alder seedling establishment on new sandbars and on banks with receding floodwaters is common, although other substrates also provide favorable establishment sites. After a flood on the Connecticut River, for example, speckled alder seedlings were noted in a sugar maple swamp in an oxbow [170]. On Lassen National Forest, thinleaf alder established most often near wide stream channels on sand- or gravelbars. Thinleaf alder seedling establishment was negatively correlated with canopy cover (P=0.02) and litter depth (P=0.002) and positively correlated with solar radiation (P=0.002) [297]. In a greenhouse experiment in France, flooded European gray alder seedlings grew fastest on moist, sandy loams that were flooded and drained daily [177]. In boreal quaking aspen-paper birch ecosystems near Slave Lake, Alberta, thinleaf alder established on decaying logs and stumps [226]. Gray alder germinants apparently tolerate slightly drier conditions than willow germinants [114].
Gray alder seedlings grow rapidly under favorable conditions ([298], review by [154]). Monsen and others [256] report that thinleaf alder seedlings are "very competitive and vigorous. Once established, few plants can grow as rapidly". In central New York, annual growth increments of 4 speckled alder populations ranged from 0 to 2.8 inches (1.1 cm). Growth rate was generally greatest in midsized stems (0.8-1.5 inches (2.0-3.9 cm) DBH, P<0.01). In one population, gypsy moths removed nearly 100% of foliage in July, but stems leafed out again in late summer. Slowed growth and/or stem mortality was anticipated as a result of the defoliation but was not recorded [176]. Speckled alder seedlings proved "remarkably tough when placed in the field" after growing in a greenhouse. Ninety-seven percent survived their first year [27].
Speckled alder may grow rapidly after canopy removal (review by [143]). MacLean [236] reported that after clearcutting in boreal quaking aspen-paper birch-spruce communities in Ontario, understory speckled alder gained height growth quickly and spread vegetatively. From small clumps with few stems, speckled alder typically formed a tall, closed-shrub canopy within 10 to 12 postharvest years. Some regeneration from seed was also apparent. Best growth occurred on moist to very moist clay loams [236]. Speckled alder also grew rapidly following clearcutting on black spruce peatlands in Ontario. Ten years after harvest, speckled alder averaged 5 to 6 feet (1.5-1.8 m) tall and 16,000 to 30,000 stems/acre. Speckled alder crown closure ranged from 40% to 80% [347].
Colonizing gray alders may facilitate subsequent gray alder establishment and colony expansion. Below receding glaciers above Glacier Bay, Alaska, thinleaf alder established as widely scattered individuals. These individuals were centers of aggregation from which thinleaf alder thickets spread [75].
Ungulate browsing can substantially reduce growth of thinleaf alder on heavily browsed sites. On big game winter rangelands near the Clearwater River in northern Idaho, thinleaf alder's annual biomass accumulation averaged 0.23 g/m² in ungulate exclosures. Study plots outside exclosures, which were subject to moose, elk, and mule deer foraging, did not contain thinleaf alder, Rocky Mountain maple (Acer glabrum), or several other important browse species [4].
One study found midsized speckled alder sprouts suffered the least mortality among size classes. Over 3 growing seasons in New York, short speckled alder stems (<4.6 feet (1.4 m) tall, minimal DBH) died most often, while midsized stems (6.6-13 feet (2.0-3.9 cm) DBH) showed less mortality than larger sprouts. Sampling was conducted in 4 early-successional speckled alder thickets. Variation in stem mortality and growth was greater within populations than across sites (P<0.05 for all variables) [176].
Gray alder prefers moist to mesic sites throughout its distribution but occurs in a wide variety of plant communities within that moisture gradient. Its symbiotic relationship with nitrogen-fixing actinomycetes helps enrich soils; this affects plant community composition and succession. After fallen gray alder leaves and roots die and decay, their nitrogen is released back into the soil and becomes available to other plants [171,180,215]. An English poet wrote:
The alder, whose fat shadow nourisheth.
Each plant set there to him long flourisheth.
William Brown, Brittania's Pastorials. 1613.
Speckled alder commonly occurs or codominates with willows (Salix spp.), a mixture that may be controlled by length of flooding season. Willows may tolerate longer flooding seasons than speckled alder. A laboratory study showed speckled alder was less tolerant to continuous flooding than willow species. Speckled alders suffered 33% average mortality when water levels were kept above the root crown for 2 years, while speckled alders experienced no mortality when the water level was maintained below the root crown for the same length of time [196].
Soils: Speckled alder tolerates a wide variety of soil textures and pH but is most common on nutrient-poor soils. It grows in sandy loam [49,160], chalky, rocky till, and mucky soils [160]. In Ontario, speckled alder is an indicator of fine loamy-clayey soils with thick black humus; it is also an indicator of poor to rich fens with moderately decomposed organic soils [188]. In swamps of northern Michigan, speckled alder communities tended to occur on relatively well-drained, sandy loams, while black ash/speckled alder communities occurred mostly on poorly drained, silty clay loams [275]. In the Catskill and Adirondack mountains, speckled alder grows in limestone-, gneiss- and anorthosite-derived soils [205]. In black ash-paper birch communities of the Great Lakes states, speckled alder was noted on minerotrophic peat substrates [31], and it grew in coarse woody peats in northern white-cedar (Thuja occidentalis) swamps of northern Wisconsin [67]. It occurred on glacial till in central New York; soils were neutral to "somewhat alkaline" [176]. It is reported on soils with pH from 3.4 to 7.7 in Ohio (review by [160]). In Wisconsin, speckled alder thickets occurred on peats of pH 5.5 [85]. In jack pine (Pinus banksiana) stands in Minnesota, speckled alder was most common on medium-quality silvicultural sites (18% frequency). It also occurred on good-quality sites (7% frequency) but not on poor-quality sites (Hansen 1946 cited in [39]). In an assessment of Michigan shrub habitats, speckled alder occurred on the moistest, coolest, and most nutrient-poor sites when compared to other shrubs [36]. However, speckled alder also occurs on nutrient-rich sites [204]. On the Saskatchewan River Delta, speckled alder was positively associated with relatively nutrient-rich, shallow peat fens and levees. Soil water was alkaline and high in calcium and magnesium [97].
Elevation and topography: Speckled alder ranges from near sea level on the North Atlantic coast to about 2,710 feet (825 m) in the Appalachians [127]. It grows on low-elevation alluvial soils in Nova Scotia [295] but at "moderately high elevations" elsewhere in Canada [304]. It is restricted to high elevations in the southernmost portion of its range [160]. In a tamarack bog in Itasca State Park, Minnesota, speckled alder was more abundant on hummocks (35% cover and 10% frequency) than in depressions (2% cover and <1% frequency) [142].
Plant communities: Speckled alder occurs in forest, shrub, and herbaceous communities. It is an important component of northern spruce-fir (Picea-Abies spp.) [22,247], red-white-jack pine (Pinus strobus-P. resinosa-P. banksiana) [69], Atlantic white-cedar (Chamaecyparis thyoides) [106], and mixed-hardwood [341] forests, especially at forest and bog ecotones [247]. It also occurs in elm-ash-cottonwood (Ulmus-Fraxinus-Populus spp.) galleries and forests [108]. In Newfoundland, it occurs in rich fens dominated by pale sedge (Carex livida) [289]. Species diversity is generally high in wetland communities where speckled alder is an important to dominant component of the vegetation (for example, [33,114,356]).
Regional descriptions of plant communities with speckled alder and site characteristics of speckled alder habitats follow.
Great Lakes: Speckled alder is common in coniferous, mixed conifer-hardwood, shrubland, and graminoid wetland communities in the Great Lakes region. It is common, for example, in the understories of red pine forests and plantations. American hazelnut (Corylus americana) and beaked hazelnut (C. cornuta var. cornuta) usually dominate or codominate the understories [46]. In Voyageurs National Park, Minnesota, black spruce/speckled alder communities occurred on nutrient-poor, wet sites [207]. On the Lake Agassiz Peatlands Natural Area of Minnesota, speckled alder was abundant (covered 0.25% to 0.5% of an area) in rich swamp forests dominated by northern white-cedar, black ash (Fraxinus nigra), tamarack (Larix laricina), or white spruce (Picea glauca). It was not abundant in poor swamp forests, bogs, fens, or heaths [163]. In northern Wisconsin, speckled alder was important to dominant in northern white-cedar swamps [67]. It was also important to dominant in eastern redcedar (Juniperus virginiana) bogs of Ohio [125]. On the shores of Lake Superior, a speckled alder/red raspberry /fowl mannagrass-reed canarygrass (Rubus idaeus/Phalaris arundinacea-Glyceria striata) thicket community occurred on secondary dunes, lees of high dunes, and sand flats. This community type had the highest species richness of 4 types identified [33].
Speckled alder is occasional to invasive on open fens and bogs of the Great Lakes states. In northeastern Ohio, it is characteristic in sedge (Carex) fens. Bottlebrush sedge (C. hystericina), hairy sedge (C. lacustris), and tussock sedge (C. stricta) are typical dominants [301]. Speckled alder often dominates marginal fen or marginal bog zones, which separate the mires from the upland communities surrounding them [73].
Northeast: Speckled alder grows in coniferous forests, mixed and hardwood forests, shrublands, and open wetlands in the Northeast.
Maine: On Peak's Island, Portland, speckled alder was characteristic in the tree strata of an upland red maple (Acer rubrum) forest, parts of which had burned 3 times in 24 years, and of an unburned balsam fir (Abies balsamea) forest. At the time of the survey, speckled alder was the 2nd most common taxon on 7-year-old burned sites in the red maple forest (97% relative density and 13% frequency on 10 m² plots) and the 4th most common in the balsam fir forest (56% relative density and 16% frequency). Speckled alder clumps were also frequent in a nearby red maple swamp, where speckled alder dominated poorly drained areas of the swamp [79].
New England: In pitch pine (Pinus rigida)-hardwood swamp mosaics of New Jersey, speckled alder was a minor to codominant component of red maple-black tupelo-sweetbay/coastal sweetpepperbush (Nyssa sylvatica-Magnolia virginiana/Clethra alnifolia) swamps. It was most important on continuously flooded sites, declining on sporadically flooded or dry sites [112].
Southeast: Speckled alder occurs in mixed-hardwood, pine (Pinus spp.), and shrubland communities of the Southeast. In a 1930 study, it was a component of a climax American chestnut-yellow-poplar-eastern hemlock (Castanea dentata-Liriodendron tulipifera-Tsuga canadensis) cove forest in the Black Mountains of North Carolina [91]. Yellow-poplar became the primary dominant in many cove forests after chestnut blight decimated American chestnut populations [341]. In Georgia, speckled alder occurs in pond pine (Pinus serotina)-shrubland and bay (Magnolia and Persea spp.)-shrubland bogs. Shrub diversity is generally high [356].
The following vegetation classifications describe plant communities, and some of their distinguishing site characteristics, where speckled alder is dominant. In state and province lists, plant communities are arranged geographically from north to south and west to east.
Great Lakes Northeast Southern Appalachians Southeast CanadaThinleaf alder
Site characteristics: Thinleaf alder is most common on wet to moist sites (review by [143]). It is a frequent component of streamside vegetation throughout mountainous regions of western North America [120]. It is considered an indicator of riparian or subirrigated sites on the Shoshone National Forest, Wyoming [172]; of moist, well-drained sites—especially streambanks and springs at low elevations—in central Oregon [203]; and of moist to wet soils in subboreal spruce (Abies spp.) and pine (Pinus spp.)-spruce ecosystems of British Columbia [23]. Riparian sites with thinleaf alder may experience frequent flooding and/or scouring (for example, [104,114]).
Soils: Thinleaf alder grows on a variety of soil textures and nutrient levels. It grows in coarse-textured soils but is well-adapted to cold, "heavy" soils (review by [143]). It grows well in sand [199,339], and it is common on sandbars [339]. In the Trout Creek Mountains, thinleaf alder grows in sand- and siltbanks about 2.6 feet (0.8 m) above stream channels [114]. Soils supporting thinleaf alder are often rocky in mountainous areas [318]. In Montana, thinleaf alder communities typically develop on cobble and gravel, accumulating organic debris over time [149]. Nutrient levels of soils supporting thinleaf alder vary from poor to rich, although they are typically poor (review by [184]). Thinleaf alder typically establishes on poor, skeletal soils in primary succession [149], but it usually enriches in soils in which it grows [149]. In the understories of coniferous forests in Blue Mountains, thinleaf alder is an indicator of productive sites [144].
Elevation and topography: In the conterminous United States, thinleaf alder is primarily restricted to mid- to high-elevation mountains, mountain valleys, and mesic canyons [155,208,231,241], although it grows on low-elevation sites in Alaska and Canada [231]. In the United States, thinleaf alder ranges in elevation from near sea level in Alaska to over 10,000 feet (3,000 m) in Colorado and Arizona [127]. Thinleaf alder populations apparently do not have exacting elevational requirements. Thinleaf alder cuttings have been successfully transplanted onto sites that vary greatly in elevational range [256].
Elevational range of thinleaf alder by state State Range (feet) Arizona 5,000-9,000 [195,228] California 3,900-7,900 [167] Colorado 5,000-10,000 [155] New Mexico 6,000-9,500 [96,228,241];Thinleaf alder presence is likely more associated with moist to mesic conditions than with aspect alone. In the Wasatch Mountains of Utah, thinleaf alder was common in the bottom of Cold Canyon [272], but it was not noted on higher, north- or south-facing slopes, which may have drier soils [272]. In Lassen Volcanic National Park, California, the location of willow-thinleaf alder communities was not significantly associated with aspect, but it was positively associated with relatively moist conditions (P=0.01). Willow-thinleaf alder communities were most common on steep slopes, depressions, and valley bottoms (P≤0.002). The authors attributed their presence on steep slopes to the prevalence of intermittent streams in avalanche chutes and their presence in low areas to the prevalence of concave drainage channels [288].
Plant communities: Thinleaf alder in a mixed-conifer forest on the El Dorado National Forest, CA. Photo © 2009 Dr. Mark S. Brunell.Thinleaf alder prefers mesic to moist plant communities. These include the moist slopes of coniferous forests, riparian areas, wet meadows and grasslands, and fen and bog margins [127]. Site moisture and elevation are critical in determining relative dominance of thinleaf alder; the surrounding vegetation usually tolerates drier conditions. On the shore of Slave Lake in Alberta, thinleaf alder codominates the understory of white spruce-paper birch communities on gravel or sand beaches that are 300 feet (90 m) or less from the lake [227]. In the Trout Creek Mountains of Nevada, thinleaf alder communities are concentrated in low-elevation (4,920-5,300 feet (1,500-1,615 m)), narrow riparian corridors. Mountain big sagebrush (Artemisia tridentata subsp. vaseyana) typically dominates vegetation beyond the corridors, and plant species diversity is lower outside than within the riparian corridors [114]. Willows (Salix), red-osier dogwood, common snowberry (Symphoricarpos albus), and horsetails (Equisetum) codominate with thinleaf alder in many plant communities throughout much of thinleaf alder's distribution.
Regional descriptions of plant communities with thinleaf alder and site characteristics of thinleaf alder habitats follow.
Alaska: Thinleaf alder is reported on glacial shrublands (see Successional Status), riparian and wet-upland shrublands, and spruce-birch (Picea-Betula spp.) swamps. Thinleaf alder-willow and resin birch-thinleaf alder-willow cover types are common near timberline in interior Alaska. These communities form thickets that may be "extremely dense" or open and interspersed with reindeer lichens (Cladonia) and heath (Ericaceae) [357]. On the Tanana River of central Alaska, 5-year-old thinleaf alder communities on sandbars were codominated by feltleaf willow (Salix alaxensis), sandbar willow (S. interior), and barrenground willow (S. brachycarpa subsp. niphoclada). Balsam poplar, paper birch (B. papyrifera), and white spruce grew in the understory; meadow horsetail (E. pratense) and variegated scouringrush (E. variegatum) were dominant herbs [339]. See Successional Status for more information on this study.
Pacific Northwest: Thinleaf alder is a component of and sometimes forms glades within coniferous forests of the Pacific Northwest; it is also important to dominant in riparian corridors. Thinleaf alder is prevalent in ponderosa pine (Pinus ponderosa), Douglas-fir (Pseudotsuga menziesii), lodgepole pine (Pinus contorta), and fir-spruce (Abies-Picea spp.) communities [184]. Thinleaf alder glade openings generally occur on wet to mesic sites where thinleaf alder outcompetes conifers for soil moisture [92].
California: Thinleaf alder grows in coniferous, western hardwood, riparian, and other wetland communities in California. The photo above shows a typical Californian thinleaf alder habitat. Thinleaf alder is frequently found on the edges of ponds, bogs, and fens [242]. In the Klamath Mountains and Sierra Nevada, it grows on the margins of California pitcher plant (Darlingtonia californica) bogs [221]. Prior to extensive water diversions, thinleaf alder was likely important in quaking aspen-black cottonwood (Populus balsamifera subsp. trichocarpa) riparian corridors leading to Mono Lake, which is situated in the arid Mono Basin [320].
Northern and Central Rockies: Thinleaf alder is reported in coniferous forests, riparian galleries and shrublands, and wetland edges. In western Montana, thinleaf alder is frequent in Douglas-fir, western hemlock-western redcedar (Tsuga heterophylla-Thuja plicata), and grand fir (Abies grandis) forests. Surveys in the Blackfoot and Flathead valleys indicate that most thinleaf alders in these forest types grow as shrubs [121]. In southwestern Colorado, thinleaf alder grows in mixed-conifer riparian woodlands dominated by white fir (A. concolor), southwestern white pine (Pinus strobiformis), interior ponderosa pine (P. ponderosa var. scopulorum), and blue spruce (Picea pungens) [14].
In the Rocky Mountains, thinleaf alder-dominated riparian communities tend to occur on an elevational gradient just above narrowleaf cottonwood (Populus angustifolia) communities [281]. In western Colorado, Baker [15] noted that thinleaf alder was nearly always present at varying frequencies, and sometimes dominant, along narrowleaf cottonwood and blue spruce riparian forests. Thinleaf alder, red-osier dogwood, and water birch (Betula occidentalis) formed an often impenetrable shrub layer, with thinleaf alder dominant along stream margins and becoming less frequent with distance from the streams [15]. Thinleaf alder dominates in the upper reaches of the narrowleaf cottonwood-Scouler willow (S. scouleriana) formation in Boulder County; it may also dominate in canyon bottoms [364]. Its distribution extends into the mountain sagebrush-mountain grassland zone, mostly above 5,000 feet (2,000 m), in the Northern Rocky Mountains (reviews by [184,256]). In the Sawtooth National Recreation Area, Idaho, thinleaf alder dominates high-gradient streams (those on steep slopes or with rapid water flows) [173]. In northwestern Montana, thinleaf alder community types occur from 3,760 to 6,700 feet (1,150-2,040 m) elevation on moist stream edges, overflow channels, and slope seeps [32]. Thinleaf alder is common in many riparian shrublands dominated by other species, especially willows, red-osier dogwood, and Wood's rose (Rosa woodsii) (for example, [149,284]).
Southwest: In the Southwest, thinleaf alder occurs in wetlands within desert ecosystems and at high elevations. It may be a component of or locally dominant in riparian scrublands of Arizona; these scrublands are usually dominated by Bebb willow (Salix bebbiana), Scouler willow (S. scouleriana), and/or other willow species [40]. Thinleaf alder is an obligate riparian taxon in New Mexico, where it may dominate riparian shrublands solely or codominate with willows [96,276]. Its relative dominance generally increases with increasing elevation [95]. Thinleaf alder is a common shrub component of narrowleaf cottonwood communities of Arizona, New Mexico [20], and southern Colorado. Within wet areas, it sometimes grows as low as the pinyon-juniper (Pinus-Juniperus spp.) zone in northern Arizona [184]. In Great Sand Dunes National Monument, Colorado, it is an important component of narrowleaf cottonwood/Kentucky bluegrass (Poa pratensis) riparian communities [243]. Its distribution extends into the Engelmann spruce-corkbark fir zone (Picea engelmannii-Abies lasiocarpa var. arizonica), from 7,000 to 9,000 feet (2,000-3,000 m)), in the Rincon Mountains of Arizona (review by [184]). Thinleaf alder may be locally important to dominant in alpine riparian communities of the Southwest [40].
The following vegetation classifications describe plant communities, and some of their distinguishing site characteristics, where thinleaf alder is dominant or is a community type indicator. In state and province lists, plant communities are arranged geographically from north to south and west to east.
