nimet breadcrumb-navigoinnissa
This description covers characteristics that may be relevant to fire ecology and is not meant for identification. Keys for identification are available (e.g., [17,52,70,97,113,141]).
Morphology: Feltleaf willow is a tree or shrub 2 to 33 feet (0.5-10 m) tall [17,52,89,97,141]. It typically grows in clumps of 5 to 20 stems [51]. Branches are typically erect, but in exposed High Arctic and alpine sites feltleaf willow may have a prostrate or semiprostrate form [17,76,141]. Trunks may be 4 to 7 inches (10-18 cm) in diameter [141]. Heavy browsing commonly hedges feltleaf willows [20,75,125].
Leaves are deciduous, alternate, and simple. They are 2.0 to 4.3 inches (5-11 cm) long and 0.4 to 1.6 inches (1-4 cm) wide [52,76,141].
The inflorescence is a catkin. Male catkins are 1.2 to 2.0 inches (3-5 cm) long, and female catkins are 2.0 to 5.9 (5-15 cm) long [97]. The fruit is a capsule, which splits open to release the seeds. A tuft of hairs plumes each seed [76].
Willow roots are typically shallow [69]. Feltleaf willow sometimes forms adventitious roots [78].
Stand structure: Feltleaf willow stands are open to closed [45,88,134]. Closed feltleaf willow stands (canopy closure >75%) are characteristic of floodplains and outwash deposits, while open feltleaf willow stands (canopy closure 25%-74%) occupy a variety of sites from sand dunes to riverbanks [134]. Along the Tanana River floodplain near Fairbanks, feltleaf willow density was approximately 8,300 stems/ha in 8-year-old stands and 30,000 stems/ha in 15-year-old stands [151]. On the Susitna River floodplain in south-central Alaska, there were approximately 8,600 feltleaf willow stems/ha [32].
Feltleaf willows may live >80 years [51,149]. On western Victoria Island, the oldest feltleaf willow was 81 years old; 3- to 7-foot (1-2 m) tall feltleaf willows ranged from 21 to 56 years old and 5- to 7-foot (1.5-2 m) tall feltleaf willows were ≥45 years old. The youngest willows occurred closest to the active river channel, while the oldest occurred farthest away [51]. On the Tanana River floodplain, the youngest feltleaf willows (mean: 6.7 years old) occurred on vegetated siltbars and the oldest (mean: 47 years old) occurred on upper balsam poplar terraces [144].
Feltleaf willow is native to northern North America and eastern Siberia. In North America, it occurs from Alaska south to British Columbia to about 53 °N latitude, east to Québec, and north to Nunavut [17,70,72,97].
States and provinces [128]:
United States: AK
Canada: AB, BC, MB, NT, NU, QC, YT
Fire adaptations: Feltleaf willow sprouts from the root crown following fire [54,155]. Sprouts likely develop more rapidly than seedlings after fire [60,155]. Feltleaf willow's lightweight seeds may be dispersed by wind or water after fire [44,93,100,161]. Its seeds readily germinate in high light and in moist mineral soils [44]. It has a transient soil seed bank [44,50,110,144,161]. Out of 30 species examined in black spruce forests in interior Alaska, feltleaf willow ranked moderate in expected occurrence after fire. It occurred in plots after low-, moderate-, and high-severity fires in 14 black spruce communities that burned during wildfires in 2004, even though it was not observed in these plots before the fires [6,7].
Plant response to fire: Feltleaf willows typically sprout after fire [54,155]. Feltleaf willow has a transient soil seed bank [44,50,110,144,161], and seeds are unlikely to survive fire if burned [138] (see Immediate fire effects on seeds). However, wind and water may disperse seeds from nearby sources [44,93,100,161], and surviving on-site plants may produce abundant seeds [93] soon after fire.
Fire severity affects the mode of feltleaf willow postfire recovery. Following low-severity fires, most willows recover quickly, sending up new shoots from root crowns. Few, if any, willow seedlings establish following low-severity fire because organic soils are only partially consumed and prevent establishment. Following severe fires, however, the primary mode of willow recovery is seedling establishment. Severe fires that burn deeply into organic soils may kill willows but expose mineral soils, which provide excellent seedbeds for willows, including feltleaf willow [163]. A comparison of prefire and postfire vegetation at 14 burned black spruce forest sites burned in wildfires in interior Alaska during 2004 found that there was an increase in feltleaf willow occurrence in 900-m² plots, especially on high-severity and high-moisture sites [66]. Following experimental fires on black spruce/feather moss sites in interior Alaska, artificially sown feltleaf willow seeds germinated only on plots where fire removed all organic matter. On these plots, 181 seedlings out of 400 survived 3 growing seasons, but no seedlings survived on plots where burning only partially removed organic soil layers (Table 1) [163]. See the Research Project Summary of Zasada and others' [48,162,163] studies for detailed information.
