Bigleaf Maple

Bigleaf maple occurs chiefly primarily in cool, mosit habitats, being common in numerous canyons and streambank settings. The specie thrives in a variety of soil types, but most typically found in rich humus soils that are moist and gravelly. Frequent fires promote the growth of this species in many locales. The bigleaf maple is also the principal forest species in areas where the land is burned or logged, such as in some sections of southwestern Oregon. The taxon often occurs in dense stands over large tracts of land, in small groves, or scattered. It is usually found in proximity to both evergreen broad-leaved species or coniferous trees, such as lowland Douglas firs, Quercus spp., California bay laurel, Red alder, Pacific madrone, Cypress spp., California redwood, and California laurel.

Acer macrophyllum (bigleaf or Oregon maple) is a large deciduous tree in the genus Acer that has the largest leaves of any maple species—the 5-lobed leaves are usually 15–30 cm across, but 60 cm leaves have been noted. It is native to western North America, mostly near the Pacific coast, from southernmost Alaska to southern California. Some stands are also found inland in the foothills of the Sierra Nevada mountains of central California, and a tiny population occurs in central Idaho.

Bigleaf maple can grow up to 35 m tall, but more commonly grows 15 m to 20 m tall. The flowers are produced in spring in pendulous racemes 10–15 cm long, greenish-yellow with inconspicuous petals. The fruit is a paired samara (winged nutlet), each seed 1-1.5 cm diameter with a 4–5 cm wing.

Bigleaf maple can form pure stands on moist soils in proximity to streams, but is generally found in mixed stands in riparian hardwood forests or in relatively open canopies of conifers, mixed evergreens, or oaks (Quercus spp.). It is dominant or codominant in cool and moist temperate mixed woods.

Bigleaf maple is the only commercially important maple of the Pacific Coast region, although in some areas, it is not considered valuable and may be left unharvested or intentionally knocked over during harvest of Douglas fir (Pseudotsuga menziesii) and redwood (Sequoia spp.) stands. The wood, which is light, reddish-brown, fine-grained, moderately heavy, and moderately hard and strong, is primarily used in veneer production for furniture, but also for musical instruments, interior paneling, and other hardwood products. Lakwungen First Nations people of Vancouver Island call it the Paddle Tree and used it to make paddles and spindle wheels.

Like other maples, bigleaf has a sugary sap from which maple syrup can be made. The sugar concentration is about the same as in Acer saccharum (sugar maple), with a similar ratio of sap to syrup (it takes 35–40 liters sap to make 1 liter syrup), but the flavor is somewhat different and there is limited commercial interest in it. (See Wikipedia article in full entry for information about ethnobotanic and medicinal uses.)

The seeds provide food for squirrels, evening grosbeaks, chipmunks, mice, and a variety of birds. Elk, black-tailed and mule deer, and horses browse the young twigs, leaves, and saplings. In some forest stands, up to 60% of the seedlings over 10 inches (25 cm) tall have been browsed by deer, most several times.

Acer species are sometimes classified in their own family, Aceraceae, but have been grouped in Sapindaceae (along with Hippocastanaceae) in the most recent version of the Angiosperm Phyologeny Group system (Stevens 2001). “Macrophyllum” refers to the fact that the leaves are large—the largest of any maple species.

“Macrophyllum” refers to the fact that the leaves are large—the largest of any maple species.

Acer species are sometimes classified in their own family, Aceraceae, but have been grouped in Sapindaceae (along with Hippocastanaceae) in the most recent version of the Angiosperm Phyologeny Group system (Stevens 2001).

bigleaf maple

big-leaf maple

Oregon maple

Information on state- and province-level protection status of plants in the United States and Canada is available at NatureServe.

More info for the terms: achene, breeding system, ferns, fruit, tree

Botanical description: This description covers characteristics that may be relevant to fire ecology and is not meant for identification. Keys for identification are available in these sources: [99,102,105,115,138].