Boreal North America, general West, general Alaska Pacific Northwest California Southwest Great Basin Northern and Central Rockies Northern Great Plains CanadaUtah (see entries in Great Basin)
Northern Great PlainsGray alder tolerates full sun to light shade. It is an important colonizer in primary succession. It is also successionally important after stand-replacing events such as fire and logging [108] and in canopy gap succession [209]. Its ability to fix nitrogen (see SITE CHARACTERISTICS AND PLANT COMMUNITIES) can enhance site quality for later-successional species. Plant response to fire provides information on gray alder and postfire succession.
Speckled alder
Speckled alder prefers open sites [106,171,205] but tolerates moderate shade (Shirley 1932 cited in [39]). Studies in Michigan found that it occurred on open to closed sites but was most common on lightly shaded, cool sites [16,36]. In southern-boreal, quaking aspen forests of Quebec, speckled alder was associated with relatively high light transmission at 7 to 13 feet (2-4 m) above ground level (P<0.001). Thirty percent of full sun was the highest light level achieved on most sites [18].
Speckled alder is an important shoreline and meadow colonizer, and it is successional in mires and other wet to damp areas throughout its range [120]. In Michigan, it colonizes sand dunes by Lake Huron [13]. In New York, it is a characteristic taxon on unstable beachgrass (Ammophila breviligulata) dunelands [293]. On an estuary on the St Lawrence River, Quebec, speckled alder seedlings and saplings showed 28% cover, the greatest of any colonizing shrub taxa. Drifting ice, wave action, and frequent flooding inhibited establishment of less tolerant shrubs along the shoreline [24]. By upland oak-hickory communities, floodplains with speckled alder generally succeed to sycamore, elms, and red maple (review by [160]). Speckled alder may be invasive in sedge (Carex spp.) wetland meadows of Wisconsin, especially with fire exclusion [294]. Speckled alder is noted in the older zones of bogs in Michigan [350]. In bog succession, speckled alder generally establishes after litter from mosses and low ericaceous shrubs has formed a peat layer. Without disturbance, trees such as tamarack and black spruce establish after speckled alder, willow, and other shrubs [303]. Speckled alder may be the pioneer woody taxon in swamps that succeed to red maple [176].
The successional pathway of acidic mires and other wetland communities may alter after speckled alder establishment [9,38]. Since speckled alder is a nitrogen fixer, acid-loving bog and fen species may be replaced successionally by species with higher nutrient requirements. On a kettle bog in Ohio, speckled alder established on a Magellan's sphagnum mat and was displacing acid-loving herbs such as purple pitcher-plant (Sarracenia purpurea) and round-leaved sundew (Drosera rotundifolia) [9]. Speckled alder is more characteristic of fen and bog margins than of the mires themselves, although it sometimes establishes in mires with peaty soils [89]. On the Lac St-Francois National Wildlife Area in Quebec, speckled alder invaded a water sedge-hairy sedge (C. lacustris) fen. Over several decades, speckled alder became dominant over about 10% of the wetland that had formerly been sedge fen [38]. Woody invasion of herbaceous bogs and fens in eastern North America has been attributed to fire exclusion [9,38], although altered hydrologic regimes may also play a role [38]. A 1938 study of the speckled alder-willow high bog association in Cheboygan County, Michigan, found speckled alder and willows were casting dense shade and becoming "scraggly". They were being replaced successionally by red-osier dogwood, black spruce, tamarack, and northern white-cedar. Charred logs and stumps in the bog indicated that fire had cleared the area of trees in the past [110]. In contrast to speckled alder replacing herbs successionally in wetlands, beaked sedge has established and spread in speckled alder-withe-rod (Viburnum nudum var. cassinoides) communities of east-central West Virginia [90].
In forests, speckled alder may be important after logging, insect attacks, and/or disease. On logged black spruce forests of northeastern Ontario, speckled alder was most common in forests <40 years old, forming dense shrub layers of up to 570 to 600 stems/0.01 ha. In older stands, speckled alder was less important, forming a "diffuse canopy" on most sites. It remained dense in seeps and by open water, however. The authors surmised that speckled alder was probably present in low numbers in the prelogged forest and increased rapidly after logging [43,44]. Speckled alder was prevalent after an eastern spruce budworm attack and subsequent clearcutting in balsam fir-paper birch communities in Ontario. Speckled alder density ranged from 109 stems/ha to 6,667 stems/ha on 8- to 12-year-old clearcuts [158]. In early secondary succession, deforestation due to Dutch elm disease tended to favor speckled alder and other shrubs [108]. In hardwood swamps of central New York, speckled alder was "frequently encountered" in gap succession following death of overstory American elms to Dutch elm disease. It occurred in both small gaps created by the death of single trees and in larger gaps created by deaths of multiple trees [174].
Speckled alder is generally unimportant in late-successional forests. It was a mostly minor component of late-successional eastern hemlock-black spruce-red maple forests of northeastern Pennsylvania, attaining high density and cover only in canopy gaps [100]. However, a 1934 publication reported speckled alder as characteristic of climax balsam fir forests in Itasca County, Minnesota. It was also present in earlier succession [136].
Speckled alder may be of minor importance in old field succession. It formed thickets on old fields in New York [49,175,176]. In southeastern Ontario, speckled alder seedlings were found 19 years after abandonment of ploughed hay fields, although in low numbers (<1% frequency). Speckled alder was also present in adjacent silver maple/roundleaf serviceberry (Acer saccharinum/Amelanchier sanguinea) forest. It presumably established in the old field from wind-blown seed originating from the forest [84]. In an old-field study, speckled alder was an early-seral shrub on the Piedmont Plateau of North Carolina. It preferred wet bottomlands that had been used as hayfields, sometimes forming dense, shoulder-high thickets. Speckled alder was also noted in old fields 34 and 45 years after abandonment on a site succeeding to loblolly pine (Pinus taeda) forest. Its density in the loblolly pine habitat ranged from 1.9 stems/16 m² on a 34-year-old field to 4.1 stems/16 m² on a 45-year-old field. In an adjacent old field on logged streambanks succeeding to paper birch, speckled alder was present 6 and 14 years after abandonment at densities of <2 stems/16 m². In old fields succeeding to mixed-hardwood bottomlands, it was found in 8- and 32-year-old fields (densities not recorded). None of the old-field plant communities surveyed was older than 55 years [270].
Thinleaf alder
Thinleaf alder is moderately shade tolerant. Thinleaf alder is adapted to nearly all types of disturbance [151], including severe disturbance [32], and is most common in early succession. It can grow in forest understories, but it is found more often on open sites. Sprouts may tolerate shade better than seedlings (review by [143]). To date (2011), most successional studies on plant communities with gray alder had been conducted on Alaskan sites in primary succession.
Thinleaf alder is an early-successional shrub in riparian zones in primary succession [93]. The willow/alder stage typically forms on bare floodplains [362]. On the Tanana River in interior Alaska, it typically establishes on bare to nearly bare, recently deposited alluvium [1]. Feltleaf and/or sandbar willow may establish first [1,55]. Thinleaf alder and balsam poplar dominate in midsuccession, after which balsam poplar and finally, white spruce, dominate the overstory [1]. A 5-year-old thinleaf alder sandbar community on the Tanana River was a "nearly impenetrable" thicket of thinleaf alder, feltleaf willow, sandbar willow, and barrenground willow. The shrubs were uniformly about 10 feet (3 m) tall, 0.8 inch (2.0 cm) in stem diameter, and averaged 49,699 stems/ha. Balsam poplar, paper birch, and white spruce grew in the understory; meadow horsetail and variegated scouringrush were dominant herbs. In 15-year-old stands, feltleaf willow was overtopping thinleaf alder, and shrub density declined to 2,827 stems/ha. Groundlayer vegetation was nearly all meadow horsetail [162]. By Glacier Bay, Alaska, thinleaf alder occurs about 15 to 20 years after glacier recession, in the "late pioneer" stage. About 25 to 30 years after recession, thinleaf alder forms closed stands, presenting an "almost impenetrable barrier". At 30 to 35 years, black cottonwoods begin to establish [337].
According to a 1923 study by Cooper [76], thinleaf alder may be abundant even in late succession after glacier recession. Herbs, especially dwarf fireweed (Chamerion latifolium), dominated the northernmost, pioneer community, but thinleaf alder and willows were also establishing. Feltleaf willow-Sitka willow-thinleaf alder communities occurred in isolated patches and on midlatitude landscapes; midlatitude sites had a longer period of recession than the northern sites. Thinleaf alder was "nearly everywhere dominant" and eventually overtopped the willows. Sitka spruce forests occurred in the southernmost portion of the landscape, which had the longest time since glaciation. Thinleaf alder persisted in these late-successional forests, typically at greater abundance than in the pioneer stage [76].
The pattern of willows, and sometimes cottonwoods, establishing before thinleaf alder is typical in riparian succession. On bare gravel bars of Meadow Creek on the Starkey Experimental Forest, Oregon, thinleaf alder established at lower densities (0.96 stem/50 m²) than sandbar willow and black cottonwood [60]. Along the Animas River in southwestern Colorado, narrowleaf cottonwood/thinleaf alder communities occur upland from narrowleaf cottonwood/tickle grass communities and are considered a latter successional community type than the narrowleaf cottonwood/tickle grass community [351].
Thinleaf alder shrub communities are initiated and maintained by disturbances that are often severe. Historically in northwestern Montana, disturbances have included placer mining, ice jams, log transport [32,151], and fire. On Emigrant Creek near Burns, Oregon, thinleaf alder colonized a new alluvial fan 6.5 years after deposition following an intense thunderstorm. Cattle had grazed the area for at least 30 years [145]. Thinleaf alder snowslide communities in the Blue Mountains are maintained by avalanches and soil slippage [144]. Along the San Miguel River in southwestern Colorado, thinleaf alder shrub communities occupied less area than that of later-successional, narrowleaf cottonwood/thinleaf alder communities. Thinleaf alder shrubland also had shorter flood-return intervals (averaging <10 years) than those of narrowleaf cottonwood/thinleaf alder communities (averaging about every 50 years) [126].
Thinleaf alder may facilitate establishment of later-successional riparian species, likely due in part to its ability to fix nitrogen. On floodplains of interior Alaska, for example, balsam poplar and feltleaf willow establish in nitrogen-enriched soil beneath thinleaf alder, although root crowding and shading by thinleaf alder may interfere with growth of later-establishing species on many floodplain sites (reviews by [53,54]). On floodplains near Fairbanks, there was a "marked" increase in exchangeable soil potassium, calcium, magnesium, manganese, and phosphorus within 5 years of thinleaf alder establishment, but there was no consistent increase in soil mineral content from 5 to 20 years after thinleaf alder establishment. Soil pH decreased beneath thinleaf alder stands over 20 years, while soil cation exchange and organic matter increased. At study year 20, most of the total aboveground plant biomass (~43 kg/ha of ~48 kg/ha total) and basal area (7,142 stems/ha of 7,241 stems/ha total) was thinleaf alder [338].
Experiments on the Tanana River floodplain showed changes in soil nutrient dynamics and soil microbe community composition as aboveground succession proceeded from thinleaf alder to balsam poplar. As balsam poplar gained dominance, soil carbon became increasingly more available and soil nitrogen became increasingly less available to soil microbes. Thus, the soil biota changed from carbon-limited microbes under thinleaf alder dominance to nitrogen-limited microbes under balsam poplar dominance [70].
Thinleaf alder occurs in all stages of forest succession, although it is most prevalent in early forest succession. It pioneers in forest communities of British Columbia, sometimes persisting in mature forests [23]. Thinleaf alder is seral in Douglas-fir, spruce, and other coniferous forests in the West (for example, [150]). In forested habitats, the thinleaf alder shrub community is usually an early- to midsuccessional seral stage that arises after severe disturbance. Conifers or taller hardwoods typically replace thinleaf alder successionally [151]. Near Slave Lake in Alberta, thinleaf alder sprouts were more common on sites logged 28 years prior than adjacent sites burned by wildfire 28 years prior (P<0.05). Study sites were dominated by quaking aspen, balsam poplar, and paper birch [225]. Thinleaf alder often dominates the understory of midseral spruce/bluejoint grass forest habitat types in Montana [151]. In northwestern Montana, thinleaf alder was abundant in Engelmann spruce/skunk cabbage riparian communities from early-seral (logged and heavily grazed) to late-seral and climax stages. It dominated early stages of succession in Engelmann spruce/field horsetail and Engelmann spruce/bluejoint reedgrass riparian communities [32]. In central Alaska, thinleaf alder thickets are often replaced successionally by balsam poplar, which in turn is replaced by white spruce, then black spruce [339]. Thinleaf alder occurred late in the succession of white spruce-Engelmann spruce forests on the east slope of the Rocky Mountains in Alberta [78]. By the Peace River in northern Alberta, thinleaf alder was dominant in old-growth white spruce forests. It was most common in canopy gaps, although it persisted in the understory. It also occurred in resin birch clearcuts [332]. In central Alberta, thinleaf alder was more common in mature quaking aspen-balsam poplar-white spruce forest than on edges of 16-year-old clearcuts (P=0.05) [153].
Browsing pressure may alter succession in forest ecosystems with thinleaf alder. Browsing may favor thinleaf alder at the expense of more palatable browse species. In spruce-birch taiga forests of interior Alaska, browsing pressure by moose favored thinleaf alder and quaking aspen over more palatable willow species [52]. In northern Idaho, ungulate browsing helps maintain shrubfields, which contain thinleaf alder and other seral shrubs. Heavy browsing, however, may accelerate succession to conifer species, which are less palatable [4].The scientific name of gray alder is Alnus incana (L.) Moench (Betulaceae) [120,127,137,167,169,192,237]. There are 2 subspecies in North America:
Alnus incana (L.) Moench subsp. rugosa (Du Roi) R.T. Clausen, specked alder [120,137,192,205,237,255]
Alnus incana (L.) Moench subsp. tenuifolia (Nutt.) Breitung, thinleaf alder [120,167,179,192,355]
European gray alder, Alnus incana (L.) Moench subsp. incana, is native to western Europe [120,127]. It has been introduced in the northeastern United States [231]. Since variation in the subspecies is continuous rather than discrete, gray alder subspecies are sometimes difficult to tell apart ([127], review by [143]). Speckled alder and thinleaf alder intergrade where their ranges overlap, mostly in Saskatchewan and Manitoba [106,120,127,231].
In this review, gray alder refers to information that is general to the species. Speckled alder refers to A. i. subsp. rugosa, and thinleaf alder refers to A. i. subsp. tenuifolia.
Hybrids:
Gray alder hybridizes with European alder (A. glutinosa), an introduced species [133]. Speckled alder hybridizes and intergrades with hazel alder (A. serrulata) [120,231,295]. Speckled alder × hazel alder hybrid swarms may occur in Massachusetts and elsewhere [127]. Thinleaf alder may hybridize with red alder (A. rubra) in Idaho [202].
Gray alder helps protect and stabilize streambanks and other riparian areas [215,256,261] and is used for erosion control [348]. Banks stabilized with gray alders can withstand "relatively severe" spring run-off [200]. Gray alder's shade provides mesic habitats for groundlayer herbs [261]. Its symbiotic relationship with nitrogen-fixing bacteria makes it a good selection for planting in nitrogen-depleted soils [117]. Seeds and plants are commercially available [263].
Speckled alder: See these sources: [154,160] for propagation information.
Thinleaf alder: Thinleaf alder is used in revegetation projects [62,256]. It is recommended for riparian revegetation in the Intermountain West [59] and the Northern and Southern Rocky Mountains [58]. It is particularly recommended for high-gradient, high-velocity, low- to midorder streams [59]. See these sources: [104,154,183,256,309] for propagation information.
Cloning is apparently the primary means of spread in established stands of gray alder (review by [143]). Gray alder sprouts from the root crown [35,38,175,208]. It can also sprout from roots, including root offsets [175,176,298], and layers. Root sprouting and layering are apparently less important than root-crown sprouting [176], although root sprouts distant from the parent plant have been noted for both speckled alder and European gray alder (review by [143]). Haeussler and others [143] report that sprouting "can be expected" after mechanical site preparation. In a Magellan's sphagnum bog in Ohio, speckled alder sprouted after cut-stump herbicide applications, growing up to 3 feet (1 m) in one growing season [9]. Gray alder does not spread rapidly, but its clones can be long-lived. In a central New York study, 4 speckled alder populations were monitored for 4 years. There was no seedling establishment on study plots during that time. Clump sprout production and stem mortality were variable within and among populations, although no clumps died out. No lateral extension of clones via root sprouting occurred. Annual sprout production averaged about 3 live stems/clump [176].
In a study comparing root anchorage of riparian species in Italy, European gray alder was less resistant to uprooting by flood than Lombardy poplar (Populus nigra) or Elaeagnus willow (Salix elaeagnos) [191]. This relative ease of uprooting may allow for vegetative spread of gray alder when root fragments are torn off, distributed downstream, and sprout.
İlk dəfə Avropada təsvir edilmişdir.
Hündürlüyü 20 m-ə qədər olan,boz,hamar qabıqlı ağacdır.Zoğları qonur və qırmızı-qonur,qısa tükcüklərlə örtülmüşdür.Tumurcuqların uzunluğu 8-15 mm,qırmızı-qonur,küt,az tükcüklü,bir az əyilmiş,yapışqanlı deyil.Yarpaqları yumurtavari-eçlipsvari,çılpaqdır,uzunluğu 4-10 sm,eni 3-6 sm-dir,üstü yaşıl,alt tərəfi bozumtul-yaşıl,nazik tükcüklüdür,kənarları sivriləşmişdir,dib tərəfləri dəyirmi,enli pazvaridir; az-az hallarda bir qədər ürəkvaridir;mişardişlidir,7-13 cüt damarı uzun,sıx tüklüdür.Saplaqlarının uzunluğu 3-4 sm-dir,üstü yumşaq tüklüdür.Mayda çiçəkləyir.Bir neçə ədəd erkək və dişi çiçəkləri keçənilki zoğların uclarında yerləşir.Erkək sırğaları 3-5 ədəd umumi salxımşəkilli çiçək qrupuna yığılmışdır.Qozaları ellipsvari,yetişdikdə qara-qonur rəngli 12-15 mm uzunluqda və 7-8 mm enindədir.Toxum,qələmlər və kök pöhrələri ilə çoxalır.Aktiv surətdə kök zoğları əmələ gətirir.Oduncağı ağ,yumşaq və yüngüldür.
Qışa,işığa,kölgəyə davamlı bitkidir.Torpağa qarşı az tələbkardır.Köklərində azot fiksə edən bakteriyalar yerləşir.
Böyük və Kiçik Qafqazda,Quba-Dəvəçi zonasında,Lənkəranda,Astarada,Masallıda və Göygöl rayonlarının meşələrində yayılmışdır.Təxminən 60 il yaşayır.
Oduncağından mebel sənayesində dülgərlik və tokarlıq işində,kömür hazırlanmasında istifadə edilir.
El vern pilós (Alnus incana), és una espècie d'arbre pertanyent a la família de les betulàcies.
És una espècie de vern amb una àmplia gamma a través de la parts més fredes de l'hemisferi nord.
Es tracta d'un arbre de petit a mitja grandària que aconsegueix els 15-20 m d'altura amb escorça llisa grisa, fins i tot en la vellesa, la seva vida arriba a un màxim de 60-100 anys. Les fulles són de color mat verd, ovoides de 5-11 cm de llarg i 4-8 cm d'ample. Les flors apareixen a principis de la primavera abans de sortir les fulles, les masculines penjant i de 5-10 cm de llarg, i les femenines d'1,5 cm de llarg i 1 cm d'ample, madurant a finals de tardor. Les llavors són petites, d'1-2 mm de llarg, de color marró clar i amb una estreta ala. El vern pilós té un sistema d'arrels superficials, i es caracteritza no només per la forta producció de plançons de soca, sinó també pels rebrots d'arrel, especialment al nord de la seva àrea de distribució. La fusta s'assembla a la del vern, però és una mica més pàl·lida i de poc valor.