Table 1. Total number of feltleaf willow germinants and willow seedlings on moderate- and high-severity plots [163] Germinants 1st-year seedlings 3rd-year seedlings ModerateBecause willow seeds are viable for only a few weeks, the time of fire may be important in determining which species of willow colonizes a burn the first postfire year [138]. Early-summer fires that occur prior to seed dispersal are most likely to favor feltleaf willow because newly dispersed seeds would be available to germinate on burned areas soon after fire. Late-summer fires are more likely to favor willows that disperse seeds in late summer and fall, such as grayleaf willow [138,158].
For further information on prescribed fire and postfire response of feltleaf willow and other plant species in Alaskan taiga, see these Fire Studies:
Fuels: Feltleaf willow stands on floodplains are moist and commonly contain few fine fuels, such as grass, so they do not burn readily [98]. However, total fuel loadings in feltleaf willow communities can be abundant. Mean total biomass of feltleaf willow can exceed 5,500 kg/ha [83,84,121,133].
FIRE REGIMES: Fire is not considered an important disturbance in feltleaf willow communities, where the main disturbance processes are frequent flooding and sediment deposition. Suarez and others [123] found no evidence of fire in a white spruce/feltleaf willow-grayleaf willow-bog blueberry community along the Agashashok River in northwestern Alaska. Parminter [99] stated that alluvial balsam poplar-white spruce floodplain forests of northern British Columbia owe their existence to fluvial processes and "have not been influenced by fire to a significant degree, if at all". Feltleaf willow may occasionally occur after fire in communities, such as black spruce forests, where fire plays a major role in ecosystem dynamics [38,99].
Find 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".
Feltleaf willow seeds do not show dormancy. Viable feltleaf willow seeds germinate in high light within 1 day of dispersal on moist seedbeds [44]. Germination of new seeds is high, often exceeding 90%. Feltleaf willow seeds germinate at a range of temperatures [44,159,160]. In a laboratory, good germination (94%-97%) occurred at temperatures from 41 to 77 °F (5-25 °C) [160]. Stratification is not required [44,159,160]. Continual freezing in a laboratory can preserve viability of feltleaf willow seeds for at least 3 years, although germination rates of frozen seeds are less than that of fresh seeds (59%-74% for seeds frozen 36 months) [160].
High soil moisture is important to feltleaf willow germination [8,161]. In a laboratory, Feltleaf willow seeds collected from riverbars in interior Alaska germinated under water [77]. In the field, the highest feltleaf willow germination percentages of previously frozen seeds occurred in plots that were watered regularly (3.2% germination) and in plots in which stones had been added (1.2%). Stones apparently provided "safe sites" protected from the drying effects of wind and sun [8].
Moist mineral soil is typically the most suitable substrate for feltleaf willow germination, but other substrates, such as moss, are adequate when moist [8,161]. Feltleaf willow germinated on a variety of mineral soils on the Sagavanirktok River floodplain, provided they were moist [93]. Densmore and Zasada [44] observed rapid germination of feltleaf willow seeds on wet silt and in shallow water on the Tanana River floodplain; many seeds germinated within 24 hours after reaching the seedbed. On moist silt, seeds germinated only after 48 hours. Hypocotyl hairs (which anchor seedlings to substrates) were less developed on moist than wet silt [44]. Forest litter prevents feltleaf willow germination [144]. In thinleaf alder, balsam poplar, and white spruce communities on the Tanana River floodplain, germination of sown feltleaf willow seeds was 0% on forest litter. It ranged from 16% to 18% where forest litter was removed and mineral soil exposed [144].
Seed dispersal in feltleaf willow normally coincides with the retreat of spring floodwaters, when soil moisture is favorable for germination [77,144]. Bare gravel with shallow subsurface water movement provides some of the best germination substrate [41]. Silt is often moist enough for feltleaf willow establishment, while sand is rarely moist enough. Only during unusually wet years will soils on sandy sites be moist enough for germination to occur [77]. In a gravel mine on the North Slope, all moist gravels were rapidly colonized by feltleaf willow; moist silts were rapidly colonized by a mixture of feltleaf willow and low-statured willows; and dry soils were colonized by low-statured willows or no willows [41]. Along the Tanana River, feltleaf willow and sandbar willow were more common than balsam poplar on wet, frequently inundated sites. Only balsam poplar and sandbar willow were commonly found on xeric, sandy sites. All 3 species grew on mesic, silty sites [77].
Mammals: Feltleaf willow is a very important browse species for moose, particularly in winter [4,25,32,58,84,91,101,107,109,151]. When browsing, moose often break and pull down feltleaf willow branches and trunks up to 1.5 inches (4 cm) in diameter [141]. Milke [90] considered feltleaf willow one of the most important moose browse species in interior Alaska because of its high palatability, wide distribution, and relatively high abundance. In some areas of the North Slope, it provided >95% of winter moose browse (Neiland and others 1981 cited in [41]). Mean browsing intensity of feltleaf willow by moose in 14 stands in Denali National Park was 65% (range: 35%-86%); browsing was heavier in pure feltleaf willow stands than in mixed stands [154]. Moose forage preferentially on new growth of previously browsed plants [14,15,92]. Use of feltleaf willow by moose in winter may increase in years of deep snow and decrease in years of shallow snow. In the Tyone Creek and Oshetna River drainages in Alaska, winter use of feltleaf willow ranged from a high of 82% during a winter of record deep snow to a low of 12% during a winter of shallow snow (P<0.01) [31]. Feltleaf willow is also important browse for caribou, reindeer [79,115,147], and muskoxen [51,111,147].