Bigleaf maple is a large, deciduous [118] tree. It is typically about 50 feet (15 m) tall at maturity [151] but sometimes grows more than 80 feet (20 m) [102,138], making it the largest maple species in North America [13]. Trees are generally as wide-spreading as they are tall. Open-grown trees usually develop broad, rounded crowns, with branches that often grow low to the ground [105] and trunks from 2 to 5 feet (0.6-2 m) DBH [40]. Shaded trees are usually pyramidal in form, with narrow crowns [105] and clear, straight boles for one-half to two-thirds of their lengths [40,105]. Bigleaf maple is most frequent and reaches best development in southern Oregon [13]. The champion tree as of 2011 was located in Marion, Oregon. It was 88 feet (27 m) tall, 305 inches (775 cm) in circumference, and had a 104-foot (32 m) spread [9]. On cutover sites, bigleaf maple usually grows in shrubby, multistemmed clumps [83,84]. It also assumes a shrubby form in montane chaparral [151].

Bigleaf maple wood is moderately hard, but it is porous and not strong [105]. Branches of mature trees are massive, spreading [105], and steeply inclined at the tips [118]. Bark is thin [146], rarely more than 0.5 inch (1.3 cm) thick [151,164].

Bigleaf maple typically supports many epiphytes. Mosses, liverworts, and ferns hang from its branches or grow in branch crotches [105,164] (see photo in the Plant communities section). Bigleaf maple's moss load is generally the greatest of all tree species in the Pacific Northwest [164]. Arno [13] estimates that in rain forests of the Pacific Northwest, a bigleaf maple tree supports about 1 ton (0.9 t) of mosses.

Comparing sizes of a human hand and a bigleaf maple leaf.

As the common name claims, the leaves of this species are big. Bigleaf maple has the largest leaves of any North American maple [105], ranging from 4 to 10 inches (10-25 cm) across [99,138]. Trees in western Oregon had a mean area of 43 inches² (280 cm²)/leaf [118]. Male and female flowers are clustered on the same raceme [99,138,146]. (See Breeding system for a more detailed explanation of bigleaf maple flowers.) The fruit is a bristly [102,138], biwinged achene [99] or samara [13,83,146,164] bearing one seed/wing [99].

Bigleaf maple is deep-rooted [47,105,151]; hence, it is ranked low in susceptibility to windthrow [47,48].

Bigleaf maples live about 50 to 200 years [13],154,40,48.

Bigleaf maple tolerates short-term flooding [151], surviving periodic flooding in both active and upper stream channels [208]. It does not tolerate sustained flooding. In British Columbia, Brink [31] observed that bigleaf maples suffered mortality following 100-year floods on the Fraser and Columbia rivers in 1948. Bigleaf maples of all age classes die if floods last for 2 months or more [151].

More info for the term: forest

1971 USDA, Forest Service map provided by [205]

Bigleaf maple grows in mountainous regions [138]. It is widespread in the Coast Ranges, the Klamath-Siskiyou Mountains, and the foothills of the Cascade Range and the northern Sierra Nevada [75,81,99,102], obtaining best development in southern Oregon [13]. Some authors place bigleaf maple's distribution as far north as the Alaska panhandle [13,99,138]. Isolated bigleaf maple populations may occur in Idaho [102].

States and provinces (as of 2011 [211]):
United States: CA, OR, WA
Canada: BC

More info for the terms: cover, forest, hardwood, ladder fuels, natural, prescribed fire, severity, succession, tree

Prescribed fire favors bigleaf maple sprouting, and fire does not control the species. The Oregon Coast Ranges study [169] suggests that bigleaf maple may be difficult to control even if prescribed fire and herbicides are used in combination. However, fire may reduce cover of bigleaf maple, other sprouting woody species, and groundlayer vegetation in the short term and prepare a site for conifer planting or natural conifer regeneration. Morris [153] noted that after Douglas-fir forests on the Coast and Cascade ranges of Oregon were logged, cover of bigleaf maple and other shrubby species was about twice as much on unburned compared to slash-burned sites in early postfire years. Five years after the logged sites on the Coast Ranges were broadcast burned, crown cover of bigleaf maple and other sprouting deciduous species was 6% on burned plots and 30% on unburned plots. In the Cascade Range, cover of bigleaf maple and other sprouting deciduous species was 11% on burned and 22% on unburned plots. Eighty-six percent of the Coast Ranges site burned at low severity, and 76% of the Cascade Range site burned at low severity [153].