El vern pilós és una espècie exigent de llum, són arbres de creixement ràpid que creixen bé en sòls pobres. A l'Europa central, és un colon de les terres al·luvials de muntanya al costat de rierols i rierols, i es desenvolupen a altures de fins a 1500 metres. No obstant això, no requereixen un sòl humit, i també solen colonitzar vessants pedregosos i superficials. A la part septentrional de la seva àrea de distribució, és un arbre comú a nivell del mar en els boscos, els camps abandonats i en rodalies de llacs. De vegades és utilitzat per al repoblament en sòls no fèrtils, que s'enriqueix per mitjà de la fixació del nitrogen pels bacteris en els nòduls de les seves arrels. Diverses espècies de lepidòpters l'utilitzen per alimentar les seves erugues.
El vern pilós fou descrit per (L.) Moench i publicat a Methodus Plantas Horti Botanici et Agri Marburgensis: a staminum situ describendi 424. 1794.
Alnus: nom genèric del llatí clàssic per a aquest gènere. incana: epítet llatí que significa "gris, canós"
Hi ha de 4 a 6 subespècies, algunes tractades com a espècies separada per alguns autors:
Hi ha una varietat especialment apreciada pels jardins pel seu viu color groc, l'Alnus incana 'Aurea', el vern daurat.
El vern pilós (Alnus incana), és una espècie d'arbre pertanyent a la família de les betulàcies.
Math o Gwernen, sef coeden gollddail bychan yw Gwernen lwyd sy'n enw benywaidd. Mae'n perthyn i'r teulu Betulaceae. Yr enw gwyddonol (Lladin) yw Alnus incana a'r enw Saesneg yw Grey alder.[1] Ceir enwau Cymraeg eraill ar y planhigyn hwn gan gynnwys Gwernen Lwyd.
Math o Gwernen, sef coeden gollddail bychan yw Gwernen lwyd sy'n enw benywaidd. Mae'n perthyn i'r teulu Betulaceae. Yr enw gwyddonol (Lladin) yw Alnus incana a'r enw Saesneg yw Grey alder. Ceir enwau Cymraeg eraill ar y planhigyn hwn gan gynnwys Gwernen Lwyd.
Olše šedá (Alnus incana) je listnatý opadavý keř nebo strom, s přímým, štíhlým kmenem (často vícekmenným) a vejcovitou nebo sloupovitou, hustou korunou, z čeledi břízovité. Dorůstá většinou do výšky 6–20 metrů, dožívá se maximálně 50 let.
Letorosty oblé až trojhranné, nelepkavé, na spodní straně stříbřitě chlupaté, na svrchní straně červenavě hnědé, později olysávající a lesklé.
Větve velmi volné, přeslenité nebo mírně nepravidelné.
Kůra je u mladých stromů tmavošedá, hladká, s průduchy, na starších olších matně šedá, podélně popraskaná, stěží vytváří tenkou borku.
Borka i ve stáří hladká, tmavošedě zelenavá, směrem nahoru vždy trochu světlejší, s nezřetelnými četnými svislými lenticelami.
Pupeny stopkaté, stopky asi 2 mm dlouhé, trochu do strany nakloněné, tupě špičaté, šedé nebo šedohnědé, plstnaté, nelepkavé.
Listy střídavé, oddálené, na vrcholu ostře špičaté nebo zašpičatělé, oválné až vejčité, na bázi uťaté až slabě srdčité, asi 4–10(–12) cm dlouhé, 3–7(–9) cm široké, zřetelně zubaté, na líci matně zelené, na rubu šedé až šedozelené, zpočátku všude chlupaté až plstnaté, později pouze na 8–12 párech výrazných postranních žilek, ty pak přesně proti sobě umístěné nebo lehce vzájemně posunuté, nelepkavé. Řapík 1,5–3 cm dlouhý. Listy se na podzim nepřebarvují, ale zůstávají až do opadu zelené.
Doba květu je od února do dubna. Květy se rozvíjejí před rašením listů, většinou o 1–2 týdny dříve než u olše lepkavé (Alnus glutinosa).
Samčí jehnědy po 3–5 na koncích větévek, převislé, v zimě nerozvité, během květu 7–9 cm dlouhé; brzy na jaře rozprašují žlutý pyl, potom 10 cm dlouhé. Okvětí 4(–6) četné, tyčinky 4(–6), prašníky žluté.
Samičí jehnědy po 4–8, načervenale purpurové, plodní šištice vejcovitě kuželovité, 10–16 mm dlouhé, přisedlé nebo krátce stopkaté.
Plodnost začíná velmi časně, někdy už v 6 letech a je častá.
Samičí jehnědy v době zralosti šišticovitě zdřevnatí a jsou asi 1–2 cm dlouhé. Samičí šištice přisedlé nebo nejspodnější na krátkých chlupatých stopkách. Nažky (drobná semena s úzkými křídly) dozrávají v září až říjnu, z šištic vypadávají až do prosince.
Roste podél řek a potoků, balvanité náplavy; také na hlinitých, jen občas zaplavovaných půdách, potřebuje ale lépe drenážovanou půdu než olše lepkavá (Alnus glutinosa). Nesnáší stagnující vodu. Vyžaduje dobře provzdušněný substrát. Dává přednost vápenatým půdám, roste i na suchých stanovištích. Rychle rostoucí mrazuvzdorná dřevina náročná na světlo, málo odolná v konkurenci jiných druhů dřevin. Potřebuje půdu, která je středně až dobře zásobená živinami.
Strom vyhání kořenové odnože, staré stromy bývají často obklopeny prstencem výmladků. Listy olše šedé se objevují brzy na jaře, stromy jsou proto s oblibou vysazovány v sadech aby chránili ovocné stromy před jarními mrazy. Protože má olše štíhlou, nepříliš hustou korunu, nesoupeří s ovocnými stromy o světlo a živiny.
Diagnostický druh asociace Alnetum incanae Lüdi 1921 (podsvaz Alnenion glutinoso-incanae), též ve společenstvech svazu Sambuco-Salicion capreae.
Stanoviště ve střední Evropě v horském pásmu 500–1500 m n. m., v lužních lesích, podél horských potoků sestupuje hluboko do nižších poloh; na mokvavých svazích, na vlhké, vodou nasáklé, občas zaplavované, vápenaté, na živiny bohaté půdě, na rozdíl od olše lepkavé (Alnus glutinosa) se vyhýbá trvale zaplavovaným půdám a snáší občasné sucho. Je to mrazuvzdorná, bohatě kořenící, světlomilná, pionýrský dřevina s hojnými kořenovými výhonky.
Střední, severní, východní a jihovýchodní Evropa (souvislé rozšíření v severní části mírného pásma, jižněji jen ostrůvkovitě, zvláště v horách; na jihu po Albánii a Bulharsko); Kavkaz, západní Sibiř.
Používá se jako přípravná a meliorační dřevina v mrazových polohách a na neplodných půdách, za cílem zpevnění sesuvných svahů nebo zpevnění čerstvých násypů a navážek nebo jako dřevina krycí a výchovná. Je vhodná k zalesňování extrémních stanovišť. Dřevo je velmi lehké, měkké, málo trvanlivé. V zahradách a parcích se pěstuje v několika kultivarech: s dřípenými listy (cv. Angustissima, cv. Angermannica, cv. Lobata, cv. Laciniata, cv. Pinnatipartita, cv Semipinnata; vesměs jsou virového původu), s listy žlutými (cv. Aurea) nebo s převislými větvemi (cv. Pendula).
Olše žijí v symbióze s bakteriemi, s jejichž pomocí dokážou vázat vzdušný dusík. Aby pokryly potřebu dusíku nutného k syntéze proteinů, čerpají ho nejen z půdy, ale i ze vzduchu. Stromům to umožňuje růst i na půdách chudých dusíkem, proto jsou také vysazovány na mrtvých půdách, což vede k obohacení půdy cennými dusíkatými sloučeninami a tím i k zlepšování půd a každoročním shazovaným listí podporují tvorbu humusu. Olše jsou proto vysoce ceněnou pionýrskou dřevinou.
Od olše lepkavé (Alnus glutinosa) se olše šedá (Alnus incana) liší nestopkatými, přisedlými samičími jehnědami a také vyšším počtem postranních žilek (8–12 proti 5–8 u olše lepkavé).
Blízce příbuzný druh, olše zelená (Alnus viridis), je až 4 m vysoký keř s přisedlými špičatými pupeny. Vyskytuje se v alpských křovinách.
Obrázky, zvuky či videa k tématu olše šedá ve Wikimedia Commons
Olše šedá (Alnus incana) je listnatý opadavý keř nebo strom, s přímým, štíhlým kmenem (často vícekmenným) a vejcovitou nebo sloupovitou, hustou korunou, z čeledi břízovité. Dorůstá většinou do výšky 6–20 metrů, dožívá se maximálně 50 let.
Gråel (Alnus incana), ofte skrevet grå-el, er et op til 20 m højt træ, der vokser på fugtig bund i skove og moser.
Gråel er et stort, løvfældende træ med en slank og opret vækstform. Der er som regel kun én, lige gennemgående stamme. grenene er først stejlt oprette, senere noget mere udstående og overhængende. Barken er først glat og grønligt mørkegrå, senere får den lyse korkporer og bliver mørkegrå, og til sidst er den mørkegrå og furet.
Knopperne sidder spredt og er kortstilkede. De er ovale til omvendt ægformede. Farven er gråviolet med blåhvid dug. Bladene er ægformede med savtakket rand og grovere lapper ved spidsen. Bladet har tydelig spids. Oversiden er matgrøn, mens undersiden er hvidligt grågrøn. De grønne blade falder først af inde i november.
Han- og hunblomster er samlet i særskilte rakler. Blomstringen finder sted i marts-april, i gunstige vintre allerede fra slutningen af februar. Hunraklerne bliver ved modenhed til "ellekogler". De er ægformede med kort stilk. Frøene modner godt og spirer villigt.
Rodnettet består af grove, højtliggende hovedrødder og fint forgrenede siderødder. Som alle El kan også denne forsyne sig med kvælstof ved hjælp af aktinomyceter (Frankia sp.), som den huser i knolde på rødderne.
Højde x bredde og årlig tilvækst: 20 × 10 m (30 × 20 cm/år).
Gråel er pionertræ i det nordøstlige Europa og i Sibirien, hvor det danner skovgrænse ind mod tundraen sammen med dunbirk og bævreasp (i Sibirien også med sibirisk lærk. Træets krav til jordbunden er meget beskedne, dog trives det ikke på sur, tørveholdig jord. Det tåler frost, og det er lyskrævende, men tåler vind.
Gråel er en lidt mere robust træart end rødel, og plantes mest på sandjord. Træet er velegnet som hjælpetræ i mange plantninger. De kraftige rodskud kan dog være generende. Gråel skæres bort, når andre træer og buske vokser til.
Gråel (Alnus incana), ofte skrevet grå-el, er et op til 20 m højt træ, der vokser på fugtig bund i skove og moser.
Gråel er et stort, løvfældende træ med en slank og opret vækstform. Der er som regel kun én, lige gennemgående stamme. grenene er først stejlt oprette, senere noget mere udstående og overhængende. Barken er først glat og grønligt mørkegrå, senere får den lyse korkporer og bliver mørkegrå, og til sidst er den mørkegrå og furet.
Knopperne sidder spredt og er kortstilkede. De er ovale til omvendt ægformede. Farven er gråviolet med blåhvid dug. Bladene er ægformede med savtakket rand og grovere lapper ved spidsen. Bladet har tydelig spids. Oversiden er matgrøn, mens undersiden er hvidligt grågrøn. De grønne blade falder først af inde i november.
Han- og hunblomster er samlet i særskilte rakler. Blomstringen finder sted i marts-april, i gunstige vintre allerede fra slutningen af februar. Hunraklerne bliver ved modenhed til "ellekogler". De er ægformede med kort stilk. Frøene modner godt og spirer villigt.
Rodnettet består af grove, højtliggende hovedrødder og fint forgrenede siderødder. Som alle El kan også denne forsyne sig med kvælstof ved hjælp af aktinomyceter (Frankia sp.), som den huser i knolde på rødderne.
Højde x bredde og årlig tilvækst: 20 × 10 m (30 × 20 cm/år).
Die Grau-Erle oder Weiß-Erle (Alnus incana) ist ein Laubbaum aus der Gattung der Erlen und gehört damit zur Familie der Birkengewächse. Ihr Verbreitungsgebiet erstreckt sich über Nord-, Mittel- und Osteuropa bis zum Kaukasus, im Westen Europas fehlt sie. Im deutschsprachigen Raum kommt sie vor allem in Österreich und in Süddeutschland vor. Unterarten der Grau-Erle findet man in Nordamerika und in Asien. Das Holz der Grau-Erle wird nur selten verwendet, da sie meist krumme Stämme mit geringem Durchmesser bildet. Sie wird jedoch häufig zur Aufforstung von Abraumhalden und zur Stabilisierung von Hängen und Böschungen verwendet. Durch Symbiose mit dem Bakterium Frankia alni kann sie den Stickstoff der Luft binden und trägt durch die Anreicherung mit Stickstoffverbindungen zur Verbesserung des Bodens bei.
Die weite Verbreitung der Erlen und die oft geringen Unterschiede haben zu Uneinigkeit in der Einteilung der Arten geführt. Häufig werden Vertreter der Erle in Nordamerika und im östlichen Asien als Unterarten der Grau-Erle zugerechnet, damit ist die europäische Art nur die Nominatform. Der größte Teil des Artikels beschreibt die in Europa und Westasien auftretende Nominatform Alnus incana subsp. incana. Auf die anderen Unterarten wird in eigenen Abschnitten in der Systematik eingegangen.
Die Grau-Erle ist eine sommergrüne Baumart und erreicht eine Höhe von 10 bis 15, maximal 25 Metern, sowie einen Stammdurchmesser von bis zu 40 Zentimetern.[1] Sie ist ein- oder mehrstämmig, reich verzweigt mit dichter Krone, kann aber auch strauchförmig wachsen.[2] An ärmeren Standorten bleiben die Stämme kurz, werden krumm oder drehwüchsig und es bilden sich häufig Klebäste. Junge Zweige sind graugrün bis rötlich braun, an den Spitzen deutlich behaart und mit kleinen, rotbraunen Korkporen besetzt.[3]
Bei der Grau-Erle bleibt das Periderm als Abschlussgewebe an Stämmen und Ästen erhalten. Es wird keine Borke gebildet (Peridermbaum). Die Rinde ist hellgrau, glatt und reißt auch im Alter kaum auf. Sie ist locker mit Korkporen besetzt.
Erlen gehören zu den Splintholzbäumen, Kern- und Splintholz sind also gleichfarbig. Das Holz ist rötlichweiß, rötlichgelb bis hell rötlichbraun gefärbt. Frisch eingeschlagenes Holz erscheint durch Oxidation auffällig orangerot, die Farbe verschwindet mit dem Austrocknen des Holzes wieder. Im Holz befinden sich zahlreiche feine Gefäße, die zerstreutporig angeordnet sind. Holzstrahlen sind nur wenig ausgeprägt und fallen lediglich an den Radialflächen als unauffällige Spiegel auf. Häufig sind die Holzstrahlen jedoch zu Scheinholzstrahlen gebündelt, die deutlicher sichtbar sind. Jahresringgrenzen sind nur wenig ausgeprägt, die Jahresringe sind jedoch deutlich an dem porenärmeren und dichteren Spätholz erkennbar.[1] Das Holz der Grau-Erle ähnelt im Allgemeinen sehr dem der Schwarz-Erle, ist etwas heller, weniger grobfaserig und stärker glänzend.[3]
Die Grau-Erle bildet ein Herzwurzelsystem mit kräftigen Horizontalwurzeln. Es erstreckt sich horizontal 2 bis 3 Meter weit und erreicht auf tiefgründigen Böden eine Tiefe von 90 Zentimetern. Auf stark überfluteten Standorten bildet sie Adventivwurzeln, die sich zu Stelzwurzeln weiterentwickeln können. Die Stelzwurzeln zeigen zahlreiche Korkporen.[4]
Die Grau-Erle bildet verkehrt eiförmige, nicht klebrige[2] Winterknospen mit rot-violetten, zu Beginn dicht behaarten Knospenschuppen und bis zu 5 Millimeter langen Stielen. Endknospen und Seitenknospen werden etwa 8 Millimeter lang.
Die Laubblätter sind wechselständig angeordnet und haben 2 bis 3 Zentimeter lange Blattstiele. Die Blattspreite ist eiförmig bis elliptisch mit doppelt gesägtem Blattrand und besitzt 8 bis 12 Nervenpaare.[5] Die Blattoberseite ist dunkelgrün, die Unterseite graugrün und bei jungen Blättern grau-filzig behaart. Die Blattbasis ist rundlich oder etwas herzförmig, der Apex ist zugespitzt. Die Blattspreite wird 4 bis 10 Zentimeter, selten bis 12 Zentimeter lang und 3 bis 7 Zentimeter, selten bis 9 Zentimeter breit. Größe und Blattform variieren jedoch stark. Die Blätter werden im Herbst noch grün abgeworfen. Es werden zwei behaarte Nebenblätter gebildet, die früh abgestoßen werden.[3]
Die Grau-Erle ist wie alle Erlen windblütig und einhäusig. Die Blüten sind eingeschlechtig und in kätzchenförmigen Blütenständen zusammengefasst. Selten kommen Blütenstände mit männlichen und weiblichen Blüten oder zwittrige Blüten vor. Die Grau-Erle blüht von Februar bis März etwa drei Wochen vor der Schwarz-Erle, was die Entstehung von natürlichen Hybriden erschwert. Die Samen werden etwa zwei Monate nach der Bestäubung gebildet. Die Anlage der Blütenstände erfolgt im Herbst, sie überwintern ohne Knospenschuppen zu bilden und beginnen noch vor dem Austreiben der Blätter zu blühen.
Die männlichen Kätzchen hängen in Gruppen von drei bis fünf mit weich behaarten Stielen an Zweigspitzen. Sie sind zuerst bräunlich, 7 bis 9 Zentimeter lang und haben dunkelbraune Tragblätter, die häufig in der Mitte mit einem dunklen Fleck versehen sind. In den Achseln der Tragblätter befinden sich dreiblütige Dichasien. Die Einzelblüte hat vier Staubblätter mit anfangs rötlichen, später gelben Staubbeuteln und ein vierteiliges, oft verkümmertes Perigon.
Als weibliche Blütenstände werden an den Blattachseln sitzende oder fast sitzende Kätzchen gebildet, die eine Länge von 4 bis 15 Millimetern erreichen. Sie sind rötlich braun und setzen sich aus bis zu acht dicht behaarten Teilblütenständen zusammen, die sich zu kleinen, eiförmigen Zapfen mit einer Länge von 13 bis 16 Millimetern und einem Durchmesser von etwa 10 Millimeter auswachsen. Die Zapfen reifen in der zweiten Septemberhälfte und haben dunkle, verholzte Schuppen mit schmaler Basis und breitem Apex. Als Diasporen werden zahlreiche 3 bis 4 Millimeter lange, mit einem Flügelrand versehene, einsamige Nussfrüchte gebildet. Die weiblichen Einzelblüten haben kein Perigon und stehen paarweise in der Achsel eines Tragblattes, das später mit vier Vorblättern verwächst und zur Fruchtschuppe wird.[3]
Die Chromosomenzahl beträgt 2n = 28.[6]
Die Grau-Erle lässt sich von den beiden anderen mitteleuropäischen Erlenarten durch die mehr oder weniger deutlich zugespitzten und an der Unterseite graugrünen Laubblätter unterscheiden. Die Blätter haben mit 8 bis 10 mehr Nervenpaare als die Schwarz-Erle mit 5 bis 8 Paaren, und die jungen Blätter sind nicht klebrig wie bei der Schwarz-Erle. Die weiblichen Kätzchen und die Zäpfchen sind im Gegensatz zur Schwarz-Erle kurzgestielt, die Zäpfchen sind kleiner. Die Rinde ist stets glatt und grau, worauf sich das lateinische Art-Epitheton incana bezieht, das ‚aschgrau‘ bedeutet.[7][1]
An natürlichen Standorten verjüngt sich die Grau-Erle sowohl generativ durch Samen als auch vegetativ durch Wurzelbrut und Stockausschlag. Die reifen, mit einem schmalen Flügelsaum versehenen Früchte fallen während der Wintermonate aus den Zapfen und werden durch Wind (Anemochorie) und Wasser (Hydrochorie) verbreitet. Die Keimung erfolgt epigäisch. Grau-Erlen sind schnellwüchsig und erreichen im ersten Jahr eine Höhe von bis zu 50 Zentimetern.[4] Nach zwei Jahren können sie eine Höhe von 1,24 Metern erreichen, nach fünf Jahren von 4,3 bis 5 Metern. Nach 10 bis 15 Jahren geht das Höhenwachstum zurück. Grau-Erlen werden selten älter als 50 Jahre.[8] Unter extremen Bedingungen verliert die Vermehrung durch Samen an Bedeutung, an der Waldgrenze in Skandinavien erfolgt die Verbreitung beinahe ausschließlich vegetativ.