Numerous small mammals eat feltleaf willow. Feltleaf willow is highly preferred food of snowshoe hares [25,56,152], Alaskan hares [3], and arctic ground squirrels [5].
Birds: During winter, willow ptarmigan feed preferentially on feltleaf willow, which may make up to 80% of their diet [22,145]. In April and May, willow ptarmigan consumed feltleaf willow catkins until the supply was "completely exhausted" [94]. Northeast of Toolik Lake, willow ptarmigan browsed 42% of feltleaf willow buds [125]. Snow depth affects willow ptarmigan browsing of feltleaf willow. In an area of tall riparian shrublands at Toolik Lake Field Station, 3% of feltleaf willow buds buried beneath the snow were browsed, 90% of buds <12 inches (30 cm) above the maximum snow depth were browsed, and 45% of buds above that height were browsed [125].
Insects: See these sources for information on insects common on feltleaf willow: [57,85,87].
Palatability and nutritional value: Feltleaf willow is highly palatable to moose [108]. A review stated that high moisture, protein, and caloric contents of feltleaf willow likely explain the high preference of feltleaf willow to moose [101]. Concentrations of phenolic compounds in feltleaf willow were the lowest of 8 tree and shrub species tested in Denali National Park and Preserve, but concentrations of condensed tannins were highest [109].
Feltleaf willow is moderately to highly palatable to snowshoe hares [21,23,114]. Feltleaf willow palatability to snowshoe hares increases with increased shading and increased soil nutrients [19,20,21]. Rohleder (1985 cited in [20]) found that feltleaf willow growing under alder on the floodplain of the Chena River near Fairbanks, Alaska, was 4 times more palatable to snowshoe hares than feltleaf willow grown in full sun [20]. Feltleaf willow stump sprouts were less palatable to snowshoe hares than mature twigs from adult plants in laboratory feeding trials. Sprouts came from the confluence of the Tanana and Chena rivers near Fairbanks [23,114].
For information on nutrient concentrations in feltleaf willow, see these studies: [15,20,82,109,114,126,130,131,146].
Cover value: Feltleaf willow communities provide cover and habitat for wildlife, including moose [46,59,81,91,124,127], muskoxen [111], snowshoe hares [153], willow ptarmigan [94], and undoubtedly numerous other species. Feltleaf willow was one of the most common species used for nest sites by yellow warblers in Churchill, Manitoba [150]. In summer, brown bears in Denali National Park frequently foraged in feltleaf willow-alpine sweetvetch communities in alpine areas along the Toklat River [120].
Nonnative Species:
Nonnative, invasive yellow sweetclover appears to inhibit feltleaf willow recruitment and growth. A removal study along the Healy and Nenana rivers, Alaska, found that dense patches of yellow sweetclover reduced recruitment of feltleaf willow during the earliest seral stages of glacial floodplain succession, apparently due to shading. Feltleaf willow seedlings growing in plots with yellow sweetclover had lower survival rates than seedlings growing with native vegetation (P<0.05) [116,117]. Along the Stikine River, Alaska, feltleaf willow importance was highest in belt transects where yellow sweetclover importance was low, suggesting a negative competitive interaction [33,34].
Seeding with nonnative grasses may reduce feltleaf willow density and cover. Along the Atigun River in the central Brooks Range, feltleaf willow density, cover, and branch length were less on 11-year-old disturbed sites that were fertilized and seeded with nonnative red fescue than on adjacent disturbed sites that were naturally revegetated. Red fescue probably reduced soil moisture in the upper soil profile [43].
Feltleaf willow occurs in northern climates with large seasonal variations in light and temperature and short growing seasons [10]. It occurs throughout Alaska, where the climate varies from maritime with abundant precipitation along coastal areas in the south-central and southeastern regions to dry continental with temperature extremes in the interior. The record low and high temperatures are -80 and 100 °F (-62 and 38 °C), respectively. Abrupt spring and fall temperature changes are common. Southern coastal areas average 145 freeze-free days, while interior lowland basins average <100 freeze-free days [88].
Plant communities: Feltleaf willow dominates and is typically dense in early-seral riparian communities on newly exposed alluvial deposits that are periodically flooded (e.g., [47,70,76,88,95,129,139,141,142,143]). It is also dominant on active sand dunes [13,89,102,142,147]. Sand dune communities typically have only sparse plant cover (<1%), and the bases of feltleaf willows are often buried by wind-deposited sand [89].
