Bastard Cedar

Incense-cedar is an important commercial softwood species. Its wood, exceptionally resistant to decay and highly durable when exposed to weather, is manufactured into many products, including lumber, pencil stock (for which it is the major United States source), fence posts, shakes, and landscape timbers, which are attractive because of punky spots resulting from fungus. The tree is widely grown as a handsome ornamental.

Trees to 57 m; trunk to 3.6 m diam. Bark cinnamon brown, fibrous, furrowed and ridged. Branchlet segments mostly 2 or more times longer than wide, broadening distally. Leaves 3--14 mm, including long-decurrent base, rounded abaxially, apex acute (often abruptly), usually mucronate. Pollen cones red-brown to light brown. Seed cones oblong-ovate when closed, red-brown to golden brown, proximal scales often reflexed at cone maturity, median scales then widely spreading to recurved, distal scales erect. Seeds 4 or fewer in cone, 14--25 mm (including wings), light brown. 2 n = 22.

Calif., Nev., Oreg.; Mexico in Baja California.

Montane forests; 300--2800m.

Libocedrus decurrens Torrey, Smithsonian Contr. Knowl. 5(1) [6(2)]: 7, plate 3. 1853

More info for the term: tree

The probability of incense-cedar mortality increases with increasing char height and decreases with increasing DBH [178]. Even mature incense-cedars, however, are susceptible to fire damage. The outer bark on incense-cedar is dry, stringy, and deeply furrowed. The thick bark ridges protect the inner bark and cambium from heat injury, but the cambium under the crevices between ridges is easily damaged. As a result, many mature trees in locations subject to past fires have long, narrow fire scars. The susceptibility of incense-cedar to cambial injury from fire makes it a valuable species for tree ring-based fire history studies [226]. According to a 1961 guide for marking fire-damaged timber [225], incense-cedars are likely to survive late-season fires if cambium injury is none to moderate (<25% of cambium killed, little damage above "stump height") and crown mortality is less than 45% to 55%.

COMMON NAME:




incense-cedar

Information on state-level protected status of plants in the United States is available at Plants Database.

More info for the term: tree

This description provides characteristics that may be relevant to fire ecology, and is not meant for identification. Keys for identification are available (e.g., [51,96,97]).

Incense-cedar is an evergreen tree that grows 66 to 187 feet (20-57 m) tall and up to 4 feet (1.2 m) in diameter [48,51,64,70,73,96,97]. In presettlement giant sequoia forests, incense-cedar trees reportedly reached 225 feet (69 m) tall and 12 feet (4 m) in diameter [32,70]. At high elevations and on dry, exposed sites, trees are small and scrubby [174]. Young trees have dense, symmetrical, pyramid-shaped crowns with branches that reach to the ground. Old trees have swollen bases, rapidly tapering trunks, and open, irregular crowns. Very old trees often have dead tops. Trees grow slowly and can live over 500 years [7,48,70,73,174].

Incense-cedar bark is thick, fibrous, furrowed, and ridged [48,51,64,96,97]. The bark is usually 2 to 3 inches (5.0-7.6 cm) thick but may be as thick as 6 to 8 inches (15-20 cm) on old trees. The bark exfoliates into fibrous shreds [46]. Leaves are scale-like, 3 to 14 mm long, and form flat sprays [48,51,64,96,97]. Male cones are terminal on twigs and reach a length of 4 to 7 mm. Female cones develop on the ends of the previous year's growth and reach 0.6 to 1.5 inches (1.4-4 cm) at maturity [48,51,64,96,97,174]. They contain 4 or fewer seeds. Seeds are 8 to 12 mm long and have 2 wings of unequal length [51,64,96,97,174].

Incense-cedar has a well developed root system [174] consisting of widespreading lateral roots and several downward-growing roots. Both lateral roots and taproots branch "profusely". Because new roots commonly branch off at a 45° angle from the parent root, the root system occupies a broad lateral area with depth. Some branches from horizontal lateral roots also grow upward to within 1.2 inches (3 cm) of the soil surface [194].

More info for the term: tree

Incense-cedar is a native tree in montane forests from Oregon south through California to northern Baja California, Mexico and east to western Nevada [58,64,96,97,103,208]. In Oregon, it extends from the southeastern slopes of Mt Hood east into central Oregon and south along the Cascade Range [7]. Its California distribution includes the Siskiyou, Klamath, North Coast, Cascade, Sierra Nevada, South Coast, Transverse, and Peninsular ranges and the Modoc Plateau [205]. The US Geological Survey provides a distributional map of incense-cedar.

More info for the terms: duff, fire exclusion, fire regime, fire severity, fire-return interval, forest, fresh, fuel, fuel moisture, ladder fuels, litter, low-severity fire, mesic, natural, potential natural vegetation, potential natural vegetation group, prescribed fire, sclerophyllous, severity, shrubland, shrubs, tree, woodland, xeric

Fire adaptations: Mature incense-cedar trees have thick bark that helps protect the tree from low-severity surface fires [7,14,110,132,179,190]. Postfire regeneration is by seeds dispersed in the first postfire year or later by parent trees that survive the fire [110] and by seeds from off-site sources [4,65,197].

FIRE REGIMES: Historic ignition sources in mixed-conifer forests included both lightning and Native Americans [170,171,229,230]. The historic fire regime in mixed-conifer forests was characterized by frequent, low- to moderate-severity surface fires [41,109,112,148,202,230]. Large, severe fires were infrequent in presettlement mixed-conifer forests of Oregon and California [111], although crown fires affecting small areas were probably common (review by [230]). There is some evidence of historic high-severity fires in mixed-conifer forests in the southern Cascade Range and Klamath Mountains [22,24,164,204]. Across the mixed-conifer zone, fire severity varied with slope, aspect, and topographic position [22].

Historic fire-return intervals in mixed-conifer forests ranged from approximately 3 to 30 years [43,74,109,112,127,165,188,202,219,229]. In giant sequoia groves in the Sierra Nevada, Swetnam and others [201] reported mean historic fire-return intervals of 5 to 10 years and a maximum fire-return interval of 20 years. Throughout the mixed-conifer zone, mean fire-return intervals varied with site: mesic and/or sheltered sites burned less often than xeric and/or exposed sites [62,231]. Frequent, low-severity fires killed small trees, including incense-cedar, prevented accumulation of surface fuels, and maintained an open, park-like forest structure [27,40,45,147].

The historic fire regime in mixed-conifer forests favored ponderosa pine and other fire-adapted species over fire-susceptible species such as incense-cedar and white fir [35]. As a result of 19th century logging practices [121,196] and fire exclusion since the early 20th century, however, shade-tolerant incense-cedar and white fir have increased in mixed-conifer forests, often forming dense thickets in the understory [2,3,6,16,27,39,40,60,121,222]. In the absence of fire, incense-cedar and white fir have also proliferated in the understory of giant sequoia groves in the Sierra Nevada [209].

Contemporary fires in mixed-conifer forests are less frequent, larger, and more severe than in the past [41,62,171,189,230]. The buildup of needle litter, duff, dead wood, and understory trees provide ladder fuels and result in high-severity, stand-replacement wildfires [6,27,29,40,69,109,110,122,151,209]. Because small fires are often suppressed, very large fires are more likely to occur during severe fire weather, such as Santa Ana Winds and heat waves [144]. The 1996 Ackerson Fire in Yosemite National Park, California, burned 19,000 acres (7,700 ha) of mixed-conifer forest where dense thickets of incense-cedar and white fir had developed in the understory and created conditions conducive to severe fire [122]. In October 2003, wildfires burned approximately 740,000 acres (300,000 ha) across southern California, including approximately 25,000 acres (10,000 ha) of mixed-conifer forest [77].

Many mixed-conifer forests in the Sierra San Pedro Mártir in northern Baja California still experience an unmanaged fire regime. The fire regime there is characterized by moderate- to high-severity surface fires that create open, park-like stands of mature trees. Fires may be as large as 12,000 acres (5,000 ha) with relatively long (~50-year) fire-return intervals. The long fire-return interval in the Sierra San Pedro Mártir is attributed to slow fuel buildup resulting from relatively low photosynthesis rates in evergreen sclerophyllous shrubs and trees and high live fuel moisture in sprouting shrubs [144,151,152].