Das natürliche Verbreitungsgebiet der Grau-Erle erstreckt sich in Europa über Nord-, Mittel- und Osteuropa. Im Süden reicht ihr Verbreitungsgebiet bis zu den Seealpen und zum nördlichen Apennin und weiter östlich bis zum Balkangebirge und zum Kaukasus. Die Nordgrenze in Skandinavien liegt bei etwa 70° 30′ nördlicher Breite. Die westliche Grenze des natürlichen Verbreitungsgebiets ist nicht mehr eindeutig feststellbar, da die Art lange Zeit in Westeuropa kultiviert wurde und häufig verwilderte. Angenommen wird, dass sich die westliche Grenze vom Schweizer Jura über Ober- und Mittelrhein zum Harz und durch die Mitte Norddeutschlands zieht.[7] Die Eiszeit hat die Grau-Erle in Europa in den Karpaten und in Zentralrussland überstanden. Sehr bald nach dem Ende der Eiszeit konnte sie sich wieder nördlich der Alpen durchsetzen.[10]
Im Auftrag der deutschen Bundesanstalt für Landwirtschaft und Ernährung (BLE) wurden im Rahmen des Projekts Erfassung und Dokumentation genetischer Ressourcen seltener Baumarten in Deutschland in den Jahren von 2010 bis 2013 die Vorkommen von zehn seltenen heimischen Baumarten in den deutschen Wäldern ermittelt. Von der Grau-Erle wurden dabei in Deutschland rund 2,1 Millionen Exemplare, vorwiegend fließgewässerbegleitend in den montanen bis hochmontanen Lagen (500 m ü. NN bis 1400 m ü. NN) des Alpenvorlands und der Alpen, erfasst.[11]
Die Grau-Erle besiedelt meist die montane Stufe von 500 bis 1400 Meter Höhe, im Osten des natürlichen Verbreitungsgebietes auch tiefere Lagen.[2] In den Bayerischen Alpen erreicht sie Höhen bis 1400 Meter, im Apennin und im Tessin bis 1800 Meter und in Graubünden bis 1850 Meter, damit besiedelt sie etwas höhere Lagen als die Schwarz-Erle.[7] In den Allgäuer Alpen steigt sie bis zu etwa 1500 Metern Meereshöhe auf.[12] Sie gedeiht an Gebirgsbächen und -flüssen, am Auwald- und Augebüschrand, an Hangvernässungen und Hangrutschungen.[2] Die Art verträgt eine große Vielfalt von Klimabedingungen und gedeiht auch außerhalb ihres natürlichen Verbreitungsgebiets gut, so im atlantischen Mitteleuropa. Sie ist frostbeständig und wird durch Spätfrost nicht geschädigt. Sie ist weitgehend unempfindlich gegen Hitze und Dürre. Sie bevorzugt gut mit Wasser versorgte Standorte, meidet nasse, schlecht durchlüftete Böden, erträgt aber zeitlich begrenzte Überschwemmungen. Sie bevorzugt neutrale oder leicht basische kalkhaltige und nährstoffreiche Sand-, Schotter- und Kiesböden, sie gedeiht jedoch schlecht auf sauren Böden. Da die Grau-Erle wenige Ansprüche an den Boden stellt, besiedelt sie als Pionierpflanze beispielsweise aufgelassene Kiesgruben, Geröllhalden und frische Böschungen. Sie festigt und verbessert durch Anreicherung mit Stickstoffverbindungen den Boden.[13]
Die Grau-Erle ist eine Charakterart des Alnetum incanae aus dem Verband Alno-Ulmion.[6]
Die Grau-Erle bildet Wurzelknöllchen, in denen der Stickstoff der Luft gebunden und so für die Pflanze verwertbar wird. Das geschieht durch eine als Actinorhiza bezeichnete Symbiose mit dem Bakterium Frankia alni.[4] Dadurch steigt der Stickstoffgehalt der Blätter, und mit deren Abbau auch der Gehalt an Stickstoffverbindungen im Boden, was zu einer Bodenverbesserung führt.[13] Untersuchungen ergaben für einen 30-jährigen Grau-Erlenbestand eine jährlich gebundene Stickstoffmenge von 43 kg/ha, Dickichte aus Grau-Erlen zeigten einen Wert von 72 kg/ha, Waldbestände in den französischen Alpen auf 1450 Meter Höhe konnten jährlich 42,5 kg/ha binden.[8]
Mit mehreren Arten von Bodenpilzen, unter anderem mit dem Erlengrübling (Gyrodon lividus) und dem Kahlen Krempling (Paxillus involutus), geht die Grau-Erle eine Wurzelsymbiose (Ektomykorrhiza) ein.[4]
In Skandinavien und in den rumänischen Ostkarpaten sind die männlichen Kätzchen und die Knospen der Grau-Erle im Winter die wichtigste Nahrung des Haselhuhns (Tetrastes bonasia). Pro Tag nimmt ein Haselhuhn etwa 50 Gramm an Kätzchen und Knospen zu sich.[10]
Grau-Erlen sind besonders durch das erst zum Ende des 20. Jahrhunderts auftretende sogenannte Erlensterben gefährdet. Durch den Eipilz Phytophthora alni wird besonders an der Schwarz-Erle, aber auch an der Grau-Erle, der Grün-Erle und der Herzblättrigen Erle eine Wurzel- und Stammfäule verursacht. Die Stammfäule kann schon nach mehreren Monaten zum Absterben von Bäumen führen, sie kann sich aber auch über Jahre hinziehen.[14] Die Krankheit wurde erstmals 1993 in Südengland beschrieben.[15] Inzwischen hat sie sich auch nach Deutschland (erstmals 1995 beobachtet), Österreich, Frankreich, Belgien, Italien, Irland, Ungarn, den Niederlanden und Schweden ausgebreitet. Symptome sind eine geringe Belaubung, tote Äste und besonders kleine und helle Blätter. Typisch sind schwarzbraune, meist nässende Flecken, die sich am Stammgrund zeigen. Das unter den angegriffenen Stellen liegende Holz ist dunkelbraun bis rotbraun verfärbt und grenzt sich deutlich vom gesunden hellen Holz ab. Die Infektion erfolgt über Wunden am Stammgrund, über das Haarwurzelsystem oder durch Korkporen.[14] Analysen haben gezeigt, dass der Erreger Phytophthora alni erst in jüngerer Zeit durch Hybridisierung entstanden ist.[15]
Weiters können durch den Einfluss der Schlauchpilzart Taphrina epiphylla Hexenbesen entstehen. Dabei überwintert das Myzel in den Knospen und befällt die jungen Blätter, die dürr werden und vorzeitig abfallen. Nur bei starken Befall von bis zu 100 Hexenbesen werden die Erlen so geschwächt, dass Äste oder ganze Bäume absterben. Eine weitere Schlauchpilzart, Taphrina alni, ist der Erreger der „Kätzchenkrankheit“, dabei werden die Tragblätter der weiblichen Blütenstände befallen, die sich dadurch lappig verformen, stark vergrößern und dunkelrot verfärben und sogenannte „Narrentaschen“ bilden. Der Erlen-Schillerporling (Inonotus radiatus) aus der Familie der Stielporlingsverwandten (Polyporaceae) verursacht eine sich rasch ausbreitende Weißfäule. Er befällt häufig geschwächte Erlen an feuchten Standorten und dringt über Verletzungen in das Holz ein. Arten der Gattung Mycosphaerella aus der Ordnung der Rußtaupilzartigen verursachen an den Blattunterseiten eckige, scharf begrenzte Flecke. In Finnland wird die Erle auch vom Wurzelschwamm (Heterobasidion annosum) befallen.[8]
Unter den Schadinsekten ist der Erlenrüssler (auch Erlenwürger, Cryptorrhynchus lapathi) aus der Familie der Rüsselkäfer (Curculionidae) der gefährlichste. Die Larven überwintern in der Rinde und bohren bis zu 10 Zentimeter lange Gänge in das Holz. Die Jungkäfer fressen an den jungen Trieben. Typische Symptome des Befalls sind welke Triebe, aufgetriebene Rindenteile, Fluglöcher und Nagespäne. Mehrere Schmetterlingsarten (Lepidoptera) überwintern in den Blütenkätzchen und fressen an Früchten und Knospen, unter anderen die Gespinstmotte Argyresthia goedartella und mehrere Epinotia-Arten aus der Familie der Wickler (Tortricidae). Der Blaue Erlenblattkäfer (Agelastica alni) kann in manchen Gegenden Erlen bis zu dreimal im Jahr kahlfressen. Auch wurde erheblicher Schadfraß durch den Buchenprachtkäfer (Agrilus viridis) nach starkem Schneedruck beobachtet.[16]
Die Grau-Erle ist ein Vertreter der Gattung der Erlen (Alnus) in der Familie der Birkengewächse (Betulaceae). Sie wird in der Gattung Alnus der Untergattung Alnus zugeordnet, zu der auch die Schwarz-Erle zählt. Die Grün-Erle wird in die Untergattung Alnobetula gestellt.[17] Die Chromosomenzahl der Grau-Erle beträgt 2n = 28.[2]
Die weite Verbreitung der Erlen und die geringen Unterschiede haben zu Uneinigkeit bei der inneren Systematik geführt. Mehrere Formen werden teils als Unterarten von Alnus incana, teils als eigene Arten oder nur als Varietäten gesehen.[18] Häufig werden vier Unterarten von Alnus incana anerkannt[19]: die Nominatform Alnus incana subsp. incana, die Unterart Alnus incana subsp. hirsuta in Asien und Alnus incana subsp. rugosa und Alnus incana subsp. tenuifolia in Nordamerika. Die drei Unterarten werden auch oft als eigene Arten Alnus hirsuta, Alnus rugosa und Alnus tenuifolia gesehen. In Finnland wird noch eine rotblättrige Form Alnus incana f. rubra unterschieden. Die Grau-Erle kann mit ihren Unterarten als ein vikariierender holarktischer Artenkomplex gesehen werden.[20] Chen et al. fassen folgende Arten in den Komplex zusammen: Alnus hirsuta, Alnus incana, Alnus rugosa, Alnus rubra, Alnus inokumae, Alnus tenuifolia, Alnus sibirica und auch die Schwarz-Erle (Alnus glutinosa), dabei werden Alnus hirsuta, Alnus rugosa und Alnus tenuifolia nicht als Unterarten der Grau-Erle, sondern als eigene Arten angesehen.[17]
Neben der in Europa und in Westasien heimischen Nominatform, werden folgende Taxa häufig als Unterarten von Alnus incana angesehen. Die Zuordnung ist jedoch umstritten, die Unterarten werden von manchen Autoren als eigene Arten eingestuft, zum Teil auch als Varietäten.
Die Färber-Erle (Alnus incana subsp. hirsuta (Spach) Á.Löve & D.Löve bzw. Alnus hirsuta (Spach) Turcz., Synonym: Alnus tinctoria Sarg.) ist ein 10 bis 15, maximal bis 20 Meter hoher Baum, mit einer anfangs breit kegelförmigen Krone. Die Rinde ist schwarzbraun, die Triebe sind anfangs mit dichten Haarbüscheln besetzt, später kahl und grau bereift. Die Blätter sind breit eiförmig bis eiförmig-elliptisch, kurz zugespitzt mit keilförmiger Basis und 4 bis 9 Zentimeter lang und 2,5 bis 9 Zentimeter breit. Es werden 9 bis 12 Nervenpaare gebildet. Der Blattrand ist leicht gelappt und doppelt gesägt. Die Blattoberseite ist dunkelgrün und schwach behaart, die Unterseite ist blaugrün, und die Nerven sind rötlich braun behaart. Der Blattstiel wird 2,5 bis 4 Zentimeter lang. Die männlichen Kätzchen werden 5 bis 7 Zentimeter lang und stehen einzeln oder zu zweit. Die Zapfen stehen in Gruppen von drei oder vier, sind etwa 2,5 Zentimeter lang, kurz gestielt und sitzend.[21][22] Das Verbreitungsgebiet der Färber-Erle umfasst Japan, Korea, China, Sachalin, Kamtschatka und Ostsibirien. Sie wächst auf Höhen von 700 bis 1500 Metern.[21][22]
Die Unterart Alnus incana subsp. kolaensis (Orlova) Á.Löve & D.Löve kommt in Norwegen, Schweden und Finnland vor.[23]
Die Runzelblättrige Erle (Alnus incana subsp. rugosa (Du Roi) R.T. Clausen bzw. Alnus rugosa (Du Roi) Spreng.) wächst meist strauchförmig, seltener als Baum und wird dann bis zu 9 Meter hoch. Die Zweige sind kahl oder rostbraun behaart, die Knospen haben 2 bis 4 Millimeter lange Stiele. Die Blattspreiten sind elliptisch bis breit eiförmig mit keilförmiger oder abgerundeter Basis und spitzem oder stumpfem Apex. Sie werden 4 bis 11 Zentimeter lang und 3 bis 8 Zentimeter breit, bilden 10 bis 15 Nervenpaare und haben einen doppelt gesägten und leicht gelappten Blattrand. Die Blattoberseite ist kahl, die Unterseite ist graugrün bis blaugrün und an den Nerven bräunlich behaart. Die männlichen Blütenstände stehen in Gruppen von zwei bis vier Kätzchen und werden 2 bis 7 Zentimeter lang, die weiblichen Blütenstände bilden mehrere Gruppen von zwei bis sechs Kätzchen und stehen zur Blüte aufrecht. Die Zapfen sind eiförmig, 1 bis 1,7 Zentimeter lang und 0,8 bis 1,2 Zentimeter breit und haben 1 bis 5 Millimeter lange Stiele.[24][25]
Das natürliche Verbreitungsgebiet erstreckt sich über den Osten von Kanada (Provinzen Manitoba, New Brunswick, Neufundland und Labrador, Nova Scotia, Ontario, Prince Edward Island, Québec und Saskatchewan), die Inselgruppe Saint-Pierre und Miquelon und dem Nordosten der USA (von North Dakota und Maine bis Iowa, Illinois, West Virginia und New Jersey). Das Verbreitungsgebiet überschneidet sich im Westen, in Saskatchewan und Manitoba, mit dem Verbreitungsgebiet der Unterart tenuifolia und im Süden mit der Hasel-Erle (Alnus serrulata). Die Unterart wächst in Höhen von 0 bis 800 Metern.[25]
Die Unterart Alnus incana subsp. tenuifolia (Nutt.) Breitung wird auch als Varietät der Unterart Alnus incana subsp. rugosa eingestuft. Synonyme sind Alnus incana subsp. rugosa var. occidentalis (Dippel) C.L.Hitchc.[18] oder Alnus tenuifolia Nutt..[17] Sie unterscheidet sich von der Unterart rugosa durch die dünnere, papierartige Blattspreite und dem abgerundeteren Blattrand.[19] Sie wächst häufiger baumartig als die Unterart rugosa, kann aber ebenfalls strauchig vorkommen. Bäume erreichen eine Höhe von 12 Metern. Die Blattspreite ist eiförmig bis elliptisch, dünn, 4 bis 10 Zentimeter lang und 2,5 bis 8 Zentimeter breit. Die Blattbasis ist breit keilförmig bis abgerundet, der Blattrand ist doppelt gesägt bis gekerbt oder gelappt. Als männliche Blütenstände werden Gruppen von drei bis fünf Kätzchen von 4 bis 10 Zentimeter Länge gebildet, die weiblichen Blütenstände bestehen aus Gruppen von zwei bis fünf Kätzchen. Die Zapfen sind eiförmig, 1 bis 2 Zentimeter lang und 0,8 bis 1,3 Zentimeter breit und haben 1 bis 5 Millimeter lange Stiele.[26]
Das Verbreitungsgebiet erstreckt sich von Alaska über den Westen von Kanada (Provinzen Alberta, British Columbia, Nordwest-Territorien, Saskatchewan und Yukon) und über den Westen der USA bis Kalifornien, Colorado und New Mexico. Sie gedeiht in Höhen von 100 bis 3000 Metern und kann häufig an Flussufern in den Rocky Mountains und in anderen Gebirgslandschaften im Westen von Nordamerika gefunden werden.[26]
In den baltischen Staaten sind natürliche Hybride zwischen Grau-Erle und Schwarz-Erle (Alnus incana × Alnus glutinosa) häufig, die luxurierendes Wachstum zeigen. Die Hybriden werden durchschnittlich 16 % höher und zeigen einen 45 % größeren Brusthöhendurchmesser als die Grau-Erle und sind 12 % höher und 33 % stärker als die Schwarz-Erle. Unterscheiden kann man die Bastarde am Verhältnis der Spreitenlänge zur Spreitenbreite (Schwarz-Erle 1,15, Bastard 1,26, Grau-Erle 1,41) und an der Anzahl der Seitennervenpaare (Schwarz-Erle 6 bis 7, Bastard 7 bis 9, Grau-Erle 10 bis 12).[13]
Es werden mehrere Kulturformen unterschieden, unter anderen:[5]
Weitere zum Teil auch nur regional gebräuchliche Bezeichnungen für die Grau-Erle sind oder waren: Auerle (Österreich), preußische Erle, Roterle (Österreich) und Weißerle.[28]
Als Erlenholz wird sowohl das Holz der Grau-Erle als auch das Holz der Schwarz-Erle genutzt. Zwischen den beiden Holzarten bestehen keine nennenswerten physikalischen oder mechanischen Unterschiede. Das Holz der Grau-Erle wird jedoch weniger häufig verwendet, da sie selten nutzholztaugliche Dimensionen erreicht und die Stammform meist ungünstig ist. Nur unter optimalen Bedingungen, so im Baltikum und in Finnland, wächst sie zu gerad- und glattschäftigen, stärker dimensionierten Bäumen heran.[1]
Erlenholz ist weich und von gleichmäßiger, feiner Struktur. Es hat eine Rohdichte von 550 kg/m³ bei einer Holzfeuchte von 12 bis 15 % und gehört damit zu den mittelschweren einheimischen Holzarten. Das Holz ist wenig fest und wenig elastisch und in diesen Eigenschaften vergleichbar mit Lindenholz. Der Witterung ausgesetzt oder bei Kontakt mit der Erde ist es wenig dauerhaft, zeigt aber unter Wasser verbaut eine ähnlich hohe Dauerhaftigkeit wie Eichenholz. Das Holz ist einfach zu bearbeiten und kann mühelos gesägt, gemessert und geschält werden, es lässt sich gut fräsen, drechseln und schnitzen. Schrauben halten gut und es kann gut verleimt werden, jedoch ist das Holz wenig nagelfest und neigt beim Nageln zum Splittern. Die Oberflächenbehandlung wie Polieren, Beizen und Lackieren ist unproblematisch. Bei Kontakt mit Eisen entstehen bei Feuchtigkeit graue Verfärbungen, auch das Eisen selbst korrodiert. Auch verhält sich Erlenholz stark reaktiv in Kontakt mit Zement.[1]
Das Holz wird als Brennholz genutzt und als Faserholz, zur Herstellung von Spanplatten, Spanholzformteilen und Faserplatten. Es liefert ein gutes Ausgangsmaterial zur Papierherstellung, wird aber auch für Drechslerarbeiten und zur Herstellung von Spielwaren und Holzschuhen eingesetzt.[16] Die Erle liefert ein hochwertiges Blindholz für Möbel und Innenausbauten, aufgrund der guten Beizbarkeit wird Erlenholz auch zur Imitation von Edelhölzern verwendet. Aus Erlenholz werden spezielle Varianten von Holzkohle hergestellt, die als Zeichenkohle, Lötkohle und Laboratoriumskohle eingesetzt werden.[1]
Die Hauptnutzung der Grau-Erle ist die Stabilisierung von Hängen und Böschungen, die Wildbachverbauung und die Bodenverbesserung nährstoffarmen Ödlandes. Sie wird auch zur Aufforstung von Braunkohle- und Abraumhalden eingesetzt.[2] Man nutzt sie auch, um spätfrostgefährdete Arten zwischen den Grau-Erlen zu schützen.[16]
Die Grau-Erle oder Weiß-Erle (Alnus incana) ist ein Laubbaum aus der Gattung der Erlen und gehört damit zur Familie der Birkengewächse. Ihr Verbreitungsgebiet erstreckt sich über Nord-, Mittel- und Osteuropa bis zum Kaukasus, im Westen Europas fehlt sie. Im deutschsprachigen Raum kommt sie vor allem in Österreich und in Süddeutschland vor. Unterarten der Grau-Erle findet man in Nordamerika und in Asien. Das Holz der Grau-Erle wird nur selten verwendet, da sie meist krumme Stämme mit geringem Durchmesser bildet. Sie wird jedoch häufig zur Aufforstung von Abraumhalden und zur Stabilisierung von Hängen und Böschungen verwendet. Durch Symbiose mit dem Bakterium Frankia alni kann sie den Stickstoff der Luft binden und trägt durch die Anreicherung mit Stickstoffverbindungen zur Verbesserung des Bodens bei.