Feltleaf willow frequently occurs along shores of lakes and ponds [30,76,88,89,97,113], on mesic talus slopes [36,76,95], and in tall shrub tundra [10]. It is sparse in upland riparian terraces dominated by balsam poplar, white spruce [89,134], and/or black cottonwood [63,89]. It occurs occasionally in black spruce [76,137,140,141] and Sitka spruce [37] forest openings.Feltleaf willows may produce abundant seeds [93]. In feltleaf willow communities along river floodplains in Alaska, feltleaf willow produced from 131 to 380 viable seeds/m² [93,144]. However, feltleaf willow may not produce catkins every year. At 3 sites on the Sagavanirktok River floodplain, 58% to 78% of individuals produced catkins in 1979, and 33% to 67% produced catkins the following year [93].
Feltleaf willow sprouts may flower at 3 years old [23], while plants established from seeds flower at approximately 6 to 10 years old [93]. Seed production peaked at approximately 15 to 20 years old on the Sagavanirktok River floodplain. The most fecund plants generally grew where herbs and low shrubs were not well developed and mineral soil was exposed. These areas were periodically flooded [93].
Heavy browsing may reduce catkin abundance and thus seed production [161]. For more information, see IMPORTANCE TO LIVESTOCK AND WILDLIFE.
Figure 3. Close-up of female feltleaf willow catkins along the Meade River, Alaska. Photo courtesy of the Alaska Geobotany Center.Feltleaf willow establishes in mineral substrates that are moist throughout the growing season [100], and recruitment may be infrequent. Studies in interior Alaska along Birch Creek [35] and the Tanana River [77] found few feltleaf willow seedlings established in dry mineral soils. Late ice breakup in spring delayed feltleaf willow seed production and thus dispersal on the Mackenzie River Delta in the Northwest Territories during 2 years, leaving a very short period for seedlings to grow large enough to survive ice breakup, flooding, and sedimentation the following spring. Unusually warm temperatures and low rainfall during the 2 growing seasons reduced feltleaf willow establishment. Feltleaf willow age structure indicated that recruitment occurred infrequently. The authors concluded that feltleaf willow recruitment may only occur in years when spring ice breakup is early and summer rainfall is sufficient to provide moist soils [100]. Moore [93] concluded that warm weather and lack of rain during seed dispersal probably accounted for low seedling recruitment on the Sagavanirktok River floodplain [93].
Several years without extreme flooding may be needed for feltleaf willow seedlings to establish [144]. Moore [93] reported high mortality of feltleaf willow seedlings on the Sagavanirktok River floodplain due to burial and erosion caused by spring flooding. Extreme flooding and silt deposition killed many 1- and 2-year-old feltleaf willows on siltbars of the Tanana River floodplain [144]. Mature feltleaf willows can apparently withstand flooding for >2 weeks [100].
Seedlings can be particularly dense on freshly deposited river alluvium [93]. Seedlings were dense along the Sagavanirktok River (up to 1,210 seedlings/m²). Seedling establishment was apparently the primary means of gravelbar colonization, although feltleaf willow stems occasionally washed up and rooted on gravelbars [93]. Establishment by seed appeared to be the most common means of feltleaf willow colonization on the Mackenzie River Delta (Gill 1971 cited in [93]) and on the Tanana River floodplain [144,155]. However, Bliss and Cantlon [11] noticed only a few feltleaf willow seedlings on gravelbars of the Colville River near Umiat in Arctic Alaska, but they observed numerous examples of vegetative propagation from clumps of feltleaf willows eroded from cut banks upstream and deposited on gravelbars. At the Oumalik Test Well site on the Arctic Coastal Plain in Alaska, feltleaf willow apparently originated from seeds dispersed to the site after disturbance rather than by vegetative means [50].
Several studies noted the importance of moist, exposed mineral substrates and sparse vegetation for optimal establishment and growth of feltleaf willows [43]. Along a tributary of the upper Atigun River in the central Brooks Range, Alaska, feltleaf willow reached maximum height where exposed gravel was present and the total vascular plant cover was relatively low [43]. On the Sagavanirktok River floodplain, feltleaf willow established where mineral soils were moist most of the summer, where other vegetation was sparse, and when flooding and other physical disturbances were minimal [93]. Establishment of nonnative species may inhibit the establishment and growth of feltleaf willow. For more information, see Nonnative species.
Feltleaf willow grows best under full light [17,56,116,137,161].
Feltleaf willow plants are "fast-growing" [26]. Feltleaf willow may produce first-order branches during its first growing season [158]. On the Tanana River floodplain, 15- to 56-day-old feltleaf willow seedlings averaged 7 inches (18 cm) tall [78]. An 8-year-old feltleaf willow stem found on gravel deposits following deglaciation in Glacier Bay was 8 feet (2.4 m) tall and 2 inches (5 cm) in basal diameter [37]. On western Victoria Island, feltleaf willows grew most quickly in locations close to the river channel: >5-year-old feltleaf willows on stabilized bars 100 to 160 feet (30-50 m) from the active river channel had the largest annual growth (0.04-0.05 inch (0.9-1.2 mm) per year)) and greatest height (20-30 feet (6-9 m)) increments. The smallest annual growth increments (0.004-0.01 inch (0.1-0.3 mm) per year)) occurred farthest from the active channel [51]. Roots normally grow 2 inches (5 cm) deep in 1 growing season [43] and may grow 11 inches (29 cm) deep in 2 growing seasons [35].