Incense-cedar grows in a variety of other plant communities, all of which are subject to periodic or frequent fire. The following table provides fire regime information on vegetation communities in which incense-cedar may be important. 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 regime information on vegetation communities in which incense-cedar may occur. For each community, fire regime characteristics are taken from the LANDFIRE Rapid Assessment Vegetation Models [119]. These vegetation models were developed by local experts using available literature, local data, and/or expert opinion as documented in the PDF file linked from each Potential Natural Vegetation Group listed below. Cells are blank where information is not available in the Rapid Assessment Vegetation Model. Pacific Northwest California Great Basin     Pacific Northwest

• Northwest Woodland
• Northwest Forested

Vegetation Community (Potential Natural Vegetation Group) Fire severity* Fire regime characteristics Percent of fires Mean interval
(years) Minimum interval
(years) Maximum interval
(years) Northwest Woodland Oregon white oak-ponderosa pine Replacement 16% 125 100 300 Mixed 2% 900 50   Surface or low 81% 25 5 30 Pine savannah (ultramafic) Replacement 7% 200 100 300 Surface or low 93% 15 10 20 Ponderosa pine Replacement 5% 200     Mixed 17% 60     Surface or low 78% 13     Oregon white oak Replacement 3% 275     Mixed 19% 50     Surface or low 78% 12.5     Northwest Forested Douglas-fir (Willamette Valley foothills) Replacement 18% 150 100 400 Mixed 29% 90 40 150 Surface or low 53% 50 20 80 Oregon coastal tanoak Replacement 10% 250     Mixed 90% 28 15 40 Ponderosa pine (xeric) Replacement 37% 130     Mixed 48% 100     Surface or low 16% 300     Dry ponderosa pine (mesic) Replacement 5% 125     Mixed 13% 50     Surface or low 82% 8     Douglas-fir-western hemlock (dry mesic) Replacement 25% 300 250 500 Mixed 75% 100 50 150 Douglas-fir-western hemlock (wet mesic) Replacement 71% 400     Mixed 29% >1,000     Mixed conifer (southwestern Oregon) Replacement 4% 400     Mixed 29% 50     Surface or low 67% 22     California mixed evergreen (northern California) Replacement 6% 150 100 200 Mixed 29% 33 15 50 Surface or low 64% 15 5 30 Mixed conifer (eastside dry) Replacement 14% 115 70 200 Mixed 21% 75 70 175 Surface or low 64% 25 20 25 Mixed conifer (eastside mesic) Replacement 35% 200     Mixed 47% 150     Surface or low 18% 400     Red fir Replacement 20% 400 150 400 Mixed 80% 100 80 130 California

• California Shrubland
• California Woodland
• California Forested

Vegetation Community (Potential Natural Vegetation Group) Fire severity* Fire regime characteristics Percent of fires Mean interval
(years) Minimum interval
(years) Maximum interval
(years) California Shrubland Montane chaparral Replacement 34% 95     Mixed 66% 50     California Woodland California oak woodlands Replacement 8% 120     Mixed 2% 500     Surface or low 91% 10     Ponderosa pine Replacement 5% 200     Mixed 17% 60     Surface or low 78% 13     California Forested California mixed evergreen Replacement 10% 140 65 700 Mixed 58% 25 10 33 Surface or low 32% 45 7   Coast redwood Replacement 2% ≥1,000     Surface or low 98% 20     Mixed conifer (North Slopes) Replacement 5% 250     Mixed 7% 200     Surface or low 88% 15 10 40 Mixed conifer (South Slopes) Replacement 4% 200     Mixed 16% 50     Surface or low 80% 10     Jeffrey pine Replacement 9% 250     Mixed 17% 130     Surface or low 74% 30     Mixed evergreen-bigcone Douglas-fir (southern coastal) Replacement 29% 250     Mixed 71% 100     Interior white fir (northeastern California) Replacement 47% 145     Mixed 32% 210     Surface or low 21% 325     Red fir-white fir Replacement 13% 200 125 500 Mixed 36% 70     Surface or low 51% 50 15 50 Red fir-western white pine Replacement 16% 250     Mixed 65% 60 25 80 Surface or low 19% 200     Great Basin

• Great Basin Shrubland
• Great Basin Woodland
• Great Basin Forested

Vegetation Community (Potential Natural Vegetation Group) Fire severity* Fire regime characteristics Percent of fires Mean interval
(years) Minimum interval
(years) Maximum interval
(years) Great Basin Shrubland Montane chaparral Replacement 37% 93     Mixed 63% 54     Great Basin Woodland Ponderosa pine Replacement 5% 200     Mixed 17% 60     Surface or low 78% 13     Great Basin Forested Interior ponderosa pine Replacement 5% 161   800 Mixed 10% 80 50 80 Surface or low 86% 9 8 10 *Fire Severities
Replacement: Any fire that causes greater than 75% top removal of a vegetation-fuel type, resulting in general replacement of existing vegetation; may or may not cause a lethal effect on the plants.
Mixed: Any fire burning more than 5% of an area that does not qualify as a replacement, surface, or low-severity fire; includes mosaic and other fires that are intermediate in effects.
Surface or low: Any fire that causes less than 25% upper layer replacement and/or removal in a vegetation-fuel class but burns 5% or more of the area [88,118].

Fuels:The needles of incense-cedar are highly flammable [235,236]. They contain high amounts of volatile resins and other ether extracts. These ether extracts tend to increase in hot, dry summer months, making incense-cedar increasingly flammable as the fire season advances. Biswell [235] rated incense-cedar and mountain misery (Chamaebatia foliolosa) as the 2 most flammable plant species in California's mixed-conifer ecosystems.

Fire exclusion has resulted in an increase in understory live fuels in many mixed-conifer forests where incense-cedar seedlings and saplings often form a dense under- and midstory [2,3,3,27,39,109,121]. Due to thin bark, flammable crowns [14,35,69,100,132,219], and branches that often reach to the ground [48], young incense-cedar trees are likely to torch and act as ladder fuels [3]. Incense-cedar seedlings bark and foliage and are usually totally consumed by fire [7].

In a prescribed fire study in mixed-conifer forest in Yosemite National Park, 1 of the 4 fuel types studied was dominated by incense-cedar seedlings and saplings [213,221]. Prior to burning, mean fuel loads in this fuel type were [213]:

Prefire fine and heavy fuels (g/m²). Data are means [213].

Layer Incense-cedar fuel type surface fuels* 18.0 fresh litter 292.0 weathered litter 431.5 duff 2,830.9 total fine fuel 3,572.4 heavy fuel (>2.5 cm diameter) 1,261.3 *excluding litter

Energy released by the fire in the incense-cedar fuel type was 402.1 kcal/m². Energy release was significantly higher in the incense-cedar fuel type than in types where understory trees were less dense, except where Sierra mountain misery (Chamaebatia foliolosa) dominated the understory; in that type, incense-cedar seedlings were also abundant [221]. For further information on this study, see the Research Project Summary of Van Wagtendonk's [213,214,221] study. This and other studies have demonstrated that prescribed fires can cause some reduction in understory incense-cedar fuels [109,113,130,162,182,221].

More info for the terms: basal area, density, fire exclusion, fire severity, fire suppression, forest, fuel, fuel moisture, prescribed fire, restoration, seed, series, severity, wildfire

Prescribed fire can be used to restore and maintain historic composition and structure in mixed-conifer forests [27,40,78,209,215]. The objectives of prescribed fire in this forest type include reducing the understory density of fire-sensitive, shade-tolerant incense-cedar and white fir [233]. In a mixed-conifer forest in Yosemite National Park, for example, prescribed fire objectives include 50% reduction in total fuel load and mortality of 40% of pole size (1.0-5.9 inches (2.5-15 cm) DBH) incense-cedar and white fir [122].

Numerous case studies illustrate the effectiveness of prescribed fire in reducing understory incense-cedar density. For example, incense-cedar showed greatest mortality among conifers following 4 fire treatments in 1983 and 1984 in mixed-conifer forests of the southern Cascade Range and the northern Sierra Nevada, with mortalities near 100% on some plots. Incense-cedar was "all but eliminated" from the understory by all fire treatments. After a late-spring, moderate-severity treatment, incense-cedar density decreased from 19,967 stems/ha to 67 stems/ha [109]. For further information on this study, see the Research Project Summary describing Kauffman and others's [104,105,107,108,109] research. Mortality following a fall 2002 prescribed fire in the same study area was greatest for incense-cedar in the smallest size class [113].

Postfire percent mortality for incense-cedar in 3 DBH classes [113] 2.5-25 cm DBH 25-51 cm DBH 51-76 cm DBH 27.11 2.11 6.67

Near the Plumas National Forest, California, prescribed fire in a mixed-conifer-California black oak forest with an incense-cedar component successfully reduced fuel loads. When a wildfire burned through the site previously burned under prescription, fire severity and fire suppression costs were less compared to adjacent land where fire had been excluded [155]. For further information on this study, see the Research Paper by Moghaddas [155]. A 1990 fall prescribed fire in the Tharp Creek Watershed of Sequoia National Park, California, produced 16.4% and 17.8% average annual incense-cedar mortality on 2 white fir-mixed conifer sites monitored for 5 years after fire. Mortality was concentrated in the subcanopy [162]. For more information, see the Research Paper by Mutch and Parsons [162].