Die weite Verbreitung der Erlen und die oft geringen Unterschiede haben zu Uneinigkeit in der Einteilung der Arten geführt. Häufig werden Vertreter der Erle in Nordamerika und im östlichen Asien als Unterarten der Grau-Erle zugerechnet, damit ist die europäische Art nur die Nominatform. Der größte Teil des Artikels beschreibt die in Europa und Westasien auftretende Nominatform Alnus incana subsp. incana. Auf die anderen Unterarten wird in eigenen Abschnitten in der Systematik eingegangen.
Baltalksnis (luotīnėškā: Alnus incana, šalėp Jorbarka da saka baltelksnis) ī vėina ėš dvījū alksniu (Alnus) mediu rūšiū, katros aug Lietovuo.
Aug opiu, opaliu, ežerū pakronties, mišriūs medies, ėškartūs, anėm patink šlapės vėitas ale aug ė sausūs medies. Neaug ten, kor nūlatuos stuov ondou. Gerā ataug tīrūs, apleistūs sklīpūs. Miegst vėdotėnėškā derlingas, driegnuokas, kalkingas dirvas.
Baltalksnis kap būn jauns ta aug nuognē spierē, ale paskom augėms solietie. Ons žemesnis kap joudalksnis ī, vuo sīkēs ožaug ė kap krūms. Būdings augoms 10-15 m ī, sīkēs lėgė 20 m. Aug trompā, baltalksnė omžios sėik lėgė 50-70 metu. Žīda kor tās kuova pabonguo, balondė pradiuo.
Baltalksnė medėina rausva, minkšta, tvirta ondenie, ėlgā nepūn. Ka rāstā nie stuori, ta retā kūmet ėš baltalksnė pjaun lėntas.
Baltalksnis (luotīnėškā: Alnus incana, šalėp Jorbarka da saka baltelksnis) ī vėina ėš dvījū alksniu (Alnus) mediu rūšiū, katros aug Lietovuo.
Aug opiu, opaliu, ežerū pakronties, mišriūs medies, ėškartūs, anėm patink šlapės vėitas ale aug ė sausūs medies. Neaug ten, kor nūlatuos stuov ondou. Gerā ataug tīrūs, apleistūs sklīpūs. Miegst vėdotėnėškā derlingas, driegnuokas, kalkingas dirvas.
Baltalksnis kap būn jauns ta aug nuognē spierē, ale paskom augėms solietie. Ons žemesnis kap joudalksnis ī, vuo sīkēs ožaug ė kap krūms. Būdings augoms 10-15 m ī, sīkēs lėgė 20 m. Aug trompā, baltalksnė omžios sėik lėgė 50-70 metu. Žīda kor tās kuova pabonguo, balondė pradiuo.
Baltalksnė medėina rausva, minkšta, tvirta ondenie, ėlgā nepūn. Ka rāstā nie stuori, ta retā kūmet ėš baltalksnė pjaun lėntas.
Leaibi (Alnus incana) lea sogiid čerdii ja leaibbiid sohkii gullevaš lastamuorra.
Szarô òlszô abò szarô ólszka (Alnus incana (L.) Moench) - to je roscëna z rodzëznë brzózkòwatëch (Betulaceae Gray). To drzéwiã abò wiôldżi czerz colemało rosce kòl rzéków, téż na Kaszëbach.
Пурысь лулпу (лат. Alnus incana) — Betulaceae семьяысь Евразиын но Уйпал Америкаын будӥсь лулпу. Ӝуждалаез ог 15-20 м, модослэн диаметрез 40 см. Пурысь лулпулэн курез ӟарыт-пурысь, йылысьтыз куаръёсыз йылсоесь.
Пурысь лулпу (лат. Alnus incana) — Betulaceae семьяысь Евразиын но Уйпал Америкаын будӥсь лулпу. Ӝуждалаез ог 15-20 м, модослэн диаметрез 40 см. Пурысь лулпулэн курез ӟарыт-пурысь, йылысьтыз куаръёсыз йылсоесь.
Руд ловпу (лат. Alnus incana) —быдмассэзлӧн кыдз котырись ловпу увтырын торья вид. Ловпуыс быдмӧ 15-20 метра вылына да овлӧ 40 см кыза диаметрын. Ловпу пантасьӧ Евразияын да Ойвыв Америкаын.
Руд ловпу (лат. Alnus incana) —быдмассэзлӧн кыдз котырись ловпу увтырын торья вид. Ловпуыс быдмӧ 15-20 метра вылына да овлӧ 40 см кыза диаметрын. Ловпу пантасьӧ Евразияын да Ойвыв Америкаын.
Alnus incana, the grey alder or speckled alder, is a species of multi-stemmed, shrubby tree in the birch family, with a wide range across the cooler parts of the Northern Hemisphere. Tolerant of wetter soils, it can slowly spread with runners and is a common sight in swamps and wetlands. It is easily distinguished by its small cones, speckled bark and broad leaves.
It is a small- to medium-sized tree 15–20 metres (49–66 ft) tall with smooth grey bark even in old age, its life span being a maximum of 60 to 100 years. The leaves are matte green, ovoid, 5–11 centimetres (2–4+1⁄4 in) long and 4–8 cm (1+1⁄2–3+1⁄4 in) broad. The flowers are catkins, appearing early in spring before the leaves emerge, the male catkins pendulous and 5–10 cm (2–4 in) long, the female catkins 1.5 cm (5⁄8 in) long and one cm broad when mature in late autumn. The seeds are small, 1–2 millimetres (1⁄32–3⁄32 in) long, and light brown with a narrow encircling wing. The grey alder has a shallow root system, and is marked not only by vigorous production of stump suckers, but also by root suckers, especially in the northern parts of its range. The wood resembles that of the black alder (Alnus glutinosa), but is somewhat paler and of little economic value.
There are four to six subspecies, some treated as separate species by some authors:
A. incana subsp. incana range
A. incana subsp. rugosa range
A. incana subsp. tenuifolia range
Alnus incana is a light-demanding, fast-growing tree that grows well on poorer soils. In central Europe, it is a colonist of alluvial land alongside mountain brooks and streams, occurring at elevations up to 1,500 metres (4,900 ft). However, it does not require moist soil, and will also colonize screes and shallow stony slopes. In the northern part of its range, it is a common tree species at sea level in forests, abandoned fields and on lakeshores. Several species of Lepidoptera use grey alder as a food plant for their caterpillars. In the boreal forest area of Canada, A. incana is often associated with black spruce in the forest type termed black spruce–speckled alder.[7] The larvae of the alder woolly sawfly sometimes cause considerable defoliation to the grey alder.[8]
A. rugosa provides cover for wildlife, is browsed by deer and moose, and the seeds are eaten by birds.[9]
Pedunculagin is an ellagitannin found in the Manchurian alder (A. hirsuta var. microphylla).[10]
The tree is cultivated in parks and gardens. The cultivar 'Aurea', with green-gold leaves, has gained the Royal Horticultural Society's Award of Garden Merit.[11]
It is sometimes used in afforestation and agroforestry in non-fertile or wet soils which it enriches by means of nitrogen fixing bacteria in its root nodules.
Alder is an excellent tree for coppicing[12] and pollarding. Its cut branches may be fed to browsing livestock such as cows and goats, then used for kindling, firewood, or light construction - while root systems fertilize adjacent agricultural plots via nitrogen fixation.
The Zuni people use the bark of the tenuifolia subspecies to dye deerskin reddish brown.[13]
The Ho-Chunk people eat the bark of the rugosa subspecies when their stomachs are "sour" or upset.[14]
Its wood and bark are used in smoking meat,[15] particularly fish[16] and duck.[17]
Alnus incana, the grey alder or speckled alder, is a species of multi-stemmed, shrubby tree in the birch family, with a wide range across the cooler parts of the Northern Hemisphere. Tolerant of wetter soils, it can slowly spread with runners and is a common sight in swamps and wetlands. It is easily distinguished by its small cones, speckled bark and broad leaves.
La griza alno, blanka alno (aŭ latine Alnus incana), estas foliarbo el la genro de la alnoj kaj el la familio de la Betulacoj (Betulaceae). Ĝia disvastigejo etendiĝas trans norda, meza kaj orienta Eŭropo ĝis Kaŭkazo. En okcidenta Eŭropo la griza alno mankas. Subspecioj de la griza alno troviĝas en Nordameriko kaj Azio. La ligno de “Alnus incana” estas nur malofte uzata, ĉar la arbo ofte havas nerektajn trunkojn kun maldika perimetro. Ĝi ofte estas uzata por plantigi novajn arbarajn areojn sur kaj por stabiligi deklivojn kaj talusojn. Pro la simbiozo kun la bakterio Frankia alni ĝi povas fiksi nitrogenon el la aero kaj tiel altigas la nitrogenon en la grundo.
La griza alno estas somerverda arbo, kiu atingas alton de 10 ĝis 15, maksimume 25 metroj. La arbo estas unu aŭ plurtrunka, havante multajn branĉojn kaj densan kronon. Ĝi ankaŭ povas kreski arbuste. Junaj branĉoj estas grize verdaj ĝis ruĝe brunaj, ĉe la pinto estas haroj kaj ekzistas malgrandaj ruĝe brunaj lenticeloj.
La planto ne havas ritidomon kaj la peridermo transprenas la taskojn de la ritidomo. Do ĝi estas tipa peridermarbo. La arboŝelo estas helgriza, glata kaj apenaŭ ne disŝiriĝas maljunaĝe. Ĝi estas kovrata de lenticeloj.
Alnoj apartenas al la alburnarboj. La durameno kaj la alburno havas la saman koloron. La ligno estas ruĝece blanka ĝis helruĝece bruna. Freŝe faligitaj trunkoj havas ruĝan koloron, la koloro malaperas dum la sekigado de la ligno. La ligno de la griza alno similas al tiu de la nigra alno. Ĝi nur estas iomete pli hela kaj havas malpli da malfajnaj fibroj kaj la folioj pli brilas.
La griza alno havas renverse ovoformajn, kaj ne gluecajn vintrajn burĝonojn. La folioj estas alterne starantaj havante 2 ĝis 3 cm longajn folitigojn. La supra folisurfaco estas malhelverda, la malsupra surfaco grize verda kaj la junaj folioj havas grize peltan hararon.
La griza alno estas kiel ĉiu alno anemofila kaj monoika. La floroj estas unuseksaj kaj kunigitaj en amentoj. La griza alno floras de februaro ĝis marto, tri semajnojn antaŭ la nigra alno.
La kromosomnombro estas 2n = 28.
La griza alno distingiĝas pro siaj pli pintaj folioj kaj la malsupra folisurfaco disde la du aliaj mezeŭropaj alnoj. La junaj folioj ne estas gluecaj, kiel ĉe la nigra alno.
En la naturaj kreskejoj la arbo multobliĝas kaj per generativa multobligado per semoj kaj ankaŭ per vegetativa multobligado per draĵoj kaj ŝosoj. Dum la vintro la strobiloj disvastiĝas per vento (anemoĥorio) kaj akvo (hidroĥorio). Grizaj alnoj kreskas rapide. Ili atingas en la unua jaro altecon de ĝis 50 cm.
La natura disvastigejo de la griza alno etendiĝas en Eŭropo trans norda, meza kaj orienta Eŭropoj. En la sudo la planto kreskas nature de la Maralpoj kaj ĝis la nordaj Apeninoj kaj pluen al la Balkana montaro al Kaŭkazo. La norda limo en Skandinavio estas ĉ. 70° 30′ de norda latitudo.
La griza alno formiĝas ĉe la radikoj nodetojn kie la bakterio Frankia alni transformas la nitrogenon en la aero al nitrogeno, kiun la planto povas uzi. Tiu okazas per simbiozo de Aktinorizo kun la radikoj de la alno. Esploroj montris, ke 30jara plantejo de griza alno liveras po 43 kg/ha da nitrogeno por jaro, kiun la plantoj povas uzi. La jara kvanto de nitrogeno en montara arbaro de alnoj ekzemple en la francaj Alpoj estas 42,5 kg/ha.
Griza alnoj estas precipe en danĝero pro la t.n. alna morto. La fungo Phytophthora alni damaĝas ĉefe nigrajn, grizajn, verdajn kaj korfoliajn alnojn. La lingvovora fungo kaŭzas trunkpudradon.
Plia malsano ĉe alnoj estas sorĉistinaj balailoj, kio estas kaŭzita de la fungo Taphrina epiphylla kaj aliaj fungaj malsanoj. La alno estas ankaŭ atakataj de damaĝbestoj, kiel Kurkuliedoj kaj aliaj.
La genro Alno apartenas al la familio de la Betulacoj (Betulaceae). Ĝi estas enordigita en la genro Alnus (alno) al kiu apartenas ankaŭ la nigra alno. La verda alno apartenas al la subgenro Alnobetula.
La vasta disvastigo de la alnoj kaj la malgrandaj diferencoj kaŭzas neunuecan internan sistematikon. Pluraj formoj parte estas rigardataj kiel subspecio de Alnus incana aŭ kiel nuraj varioj. Ofte oni diferencigas kvar subspeciojn de Alnus incana nome la jenaj:
La kvar subspecioj ofte estas rigardataj kiel propraj specioj:
Tinktura alno (Alnus incana subsp. hirsuta (SPACH) Á.LÖVE & D.LÖVE respektive Alnus hirsuta (SPACH) TURCZ., sinonimo: Alnus tinctoria SARG.) estas 10 ĝis 15, maksime ĝis 20 m alta arbo kun junaĝe larĝa globforma arbokrono. La arboŝelo estas nigre bruna. La disvastigejo de la tinktura alno estas Japanujo, Koreujo, Ĉinujo, Saĥalino, Kamĉatko kaj orienta Siberio. Ĝi kreskas en alteco de 700 ĝis 1500 m.
La subspecio Alnus incana subsp. kolaensis (ORLOVA) Á.LÖVE & D.LÖVE hejmiĝas en Norvegio, Svedio kaj Suomio.
La sulkofolia alno (Alnus incana subsp. rugosa (DU ROI) R.T. CLAUSEN respektive Alnus rugosa (DU ROI) SPRENG.) kreskas plej ofte kiel arbusto, malofte kiel arbo. Ĝi atingas altecon de 9 m. La branĉoj estas kalvaj aŭ rugebrune haraj. La natura disvastigejo estas la oriento de Kanado, la (provincoj Manitobo, Nov-Brunsviko, Novlando kaj Labradoro, Nova Scotia, Ontario, insulo de Princo Eduardo, Kebekio kaj Saskaĉevano), la insuloj Sankta-Piero kaj Mikelono kaj la nordoriento de Usono (de Norda Dakoto kaj Majno ĝis Iovao, Ilinojso, Okcidenta Virginio kaj Nov-Ĵerzejo).
La subspecio Alnus incana subsp. tenuifolia (NUTT.) BREITUNG estas ankaŭ rigardata kiel vario de la subspecio Alnus incana subsp. rugosa . Sinonimoj estas Alnus incana subsp. rugosa var. occidentalis (DIPPEL) C.L.HITCHC. aŭ Alnus tenuifolia NUTT. Ĝi diferenciĝas de la subspecio rugosa pro maldikaj, papirecaj foliplatoj kaj la rondigita folirando. Ĝi kreskas ofte arbece. Ĝi tamen povas kreski arbuste. Arboj atingas altecon de ĉ. 12 m. Ĝia disvastigejo etendiĝas de Alasko trans la okcidento de Kanado (provincoj Alberto, Brita Kolumbio, Nordokcidentaj Teritorioj, Saskaĉevano kaj Jukonio) trans la okcidento de Usono en Kalifornio, Kolorado kaj Nov-Meksikio. Ĝi bone kreskas en alteco de 100 ĝis 3000 m super marnivelo. Ofte ĝi kreskas apud riveroj en la Rokmontaro kaj aliaj montaroj en la okcidento de Nordameriko.
En la baltaj ŝtatoj naturaj hibridoj inter griza alno kaj nigra alno (Alnus incana × Alnus glutinosa) estas oftaj. Tiu ĉi hibridoj kreskas 16 % pli alten kaj havas 45 % pli grandan trunkan diametron ol la griza alno. Oni distingas plurajn kultivarojn:
La griza alno, blanka alno (aŭ latine Alnus incana), estas foliarbo el la genro de la alnoj kaj el la familio de la Betulacoj (Betulaceae). Ĝia disvastigejo etendiĝas trans norda, meza kaj orienta Eŭropo ĝis Kaŭkazo. En okcidenta Eŭropo la griza alno mankas. Subspecioj de la griza alno troviĝas en Nordameriko kaj Azio. La ligno de “Alnus incana” estas nur malofte uzata, ĉar la arbo ofte havas nerektajn trunkojn kun maldika perimetro. Ĝi ofte estas uzata por plantigi novajn arbarajn areojn sur kaj por stabiligi deklivojn kaj talusojn. Pro la simbiozo kun la bakterio Frankia alni ĝi povas fiksi nitrogenon el la aero kaj tiel altigas la nitrogenon en la grundo.
Alnus incana, el aliso gris o aliso cano, es una especie de árbol perteneciente a la familia de las betuláceas.
Es una especie de aliso con una amplia gama a través de las partes más frías del hemisferio norte.
Se trata de un árbol de pequeño a mediano tamaño que alcanza los 15-20 m de altura con corteza lisa gris, incluso en la vejez, su vida alcanza un máximo de 60-100 años. Las hojas son de color mate verde, ovoides de 5-11 cm de largo y 4-8 cm de ancho. Las flores aparecen a principios de la primavera antes de salir las hojas, las masculinas colgante y de 5-10 cm de largo, y las femeninas de 1,5 cm de largo y 1 cm de ancho, madurando a finales de otoño. Las semillas son pequeñas, de 1-2 mm de largo, de color marrón claro y con una estrecha ala. El aliso gris tiene un sistema de raíces superficiales, y se caracteriza no solo por la fuerte producción de retoños de tocón, sino también por los retoños de raíz, especialmente en el norte de su área de distribución.
Alnus incana es una especie exigente de luz, son árboles de crecimiento rápido que crecen bien en suelos pobres. En Europa central, es un colono de las tierras aluviales de montaña junto a arroyos y riachuelos, y se desarrollan a alturas de hasta 1500 metros. Sin embargo, no requieren un suelo húmedo, y también suelen colonizar laderas pedregosas y superficiales. En la parte septentrional de su área de distribución, es un árbol común a nivel del mar en los bosques, los campos abandonados y en cercanías de lagos. A veces es utilizado para la forestación en suelos no fértiles, que se enriquece por medio de la fijación del nitrógeno por las bacterias en los nódulos de sus raíces. La madera se asemeja a la del aliso negro, pero es algo más pálido y de poco valor.
Alnus incana fue descrita por (L.) Moench y publicado en Methodus Plantas Horti Botanici et Agri Marburgensis : a staminum situ describendi 424. 1794.[1]
Alnus: nombre genérico del latín clásico para este género.[2]
incana: epíteto latíno que significa "gris, canoso"[3]
Hay cuatro a seis subespecies, algunas tratadas como especies separada por algunos autores:
Hay una variedad especialmente apreciada para los jardines por su vivo color amarillo, el Alnus incana 'Aurea', Aliso dorado.
Alnus incana, el aliso gris o aliso cano, es una especie de árbol perteneciente a la familia de las betuláceas.
Hall lepp ehk valge lepp (Alnus incana) on kaseliste sugukonda lepa perekonda kuuluv mitmeaastane heitlehine lehtpuuliik.