Abundant winter precipitation may benefit feltleaf willow. Feltleaf willow ring widths of plants along the Kuujjua River on Victoria Island, Northwest Territories, were positively correlated with winter precipitation and thus the amount of spring flooding [157].
Sediment deposits may stimulate the formation of adventitious roots by feltleaf willow. Feltleaf willow occupies sites that may receive large amounts of sediment (2-4 inches (5-10 cm)) during spring ice breakup and flooding [100]. On the Tanana River floodplain, the number of adventitious roots per feltleaf willow seedling was positively correlated with the depth of silt deposited after flooding (r²=0.54, P<0.01) [78]. Bliss and Cantlon [11] noted that the best development of feltleaf willow along the Colville River occurred near or adjacent to the stream channel, where flooding occurs each spring.
Feltleaf willow typically occurs in mineral soils. It is most common in gravel but is also common in sand and silt [11,17,61,71,76,112,113,137,143]. Organic soils in feltleaf willow communities tend to be absent or thin [13,137,143], while litter cover is variable [13,51]. In a 10- to 20-year-old feltleaf willow floodplain community along the Tanana River in interior Alaska, organic soil layers were thin and thoroughly mixed with recent flood deposits of silt and sand [143]. Feltleaf willow occurred on linear sand dunes of the Copper River Delta in southeastern Alaska. The dunes had no soil horizon development and thin litter cover [13]. On western Victoria Island in the Northwest Territories, litter was 2 to 4 inches (4-10 cm) deep in dense feltleaf willow stands. Soils were primarily coarse gravel with variable amounts of sand [51].
Feltleaf willow is most common in slightly acidic to mildly alkaline soils (6.2-7.6 pH) (e.g., [112,119]).
Feltleaf willow occurs in wet to dry soils [76,89] that are well drained to moderately well drained [13,51,61,89,95,112]. feltleaf willows typically establish in soils that are moist and periodically flooded, but individuals may persist in dry, unflooded soils [102] (see Seedling establishment and plant growth). Soils are typically aerated [51,78]. Feltleaf willow is considered a facultative species in Alaska, meaning that it is equally likely to occur in wetlands and nonwetlands [105,128].
Permafrost commonly underlies feltleaf willow communities [61]. Where permafrost occurs in feltleaf willow communities, soils are typically deeply thawed (3-5 feet (1-1.5 m)) in summer [10,11,61,112,119], which provides large rooting space and favorable soil temperatures for feltleaf willow [112]. Along main river channels in Alaska and Canada where water runs nearly year-round, feltleaf willow may grow near the river channels where ground does not completely freeze or freezes only for a short period during winter [51,137]. Viereck [137] examined soil temperature changes during plant succession at 4 sites along the Chena River in interior Alaska that represented a successional sequence from early successional stages dominated by feltleaf willow (along the floodplain and low terraces), through intermediate stages dominated by balsam poplar and white spruce, to late successional stages dominated by white spruce and black spruce (on upper terraces). In feltleaf willow stands, soils 1) thawed earlier in spring, 2) were warmer during summer, and 3) froze earlier and deeper in fall than in the other communities. Soils froze latest in the white spruce and white spruce-black spruce stands due to a thick, insulating moss layer. He concluded that floodplain feltleaf willow stands without permafrost would eventually succeed to upper terraces of white spruce and black spruce and then to black spruce wetlands with permafrost [137]. Reduced active layer depth, lower soil temperatures, and higher soil moisture apparently reduce the competitiveness of feltleaf willow on upper terraces [112].
Soils in lowland riparian feltleaf willow communities often contain higher nutrient levels than adjacent uplands [10,51]. Nonetheless, soils in feltleaf willow communities often have low nitrogen availability and very low organic matter content [112].
Feltleaf willow is an early-seral species [132]. It is shade intolerant [17,56,116,137]. Flooding and sediment deposition are the most important factors setting back plant succession in feltleaf willow communities [93,95,123]. Feltleaf willow communities are usually short-lived. Density and cover peak within approximately 10 to 20 years after disturbance [24,64,74,133,144,155]. Rapid sprouting, abundant wind-dispersed seed, and rapid germination allow feltleaf willow to quickly colonize moist, disturbed sites [10,77,100,139]. It is one of the first species to colonize newly formed gravel, sand, and silt riverbars [139]. It also pioneers on sand dunes [102]; recently deglaciated sites [95,106,136]; burns [38,99]; and sites disturbed by mining [39,41], road construction [8,9,74], and oil drilling [50].