Prescribed fires in Cuyamaca Rancho State Park demonstrated the effectiveness of spring and late fall underburns in controlling young incense-cedars. Incense-cedar showed significant reductions in both sapling (P<0.02) and seedling densities (P<0.01) after burning [130]. For further information on this study, see the Research Project Summary of Martin and Lathrop's [123,130,131] study. Prescribed burns in mixed-conifer forest in Sequoia and Kings Canyon National Parks reduced the density of small (1-3.5 inches (2.5-9 cm)) incense-cedar by 56% [182].

Typically, prescribed fires in the mixed-conifer zone are conducted in late fall. With relatively low temperatures and high humidity, these late-season fires are generally lower severity than midseason fires and therefore may not kill a sufficient percentage of understory trees to meet restoration objectives. In a series of prescribed fires in Yosemite National Park, total understory incense-cedar basal area was significantly affected by fuel type and fuel moisture. On incense-cedar fuel plots, only plots at the 10% fuel moisture content were sufficiently dry to kill incense-cedars 3 to 10 feet (1-3 m) in height [221]. For further information on this study, see the Research Project Summary of Van Wagtendonk's [213,214,221] study.

A combination of thinning and prescribed burning may more effectively move stands with dense incense-cedar understories toward historic conditions than thinning or prescribed burning alone [166]. Application of 2 or 3 burns may also help to incrementally reduce fuel loadings in such stands [40,109]. Understory thinning may be necessary to allow successful application of prescribed fire in dense stands with high fuel loads [19,29,40,59,60,63,156]. On the Blacks Mountain Experimental Forest in northeastern California, prescribed burning was conducted in October 1959 to kill dense incense-cedar seedlings and saplings beneath a mature stand of ponderosa pine [78]. Due to abundant fuels on the site, the fire was more severe than expected and reached the canopy in some areas. Although the main objective of the fire was met (the incense-cedar understory was reduced from 1,031 to 16 live trees), Gordon [78] recommended against future burning under such extreme fuel conditions.

Even with a combination of fire and thinning treatments, restoring historic composition and structure to mixed-conifer forests after nearly 100 years of fire exclusion may be difficult. Although fire and thinning treatments kill incense-cedar seedlings and saplings, posttreatment seed rain and seedling establishment are often high. Fall prescribed fire and thinning treatments in an unmanaged, old-growth mixed-conifer forest at the Teakettle Experiment Forest, California, resulted in greater incense-cedar sapling reduction in burned vs. unburned treatments (P=0.030) and in thinned vs. unthinned treatments (P=0.036). Incense-cedar seedlings were also significantly reduced in both burned (P=0.0052) and thinned (P=0.0021) sites. Posttreatment seed rain and seedling establishment, however, were up to an order of magnitude higher for incense-cedar and white fir than for pines (Pinus spp.). Under these conditions, stand structure and composition returns to pretreatment conditions within a few years [233]. Regular prescribed fires may be necessary to maintain low density of understory incense-cedars [130]. Incense-cedar seedling establishment is reduced by overstory thinning of large, seed-producing incense-cedar trees. For managers attempting to accelerate old-growth development, however, removal of large incense-cedars may not be a desirable option [233].

For more information on prescribed fire techniques and prescribed fire effects in mixed-conifer forests, see these sources: [27,30,217,218,220].

More info on this topic.

More info for the term: phanerophyte

RAUNKIAER [176] LIFE FORM:
Phanerophyte

More info for the terms: forest, mesic, serpentine soils, xeric

Incense-cedar grows on a wide variety of sites ranging from shaded stream courses to exposed slopes [99]. It grows well on hot, dry sites and commonly occupies an upper canopy position on southwest-facing slopes [174]. It is common on xeric sites in the mixed-conifer zone of southern Oregon and California [34,62,68,73,174,182] and is found on exposed serpentine ridges in the Santa Lucia Range, California [81].

Incense-cedar also occurs on cool, moist sites [73,103,110,172,182], although it often is subdominant to other species on such sites [174]. It occurs in riparian woodlands [133] and is classified as a facultative riparian conifer in the eastern Sierra Nevada (Taylor and Davilla 1985, cited in [89]). In the Santa Lucia Range, incense-cedar is concentrated in deep canyons and shady ravines [81,82]. In the McKenzie River Valley, Oregon, incense-cedar is found on alluvial landforms where the water table remains close to the surface year-round [92]. At the southern extent of mixed-conifer forest in the Sierra San Pedro Mártir in northern Baja California, incense-cedar occurs almost exclusively on mesic sites including riparian habitats [16,146,150].

Elevation: Incense-cedar occurs between 165 and 6,600 feet (50-2,010 m) in the northern portion of its range and between 3,000 and 9,700 (910-2,960 m) feet at its southern limit. In the Sierra Nevada, incense-cedar grows best between 2,000 and 6,900 feet (610-2,100 m) [174].

Elevational ranges of incense-cedar Location Elevation California 980-8,200 feet [96,121,161] Nevada 5,000-7,000 feet [103] Baja California, Mexico 3,600-7,900 feet [146,150]

Soils: Incense-cedar grows in many soil types originating from a wide variety of parent rocks including rhyolite, pumice, andesite, diorite, sandstone, shale, basalt, peridotite, serpentinite, granite, and limestone [174]. Incense-cedar is an indicator of serpentine soils in portions of the Klamath Mountains and California's Coast Ranges [80,80,115]. Its ability to extract soil phosphorus and calcium and exclude surplus magnesium allows incense-cedar to grow on soils derived from peridotite or serpentinite [174]. Texture of soils supporting incense-cedar varies from coarse sand to fine clay [174,193]. The best incense-cedar stands are generally found on deep, well-drained, sandy loam and clay loam soils [174]. Incense-cedar grows in pH ranges from strongly acid to nearly neutral [174], although it has a slight affinity toward basic soil conditions [9].

Moisture: Incense-cedar is very drought tolerant [7,206]. It closes its stomata to control water loss on dry sites [95]. Summer precipitation is usually less than 1 inch (25 mm)/month. Incense-cedar can grow on sites that receive as little as 15 inches (380 mm) of annual precipitation [174], but annual precipitation (including snow) varies from 20 to 80 inches (510-2,030 mm) across its range [174,193]. Incense-cedar is intolerant of flooding [228].

Temperature: Incense-cedar is tolerant of heat [62] and somewhat resistant to frost injury [67]. Annual temperature extremes across the range of incense-cedar are -30 °F to 118 °F (-34 °C to 48 °C) [174].

More info for the terms: cone, forest, severity

Young incense-cedar trees are usually killed by fire due to thin bark and flammable crowns [14,35,69,100,132,219]. They often have branches that reach to the ground [48] and are therefore likely to torch [3]. Mature incense-cedars have thick bark and are more fire resistant than young trees [40,100,132,199,211,219]. Mature trees may survive or be killed by fire, depending on the severity of the fire [110,219].

Incense-cedars growing on moist, protected sites are likely to survive fire. Incense-cedars surviving the 1991 Warner Creek Fire on the Willamette National Forest, Oregon, for example, were located on a low slope near a riparian area [175]. Following the August 1977 Marble Cone Fire in Monterey County, California, the only remaining incense-cedar stands were located in deep, moist canyons where the fire was not severe [82].

More info for the terms: cover, density, forest, tree

Mule deer in California and Nevada browse incense-cedar [99,124,125,181]. A variety of insectivorous birds forage on incense-cedar [37,157,158,159]. White-headed woodpeckers, brown creepers, red-breasted nuthatches, and golden-crowned kinglets are among the species that exhibit the greatest use of incense-cedar [157,159]. Brown creepers forage for arthropods on the surface of incense-cedar bark more than that of any other tree species in mixed-conifer forests on the western slope of the Sierra Nevada. They forage significantly more (P<0.05) on incense-cedar in January and February than in the spring and summer months [1].

Palatability/nutritional value: Incense-cedar seeds contain a pungent resin that makes them unpalatable to rodents [4]. Incense-cedar seeds ranked 7th out of 8 conifer species in order of preference by rodents in the Redwood Mountains giant sequoia grove in California [91]. However, incense-cedar seeds are reportedly a preferred food of dusky-footed woodrats in mixed-conifer forests of Lassen County, California [141].

Cover value: A variety of raptors roost and/or nest in large incense-cedars. The majority of known northern and California spotted owl sites are in mixed-conifer forest [44,79,224]. In the San Bernardino Mountains, California, spotted owl nests were found in 3 incense-cedar trees averaging 46 inches (117 cm) DBH, 131 feet (40 m) tall, and 193 years old. Average nest height was 83 feet (25 m) above ground [85]. Great gray owls are also common in mixed-conifer forest [212,232] and are known to nest in large, broken-topped incense-cedars [23]. In a Klamath County, Oregon, mixed-conifer forest, incense-cedar accounted for 3% of 76 bald eagle roost trees [54].