Puu lehed on hallikasrohelised ja läiketa, leheserva tipp on teritunud. Puu tüve koor on hallikat värvi ja sile.
Hall lepp kasvab kuni 15 meetri kõrguseks[1]. Eesti kõrgeim hall lepp (31m, diameeter 32 cm) kasvab Järvseljal [2].
Kasvab nii Euroopas, Aasias kui ka Põhja-Ameerikas. Eestis on tavaline puuliik, vähem leidub teda saartel. Halli leppa võib leida näiteks segametsadest, veekogude kallastelt ja puisniitudelt.
Hall lepp ehk valge lepp (Alnus incana) on kaseliste sugukonda lepa perekonda kuuluv mitmeaastane heitlehine lehtpuuliik.
Haltz zuria (Alnus incana) haltzen generoko hosto galkorreko zuhaitza da, Ipar hemisferioan jatorria duena.[1]
Bataz beste, 15–20 metroko altuera du.
Adituen arabera, 4-6 azpiespezie ditu (batzuk ezpezie ezberdintzat jotzen dute):
Artikulu hau biologiari buruzko zirriborroa da. Wikipedia lagun dezakezu edukia osatuz. Haltz zuria (Alnus incana) haltzen generoko hosto galkorreko zuhaitza da, Ipar hemisferioan jatorria duena.
Bataz beste, 15–20 metroko altuera du.
Harmaaleppä (Alnus incana) on koivukasvien heimoon ja leppien sukuun kuuluva, pohjoisen pallonpuoliskon viileämmillä alueilla elävä puulaji. Harmaaleppä on saanut nimensä runkonsa ja oksiensa harmaasta kuoresta. Se kasvaa monenlaisilla kasvupaikoilla, esimerkiksi rannoilla, metsänlaidoissa ja vanhoilla laidunalueilla. Harmaaleppä menestyy kuivemmilla mailla kuin tervaleppä. Kasvutavaltaan se on usein pensasmainen. Harmaaleppä on tavallinen puu Suomen luonnossa ja sitä tavataan lähes koko maassa.
Harmaaleppä kasvaa pensaana tai puuna. Yksirunkoisena se saattaa kasvaa 15–20 metrin korkuiseksi, ja sen kuori on läpi elinkaaren vaaleanharmaa. Puu voi elää 60–100-vuotiaaksi. Latvus on kartiomainen ja runko sileä. Vihreät ja soikeat lehdet ovat 5–11 senttimetrin pituisia ja 4-8 senttimetriä leveitä. Kukinta tapahtuu varhain keväällä. Hedekukinnot ovat 5–10 senttimetrin pituisia, vaaleanruskeita norkkoja. Myöhään syksyllä emikukinnot kuivuvat 1,5 senttimetrin pituisiksi ja 1 senttimetrin paksuisiksi, käpymäisiksi siemenpesiksi. Harmaalepän siemenet ovat ruskeita, 1–2 millimetrin pituisia, ja niitä ympäröi ohut siiveke. Puulla on laaja ja monihaarainen juuristo. Juurimukuloissa elävä Frankia-sienibakteeri pystyy sitomaan typpeä ilmasta puun tarpeisiin.[2] Harmaaleppä ja tervaleppä ovat Suomessa ainoat puulajit, joka antavat lehtiensä pudota vihreinä, koska niiden ei tarvitse varastoida lehdissä olevia typpiyhdisteitä.
Suomen suurimman harmaalepän ympärysmitta on 178 senttimetriä.[3]
Harmaaleppää tavataan Euroopassa Fennoskandian, Ranskan ja Saksan itäosien, Italian, Kreikan ja Bulgarian pohjoisosien ja Venäjän länsiosien rajoittamalla alueella. Aasiassa harmaaleppä kasvaa Kaukasuksella, Siperiassa, Kamtšatkan niemimaalla ja Japanissa. Pohjois-Amerikassa kasvavat harmaalepän alalajit amerikanharmaaleppä (Alnus incana subsp. rugosa) ja Alnus incana subsp. tenuifolia,[4] joita pidetään joskus omina lajeinaan.[5][6] Suomessa harmaaleppä kasvaa Ahvenanmaata, eteläisiä rannikkoseutuja ja Lapin pohjoisosia lukuun ottamatta koko maassa. Puu viihtyy parhaiten kalkkipitoisilla, ravinteikkailla ja kosteilla mailla.[2]
Harmaalepän Suomessa laajalle levinneet alalajit ovat nimirotu etelänharmaaleppä Alnus incana subsp. incana, jota tavataan kautta maan, ja Alnus incana subsp. kolaënsis, kuolanharmaaleppä, joka esiintyy Lapissa. A. glutinosa x incana, harmaa- ja tervalepän risteymä on tavallinen Etelä- ja Keski-Suomessa.[2] Tavallisimmat Suomessa tavattavat liuskalehtiset muodot ovat A. incana subsp. incana f. laciniata, sulkaharmaaleppä ja A. incana subsp. incana f. angustissima, hapsuharmaaleppä.[7] Kuolanharmaalepän lehdet muistuttavat tervalepän lehtiä, mutta niiden kärjet eivät ole sisäänpäin kääntyneitä. Liuskalehtisissä muodoissa sulkaharmaalepän lehtilavat ovat lähes sileäreunaisia, hapsuharmaalepän sahalaitaisia. Uudeltamaalta ja Pohjois-Karjalasta on löydetty punaharmaaleppiä (f. Rubra), joissa lehtilavan alaosa on punainen. Puutarhakäyttöön levinneen mukuraharmaalepän (f. Sääksmäki) runko sisältää runsaasti visamuodostelmia.[8] Riippaharmaalepän (f. Pendula) oksat riippuvat riippakoivun tavoin.
Nopeakasvuisena ja sopeutuvaisena puuna harmaaleppä leviää nopeasti uusille alueille.
Harmaaleppä on yksikotinen, eli yksilö pystyy tuottamaan yhtä aikaa sekä hede- että emikukintoja. Kukinnot ja kukat ovat yksineuvoisia, eli heteet ja emit kasvavat eri kukinnoissa. Kevyet siemenet kulkeutuvat laajalle alueelle tuulten ja sulamisvesien avulla. Siementen avulla tapahtuvan lisääntymisen ohella harmaalepän laaja juuristo tekee hyvin juuri- ja kantoversoja.[7] Harmaaleppä on pioneeripuulaji.[9]
Harmaaleppä kuolee lahovikaisena tavallisesti 50 ikävuoden vaiheilla. Lahoamista aiheuttavat käävät, erityisesti lepänkääpä (Inonotus radiatus),[10] taulakääpä (Fomes fomentarius) ja pakurikääpä (Inonotus obliquus). Lepän lehtiä tuhoavia hyönteisiä ovat lepänlehtikuoriainen (Melasoma aenea) ja leppäkemppi (Psylla alni). Muita tuholaisia ovat raitakärsäkäs (Cryptorhychus lapathi), puuntuhooja (Cossus cossus), lehtisiipiset (Sesiidae), isoleppäkirva (Clethrobius giganteus)[2], korukirvat (Pterocallis) ja äkämäpunkit (Eriophyidae), erityisesti lepänäkämäpunkki (Eriophyes laevis).[10]
Hirvet ja muut nisäkkäät eivät tavallisesti syö lepän lehtiä, sillä lehtien sisältämät alkaloidit aiheuttavat kitkerää makua.[10] Samasta syystä leppä näyttää säästyvän monilta koivuja ja haapoja tuhoavilta hyönteisiltä.[2]
Harmaaleppää käytetään metsänhoidossa suojuspuuna. Hyvällä kasvupaikalla se kasvaa nopeasti, ja tukkipuuta siitä saadaan 30 vuodessa. Tuoreena puuaines lahoaa helposti, mutta kuivuttuaan se on kestävää.[11] Sahatavarana se on kaunista, vaaleata puuta, mutta runsaat mustat kuivat oksat alentavat sahatavaran saantoa, aivan kuin tervalepälläkin. Pyyt ja liito-oravat syövät sen norkkoja ja lehtiä, vihervarpuset ja urpiaiset siemeniä. Tikat kovertavat pesäkolonsa mielellään harmaalepän pehmeään puuhun. Luonnon monimuotoisuuden kannalta harmaaleppä on tärkeä puu, sillä sen elinkaari on lyhyt ja se tuottaa nopeasti lahopuuta.
Kotitaloudessa harmaaleppää käytetään polttopuuna. Sitä pidetään parhaana puulajina kalan ja lihan savustamiseen.[9] Puutarhassa harmaaleppä soveltuu nopeakasvuisena suojuspuuksi hitaammin kasvaville puille. Harmaaleppä parantaa maaperää ja kestää hyvin leikkaamista.[8]
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Harmaaleppä (Alnus incana) on koivukasvien heimoon ja leppien sukuun kuuluva, pohjoisen pallonpuoliskon viileämmillä alueilla elävä puulaji. Harmaaleppä on saanut nimensä runkonsa ja oksiensa harmaasta kuoresta. Se kasvaa monenlaisilla kasvupaikoilla, esimerkiksi rannoilla, metsänlaidoissa ja vanhoilla laidunalueilla. Harmaaleppä menestyy kuivemmilla mailla kuin tervaleppä. Kasvutavaltaan se on usein pensasmainen. Harmaaleppä on tavallinen puu Suomen luonnossa ja sitä tavataan lähes koko maassa.
Alnus incana
L'aulne blanc, aulne rugueux, aulne de montagne, arcoce ou varne est un arbre, de la famille des bétulacées, originaire des régions tempérées de l'hémisphère nord.
Du latin incanus : « couvert de poils blanc grisâtre ».
Les fleurs mâles sont regroupées en grands chatons jaunes pendants terminaux. Les fleurs femelles, beaucoup plus discrètes, rougeâtres, dressées, sont disposées plus haut que les fleurs mâles sur le rameau.
Feuille alterne avec un long pédoncule, ovale, aiguë, doublement dentée.
Radicelles portant des nodosités abritant des bactéries qui peuvent transformer l'azote atmosphérique en substances assimilables par les plantes.
Si on le nomme Incana, c'est à cause de son écorce grise et ses feuilles vert grisâtre sur le revers [1].
C'est une espèce rustique s’accommodant aux situations froides.
Cet arbre est fréquent en montagne, où il affectionne les zones humides, les bords de ruisseaux et les marécages. On le rencontre à une altitude maximum de 1 800 m. On le trouve dans les forêts ripicoles des alpes et du Jura.
Grâce à sa souplesse et sa capacité de produire des rejetons les arbustes de cette espèce résistent largement aux dommages qu'engendrent les avalanches. Les aulnes colonisent ainsi très souvent les talwegs, qui constituent des corridors d'avalanches fréquentes.
Il s'hybride avec Alnus glutinosa.
Les racines des aulnes sont associées à des bactéries fixatrices d'azote (Frankia). Pour cette raison, on utilise cet arbre pour végétaliser des sols infertiles. On s'en sert aussi pour la fixation des sols (terrils, carrières), le reboisement des terrains calcaires et l'ancrage contre les glissements de terrain.
En Wallonie (sud de la Belgique), il a été planté en bordure des zones d'enrésinement pour les protéger des feux de forêt. Mais sa faculté de rejeter de souche en a fait une espèce invasive et il est maintenant vivement éradiqué par coupe et étrépage du sol[réf. nécessaire].
Selon une étude ethnobotanique et du patois local, faite par Françoise et Grégoire Nicollier à Bagnes (France) et publiée en 1984, « l'écorce et les feuilles donnent une teinture jaune ; l'écorce est utilisée aussi contre les maux de cou, le gonflement des amygdales, la fièvre ; les feuilles, pour soulager les inflammations des pieds ; les feuilles donnent un excellent fourrage pour les porcs, les chèvres et les vaches (elles constituent leur dessert d'hiver) »[2].
Alnus incana 'Aurea' : hauteur de 6 m. Très remarqué pour son jeune bois en hiver jaune -rougeâtre. écorce dorée, feuillage jaune.
Alnus incana ' Laciniata' : hauteur de 20 m. Les feuilles peuvent être très différentes les unes des autres. Ressemble à l'Alnus glutinosa 'Laciniata' avec des feuilles plus grandes et plus fines.
Alnus incana 'Pendula' : formé en pépinière sur un tronc tuteuré. Arbre pleureur aux formes étranges.
Alnus incana 'Ramulis coccineis' : similaire à l'Aurea'. Chatons rose saumoné et rameaux rouge-orangé.
Alnus incana
L'aulne blanc, aulne rugueux, aulne de montagne, arcoce ou varne est un arbre, de la famille des bétulacées, originaire des régions tempérées de l'hémisphère nord.
Hórska wólša (Alnus incana, syn.: Betula alnus L. var. incana L.) je štom ze swójby brězowych rostlinow (Betulaceae).
Hórska wólša je štom abo wulki kerk, kotryž docpěwa wysokosć wot 20 (10-25) m.
Króna je njeprawidłownje kehelojta. Hałuzy zwjetša horje sahaja. Młode hałuzy su oliwozelene do swětłobrune, lochko kosmate ale nic lěpjate.
Skora je hładka a swětłošěra abo běłošěra.
Rostlina nabohaćuje dusyk z pomocu dusyk zwjazowacymi hribami, z kotrymiž je wólša žiwa ze symbiozu.
Zymske pupki su dołhojće-jejkojte, čerwjenobrune, docpěwaja dołhosć wot něhdźe 8 cm a su hač do 5 mm dołho stołpikate.
Łopjena su měnjate, jejkojto-eliptiske, poněčim přikónčene, dwójce rězane na delnim boku šěrozelene a 2-3 cm dołho stołpikate. Wone docpěwaja dołhosć wot 4 hač do 10 cm a w nazymje njepřebarbja.
Kćěje wot februara (měrca) hač do apryla. Micki so před łopjenami jewja. Muske micki su načerwjeń brune, steja po třoch hač po pjećoch a docpěwaja dołhosć wot 7 hač 10 cm. Žónske micki su sedźace a docpěwaja wulkosć wot 3 hač 5 mm.
Płódnistwa su hablojte, jejkojte, wodrjewjace, ćmowobrune a docpěwaja dołhosć wot 13 hač do 16 mm a šěrokosć wot 10 mm. Bóčne płódnistwa su krótko stołpikate abo sedźace. Worjechi docpěwaja wulkosć wot 2 hač do 3 mm a njesu na boku wuske křidleška. Płody wot septembra hač oktobra zezrawja.
Rosće w łučinowych lěsach, na hórskich rěčkach a alpowych rěkach. Wutraje a suche a mokre stejnišća. Preferuje wutkate a bazowe, často wapnite, hlinjane, šotrowe a šćerkowe pódy.
Rostlina je w sewjernej a srjedźnej a wuchodnej Europje, južnje hač do srjedźneje Italskeje a Balkanskeje połkupy a wuchodnje hač do Kawkaza rozšěrjena.
Nimo w Europje domjaceje nominatoweje formy, so sćěhowace tři taksony často jako poddružiny wot Alnus incana wobhladaja. přirjadowanje je tola diskutowane, poddružiny buchu wot někotrych awtorow jako swójske družiny zastopnjowane, zdźěla tež jako wariety.
Hórska wólša (Alnus incana, syn.: Betula alnus L. var. incana L.) je štom ze swójby brězowych rostlinow (Betulaceae).
Gráelri (Alnus incana) er meðalstórt tré af birkiætt. Það verður 15-20 metra hæst og vaxtalag er frá margstofna tré eða runna til einstofna trés með keilulaga krónu. Tréð hefur svepprót eins og önnur elri.
Undirtegundir eru 4-6 talsins. Sumir líta á einstakar undirtegundir sem sér tegund.
Gráelri verður allt að 15 metrar á Íslandi. Það blómstrar reklum snemma vors og blóm skemmast oft í vorfrostum sem dregur úr frætekju. Þrátt fyrir það er kal á sprotum sjaldgæft. Norsk og finnsk kvæmi eru vel aðlöguð íslenskum aðstæðum. Blæelri hefur einnig verið reynt á Íslandi. Reynsla er lítil en blæelri er hraðvaxnara en evrópska systurtegund sín. [2]
Lauf gráelris
Stofn.
Könglar.
Reklar.
Á Austurvelli eru stæðileg gráelri( til hægri).
Gráelri (Alnus incana) er meðalstórt tré af birkiætt. Það verður 15-20 metra hæst og vaxtalag er frá margstofna tré eða runna til einstofna trés með keilulaga krónu. Tréð hefur svepprót eins og önnur elri.
L'ontano bianco o ontano grigio (Alnus incana (L.) Moench) è un albero caducifoglio della famiglia delle Betulacee.[1]
È un albero di taglia piccola-media e di rapido accrescimento, che arriva a misurare 15–20 m di altezza. La corteccia si mantiene grigia sino alla fine del suo ciclo vitale, che arriva a 60-100 anni.
Le foglie sono di colore verde opaco, ovoidali; misurano circa 5–11 cm di lunghezza e 4–8 cm di larghezza.
I fiori nascono all'inizio della primavera, prima che spuntino le foglie.
I semi sono piccoli, da 1 a 2 mm di lunghezza, di colore marrone chiaro.
Apparato radicale fittonante, azotofissatore.
È diffuso in gran parte dell'emisfero settentrionale, dagli Stati Uniti all'Europa e all'Asia nord-occidentale. In Italia è presente sulle Alpi e nel Nord dell'Appennino. Fino alla fine del XX secolo era presente anche lungo il tratto di pianura del fiume Panaro, nella Valle Padana a quote inferiori ai 100 m.
Nella parte settentrionale della sua area di distribuzione, è un albero comune nei boschi a livello del mare, nei campi abbandonati e in prossimità di fiumi e laghi, fino a 1200 m di quota.
L'ampia diffusione circumboreale e le piccole differenze morfologiche che caratterizzano il genere Alnus hanno comportato notevoli difficoltà e controversie sulla classificazione tassonomica di questo taxon[2]. Recenti studi genetici propongono di raggruppare all'interno del complesso Alnus incana molte specie prima considerate separate e individuare quattro principali sottospecie:[1]
Il legno di ontano grigio è usato raramente, perché è costituito da tronchi di piccolo diametro, prevalentemente storti. Tuttavia, è spesso utilizzato per il rimboschimento delle colline di terre alluvionali e per la stabilizzazione di pendii e scarpate.
Alnus incana è una specie che necessita di molta luce; cresce bene anche in suoli molto poveri grazie alla sua altissima capacità fertilizzante del terreno, ottenuta in simbiosi con il batterio Frankia, in grado di elaborare grandi quantità di composti azotati.
L'ontano bianco o ontano grigio (Alnus incana (L.) Moench) è un albero caducifoglio della famiglia delle Betulacee.
Baltalksnis (lot. Alnus incana) – beržinių (Betulaceae) šeimos, alksnių (Alnus) genties lapuotis medis, retkarčiais išaugantis kaip didelis krūmas.
Tai viena iš nedaugelio natūraliai augančių Lietuvoje, mūsų krašto medžių rūšių.
Baltalksnis paplitęs visoje Šiaurės ir Vidurio, Rytų Europoje bei šiaurės Kaukaze.
Natūraliai paplitęs visoje Lietuvoje, retas Lietuvos pietinėje dalyje – Vilkaviškio, Marijampolės, Alytaus savivaldybėse, bet dažnesnis Utenos ir Biržų miškų urėdijose. Auga upių, upelių, ežerų pakrantėse, mišriuose miškuose, kirtimuose, mėgsta drėgnas vietas bet auga ir sausame miške. Neauga ten, kur visada stovi vanduo. Gerai atželia dykvietėse, apleistuose sklypuose. Mėgsta vidutiniškai derlingus, drėgnokus, kalkingus priesmėlių ir priemolių dirvožemius.
Tai labai greitai augantis medis, ypač pirmuosius 10–15, vėliau augimo tempai sulėtėja. Per pirmus metus gali pasistiebti iki 50 cm, po dvejų metų jau iki 1,24 m, po penkerių metų gali būti paaugę nuo 4,3 iki 5 metrus aukščio. Baltalksnis žemesnis už juodalksnį, o kartais išauga ir kaip krūmas, kurio matmenys kur kas mažesni nei išaugančio medžiu. Užaugančių medžiais baltalksnių aukštis įprastai apie 10-15 m, kartais iki 20 m, didžiausias aukštis beveik iki 28 m. Jų kamienas plonas – iki 40 cm skersmens. Dabar žinomas aukščiausias, išmatuotas baltalksnis auga Tusulos savivaldybėje Ruotsinkylä vietovėje netoli Helsinkio (Suomija), jo aukštis 27,20 m, kamieno apimtis 1 m.