Floodplains: The generalized pathway of floodplain primary succession in the Alaskan taiga starts with a bare alluvium stage and progresses through stands dominated by feltleaf willow, alder (thinleaf alder or mountain alder, depending on latitude and elevation), balsam poplar, white spruce, and finally black spruce (e.g., [1,20,47,65,129,132,135,137,139,143]). Alder often establishes within 5 years of initial feltleaf willow colonization [139]. The development of an alder overstory coincides with reduced feltleaf willow density [32,144]. Heavy browsing of feltleaf willow by snowshoe hare, moose, and possibly willow ptarmigan may accelerate the decline of feltleaf willows in these early-seral stands [20,26,64,125,144]. Balsam poplar often establishes with or shortly after alder and begins to dominate 20 to 30 years after feltleaf willow first colonizes the site. By this stage in succession, overstory shade has reduced feltleaf willow to a few scattered individuals [139]. On the Tanana River floodplain, the oldest feltleaf willow was 48 years old and was found in the balsam poplar stage of succession [144] (see Stand structure). Succession may be interrupted at any stage by frequent flooding, ice scouring, shifting channels, and sediment deposition [93,95].Above treeline in Alaska, floodplain succession generally progresses from a pioneer perennial herb community to an feltleaf willow community. This is followed by a low-statured mountain alder-willow-heath community, and finally to cottongrass tussock-heath tundra or wet sedge tundra as depth of thaw increases [10,11,12,41,118]. Vegetation succession is determined in part by substrate and moisture availability. Feltleaf willow stands are most likely to establish on gravelbars. As silt accumulates on these bars, low-statured willows establish to form a mixed stand. Occasionally the initial substrate is silty and a mixed stand may establish immediately [11,41,93].
Dunes: American dunegrass and feltleaf willow are important pioneer species on open sand dunes. Entireleaf mountain-avens and red fruit bearberry succeed the pioneer stage in areas with moderate rates of sand deposition. Feltleaf willow persists in this stage of dune succession by rooting of stems as sand accumulates around plants [102]. Mountain-avens persists and forms mats as dunes stabilize [10,102]. Mountain-avens mats eventually succeed to communities characterized by witch's hair lichen and dwarf evergreen shrubs [102].
Deglaciated sites: In southeastern Alaska, the primary successional sequence following glacial retreat starts with a mountain-avens-perennial herb stage, followed by Sitka alder-feltleaf willow-Sitka willow thickets, Sitka spruce-black cottonwood transition forest, Sitka spruce forest, western hemlock-mountain hemlock forest, and finally muskeg. Feltleaf willow is present in the first 3 stages of succession and is densest in the alder-willow thicket stage [2,37,106].
Burns: Feltleaf willow is common after fire. It was present in mesic willow-polargrass-tall cottongrass communities within 4 years of pile burning on the Oumalik Test Well site [49]. In the Lower Sheenjek River Valley in northeastern Alaska, feltleaf willow was one of the dominant plants on 2 "recent" wildfire burns [80]. It was common on an 11-year-old burn in bottomland black spruce forest in interior Alaska. At this site, feltleaf willow, grayleaf willow, and tea-leaf willow constituted 11,757 shrubs/ha [155]. A generalized pathway of postfire succession in mesic black spruce sites starts with a newly burned stage (~0-1 years after fire), followed by a moss-herb stage (~1-5 years after fire). These are followed by a tall shrub-sapling stage (~5-30 years after fire), a dense tree stage (~30-55 years after fire), a mixed hardwood-black spruce stage (~56-90 years after fire), and finally, a black spruce stage (~91+ years after fire). In various locations in interior Alaska, feltleaf willow was densest (25 stems/ha) in the tall shrub-sapling stage and the mixed hardwood-black spruce stage (16 stems/ha) and absent from the other stages [53]. See the Research Paper of Foote's [53] study for detailed information.The scientific name of feltleaf willow is Salix alaxensis Anderss. Cov. (Salicaceae) [17,52,70,72]. Two varieties, overlapping in geographic range but differing in physical characteristics [17,97], are recognized:
Salix alaxensis var. alaxensis [17,76,113,128]
Salix alaxensis var. longistylus (Rydb.) Schneid. [17,76,113,128,141]
Potential hybrids between feltleaf willow and grayleaf willow (Hultén 1943 cited in [113]), woolly willow [29], and Richardson willow (Argus 1973 cited in [17]) were reported.
See the Appendix
for scientific names of lichens and plants named in this review and for links to available FEIS reviews.