Small incense-cedar trees create a dense understory that provides cover for small birds, particularly during winter [121,157]. Experimental reduction of incense-cedar density resulted in decreases in the numbers of many bird species; approximately 150 incense-cedar trees <20 cm DBH/ha were required to maintain bird abundance and diversity [157]. Although retention of small incense-cedars is generally contrary to current forest management objectives in mixed-conifer forests, Morrison and others [158] recommend maintaining a high diversity of tree species and size classes throughout the mixed-conifer zone of the Sierra Nevada in order to maintain diverse and abundant bird communities.

More info for the terms: association, cover, cover type, forest, herbaceous, serpentine soils, shrub, tree

Incense-cedar is an important component of mixed-conifer forests in southern
Oregon, California, and northern Baja California
[10,16,71,73,96,103,145,191,207]. Incense-cedar is also common in white fir (Abies concolor) forests at
the upper margin of the mixed-conifer zone in southwestern Oregon [10,73] and
northern California [182] and giant sequoia (Sequoiadendron giganteum)
groves in the Sierra Nevada mixed-conifer zone of California [5,14,33]. In
Sierra Nevada mixed-conifer forests it may account for half of the stems in a
stand [174]. For information on tree, shrub, and herbaceous
species associated with incense-cedar in mixed-conifer forests, see these
sources: [10,15,16,71,172].

Incense-cedar is a minor
component of the other forest types in which it is found [174]. It occurs with Shasta red fir (Abies
magnifica var. shastensis) [11,73] and California red fir
(A. magnifica) [15,73]. It grows
in Douglas-fir-western hemlock (Pseudotsuga menziesii-Tsuga heterophylla)
forests [71,73,160] and in grand fir (A. grandis) forests in southern
Oregon [73]. It is a minor component of mixed-evergreen forests in southwestern
Oregon and California [16,38,71,73,84,96,97,163] and of redwood (Sequoia sempervirens)
forests in north coastal California [71,234].

Incense-cedar occurs with bigcone Douglas-fir (P. macrocarpa)
in southern California [140] and with Jeffrey pine (Pinus
jeffreyi) and ponderosa pine (Pinus ponderosa var. ponderosa) throughout much of
its range [15,87,182]. Incense-cedar and Jeffrey pine are common associates on serpentine soils
[10,53,73,101]. On the east side of the Oregon Cascade Range,
incense-cedar occurs in dry ponderosa pine forests [200].
On the eastern slope of the Sierra Nevada, it grows with ponderosa
pine, Jeffrey pine, sugar pine (P. lambertiana), and white fir
[25,45,103,120]. Incense-cedar grows with Oregon white oak (Quercus garryana)
[7,73,195] and California black oak (Q. kelloggii) in southern Oregon and
California [7,134]. It is a minor associate in canyon live oak (Q. chrysolepis) forests [128] and
may also extend into the chaparral zone in California [26,31,185].

Incense-cedar is rarely found in pure stands [114,174].

Vegetation types describing plant communities where incense-cedar is a dominant species are listed below.

Oregon:

• Douglas-fir-incense-cedar association


• Douglas-fir-incense-cedar-Jeffrey pine association [10]


• Douglas-fir-incense-cedar/pinemat manzanita (Arctostaphylos nevadensis) association [73]


• Douglas-fir-incense-cedar/Piper's Oregon-grape (Berberis piperiana) association [10]


• incense-cedar/common whipplea (Whipplea modesta) community type


• incense-cedar/little prince's pine (Chimaphila menziesii) community type [142]


• Jeffrey pine-incense-cedar-Douglas-fir association


• Jeffrey pine-incense-cedar/huckleberry oak (Q. vaccinifolia) association


• Jeffrey pine-incense-cedar/whiteleaf manzanita (A. viscida) association


• western hemlock-incense-cedar-salal (Gaultheria shallon) association [10]


• white fir-incense-cedar/dwarf Oregon-grape (B. nervosa) association [8]


• white fir-incense-cedar/western starflower (Trientalis latifolia) association [10]


• white fir-ponderosa pine-incense-cedar/serviceberry (Amelanchier spp.) forest type [98]

California:

• Douglas-fir-incense-cedar/purple needlegrass (Nassella pulchra) association


• Douglas-fir-incense-cedar-California black oak/purple needlegrass association


• white alder (Alnus rhombifolia)-Douglas-fir-incense-cedar/Himalayan
  blackberry (Rubus discolor) association [198]

California and Oregon:

• Society of American Foresters Sierra Nevada mixed-conifer cover type [203]

More info for the term: tree

Tree

More info for the terms: forest, seed, tree, wildfire

Incense-cedar is highly susceptible to pocket dry rot, particularly in the mild,
western portions of incense-cedar's range [42,227]. Pocket dry rot is most prevalent in
trees >150 years old and commonly enters the tree through fire scars and the
wounds caused by broken branches [227]. An estimated 81% of pocket dry rot infections enter through fire scars
[36]. In parts of the Sierra Nevada, 75% to 100% of mature trees are infected (Bega
1978, cited in [174]). In a 1958 Forest Service, US Department of Agriculture publication, Wagener and Bega
[227] estimated that pocket dry rot resulted in
more than 36% cull of the standing volume of incense-cedar in California. Cull
may be as high as 77% for "overmature" trees [174]. During logging operations in the late 1800s in Sierra Nevada
mixed-conifer forests, many incense-cedars were left standing as seed trees due
to pocket dry rot that made their
lumber virtually worthless. These trees self-seeded, resulting in a dense
understory of incense-cedar after pines resumed canopy dominance in cutover
stands. Wildfire exclusion after the turn of the century further favored the
incense-cedars, allowing them to persist in dense understories [121,196].

Incense-cedar is susceptible to a variety of other pathogens including annosus
root disease (Heterobasidion annosum) [55,121,129,180], the trunk rot fungus Oligoporus amarus
[15], incense-cedar rust (Gymnosporangium libocedri) [15,168],
and the western conifer seed bug (Leptoglossus occidentalis) [61].
Incense-cedar mistletoe (Phoradendron libocedri) is common in incense-cedar crowns [76].
Incense-cedar is occasionally infested with mountain pine beetles (Dendroctonus
ponderosae), but the beetles rarely produce broods in incense-cedar [94].

Incense-cedar is less susceptible to ozone-induced injury than other western
conifers [143]. In the San Bernardino Mountains, areas of mixed-conifer forest
may eventually shift in dominance to incense-cedar as
ozone-susceptible ponderosa pine declines (McBride 1985, cited in [83]).

Information on the effects of herbicides on incense-cedar is provided in Conard and Emmingham [49].

More info for the terms: softwood, tree

Incense-cedar is an important commercial softwood species [42,93]. Although standing trees are highly susceptible to pocket dry rot (Polyporus amarus), products manufactured from incense-cedar wood are extremely durable and decay resistant [42]. Incense-cedar wood is used for many products including lumber, fence posts, railroad ties, venetian blinds, greenhouse benches, siding, decking, cedar chests, and shingles [51,64,103,121]. It is the major source of pencil stock in the United States [64,103]. Incense-cedar is also widely grown as an ornamental tree [64,97,114].

California Indians used incense-cedar bark to construct conical-shaped bark houses that were used shelter during acorn gathering times in fall. In some areas, incense-cedar slabs were used in more permanent house construction [21]. Incense-cedar leaves were used by Native Americans of Mendocino County, California, in the process of leaching acorn meal and in a decoction for relieving stomach upset. Small limbs were sometimes used for bows [47].

Miwok house of incense-cedar bark slabs.

More info on this topic.

More info for the terms: forest, seed

Incense-cedar has a long growing season that ranges from 91 to 146 days [66,174]. The growing period for incense-cedar at the California Forest and Range Experiment Station in the Sierra Nevada was longer and ended later for incense-cedar than for any of 5 other conifer species studied [66]. Like other members of the cypress family, incense-cedar does not form overwintering buds. Its shoot tips stop growing in the fall and resume growth in the spring [66,90,120]. Seasonal radial growth starts in the spring before height growth [174]. At the California Forest and Range Experiment Station, the 8-year average start date of height growth was 24 May, and the 7-year average start date of radial growth was 15 April [66]. Male cones open and shed pollen in late winter and early spring [7,48,120,174]. Female cones develop in 1 year, maturing by late summer or early fall [48,96,120,174,193]. Seed dispersal begins in late August at low elevations and in October at high elevations and continues into the winter months [65]. On the Challenge Experimental Forest, dissemination of incense-cedar seeds began on 15 September [139].