Tai labai trumpaamžis augalas, jo amžius siekia 50-70 metų, derėti pradeda 7-10 metų amžiaus.
Kamieno ir šakų žievė pilka, lygi, plona, blizganti, beveik visą amžių išlieka lygi, nesutrūkinėjusi. Iš žievės baltalksnius nesunku atskirti nuo juodalksnių, kurių žievė tamsi ir maždaug 20-25 metų amžiuje trūkinėja. Jauni ūgliai pilkai rusvi, tribriauniai, plaukuoti, nelipnūs. Pupurai rudai violetiniai, buki su 2, kartais 3 žvyneliais, atspurę, trumpakočiai. Lapai ovalūs arba kiaušiniški, 4-10 cm ilgio ir 3,5-7 cm pločio, su nusmailėjusiomis viršūnėmis, jų kraštai pjūkliški, pamatas plačiai pleištiškas. Viršutinė pusė žalia, apatinė pilkai ar melsvai žalia, su plaukeliais, rudenį nepagelsta. Žiedai vienalyčiai – vyriškieji karančiuose žirginiuose, moteriški – trumpuose kankorėžėliuose. Kuokeliniai žirginiai po 3-5, nusvirę, 5-8 cm ilgio, gelsvai rausvi. Piesteliniai žirginiai po 3-8, kartais iki 10, trumpu koteliu arba bekočiai, subrendę apie 1,5 cm ilgio bei rudi. Vaisiai – sparnuoti plokšti riešutėliai. Riešutėliai subręsta spalio mėnesį, skaidosi rudenį ir žiemą.
Baltalksnis pradeda žydėti kai vidutinė paros oro temperatūra pakyla virš nulio. Vidutinė žydėjimo pradžia Kauno apylinkėse – kovo 28 d. Anksčiausiai pražįsta apie vasario 25 d., vėliausiai apie balandžio 22 d. Žydi apie 11 dienų prieš išsiskleidžiant lapams.
Dauginasi sėklomis, šaknų atžalomis ir rečiau kelmo ataugomis.
Kankorėžėliai naudojami kaip tanidinė žaliava, lapai, žievė, pjuvenos – kailiams raugti ir dažams. Dėl ankstyvo žydėjimo vertinamas bitininkystėje. Parkuose kartais auginamos karpytalapė ir geltonlapė dekoratyvinės baltalksnio formos. Vaistams vartojami sumedėję žirginiai (kankorėžėliai), žievė bei lapai. Medicinos praktikoje alksnio preparatai vartojami virškinamojo trakto sutrikimams gydyti bei viduriavimui stabdyti. Baltalksnio preparatai pasižymi sutraukiančiomis, kraują stabdančiomis, prakaitavimą skatinančiomis, priešuždegiminėmis ir skausmą raminančiomis savybėmis.
Baltalksnio mediena rausva, minkšta, patvari vandenyje, ilgai nepūna. Kadangi rąstai būna nestori, retai kada iš baltalksnių pjaunamos lentos, nors visomis savybėmis baltalksniai prilygsta juodalksnio medienai.
Lapai greit supūva, o dirvožemį praturtina (pagerina) azotu, dėl jo šaknyse gyvenančių ir azotą fiksuojančių bakterijų. Medis atsparus šalčiams.
Kartais natūralioje gamtoje baltalksniai kryžminasi su juodalksniais ir tokie hibridai vadinami:
Mokslinio, lotynų kalba rūšies pavadinimo autorius Conrad Moench 1744–1805 metais. Lietuviškas pavadinimas kilęs nuo žievės spalvos, kuri medžiui sulaukus 15-16 metų darosi pilkai sidabrinė (nors jaunesnių medžių – pilkai ruda).
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Baltalksnis (lot. Alnus incana) – beržinių (Betulaceae) šeimos, alksnių (Alnus) genties lapuotis medis, retkarčiais išaugantis kaip didelis krūmas.
Tai viena iš nedaugelio natūraliai augančių Lietuvoje, mūsų krašto medžių rūšių.
Baltalksnis (Alnus incana (L.) Moench) ir daudzgadīgs bērzu dzimtas koks. Latvijā bieži sastopams.
Tas ir līdz 20 m garš, vasarzaļš, vienmājas koks. Miza pelēka, gluda. Lapas veselas, olveidīgas ar nevienādi zobainu malu. Lapas pamats ieapaļš. Virspuse zaļa, kaila, apakšpuse pelēka, tūbaina. Vīrišķie un sievišķie ziedi atrodas šķirti uz viena un tā paša koka. Vīrišķās ziedu spurdzes garas, nokarenas, sievišķās īsas, gandrīz sēdošas. Zied pirms lapu plaukšanas marta beigās un aprīlī, sēklas izbirst oktobrī.
Aug mitrās un krūmainās pļavās, zāļu purvos, upju ielejās pieupes uzskalotās augsnēs. Primāros mežos sastopams reti. Kā pioniersuga strauji aizaudzē nekoptas ganības, pamestas pļavas un tīrumus.
Baltalksnis aug dažviet Eiropā (Rietumeiropā, Skandināvijā, Alpu malā), Āzijā un Ziemeļamerikā.[1]
Baltalkšņa koksne galvenokārt tiek izmantota šķeldas un kurināmā sagatavošanai, mazāk tarai, šķiedras un plātņu ražošanai, kokogļu gatavošanai, gaļas un zivju kūpināšanai.[2]
Baltalksnis (Alnus incana (L.) Moench) ir daudzgadīgs bērzu dzimtas koks. Latvijā bieži sastopams.
De witte els, grauwe els of grijze els (Alnus incana) is een boom die behoort tot de berkenfamilie (Betulaceae). De boom komt van nature voor in Noord- en Midden-Europa, Noord-Amerika en West-Azië.
De boom kan tot 15(25) m hoog worden en heeft een grillig gevormde stam. De piramidale, afgeronde kroon is half open. De gladde bast is grijs en de zeer kort gestelde knoppen hebben en blauwachtige kleur. Het iets grijsgroene blad is eirond tot langwerpig eirond, heeft een dubbel gezaagde bladrand en een spitse top. Het jonge blad is dicht behaard en is bezet met papillen.
De witte els is eenhuizig. De boom bloeit in februari en maart. De geel gekleurde, mannelijke katjes hangen, terwijl de kleine, roodgekleurde, vrouwelijke katjes rechtop staan.
De gevleugelde vrucht is een nootje. Het zaad is rijp in oktober en november.
De boom komt voor in loofbossen op kalkhoudende, vrij natte tot vochtige grond. De soort kan ook goed op droge grond gedijen.
Het hout is zacht en fijn, met een regelmatige tekening, en goed te bewerken. Buiten is het niet duurzaam, tenzij continu onder water (vroeger werden er wel heipalen van gemaakt). Het hout van de witte els is lichtbruin tot geel van kleur en er zitten, regelmatig verdeeld, kleine spiegels in het hout. Het glanst daardoor een beetje.
Er worden door sommige taxonomen de volgende ondersoorten onderscheiden:
Alnus incana subsp. incana
Alnus incana subsp. rugosa
Alnus incana subsp. hirsuta
De cultivar Alnus incana 'Aurea' (ook wel goudels genoemd) wordt gebruikt voor aanplant in stedelijk gebied. Deze is in 1892 in Duitsland ontwikkeld, wordt 5–10 m hoog en heeft geel blad.
De witte els, grauwe els of grijze els (Alnus incana) is een boom die behoort tot de berkenfamilie (Betulaceae). De boom komt van nature voor in Noord- en Midden-Europa, Noord-Amerika en West-Azië.
De boom kan tot 15(25) m hoog worden en heeft een grillig gevormde stam. De piramidale, afgeronde kroon is half open. De gladde bast is grijs en de zeer kort gestelde knoppen hebben en blauwachtige kleur. Het iets grijsgroene blad is eirond tot langwerpig eirond, heeft een dubbel gezaagde bladrand en een spitse top. Het jonge blad is dicht behaard en is bezet met papillen.
De witte els is eenhuizig. De boom bloeit in februari en maart. De geel gekleurde, mannelijke katjes hangen, terwijl de kleine, roodgekleurde, vrouwelijke katjes rechtop staan.
De gevleugelde vrucht is een nootje. Het zaad is rijp in oktober en november.
De boom komt voor in loofbossen op kalkhoudende, vrij natte tot vochtige grond. De soort kan ook goed op droge grond gedijen.
Het hout is zacht en fijn, met een regelmatige tekening, en goed te bewerken. Buiten is het niet duurzaam, tenzij continu onder water (vroeger werden er wel heipalen van gemaakt). Het hout van de witte els is lichtbruin tot geel van kleur en er zitten, regelmatig verdeeld, kleine spiegels in het hout. Het glanst daardoor een beetje.
Gråor eller gråolder (Alnus incana) er eit tre av oreslekta i bjørkefamilien.
Gråora kan på god jord bli oppunder tjue meter høg med stamme og kjegleforma krone. På skrinnare jord eller myrjord veks ho ofte buskaktig.
Gråora har glatt grå bark med eit grønt skjer. Eldre bark kan få eit fåtal djupe furer nedst på stammen. Vinterknoppane er purpurraude, skota er raudbrune på oversida og olivengrøne på undersida. Blada er skarpt tanna matt grøne på oversida og grålege på undersida. Unge blad er hårete over det heile; eldre blad er hårete berre langs nervebanane.
Gråora er av dei tre som blomstrar tidlegast, i Noreg blomstrar ho gjerne i april. Horaklene sit i grupper på 3 til 8 på lysbrune, finhåra stilker. Frøet sit i ein nøttefrukt som flyt godt, slik at ora lett spreier seg langs vassdrag.
Gråor finst i fleire område på den nordlege halvkula. I Noreg veks treet vilt over nesten heile landet.
Gråora veks gjerne på flaummark og i fuktige lier, helst på leirgrunn. Ho er hardfør og toler godt frost.
Gråora er rask til å etablere seg på nye flater, som på rasmark. Treet veks raskt, men det vert ikkje særleg gammalt, ofte berre 40 år, men kan og bli opptil 200 år.
Ora veks i symbiose med soppen Schinzia alni, som lever i knollar på orerøtene. Desse tar opp nitrogen frå lufta. Den rike tilgangen på nitrogen gjer at ora kan tillate seg å felle grøne blad. Slik aukar næringsinnhaldet i skog med oretre.
Utbreiinga til A. incana subsp. incana
Utbreiinga til A. incana subsp. rugosa
Utbreiinga til A. incana subsp. tenuifolia
Vanleg gråor, ssp. incana, er i Noreg vanlegast i låglandet, men manglar ytst på kysten.
Kolagråor, ssp. kolaensis, har meir nordaustleg utbreiing, og er vanleg i fjellskogen.
Mellomformer av underartane er vanlege.
Zunifolk har tradisjonelt brukt gråorbark til å gje hjorteskinn ein raudbrun let.[1]
Veden er laus og lett. Sidan han er lett, er brennverdien tilsvarande låg, omtrent som for gran, med tørr gråorved har den fordelen at han gir lite røyk og lite gnistar.
Under andre verdskrigen vart gråora sterkt etterspurt som brensel i gassgeneratorar, som også vart bruka til framdrift av bilar.
Gråor eller gråolder (Alnus incana) er eit tre av oreslekta i bjørkefamilien.
Gråor eller gråolder (Alnus incana) er et løvtre av oreslekta innenfor bjørkefamilien. Den kan på god jord bli opptil 20 meter høy med stamme og kjegleforma krone. På fattigere jord eller myrjord vokser den ofte buskaktig.
Gråora har glatt grå eller lysegrå bark med et grønt skjær. Eldre bark kan få noen dype furer nederst på stammen. Vinterknoppene er purpurrøde, skuddene er rødbrune på oversida og olivengrønne på undersida. Årskvistene er brungrå og kan være filthårete. Bladene er skarpt tannede og mattgrønne på oversida og grålige på undersida. Unge blad er hårete over det hele, mens eldre blad er hårete bare langs nervebanene. Bladplaten er spist eggeformet eller oval, den er rund eller bare svakt spiss i bunnen, men tydelig spiss ytterst. Nervene er tydelige, oppå er de ofte gulgrønne.
Gråora er blant de trærne som blomstrer tidligst; i Norge blomstrer den gjerne i mars samtidig med hassel. Hunnraklene sitter i grupper på 3 til 8 på lysebrune, finhårede stilker. Frøet sitter i en nøttefrukt som flyter godt, slik at ora lett sprer seg langs vassdrag.
Ora vokser i symbiose med soppen Schinzia alni, som lever i knoller på orerøttene. Disse tar opp nitrogen fra lufta. Den rike tilgangen på nitrogen gjør at ora kan tillate seg å felle grønne blader. Slik øker næringsinnholdet i skog med oretrær.
Gråor finnes i Nord- og Øst-Europa og i Kaukasus. I Norge vokser gråor vilt over nesten hele landet. Gråor vokser gjerne på flommarker og i fuktige lier, og helst på leirgrunn. Den er hardfør og tåler godt frost. Gråora er rask til å etablere seg på nye flater, som på rasmark. Treet vokser raskt, men det blir ikke særlig gammelt, ofte bare 40 år, men kan også bli opptil 200 år.
I Sibir, Øst-Asia og Nord-Amerika finnes nærstående former som enten regnes som underarter av gråor, eller som egne arter.
Vanlig gråor, ssp. incana, er i Norge vanligst i lavlandet, men finnes ikke ytterst på kysten.
Kolagråor (Alnus incana subsp. kolaensis) er en underart som har en mer nordøstlig utbredelse, og er vanlig i fjellskogen nord i Norge og Finland. Den er en busk, og barken dens er brun eller rødbrun. Både knoppene og kvistene er snaue uten hår. Bladplaten blir inntil 5 cm lang, og er rund med svake lapper, og fint tannet. Spissen er butt og bladbunnen er rund eller svakt hjerte-innsnevret mot den rød-gule bladstilken. Bladene er grønne både oppå og under, og nervene er litt lysere gulgrønne.
Sølvgråor (Alnus incana var. argentata) er en varietet av gråor, og vokser i Sverige bare helt innerst i Bottenviken (Tornedalen). Videre vokser den langs hele vestkysten av Finland og nedover i sørlige Finland. Bladet er mørk grønt og tett besatt med sølvgrå hår på oversiden. Det er ganske grovt tannet og nervene oppå er litt nedfuret i bladplaten.
Mellomformer av underartene er vanlige.
Veden er løs og lett. Ettersom den er lett er brennverdien tilsvarende lav, omtrent som for gran, med tørr gråorved har den fordelen at den gir lite røyk og lite gnister.
Under andre verdenskrig ble gråor sterkt etterspurt som brensel i gassgeneratorer, som også ble brukt til framdrift av biler.
Å putte blader fra svart- eller gråor i skoene skal lindre sprukken hud og forebygge gnagsår, ifølge et gammelt kjerringråd, samt hjelpe mot svettelukt om man legger bladene i skoene over natt.
Gråor eller gråolder (Alnus incana) er et løvtre av oreslekta innenfor bjørkefamilien. Den kan på god jord bli opptil 20 meter høy med stamme og kjegleforma krone. På fattigere jord eller myrjord vokser den ofte buskaktig.
Gråora har glatt grå eller lysegrå bark med et grønt skjær. Eldre bark kan få noen dype furer nederst på stammen. Vinterknoppene er purpurrøde, skuddene er rødbrune på oversida og olivengrønne på undersida. Årskvistene er brungrå og kan være filthårete. Bladene er skarpt tannede og mattgrønne på oversida og grålige på undersida. Unge blad er hårete over det hele, mens eldre blad er hårete bare langs nervebanene. Bladplaten er spist eggeformet eller oval, den er rund eller bare svakt spiss i bunnen, men tydelig spiss ytterst. Nervene er tydelige, oppå er de ofte gulgrønne.
Gråora er blant de trærne som blomstrer tidligst; i Norge blomstrer den gjerne i mars samtidig med hassel. Hunnraklene sitter i grupper på 3 til 8 på lysebrune, finhårede stilker. Frøet sitter i en nøttefrukt som flyter godt, slik at ora lett sprer seg langs vassdrag.
Ora vokser i symbiose med soppen Schinzia alni, som lever i knoller på orerøttene. Disse tar opp nitrogen fra lufta. Den rike tilgangen på nitrogen gjør at ora kan tillate seg å felle grønne blader. Slik øker næringsinnholdet i skog med oretrær.
Costo artìcol a l'é mach në sbòss. Da finì.
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Costo artìcol a l'é mach në sbòss. Da finì.
DistribussionDa finì.
NotissieDa finì.
Multimedia w Wikimedia Commons Olsza szara (Alnus incana (L.) Moench) – gatunek rośliny należący do rodziny brzozowatych (Betulaceae A. Gray)[2]. Występuje naturalnie na obszarze niemal całej Europy, na Kaukazie, w zachodniej Syberii oraz Ameryce Północnej[3]. W Polsce olsza szara występuje przede wszystkim w dolinach górskich oraz na nizinach przy brzegach rzek[4]. Jako roślina pionierska i bardzo odporna na zanieczyszczenie powietrza uważana jest za doskonały gatunek do rekultywacji nieużytków poprzemysłowych[5]. Dzięki symbiozie z bakteriami wiąże azot atmosferyczny do gleby, a rozwinięty system korzeniowy umacnia brzegi rzek i skarpy[6].
Gatunek ten rośnie naturalnie na obszarze niemal całej Europy, na Kaukazie, w zachodniej Syberii oraz Ameryce Północnej[3]. Jej zasięg na północ sięga do około 70° szerokości geograficznej – został zaobserwowany nawet na skraju tundry[4]. W Europie i Azji występują podgatunek nominatywny oraz podgatunek A. incana subsp. kolaensis[7][8], natomiast w Ameryce Północnej podgatunki A. incana subsp. rugosa i A. incana subsp. tenuifolia[9][10]. Olsza szara został zarejestrowana w takich państwach jak Francja, Włochy, Szwajcaria, Austria, Niemcy, Norwegia, Szwecja, Finlandia, Polska, Czechy, Słowacja, Węgry, Słowenia, Chorwacja, Bośnia i Hercegowina, Serbia, Czarnogóra, Albania, Macedonia, Bułgaria, Rumunia, Ukraina, Rosja, Gruzja, Azerbejdżan, Armenia, Turcja, Kanada oraz Stany Zjednoczone[3], a według innych źródeł jest spotykana także w Hiszpanii, Irlandii, Wielkiej Brytanii, Danii, Holandii, Belgii, Luksemburgu, Grecji, Mołdawii, na Białorusi, Litwie, Łotwie oraz w Estonii[11].
W Polsce naturalne występowanie olszy szarej charakteryzuje wyraźna dysjunkcja zasięgu. Gatunek ten występuje przede wszystkim w dolinach górskich i podgórskich (częściej w Karpatach, rzadziej w Sudetach)[4] oraz w Polsce północno-wschodniej. Na nizinach spotykany jest przy brzegach rzek spływających z gór, dzięki unoszeniu nasion przez wodę.[12] Dlatego spotkamy go w dolinach Wisły i Odry, zaś jedynie wyjątkowo w dolinach tych ich dopływów, które nie spływają z gór (Bug, Warta, Noteć i in.). W Rosji gatunek ten rośnie w jej europejskich części, zachodniej Syberii, na Przedkaukaziu oraz w Dagestanie[3]. We Włoszech został odnotowany w regionach Dolina Aosty, Emilia-Romania, Friuli-Wenecja Julijska, Lacjum, Liguria, Lombardia, Marche, Piemont, Sardynia, Toskania, Trydent-Górna Adyga i Wenecja Euganejska[11]. We Francji występuje powszechnie w górach Jura i Alpach oraz w Alzacji[6], jednak został zaobserwowany w takich departamentach jak Finistère, Calvados, Orne, Manche, Eure-et-Loir, Sekwana i Marna, Yvelines, Essonne, Hauts-de-Seine, Sekwana-Saint-Denis, Dolina Oise, Somma, Sekwana Nadmorska, Nord, Oise, Pas-de-Calais, Aisne, Ardeny, Marna, Meurthe i Mozela, Dolny Ren, Górny Ren, Górna Marna, Górna Saona, Wogezy, Yonne, Territoire-de-Belfort, Côte-d’Or, Doubs, Nièvre, Jura, Saona i Loara, Creuse, Pireneje Wysokie, Aveyron, Cantal, Ain, Rodan, Isère, Sabaudia, Górna Sabaudia, Ardèche, Drôme, Alpy Górnej Prowansji, Alpy Wysokie, Alpy Nadmorskie, Delta Rodanu, Var i Vaucluse[13], a według innych źródeł także w departamentach Loara, Górna Loara, Ariège, Pireneje Wschodnie, Żyronda, Cher, Indre i Loara, Maine i Loara, Loiret, Eure, Aube, Moza oraz Mozela[14]. Ponadto rośnie na francuskim archipelagu Saint-Pierre i Miquelon w Ameryce Północnej[15]. W Kanadzie został zarejestrowany we wszystkich prowincjach i terytoriach oprócz Nunavut. W Stanach Zjednoczonych jest spotykany na Alasce, w stanie Waszyngton, Oregonie, Kalifornii, Nevadzie, Arizonie, Nowym Meksyku, Kolorado, Utah, Wyoming, Idaho, Montanie, Dakocie Północnej, Minnesocie, Iowa, Wisconsin, Michigan, Illinois, Indianie, Ohio, Wirginii Zachodniej, Wirginii, Maryland, Pensylwanii, Rhode Island, New Jersey, stanie Nowy Jork, Massachusetts, Connecticut, New Hampshire, Vermont oraz Maine[3][16].