Salix alaxensis is a species of flowering plant in the willow family known by the common names Alaska willow and feltleaf willow. It is native to northern North America, where it occurs throughout Alaska and northwestern Canada.[1]
This plant is a shrub or tree up to 9 m (30 ft) tall. The stem diameter is up to 18 cm (7.1 in). In harsher climates, it remains much smaller. The smooth, gray bark becomes furrowed and scaly with age.[1] The leaves are up to 11 cm long and have woolly undersides.[2]
The species is dioecious, with male and female reproductive parts on separate individuals. The inflorescence is a catkin up to 10 cm long. The fruit is a capsule. The seed has a downy layer of fibers that helps it disperse via wind and moving water. The seed remains viable for about a week, but it germinates within 24 hours of deposition upon a moist soil substrate. It does not germinate easily on dry soils or forest litter. The plant primarily reproduces sexually, via seed, but it can also reproduce vegetatively. It can resprout easily, and if stem fragments break off, they can often take root and grow into new plants.[1]
Moose are especially fond of this plant, pulling down and breaking branches up to 4 cm in diameter[3] and eating up to 90% of the twigs on the plant. In some areas of northern Alaska, this plant provides 95% of the winter food for moose.[1] Snowshoe hares also prefer it.[1] In northern Alaska, this may be the only source of fuel wood.[1] It is one of the tallest willows in the Canadian Arctic Archipelago.[4]
This willow is commonly dominant in willow communities across its range. Other willows in the habitat may include Bebb willow (S. bebbiana), grayleaf willow (S. glauca), Sitka willow (S. sitchensis), Pacific willow (S. lasiandra), barren-ground willow (S. brachycarpa), and halberd willow (S. hastata). It grows along rivers and streams and lakes. It grows in forested habitat, but it does not tolerate shade, so it persists only in open areas. Because it germinates quickly, it easily colonizes disturbed habitat, such as riverbanks scoured by recent floods and areas where glaciers have receded. It grows in early stages of succession, and after a few decades, it is shaded out by poplars and other trees as the habitat turns into forest.[1] This plant is fire-adapted and can resprout after its aboveground parts are burned away. The wind-dispersed seeds then land on the burned soil and colonize the terrain.[1]
Native Americans used parts of willows, including this species, for medicinal purposes, basket weaving, to make bows and arrows, and for building animal traps.[1]
This plant is used for habitat restoration and revegetation of disturbed sites, such as pipelines. Cultivars have been developed, such as 'Rhode', which has been used for revegetation efforts. Cuttings and bundles of dormant branches can be directly planted in the ground and will take root.[1]
Salix alaxensis is a species of flowering plant in the willow family known by the common names Alaska willow and feltleaf willow. It is native to northern North America, where it occurs throughout Alaska and northwestern Canada.
Salix alaxensis, le saule d'Alaska (en anglais : Alaska willow et feltleaf willow (saule feutré)), est une espèce de saules de la famille des Salicaceae, originaire d'Amérique du Nord.
Salix alaxensis est originaire du nord du Canada et de l'Alaska[2].
Ce saule est un buisson ou un arbre pouvant atteindre 9 m de haut. Le diamètre du tronc va jusqu'à 18 cm. Dans un climat plus sévère, il se maintient à une taille plus réduite. La jeune écorce grise et lisse devient sillonnée et écailleuse avec l'âge[2]. Les feuilles au revers soyeux mesurent jusqu'à 11 cm de long[3].
C'est le plus grand saule de l'archipel arctique canadien[4].
Dioïque, l'espèce présente une inflorescence sous forme de chatons de 10 cm de long. Le fruit est une capsule. La graine est munie d'une enveloppe duveteuse qui l'aide à la dispersion grâce au vent et aux eaux courantes. Elle reste viable pendant environ une semaine mais elle germedans les 24 heures de son dépôt sur un sol humide. Elle germe difficilement sur sol sec ou litière forestière. La reproduction se fait également par éléments végétatifs. La plante peut se marcotter ou se bouturer quand des morceaux de rameaux sont brisés et déposés sur la terre ou même sur d'autres plantes[2].
Dans son environnement, c'est l'espèce dominante parmi les autres saules. Dans son habitat, on trouve également le Saule de Bebb (S. bebbiana), le Saule glauque (S. glauca), le Saule sitka (S. sitchensis), le Saule brillant (S. lucida), barren-ground willow (S. brachycarpa), et le Saule hasté (S. hastata). Il pousse le long des rivières, ruisseaux et lacs, dans les zones forestières mais ne tolère pas l'ombre. Aussi, il prolifère surtout en zones ouvertes. Comme il germe rapidement, il colonise les secteurs perturbés tels les rivages récemment inondés ou des lieux dégagés par le retrait des glaciers. L'arbre pousse en premier dans les successions colonisatrices du terrain et, quelques décades plus tard, , les zones sont envahies par des peupliers ou d'autres arbres faisant de leur habitat de nouvelles forêts[2].
L'espèce résiste au feu et se régénère après les incendies. Le vent disperse les graines sur les sols nus ; elles peuvent facilement coloniser les zones atteintes[2] .
Les natifs nord-américains utilisaient cette plante et d'autres de la même famille pour se soigner, fabriquer des paniers tressés en vannerie, des arcs et des flèches et des pièges pour attraper des animaux[2].