More info for the terms: basal area, density, fire exclusion, forest, low-severity fire, seed, stand-replacement fire

Incense-cedar reproduces after fire by seed blown into fire-created canopy gaps by wind. Seeds disperse from surviving parent trees and from off-site sources [50,110,197]. Two years after the October 2003 Cedar Fire in Cuyamaca Rancho State Park, California, thousands of incense-cedar seedlings were observed in a stand with surviving, adult incense-cedars [69]. Severe, stand-replacement fire, however, may kill most seed-bearing incense-cedars. The establishment rate of incense-cedar seedlings within fire-killed stands decreases with distance to the nearest seed source [77]. The stand-replacing portion of the Cedar Fire burned nearly 10,000 acres (4,000 ha) of mixed-conifer forest. In a study of postfire regeneration 4 years later, incense-cedar seedlings were absent from all but 1 of 8 plots. The only plot with incense-cedar seedlings had surviving trees nearby [77]. Incense-cedar seedlings that establish after fire are generally suppressed in the early seral stages by shade-intolerant, fast-growing species such as ponderosa pine and sugar pine. Incense-cedar is shade tolerant, however, and can persist in the understory for many years [45].

Incense-cedar increases in the absence of fire [6,14,100,187]. Historically, frequent, low-severity fire thinned sapling and pole-sized incense-cedars in the understory of mixed-conifer forests [77]. Fire exclusion since the early 1900s has allowed continuous recruitment of incense-cedar and white fir, resulting in dense understory thickets of these shade-tolerant, fire-sensitive species in many mixed-conifer forests [16,19,69,77,109,223]. A study of 68 field quadrats in southern California mixed-conifer forest 60 years after the 1929 to 1934 California Vegetation Type Map Survey showed a 74% increase in stem density, due primarily to a 10-fold increase in incense-cedar and white fir <13 inches (33 cm) DBH [149,151]. In Cuyamaca Rancho State Park, density of pole-sized conifers has increased by 250% since the late 1920s, while old-growth trees have decreased by 40%. Incense-cedar has increased by nearly a factor of 4, largely due to the ingrowth of small trees [77]. In a Sierran mixed-conifer forest, white fir and incense-cedar were 2 to 4 times as important in the sapling layer as in the overstory [17].

Importance values (relative basal area + relative density + relative frequency) of incense-cedar and white fir in 3 size classes in Placer County Big Trees Grove, California [17]   <3 cm DBH
(saplings) 30-40 cm DBH >40 cm DBH
(overstory trees) incense-cedar 62 35 27 white fir 132 123 36

Although incense-cedar establishes readily in the absence of fire, it only persists in a stand if fire is absent until young trees are large enough to survive low-severity fire [100].

More info for the terms: adventitious, crown residual colonizer, initial off-site colonizer, root crown, secondary colonizer, seed, tree

POSTFIRE REGENERATION STRATEGY [197]:
Tree without adventitious buds and without a sprouting root crown
Crown residual colonizer (on site, initial community)
Initial off-site colonizer (off site, initial community)
Secondary colonizer (on-site or off-site seed sources)

More info for the terms: cover, density, duff, forest, litter, monoecious, seed, selection, stratification, tree

Incense-cedar reproduces by seed [51,64,96,97].

Pollination: Incense-cedar is wind pollinated [174].

Breeding system: Incense-cedar is monoecious [48,174,205].

Seed production: Incense-cedar seed production varies by tree, year, and location [174]. Trees can produce up to 186,000 seeds/acre (review by [117]). In a heavy seed production year, incense-cedar may produce up to 405,000 seeds/acre [69]. There are approximately 15,000 to 16,000 seeds/lb [4,7,56].

Trees produce abundant seeds every 3 to 6 years. In some years trees produce no seeds [174], (Habeck 1992a, cited in [69]). On the Challenge Experimental Forest in Yuba County, California, incense-cedar produced 10 seed crops in 24 years. Of these, 1 crop was considered "medium to heavy", and 9 crops were considered "very light to light" [139].

Seed dispersal: Incense-cedar seeds are wind dispersed [7]. Because the seeds are light and have a large wing averaging 1 inch (2.5 cm) in length, they fall slowly (5.9 feet (1.8 m)/s in still air) and may be carried great distances by wind [4,65]. In a study of seed dissemination in north-central California, 100% of incense-cedar seeds counted fell within 200 feet (60 m) of the parent tree [137].

Seed banking: No information is available on this topic.

Germination: Incense-cedar seeds germinate well on bare soil and in light litter (review by [117]). Seeds can also germinate on a well-developed duff layer [106]. In a greenhouse experiment, incense-cedar germination was 19% on basalt-derived soil and 18% on sandstone-derived soil [153]. Although germination may be as high as 98% under controlled conditions [174], field germination rates usually vary between 20% and 40% (review by [117]). Incense-cedar germination is "improved" with cold stratification at 37 to 41 °F (3-5 °C) for 8 weeks [193]. The optimum germination temperature for incense-cedar is 68 °F (20 °C) (Barton 1930, cited in [20]).

Seedling establishment/growth: Incense-cedar seedlings can establish in shade and in heavy litter or brush cover [7,14,86,106,179]. Seedlings can also establish on mineral soil [7]. In a study of conifer regeneration after logging on the Stanislaus-Tuolumne Experimental Forest, California, incense-cedar germinated best in half shade on bare soil but survived best in half shade on "medium" litter [192].

Incense-cedar seedling density after logging is variable. On the Stanislaus-Tuolumne Experimental Forest, incense-cedar seedling density was 1,080 to 2,190 stems/acre 11 to 12 years after clearcutting [192]. Incense-cedar seedlings were uncommon, however, following clearcutting in Yuba County, California. The seedlings present were concentrated near the shaded edge of the clearcut [138]. On the Challenge Experimental Forest, incense-cedar seedlings were abundant 9 years after shelterwood cutting and absent after clearcutting [183].

Number of incense-cedar seedlings by cutting method 9 years after treatment [183] Treatment Number of seedlings Single-tree selection 44 Group selection 16 Shelterwood 470 Seedtree 67 Clearcut 0

Seedling growth is slow [12,192]. Low sunlight and heavy deer browsing are some of the factors that inhibit seedling growth [174]. Incense-cedar often reaches only 3 to 6 inches (8-15 cm) in height after 3 to 5 years. On the Stanislaus-Tuolumne Experimental Forest, the average height of incense-cedar seedlings 12 years after logging was 8 inches (20 cm) [192]. On very dry sites or in dense shade, saplings may only reach 3 feet (0.9 m) in 30 years [7]. The rate of shoot elongation in incense-cedar varies in relation to moisture availability. In a greenhouse experiment, incense-cedar growth rate accelerated after watering and slowed with increasing water stress [90]. Given sufficient water, seedling growth is faster in forest openings than in shade [7].

Incense-cedar seedlings have well-developed root systems [73]. In the first growing season, roots may extend to a depth of 12 inches (30 cm) [65]. Root growth of incense-cedar seedlings after 2 years was greatest in deep, loamy sand at low elevation [194]. Lateral root length was calculated as the average length of the 4 longest lateral roots.

Average root lengths of incense-cedar grown on 3 soil types in the South Umpqua River drainage, Oregon [194]. Soil texture Soil depth (cm) Elevation (m) Taproot length (cm) Lateral root length (cm) Average top:root ratio Loamy sand 180 210 126.5 130.3 0.45 Loam 100 1,010 79.3 43.2 0.36 Clay loam 160 850 90.3 33.0 0.25

Incense-cedar seedlings are susceptible to mortality from a variety of causes. The average survival rate of first-year incense-cedar seedlings on the Stanislaus-Tuolumne Experimental Forest was 10.3%. Cutworms and drought were the greatest causes of seedling mortality [67].

Causes of mortality and percent of first-year incense-cedar seedlings killed over 8 years [67] Frost Rodents Insect (cutworms) Fungi Heat Drought Misc. 2.4 4.8 52.0 3.1 0.0 19.8 6.2

Vegetative regeneration: Incense-cedar does not reproduce vegetatively [40,110].

More info on this topic.

More info for the terms: fire exclusion, forest, low-severity fire, succession, tree

Incense-cedar is shade tolerant [13,59,69,73,167]. Seedlings establish readily in shade, and trees persist in the shaded understory for long periods [14,86,169,179]. In a second-growth mixed-conifer forest in Tulare County, California, growth rings indicated that most of the incense-cedars with a small DBH were nearly as old as the largest individuals [28]. In the northern Oregon Cascade Range, however, incense-cedar is less tolerant of shade than western hemlock, western redcedar (Thuja plicata), and grand fir. It requires occasional disturbance to persist in these stands [7].

In many stands, incense-cedar is an important component of both the understory and the overstory [52,75]. It occupies a "subdominant" crown position in several forest types [174]. Incense-cedar attains canopy tree status by releasing in canopy openings [73,120,216]. Incense-cedar is reported as a late-seral canopy dominant in dry mixed-conifer forests of the western Oregon Cascade Range [57,73], in portions of the white fir zone in southern Oregon [73], and in some mixed-conifer forests [72,184]. Incense-cedar is also a pioneer species in many areas, including high ridges in the Umpqua River drainage and meadow communities in central and southern Oregon [73,86,154,210].