Rośnie na brzegach rzek, na terenach wilgotnych, bogatych w składniki odżywcze. W górach Kaukaz występuje do wysokości 1000 m n.p.m.[5], we Włoszech do 1300 m n.p.m.[11], a we Francji do 1500 m n.p.m.[6] Preferuje stanowiska w półcieniu lub w całkowitym zacienieniu[18]. Najlepiej rośnie na podłożu o obojętnym jak i lekko zasadowym odczynie (od 6,8 do 7,2 w skali pH)[15] (w przeciwieństwie do olszy czarnej (Alnus glutinosa), która unika gleb wapiennych)[6]. Występuje od 2 do 6 strefy mrozoodporności[18]. Charakteryzuje się silnym wzrostem[5]. Jak na drzewo jest gatunkiem krótko żyjącym – rzadko żyje dłużej niż 40 lat[15]. Roślina jednopienna[5]. Kwitnie od lutego do marca[18], a według innych źródeł od marca do kwietnia[6]. Jest rośliną wiatropylną[18].
Roślina znosi klimat morski[18]. W klasyfikacji zbiorowisk roślinnych gatunek charakterystyczny dla All. Alno-Ulmion, Ass. Alnetum incanae[19].
Potrafi wiązać azot atmosferyczny dzięki symbiozie z bakteriami, udostępniając go później innym roślinom. Także liście, bogate w azot, po opadnięciu poprawiają jakość gleby. Dzięki rozwiniętemu systemowi korzeniowemu wzmacnia brzegi rzek i skarpy. Jego drewno po ścięciu nie zmienia barwy na czerwonopomarańczową jak ma to miejsce u olszy czarnej[6].
Na glebach żyznych i wilgotnych tworzy zwarte zarośla i wyrasta w drzewa, na glebach suchych i ubogich zawsze pozostaje krzewem dającym dużo odrośli korzeniowych. W górach sięga zazwyczaj po regiel dolny, najwyżej po 1281 m n.p.m. Megafanerofit. Liczba chromosomów 2n = 28[potrzebny przypis].
Gatunek zróżnicowany na cztery podgatunki[2]:
Kiełkuje większość świeżych nasion tego gatunku bez wstępnej obróbki. Jeśli nasiona są wysuszone, konieczna jest wilgotno-chłodna stratyfikacja w temperaturze 5 °C (41 °F) przez 180 dni[15].
Olsza szara (Alnus incana (L.) Moench) – gatunek rośliny należący do rodziny brzozowatych (Betulaceae A. Gray). Występuje naturalnie na obszarze niemal całej Europy, na Kaukazie, w zachodniej Syberii oraz Ameryce Północnej. W Polsce olsza szara występuje przede wszystkim w dolinach górskich oraz na nizinach przy brzegach rzek. Jako roślina pionierska i bardzo odporna na zanieczyszczenie powietrza uważana jest za doskonały gatunek do rekultywacji nieużytków poprzemysłowych. Dzięki symbiozie z bakteriami wiąże azot atmosferyczny do gleby, a rozwinięty system korzeniowy umacnia brzegi rzek i skarpy.
Alnus incana é uma espécie de planta com flor pertencente à família Betulaceae.
A autoridade científica da espécie é (L.) Moench, tendo sido publicada em Methodus Plantas Horti Botanici et Agri Marburgensis : a staminum situ describendi 424. 1794.
Trata-se de uma espécie presente no território português, nomeadamente no Arquipélago dos Açores.
Em termos de naturalidade é introduzida na região atrás indicada.
Não se encontra protegida por legislação portuguesa ou da Comunidade Europeia.
Alnus incana é uma espécie de planta com flor pertencente à família Betulaceae.
A autoridade científica da espécie é (L.) Moench, tendo sido publicada em Methodus Plantas Horti Botanici et Agri Marburgensis : a staminum situ describendi 424. 1794.
Síva jélša (znanstveno ime Alnus incana) je listopadno drevo severne poloble.
Ime »siva« je drevo dobilo po obarvanosti mladih poganjkov in listnih pecljev. Drevo zraste od 10 do 20 metrov visoko, ima pa gladko, svetlečo skorjo svetlo sive barve.
Listi so jajčasto elipsaste oblike, nameščeni pa so na peclju z dlakavim prilistom. Listni rob je dvojno narezan, pri dnu pa je zaokrožen. Zgornja stran je gladka in temno zelene barve, spodnja pa svetlo siva in dlakava.
Drevo ima enospolne cvetove, ki so združeni v mačice. Moški cvetovi se na drevesu pojavijo pred listi in so dolgi ter viseči. Ženski cvetovi so manjši in krajši ter nimajo pecljev. Združeni so v socvetja, v katerih je od 2 do 5 cvetov. Plodovi so podobni storžkom in so združeni v soplodja. Drobni okrogli oreški z olesenelimi luskami so glavni način razmnoževanja sive jelše.
Siva jelša je hitro rastoče drevo, ki uspeva tudi v slabših pogojih. Rada se zadržuje v bolj vlažni zemlji in dobro prenaša mraz. Razširjena je v višjih območjih severne Evrope, srednje in severne Azije ter v Severni Ameriki. Z listi sive jelše se prehranjujejo nekatere gosenice.
Obstaja več podvrst sive jelše, ki jih nekateri avtorji smatrajo za samostojne vrste:
Síva jélša (znanstveno ime Alnus incana) je listopadno drevo severne poloble.
Gråalen (Alnus incana) (vital[1]) är ett tidigt blommande hängeträd och tillhör alsläktet. Den är en av de två vanliga alarna i Sverige; den andra är klibbalen. I stora delar av Götaland kallades den i äldre tid arre.[2]
Gråalen invandrade från Finland omkring 3000 f.Kr., ungefär samtidigt som granen kom från samma håll. Den spred sig mot fjällkedjan till skogsgränsen och i fjällskogsbältet har den fortfarande sin västligaste utbredning. I norra Svealand mötte gråalen sin släkting, klibbalen, och gråalen har idag sin sydliga utbredning ungefär till norrlandsgränsen.[3]
Gråalen är idag Gästriklands landskapsträd.[3]
Gråalen är ett mindre träd (dock i planteringar någon gång mycket storväxt) med slät, vitgrå bark och gråaktiga och håriga bladundersidor.[1] Bladskivan är äggrund och tillspetsad. Blomningen inträffar något tidigare än hos klibbalen.
Inte bara hanhängena övervintrar utan skyddsblad (som hos hassel och björk) utan även honaxen. Innanför hanhängets skärmblad sitter 4 förblad och 3 blommor med tydlig, 4-bladig kalk; inom honaxets skärmblad sitter 4 förblad och 2 blommor, som består av endast en pistill (jämför med hasseln och björken!). I motsats till björkarna får alsläktet förvedad fruktställning, eller "kotte" med kvarsittande fjäll, som till följd av sin uppkomst är mer eller mindre tydligt 5-flikiga. Nöten saknar hinnkanter. Alarna skiljer sig från våra övriga träd genom sina skaftade knoppar.
Gråalens huvudområde är de lägre fjälltrakterna, där den på stränder och annan fuktig mark bildar stora bestånd och täta snår i sällskap med fjällbjörk och stora viden. Den går dessutom, fast sällsynt, långt ned i söder, ända till sydöstra Skåne.
I mellersta Skandinavien och Finland finns också andra alar, som sannolikt är hybrider mellan klibbal (A. glutinosa) och gråal. De går under det vetenskapliga namnet (Alnus × pubescens Tausch). Hybriden finns i vida trakter av Norrland och Lappland, där åtminstone klibbalen inte finns numera. Man kan därför anta att klibbalen, som är mindre härdig, förr haft större utbredning mot norr, men dragit sig tillbaka av klimatologiska skäl, vilka däremot ej haft något inflytande på den härdigare hybriden.
Arten har stort utbredningsområde och tre underarter kan urskiljas:
Tidigare räknades lappal (A. kolaensis) som en underart, men upptas här som självständig art.
Wikimedia Commons har media som rör Gråal.
Gråalen (Alnus incana) (vital) är ett tidigt blommande hängeträd och tillhör alsläktet. Den är en av de två vanliga alarna i Sverige; den andra är klibbalen. I stora delar av Götaland kallades den i äldre tid arre.
Alnus incana là một loài thực vật có hoa trong họ Betulaceae. Loài này được (L.) Moench mô tả khoa học đầu tiên năm 1794.[2]
Alnus incana là một loài thực vật có hoa trong họ Betulaceae. Loài này được (L.) Moench mô tả khoa học đầu tiên năm 1794.
Почки стебельчатые, яйцевидные или яйцевидно-шаровидные, на вершине слегка притуплённые, пушистые. Листья расположены в три ряда[2], очерёдные, овальные, овально-ланцетные или яйцевидно-округлые, реже эллиптические, длиной 4(4,5[3])—10 см, шириной 3,5—7 см, острые или остроконечные, реже притуплённые, с округлым или слабо сердцевидным основанием, остро-двоякопильчатые, молодые густо-пушистые, не липкие, взрослые сверху почти голые, снизу серо-зелёные, без бородок в углах нервов, на мягко волосистых или войлочных черешках длиной 1—2(3[3]) см. Молодые листья не клейкие[5].
Тычиночные серёжки вершинные, собраны по три—пять вместе, сидячие или на коротких пушистых ножках, содержат при каждой чешуйке по три цветка с четырьмя тычинками с раздвоенными пыльниками[2]. Пестичные цветки собраны по восемь—десять пучками на общем цветоносе, то под мужскими серёжками, то на вершинах ветвей, эллиптические, чёрно-бурые, длиной около 1,5 см, диаметром 7—8 см, содержат при каждой чешуйке по два цветка; пестик с двумя нитевидными пурпуровыми рыльцами, выступающими из-за чешуй[2]. Цветёт в марте — апреле, до появления листьев, на одну—две недели раньше, чем ольха клейкая[5].
Плоды — обратнояйцевидные орешки с узкими, перепончатыми крыльями, 10 мм длиной и 7—8 мм шириной[3], созревающие в шишках, вдвое легче, чем у ольхи клейкой. Плоды созревают осенью, осыпаются и разносятся ветром[5]. В 1 кг 1 430 000 орешков; вес 1000 орешков — 0,5—0,9 г.
Плодоношение ежегодно, обильное. Семенные экземпляры начинают плодоносить с восьми—десяти лет; порослевые с пяти—семи лет[5].
В природе ареал вида охватывает практически всю территорию Европы, Малую Азию, Закавказье, Западную Сибирь и Северную Америку[7]. Северная граница ареала начинается в Швеции, проходит через Кольский полуостров, через весь север европейской части России и через всю Сибирь до Камчатки. Растёт в Сербии, Северной Италии и во Франции. Больше всего её на севере и северо-востоке европейской части России[3].
Растёт на равнинах в лесной и, реже, лесостепной и лесотундровой зоне. Образует так называемые сероольшатники — кустарниковые и мелколесные заросли на заболоченных опушках, болотах, у берегов рек, на лесосеках, пожарищах и заброшенных пашнях. Встречается вдоль ручьев и рек вместе с ивами и чёрной ольхой. Чистых насаждений не образует, вопрос о первичности или вторичности сероольшатников по балкам, оврагам и окраинам болот остаётся нерешённым. Благодаря обильному плодоношению, лёгкости распространения семян и хорошей их всхожести быстро заселяет вырубки, гари, заброшенные пашни, образуя временные ассоцияации, постепенно сменяющимися первичными фитоценозами. Чаще всего сероольшатники образуются на месте еловых и мелколиственных лесов, обратная смена ольхи елью происходит в течение 50—60 лет. Пастьба скота и вырубка леса в таких зарослях способствует более быстрому вегетативному размножению ольхи и более длительному существованию её ассоциаций. На Кавказе поднимается до 2000 м над уровнем моря, встречаясь единично или группами в среднем и верхнем горном поясах, на заброшенных пашнях и лесных полянах[4].
В Сибири, Забайкалье и Приамурье сосуществует рядом с близким видом ольхой пушистой (Alnus hirsuta (Spach) Rupr.) и замещается ей[5].
К почвам менее требовательна, чем чёрная ольха, хотя на бедных сухих песчаных почвах встречается редко; заболачивание переносит лучше, чем чёрная ольха. Предпочитает известковую, влажную почву и свободное стояние, хотя часто растёт и в густых посадках[3]. Сама обогащает почву азотом. Зимостойка. Теневыносливее, чем осина и берёза повислая, но предпочитает хорошо освещённые местообитания.
Наиболее распространёнными типами сероольшатников являются кисличный и снытевый на свежих дерново-подзолистых, сильно- или средне-оподзоленных почвах. Они возникают на месте ельников кисличных или сероольшатников черничных. В кисличных и снытевых сероольшатниках происходит интенсивное восстановление ели и быстрая смена их ельниками. По берегам рек, ручьёв, в оврагах, увлажнённых понижениях на перегнойно-глеевых, суглинистых и глинистых почвах, на небольших участках возникают таволговые и крупнопапоротниковые сероольшатники. Они возникают на месте хвойных, широколиственно-еловых и широколиственно-елово-черноольховых лесов и способны к длительному существованию. На песчаных и слабо увлажнённых почвах сероольшатники возникают редко и быстро сменяются сосной и елью. Такие сероольшатники возникают на гарях и вырубках сосняков брусничных. Ещё реже возникают осоковые сероольшатники на переувлажнённых почвах. Они недолговечны и имеют примесь берёзы, ивы. На небогатых свежих почвах водоразделов на месте ельников черничных возникают очень кратковременные сероольшатники черничные, сменяющиеся черноольшатниками кисличными и вейниковыми. Сероольшатники злаковые возникают на месте заброшенных пашен. Они неустойчивы и сменяются ельниками[4].
Ольха серая образуется много семян, но прорастает только их небольшая часть. Более эффективно вегетативное размножение обильными корневыми отпрысками. Растёт быстро. Живет 50—70, редко 150 лет[5].
Ольха серая в лесомелиоративных насаждениях используется на севере лесостепи для закрепления берегов рек, склонов и оврагов.
Древесина плотная, мягкая, отличается от древесины ольхи чёрной (Alnus glutinosa) более красным цветом; используется для производства столярных и токарных изделий, а также на подводные постройки[2]. Древесина ольхи серой имеет ряд полезных свойств, важных в строительстве. Она практически не поглощает пары, содержащиеся в воздухе, и жидкости, попадающие на её поверхность. Древесина не трескается и не усыхает под воздействием жара или резкого охлаждения. Масло, содержащееся в древесине, источает приятный древесный аромат. В лучших древостоях запас древесины достигает 250 м³/га[5].
Дрова из ольхи серой горят хорошо, но уголь не удерживает жару. Ольховые дрова использовались русскими крестьянами для выжигания сажи из печных труб, особенно после использования берёзовых дров. Дрова ценятся для производства рисовального (чертёжного) угля и угля, идущего на изготовление пороха. Ольховая стружка считается лучшей для упаковки фруктов[2].
Ольха серая весной даёт пчёлам много пыльцы, которой укрыты молодые листочки и побеги. Пчеловоды рекомендуют подкармливать пчёл пыльцой ольхи ещё до её цветения. Для этого срезают веточки, кладут в тёплом помещении в сито, застелённое бумагой. Как только пыльники откроются, сито осторожно встряхивают, и пыльца высыпается на бумагу. Её смешивают с мёдом и сахарным сиропом и дают пчёлам[2].
Листья идут на корм козам и овцам[2]. Почки и верхушки ветвей служат кормам рябчикам и тетеревам в зимний период[2].
В шишках ольхи серой содержатся алкалоиды, дубильные вещества, фенолкарбоновые кислоты, флавоноиды, жирное масло, тритерпеноиды, алифатические спирты, стероиды. Кора содержит тритерпеноиды, дубильные вещества. Листья ольхи содержат провитамин А (каротин), витамин С, фенолкарбоновые кислоты, дубильные вещества, антоцианы.
Препараты коры и шишек ольхи серой оказывают вяжущее, противовоспалительное, кровоостанавливающее действие, а свежие листья являются потогонным средством. Препараты шишек ольхи применяются при лечении острых и хронических воспалений тонких (энтероколитах) и толстых (колитах) кишек.
В официнальной медицине препараты из ольхи серой применяют как вяжущее и кровоостанавливающее средство, особенно при заболеваниях желудочно-кишечного тракта, острых и хронических энтеритах и колитах. Отмечено благотворное действие отваров коры, шишек и листьев ольхи при суставном ревматизме, простудных заболеваниях и поносах у детей.
Отвары коры обладают противомикробным действием и снижают риск проявления аллергии, применяются при ревматическом полиартрите и в случае простудных заболеваний.
Ольха серая, как и другие виды ольхи, обогащает почву азотом[5].
На ольхе серой паразитируют несколько видов аскомицетов рода Тафрина (Taphrina). Taphrina alni поражает женские серёжки, вызывает листовидные разрастания их чешуек; Taphrina epiphylla вызывает появление «ведьминых мётел», пятнистость и сморщивание листьев[8].
Вид Ольха серая входит в род Ольха (Alnus) подсемейства Берёзовые (Betuloideae) семейства Берёзовые (Betulaceae) порядка Букоцветные (Fagales).
По данным The Plant List на 2013 год, в синонимику вида входят[9]:
В рамках вида выделяют несколько разновидностей[7]:
Почки стебельчатые, яйцевидные или яйцевидно-шаровидные, на вершине слегка притуплённые, пушистые. Листья расположены в три ряда, очерёдные, овальные, овально-ланцетные или яйцевидно-округлые, реже эллиптические, длиной 4(4,5)—10 см, шириной 3,5—7 см, острые или остроконечные, реже притуплённые, с округлым или слабо сердцевидным основанием, остро-двоякопильчатые, молодые густо-пушистые, не липкие, взрослые сверху почти голые, снизу серо-зелёные, без бородок в углах нервов, на мягко волосистых или войлочных черешках длиной 1—2(3) см. Молодые листья не клейкие.
Тычиночные серёжки вершинные, собраны по три—пять вместе, сидячие или на коротких пушистых ножках, содержат при каждой чешуйке по три цветка с четырьмя тычинками с раздвоенными пыльниками. Пестичные цветки собраны по восемь—десять пучками на общем цветоносе, то под мужскими серёжками, то на вершинах ветвей, эллиптические, чёрно-бурые, длиной около 1,5 см, диаметром 7—8 см, содержат при каждой чешуйке по два цветка; пестик с двумя нитевидными пурпуровыми рыльцами, выступающими из-за чешуй. Цветёт в марте — апреле, до появления листьев, на одну—две недели раньше, чем ольха клейкая.
Плоды — обратнояйцевидные орешки с узкими, перепончатыми крыльями, 10 мм длиной и 7—8 мм шириной, созревающие в шишках, вдвое легче, чем у ольхи клейкой. Плоды созревают осенью, осыпаются и разносятся ветром. В 1 кг 1 430 000 орешков; вес 1000 орешков — 0,5—0,9 г.
Плодоношение ежегодно, обильное. Семенные экземпляры начинают плодоносить с восьми—десяти лет; порослевые с пяти—семи лет.
Число хромосом 2n = 28.
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