Sur les sites perturbés, on l'utilise pour reconstituer des berges ou stabiliser les sols, par exemple après la mise en place de pipelines. Des cultivars ont été développés tel 'Rhode', employé dans des actions de revitalisation. Des boutures ou directement des branches peuvent être plantés dans le sol et prendre facilement racine[2].
Dans le nord de l'Alaska, c'est parfois aussi le seul combustible[2].
L'Élan est particulièrement friand de ce végétal, pliant vers lui des branches allant jusqu'à 4 m et mangeant 90 % des brindilles directement sur l'arbre. Dans certaines régions du nord de l'Alaska, cette plante produit 95 % de la nourriture des élans en hiver[2]. C'est aussi la nourriture préférée du lièvre d'Amérique[2].
Salix alaxensis, le saule d'Alaska (en anglais : Alaska willow et feltleaf willow (saule feutré)), est une espèce de saules de la famille des Salicaceae, originaire d'Amérique du Nord.
Alaskavíðir eða tröllavíðir (fræðiheiti: Salix alaxensis) er hraðvaxta og hávaxinn sumargrænn runni af víðiætt með ílöng lauf sem eru græn og slétt að ofan en grá og loðin að neðan. Börkurinn er grár og sléttur. Af honum eru tvö afbrigði: alaxensis og longistylis. Hann er upprunninn í Alaska en hefur verið fluttur út, meðal annars til Íslands, vegna þess hve harðger hann er. Hann er notaður tímabundið í skjólbelti þar sem hann vex mjög hratt upp og verður um 6 til 8 m á hæð. Hann er skriðull og lágvaxinn norðarlega á útbreiðslu svæði sínu.
Ця рослина є чагарником або деревом заввишки 1–7(9) м. Діаметр стовбура до 18 см. Молода гладка сіра кора стає борознистою і лускатою з віком Гілки жовто-коричневі або червоно-коричневі, не сизі, голі або ворсисті; гілочки сіро-коричневі або червоно-коричневі, майже безволосі або ворсисті. Листя: прилистники листоподібні, 3–23 мм, верхівки від загострених до гострих; черешки від опуклих до плоских або неглибоко рифлених зверху, 3–20 мм, опушені зверху; найбільші листові пластини 50–110 × 13–35 мм, у 2–4 рази довше ширини, основи клиновиді або опуклі, краї цілі або городчаті, низ шерстистий, верх тьмяний слабо або помірно ворсистий; юні листки з червонуватими або жовтувато-зеленими пластинами (колір часто затемнюється волосками), дуже щільно шерстисті на нижній поверхні, волосся біле. Сережки квітнуть до того як з'являються листки; тичинкові — товсті 23–55 × 13–27 мм, маточкові — щільно квіткові, від струнких до товстих, 33–103 × 8–22 мм; квіткові приквітки коричневого або чорного кольору, (1.5)2–2.5 мм, вершини від гострих до опуклих, знизу бідно волохаті. Тичинкові квітки: нектарники від вузько довгастих до довгастих, 0.5–1.4 мм; пиляки фіолетові й жовтіють, довго-циліндричні, 0.6–0.9 мм. Маточкові квіти: нектарники вузько довгасті, 0.6–1.6 мм. Капсули 4–5 мм.
Насіння має пухнастий шар волокон, що допомагає йому поширитися за допомогою вітру і рухомої води. Насіння залишається життєздатним протягом тижня, але проростає за 24 години після потрапляння до вологого ґрунтового субстрату. Насіння легко не проростає на сухих ґрунтах або лісовій підстилці. Рослина в основному відтворюється статевим шляхом, за допомогою насіння, але також може відтворюватися вегетативно.
Азія (східний та північний Сибір); Північна Америка (Канада, Аляска (США)). Вид інтродукований до Ісландії. Зростає вздовж річок, струмків і озер. Також росте в лісовому середовищі існування, але не терпить тіні, тому тримається відкритих майданчиків. Оскільки проростає швидко, легко колонізує порушені середовища проживання. Ця рослина адаптована до вогню і може відновитися після того, як надземні частини згорять. Вітром підхоплене насіння може приземлитися на обпалений ґрунт і колонізувати територію.
Ця рослина використовується для відновлення довкілля і рекультивації порушених ділянок. Корінні американці використовували частини верб, у тому числі цього виду, в лікувальних цілях, для плетіння кошиків, щоб зробити луки і стріли, а також для створення пасток на тварин.
Лосі особливо люблять цю рослину. У деяких районах на півночі Аляски, ця рослина забезпечує 95% зимового корму для лосів. Заєць американський також полюбляє цю вербу.
Галузка
Морфологія
Поширення в Північній Америці
Поширення в Ісландії
Salix alaxensis là một loài thực vật có hoa trong họ Liễu. Loài này được (Andersson) Coville miêu tả khoa học đầu tiên năm 1900.[1]
Salix alaxensis là một loài thực vật có hoa trong họ Liễu. Loài này được (Andersson) Coville miêu tả khoa học đầu tiên năm 1900.
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