Although recruitment of incense-cedar is not fire-dependent [110], fire does influence its succession. The historic regime of frequent, low-severity fire in mixed-conifer forests favored ponderosa pine and other fire-adapted species over fire-susceptible species such as incense-cedar and white fir [14,35,86,100,219]. After decades of fire exclusion, many mixed-conifer forests in Oregon and California now have dense understories dominated by incense-cedar and other shade-tolerant species [15,16,124,169]. In the long absence of fire or other disturbance, subcanopy incense-cedars eventually grow into the overstory of mixed-conifer forests [72].

Libocedrus decurrens Torr. [161]

The scientific name of incense-cedar is Calocedrus decurrens
(Torr.) Florin (Cupressaceae) [51,58,64,96,97,102,103].

Incense-cedar is used for erosion control along road cuts and along streams between 2,000 and 6,000 feet (600-1,800 m) elevation in southern California [99]. Incense-cedar seedlings planted in the spring were more successful than fall plantings in an area disturbed by landslides and avalanches near Lake Tahoe, California [18]. Information on propagation of incense-cedar is provided in Kruckeberg [114].

Rarely found in pure stands, incense-cedar grows in several forest cover types where it occupies a subdominant crown position. Except in Sierra Nevada Mixed Conifer (Society of American Foresters Type 243) (5) where its stocking may account for half of the stems in a stand (20,26), incense-cedar is a minor component of the cover types in which it is found. These cover types include Pacific Douglas-Fir (Type 229), Pacific Ponderosa Pine-Douglas-Fir (Type 244), California Black Oak (Type 246), Jeffrey Pine (Type 247), and Pacific Ponderosa Pine (Type 245). Southern and drier portions of the types Oregon White Oak (Type 233) and Douglas-Fir-Tanoak-Pacific Madrone (Type 234) as well as inland extensions of Port-Orford-Cedar (Type 231) also contain incense-cedar.

In the northern part of its range, incense-cedar often is found with coast Douglas-fir (Pseudotsuga menziesii var. menziesii), ponderosa pine (Pinus ponderosa var. ponderosa), sugar pine (P. lambertiana), western white pine (P. monticola), Jeffrey pine (P. jeffreyi), California white fir (Abies concolor var. lowiana), grand fir. (A. grandis), western hemlock (Tsuga heterophylla), western redcedar (Thuja plicata), Port-Orford-cedar (Chamaecyparis lawsoniana), Oregon white oak Quercus garryana), California black oak (Q. kelloggii), tanoak (Lithocarpus densiflorus), giant chinkapin (Castanopsis chrysophylla), and Pacific madrone (Arbutus menziesii). In the central part, it grows with coast Douglas-fir, ponderosa pine, sugar pine, Jeffrey pine, Sierra lodgepole pine (Pinus contorta var. murrayana), California white fir, California red fir (Abies magnifica), giant sequoia (Sequoiadendron giganteum), California black oak, tanoak, giant chinkapin, and Pacific madrone. In the southern part, common associates are Jeffrey pine, ponderosa pine, sugar pine, Coulter pine (Pinus coulteri), bigcone Douglas-fir (Pseudotsuga macrocarpa), and California black oak. Tree associates on ultramafic soils include Jeffrey pine, western white pine, sugar pine, knobcone pine (Pinus attenuata), and coast Douglas-fir.

Common brush species growing with incense-cedar are greenleaf manzanita (Arctostaphylos patula), mountain whitethorn (Ceanothus cordulatus), deerbrush (C. integerrimus), snowbrush (C. velutinus), littleleaf ceanothus (C. parvifolius), bearclover (Chamaebatia foliolosa), bush chinkapin (Castanopsis sempervirens), salal (Gaultheria shallon), and coast rhododendron (Rhododendron californicum) (22). On ultramafic soils, sclerophyllous shrubs predominate and include barberry (Berberis pumila), silk-tassel (Garrya buxifolia), tanoak, huckleberry oak Quercus vaccinifolia), coffeeberry (Rhamnus californica), western azalea (Rhododendron occidentale), and red huckleberry (Vaccinium parvifolium) (32).

Incense-cedar's natural range is characterized by dry summers, usually with less than 25 mm (1 in) precipitation per month; annual temperature extremes are -34° to 48° C (-30° to 118° F). Annual precipitation, part of which is snow, varies from 510 to 2030 mm (20 to 80 in). Precipitation may be as low as 380 mm (15 in) a year for incense-cedar found on the east side of the Cascades and in the Warner Mountains in Oregon and California (22).

Overmature incense-cedars are more defective than their associates. The amount of cull increases with age of the trees and varies among stands (22). Average cull percents based upon gross volume are 4 to 6 percent for immature dominants, 21 percent for mature dominants, and 68 to 77 percent for overmature dominants.

The single most destructive agent affecting incense-cedar is the pocket dry rot (Tyromyces amarus). Pocket dry rot is most common in trees growing on good sites. In parts of the Sierra Nevada, 75 to 100 percent of the mature trees are infected. Trees on marginal sites near incense-cedar's eastern limit usually are infected less (2).

The spores of pocket dry rot must be deposited on an open wound to infect trees because the mycelium cannot penetrate through the bark into the heartwood (14). The most prevalent port of entry is through fire scars (84 percent). Knots (10 percent) are next in frequency And injuries resulting from lightning and frost (6 percent) are least (22). Pocket dry rot seems relatively resistant to heartwood extractives that are toxic to other heart-rotting fungi and may actually detoxify them (34). This unusual ability may explain the apparent anomaly of highly defective heartwood in live, overmature trees and high durability of heartwood in sawn products.

In management of young-growth incense-cedar, the age at which dry rot begins to cause losses is of primary significance. Suppressed trees are subject to severe dry rot infection after they reach 165 years, but dominant trees generally are safe until 210 years old (22). Because the rotation age of young-growth stands is considerably less than these critical ages, pocket dry rot should not cause severe cull in managed stands. Two other fungi that occasionally rot the heartwood of living incense-cedar are Phellinus pini and Phaeolus schweinitzii (10).

Root disease kills more incense-cedar trees than any other pathogen (24). Of the three facultative, parasitic fungi found attacking incense-cedar roots, Armillaria sp., Heterobasidion annosum, and Phellinus weiri, probably the most destructive is Heterobasidion annosum. More than 100 H. annosum infection centers have been confirmed on developed sites in Yosemite Valley, CA (25). Property damage caused by falling root-diseased trees has been substantial and has led to the development of a risk-rating system. On the basis of crown characteristics, the system predicts the potential for early failure of root-diseased incense-cedar (25).

The only foliage disease of any consequence is the rust caused by Gymnosporangium libocedri (10), which infects incense-cedar of all ages, causing witches' brooms, but only infrequently kills smaller branches. Although extensive infections of leaf rust retard growth, no deaths have been attributed directly to the disease. Infections in the main stem may result in burls that cause defect in lumber (2).

Ozone, the major plant-damaging constituent of photochemical oxidant air pollution, injures the foliage of many coniferous species. Incense-cedar is insensitive to injury from ozone. It appears to have sufficient numbers of tolerant individuals so that it may be planted with reasonable success in the ozone-affected forests common in the southern portion of this species' natural range (15).

Incense-cedar mistletoe (Phoradendron juniperinum subsp. libocedri) grows on incense-cedar throughout the range of the tree. This true mistletoe causes elongated swellings on the branches and occasionally on the trunk. Severe infections suppress growth but rarely kill large trees (2).

Many species of insects are found on incense-cedar, but relatively few cause serious losses. A cone sawfly (Augomonoctenus libocedrii) sometimes infests cones, resulting in damage resembling that of cone-feeding caterpillars (6). The juniper scale (Carulaspis juniperi) is a European species now distributed throughout the range of incense-cedar (6). It attacks twigs, leaves, branches, and cones, causing the foliage to turn yellow. Sometimes branches and entire trees are killed. Six species of cedar bark beetles (Phloeosinus spp.) can be found working under bark of trunks, tops, and limbs of weakened, dying, or felled trees or of broken branches (6). Although damage usually is inconsequential, beetles occasionally become sufficiently numerous and aggressive to attack and kill apparently healthy trees. Several wood borers have been found in incense-cedar, but none poses a threat to the life of the tree (6). The flatheaded cedar borer (Chrysobothris nixa) mines the bark and outer wood of limbs, trunks, and roots of weakened, dying, and dead trees, principally in the coast region. The amethyst cedar borer (Semanotus amethystinus) is similar to Chrysobothris nixa but confines its work to the inner bark and a scoring of the outer sapwood of boles and large limbs throughout the range of incense-cedar. The western cedar borer (Trachykele blondeli), like Chrysobothris nixa, can cause serious degrade and cull in trees cut for products requiring sound wood. Its larvae mine the sapwood and heartwood of living trees. Trachykele opulenta is similar to T. blondeli but less destructive. The incense-cedar wasp (Syntexis libocedrii) bores in the sapwood of fire-scorched trees in California.

Fire has played a significant role in the health and relative abundance of incense-cedar in mixed-conifer stands. Sapling incense-cedars are more readily killed by fire than most of their associates; the thick bark of mature incense-cedar offers considerable protection from fire. Intense fires indirectly result in more damage to mature trees, however, by exposing trunks to infection by pocket dry rot. As a result of fire control by land management agencies beginning about 1900, and partial cutting practices, the proportion of incense-cedar in the understory has increased. Incense-cedar is favored because it is a prolific seeder and because the shade-tolerant seedlings and saplings can persist for long periods in the understory.

Yellow-green, pollen-bearing strobili are borne terminally on twigs as early as September and reach a length of about 6 mm (0.25 in) at pollen shed in late winter to early spring. Incense-cedar is monoecious; both male and female flowers may be borne on the same twig. Cones, inconspicuous in spring, are pendent and 20 to 40 mm (0.8 to 1.5 in) long when they mature in late summer. They are composed of three pairs of opposing leathery scales. Two of the six scales become greatly enlarged and form a cover around the two scales that bear the seeds. Each seed has two wings of unequal length. Embryos have two cotyledons.

A few horticultural varieties are recognized. In southern California, especially in southwestern San Bernardino County, trees with conspicuously narrower crowns and more spire-like silhouettes than those of the Sierra Nevada are common. European experience with incense-cedar as an ornamental suggests that the columnar trees from southern California may be more sensitive to cold than are the trees from northerly sources (11).

The genetic structure of incense-cedar was studied in stands that occupy different elevations and aspects within each of three locations in the southern Cascades and Sierra Nevada (8). Genetic variation was assessed using two approaches: measuring characteristics of seedling growth and estimating allele and genotypic frequencies. Conclusions were similar for both approaches. Genetic diversity was as great among local stands as among regions, and no consistent pattern could be related to elevational or aspect differences. Growth in height and branch length was less for southern sources. Striking differences among provenances, however, like those found for Douglas-fir, lodgepole pine, and white fir, were not apparent.

No hybrids of incense-cedar are known.

Incense-cedar varies greatly in size in different parts of its range. In the Coast Ranges and in southern California, the largest trees generally are from 18 to 24 m (60 to 80 ft) tall and 90 to 120 cm (36 to 48 in) in d.b.h. In the Sierra Nevada, incense-cedars frequently grow to heights near 46 m (150 ft) with d.b.h.'s near 210 cm (84 in). The largest tree measured was 375 cm (148 in) in d.b.h. (1). A tree 69 m (225 ft) tall was reported from southern Oregon. At high elevations, especially on dry, exposed sites, trees tend to be small and scrubby.

Incense-cedar is long-lived. Large trees often are more than 500 years old (22). The oldest recorded age is 542 years for a tree only 130 cm (51 in) in d.b.h.

Growth rates of young mixed conifer stands in the central Sierra Nevada were investigated recently (3). In stands with basal areas of 23 to 69 m²/ha (100 to 300 ft²/acre), periodic annual increment of incense-cedar was 0.81 cm (0.32 in) in d.b.h. and 0.3 m (1.0 ft) in height at age 40. By age 90, periodic annual increment had declined to 0.36 cm (0.14 in) for d.b.h. and 0.2 m (0.6 ft) for height.

Incense-cedar often grows more slowly than associated conifers and is therefore a major component of the intermediate and suppressed crown classes. Seldom does it contribute more than 5 to 10 percent of the stand volume (22). At Blodgett Forest in the northern Sierra Nevada, for example, volume growth of incense-cedar was consistently slower than its associates, regardless of stand density or tree size (4). In stands of moderate density, incense-cedar grew in volume at an annual rate of 1.6 percent, compounded. The average rate for all species was 2.3 percent. On poor sites, however, open-grown incense-cedars as large as 60 cm (24 in) in d.b.h. can exceed all other species, except white fir, in basal area growth (22). On better sites, incense-cedars generally fall behind and are forced to endure more and more shade. Increasing shade further slows their growth to the point of bare existence. On such trees, 16 annual rings per centimeter (40/in) of diameter are not uncommon (12).

Incense-cedar has been rated as more shade tolerant (22) than the associated pines and Douglas-fir (16), and perhaps less tolerant than white fir and grand fir. In the seedling stage, incense-cedar can endure dense shade, especially in cool, moist environments (17). But for full development from sapling stage through maturity, it requires more light (22).

Incense-cedar shows good response to release. Much of the extremely slow growth of young reproduction results from suppression or browsing. When released, seedlings grow rapidly in height. But because height growth usually is slower than that of associated species of comparable age, incense-cedar usually is a secondary species in the final stand (22). Although shaded out, lower branches are slow to shed, even in dense stands. Many dead branches must be removed, therefore, if clear lumber is to be produced in rotations of 80 to 120 years.

From seedling stage through maturity, incense-cedar has a more spreading and extensive rooting habit than many of its associates. This extensive, well-developed root system allows it to survive droughty sites and resist windthrow. Root branching of seedlings in an artificially controlled environment was inversely proportional to growth rate (33). Rapidly growing roots produced few laterals, but when growth of these roots temporarily ceased, laterals were produced in profusion. When growth resumed, laterals again were widely spaced, resulting in a node-internode pattern.

Although incense-cedars are considered prolific seed producers, medium to heavy seed crops are borne at intervals usually averaging 3 to 6 years. Sometimes, cone crops are absent entirely (22). In a southwestern. Oregon study, medium to abundant crops appeared in only 3 years, and light or no crops were found in 12 of the 15-year reporting period (28). As many as 961,500 seeds per hectare (389,100/acre) may fall during heavy production years (22). Geographic variability in cone and seed production is great (23). Seed dispersal begins in late August at the lowest elevations and in October at higher levels. Although seedfall may extend into winter months, seed soundness seems unrelated to time of dispersal (table 1).

Table 1- Incense-cedar seedfall as measured from traps on the Stanislaus Natoinal Forest, CA (22)
Measurement date Percent of all
seed trapped Percent sound
seed 1937 October 6 11   3 October 27 36 37 November 11 53 60 1940 October 11 32 54 October 29 34 38 November 13 34   8 Incense-cedar seeds average 33,100/kg (15,000/lb) and vary from 14,100 to 63,900/kg (6,400 to 29,000/lb). Averages for collections from the northern and central part of incense-cedar's range vary from 29,800 to 44,500/kg (13,500 to 20,200/lb) (28). Because they are light in weight and have a large wing (averaging 2.5 cm (1 in) in length and nearly one-third that in width), seeds of incense-cedar fall slowly (1.8 m/s, or 5.9 ft/s, in still air) (22), and are carried great distances by wind.

Germination may be doubled by stratifying seeds at 3° to 5° C (37° to 41° F) for 30- to 60-day periods, although results are not always consistent. Germination under controlled conditions may be as much as 98 percent but usually averages 20 to 40 percent (28). These values are similar to those found under field conditions (22). Germination is epigeal (28). in nature, incense-cedar germinates on a wide range of surface conditions. Although survival is best under partial shade (22), incense-cedar seedlings survive over a broader array of site conditions than do most conifers (22,26).

Initial rates of root growth are slow to moderate in incense-cedar compared with other species. In the first season, primary roots may extend to a depth of 30 cm (12 in), compared with as much as twice that length for ponderosa pine and sugar pine (22). Incense-cedar, therefore, is particularly susceptible to drought on exposed sites during the first year. Root systems develop rapidly, however, and by the end of the second year, lateral and tap root lengths compare well with ponderosa pine (29). In an artificially controlled study (33), seedling roots showed a peak of growth in the spring, with rates averaging 3 to 5 mm (0.12 to 0.20 in) per day. Growth slowed in midsummer, but increased again in fall, averaging 1 to 3 mm (0.04 to 0.12 in) per day between October and December. Activity cycles varied for individual roots. Not all roots were active at any one time.

Incense-cedar lacks the distinct spring flush typical of many temperate conifers. Successive years' growth is not easily seen along the stem. Instead, elongation of several leaf internodes near the shoot tip in fall is arrested over winter and is not completed until the following spring. Hence, shoot growth is a more or less continuous process characterized by changes in tempo that are influenced primarily by current environment (9).

On the Stanislaus National Forest in the central Sierra Nevada, CA, at an elevation of 1600 m (5,250 ft), seasonal height growth of incense-cedar started an average of 11 days later than ponderosa pine, was similar to sugar pine, but averaged 31 days earlier than white fir (22). At Challenge Experimental Forest, 1° 30' of latitude farther north in the Sierra Nevada and 810 m (2,660 ft) lower in elevation, sugar pine and ponderosa pine began height growth 3 to 5 weeks sooner than incense-cedar, and white fir began a week later (21). On the Stanislaus National Forest, the height growth period for incense-cedar lasts an average of 91 days, a period greater than for any other native species. At Challenge Experimental Forest it lasted 112 days but stopped sooner than the height growth period for ponderosa or sugar pine.

Seasonal radial growth starts before height growth. On the Stanislaus National Forest, growth begins about April 15, some 2 weeks later than at Challenge. At both locations, however, incense-cedar begins radial growth at about the same time as ponderosa and sugar pine, but 2 weeks earlier than white fir. At both locations, the period of diameter growth for incense-cedar is second only to that for ponderosa pine, lasting 136 days at Stanislaus and 146 days at Challenge (21,22).

Naturally regenerated incense-cedar grows slowly because of low sunlight or heavy browsing, often taking 3 to 5 years to reach a height of 8 to 15 cm (3 to 6 in). Although increased sunlight favors height growth, poor initial root development of naturally regenerated incense-cedar and preferential browsing by deer may mask its ability to respond to increased light, compared with other species (table 2).

Table 2- Height growth of conifer seedlings relative to ponderosa pine under several silvicultural systems Silvicultural system Ponderosa pine Incense-
cedar  Sugar
pine White
fir Douglas-
fir Selection¹   Single-tree 1.00 1.80 2.00 2.80 1.40   Group 1.00 0.90 1.50 1.50 1.50 Shelterwood¹ 1.00 0.70 0.96 1.07 0.78 U.A.C.² 1.00 0.22 0.70 0.25 - Clearcut   Natural¹ 1.00 0.00 0.89 0.65 0.68   Planted³ 1.00 0.71 0.56 0.41 0.55 ¹Nine-year-old naturally regenerated seedlings, Challenge Experimental Forest, CA. Group selection openings were 9 to 27 m (30 to 90 ft) in diameter (13).
²Average of all natural seedlings regenerating in 12 years after Unit Area Control cuttings, Stanislaus National Forest, CA (26).
³Six-year-old seedlings from local seed, Challenge Experimental Forest, CA (21). Incense-cedar raised from local seed and planted as 1-0 stock in a fresh clearcut at Challenge Experimental. Forest, however, grew faster than three other species, and at 6 years from planting was second only to ponderosa pine in both height and standing biomass (21). Apparently, the well-developed root systems of planted seedlings provide enough water uptake to sustain vigor, which helps seedlings resist browsing pressure.

Established incense-cedar seedlings are remarkably drought tolerant. The species has been ranked more tolerant than sugar pine or ponderosa pine, Douglas-fir, or grand fir when grown in pumice, and second only to ponderosa pine when grown in sand (19). The tolerance was attributed to a complete occupancy of the soil mass by incense-cedar roots. In a controlled experiment, artificial dew more than doubled the survival period of incense-cedar seedlings grown in soils dried to permanent wilting point (31). Dew helped incense-cedar tolerate drought better than ponderosa pine and Jeffrey pine, although pines were more tolerant when dew was withheld. At Challenge Experimental Forest, predawn measurements of xylem moisture tension in September showed that incense-cedar, ponderosa pine, and sugar pine were similar to each other and significantly lower in water stress than Douglas-fir or white-fir (21).

Although drought may kill many first-year seedlings, particularly on compacted landings and skid trails, insects usually account for greater losses. Cutworms destroy many seedlings. Rodents are generally of only minor importance. During a 5-year period, 53 percent of the 1- to 2-month-old incense-cedar seedlings on Stanislaus National Forest plots were destroyed by cutworms (Noctuidae larvae) (22). The seed-to-seedling ratio on four cutover plots varied from 20:1 to 355:1 (22). Seedling tap roots may be damaged by root rot, but recovery can be rapid and tops may show no sign of attack (27).

Incense-cedar grows on many kinds of soils developed from a wide variety of parent rocks-rhyolite, pumice, andesite, diorite, sandstone, shale, basalt, peridotite, serpentinite, limestone, and granitic or metamorphic: equivalents. It is particularly adept at extracting soil phosphorus (21) and calcium (35), and excluding surplus magnesium.

Soils supporting incense-cedar vary greatly. Reaction ranges from nearly neutral to strongly acid. Textures vary from coarse sands to very fine clays. The best stands generally are found on deep, well-drained, sandy loam soils developed on granitic rocks and sandstone; deep clay loams developed on basalt and rhyolite; and occasionally on deep, coarse-textured, well-drained soils developed from pumice.

In California, incense-cedar grows best on deep, slightly to moderately acid Ultic Haploxeralfs, such as the Holland series weathered from granitic rock, and the Cohasset series derived from andesite and basalt. Incense-cedar also grows on infertile soils derived from peridotite or serpentinite throughout the Sierra Nevada and tends to be restricted to these soils in western portions of the north Coast Ranges and Klamath Mountains (7). Although it is a good competitor on these soils because of its apparent ability to extract calcium and exclude magnesium, its growth is considerably less than on more fertile sites. Apparently the high calcium-extracting ability of incense-cedar may interfere with magnesium and micronutrient uptake on limestone. Incense-cedars are rare on limestone soils, and the trees that do grow there contain high concentrations of calcium and low concentrations of manganese and zinc (35).

Incense-cedar grows at elevations between 50 and 2010 m (165 and 6,600 ft) in its northern extreme (30), and between 910 and 2960 m (3,000 to 9,700 ft) in its southern limits. In the Sierra Nevada, the tree grows best at elevations between 610 and 2100 m (2,000 to 6,900 ft). Once established, incense-cedar is a good competitor on hot, dry sites and commonly shares an upper canopy position on southwestern slopes. On cooler, moister aspects, it is usually subdominant to other species.

The outstanding durability and resistance to decay of lumber from incense-cedar heartwood make it ideal for exterior use where moisture is present. This wood gives long service with little maintenance in such uses as mud sills, window sashes, sheathing under stucco or brick veneer construction, greenhouse benches, fencing, poles, and trellises (12). Incense-cedar also is used extensively for exterior siding because it is dimensionally stable and holds paint well, in addition to being durable.

Rich color, sound knots, and aromatic fragrance make the wood popular for interior paneling and woodwork. At present, pecky cedar (boards sawn from trees infected with pocket dry rot) is in demand for paneling and backyard fencing, thereby making a market for poor quality grades that formerly were not utilized.

Incense-cedar is ideally suited to the manufacture of pencils because it is soft, easily whittled, and has straight grain (12). Much of the top-grade lumber produced goes to this use.

Incense-cedar is cultivated widely as an ornamental tree both within its natural range and as an introduced species. The tree grows well in western and central Europe (11) and in the Eastern United States as far north as Massachusetts.

Incense-cedar does not reproduce vegetatively in nature, but can be stimulated to do so in the greenhouse (18).

Cupressaceae -- Cypress family

Robert F. Powers and William W. Oliver

Incense-cedar (Libocedrus decurrens) is the only species from the small genus Libocedrus that is native to the United States. Increasingly, it is placed in a segregate genus Calocedrus. Incense-cedar grows with several conifer species on a variety of soils, generally on western slopes where summer conditions are dry. It is long-lived and grows slowly. Most of the top-grade lumber is used for the manufacture of pencils and exterior siding.

Incense-cedar is a distinctive component of the Sierra Nevada mixed-conifer forest, where it grows as scattered individuals or in small groups (5). Its range spans about 15° of latitude and a variety of climates from the southern slope of Mount Hood in Oregon, southward through the Siskiyou, Klamath, and Warner Mountains, Cascade and Coast Ranges, and Sierra Nevada to the dry Hanson Laguna and Sierra de San Pedro Martir Ranges in Baja California (7). Incense-cedar grows from the coastal fog belt eastward to the desert fringes. It can be found in the Washoe Mountains of west-central Nevada (12).


- The native range of incense-cedar.

Tree, Evergreen, Monoecious, Habit erect, Trees without or rarely having knees, Tree with bark rough or scaly, Tree with bark shaggy or peeling, Young shoots in flat sprays, Buds not resinous, Leaves scale-like, Leaves opposite, Leaves whorled, Non-needle-like leaf margins entire, Leaf apex acute, Leaves < 5 cm long, Leaves < 10 cm long, Leaves not blue-green, Scale leaves without raised glands, Scale leaf glands not ruptured, Scale leaves overlapping, Twigs glabrous, Twigs not viscid, Twigs without peg-like projections or large fascicles after needles fall, Berry-like cones orange, Woody seed cones < 5 cm long, Bracts of seed cone included, Seeds tan, Seeds brown, Seeds winged, Seeds unequally winged, Seed wings narrower than body.

Calocedrus decurrens, with the common names incense cedar and California incense cedar (syn. Libocedrus decurrens Torr.), is a species of coniferous tree native to western North America. It is the most widely known species in the genus, and is often simply called incense cedar without the regional qualifier.