In the Sierra Nevada, a prescribed fire in riparian zones of the Blodgett Research Station significantly reduced biomass of coarse woody debris and groundlayer vegetation in the short term compared to prefire biomass. The 21-23 October fire was conducted near 1st- and 2nd-order streams dominated by bigleaf maple or incense-cedar. Surveys were conducted at postfire week 2 for fuels and postfire year 2 for vegetation. The fire killed only 8 large-diameter (4.6-15.9 inches (11.7-40.4 cm)) trees, which comprised 4.4% of the total of all large trees. Large, fire-killed trees were not differentiated by species [23].

Bigleaf maple is important as a wildlife tree and for plant community diversity in general [153]. Prescribed fires in Douglas-fir forests may help maintain large Douglas-firs in the overstory and create patches of bigleaf maple, red alder, and other hardwood within the conifer forest. Arno [12] reports that the benefits of using prescribed fire in Douglas-fir forests of the Pacific Northwest and coastal California include removing understory conifer and ladder fuels, retarding succession to late-seral species such as western hemlock, and creating openings "of all sizes" that favor bigleaf maple and other deciduous woody species.

Follow this link to the U.S. Forest Service Fire Effects Information Service to see a table with fire regime information that may be relevant to habitats in which this species occurs

More info for the terms: association, cover, fire exclusion, fire intensity, fire regime, fire-return interval, forest, hardwood, high-severity fire, ladder fuels, low-severity fire, mesic, mixed-severity fire, mixed-severity fire regime, stand-replacement fire, wildfire

Bigleaf maple experiences a wide variety of FIRE REGIMES across its distribution. Western hemlock, Douglas-fir, and mixed-evergreen forests lie on a north-south gradient along the Pacific Coast, with Douglas-fir, then ponderosa pine, attaining increasing dominance to the south. FIRE REGIMES historically reflected this gradient, with long-interval, more severe fire to the north and shorter-interval, less severe fires to the south.

Western hemlock-Sitka spruce forests have stand-replacement [123] and mixed-severity (review by [159]) fires. Douglas-fir and mixed-evergreen forests of the Pacific Northwest and northern California experience a mix of stand-replacing and understory fires. Historically, ponderosa pine and mixed-conifer forests of southern Oregon and northern California also had a mixed-severity fire regime, with a prevalence of low-severity surface fires and some patchy stand-replacement fires. For all these types, most fires occurred in summer and fall (reviews in [197]).

Bigleaf maple often lies within the riparian zones of these forests. Historical FIRE REGIMES for riparian zones of the western United States are not well studied [182,185]. In general, fires are less frequent in riparian and wetland areas of the West than in drier areas [14]. At low- to midelevations in the southern Cascade Range and Klamath Mountain regions of California, fire-return intervals in riparian areas overall are about twice those of surrounding areas, but fire intensity is generally greater when the riparian areas burn [182]. Fire-return intervals near intermittent and ephemeral streams are likely similar to those of surrounding areas [185]. In most years, perennial stream communities may serve as firebreaks (review by [182]).

Descriptions of FIRE REGIMES in plant communities in which bigleaf maple occurs follow. See the Fire Regime Table for further information on FIRE REGIMES of plant communities in which bigleaf maple may occur. Find further fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find FIRE REGIMES".

Western hemlock-dominated forests: Western hemlock-Sitka spruce forests on the coast of southern British Columbia historically experienced mixed understory-crown and crown fires. Fire-return intervals on the coast ranged from 6 to 130 years, with an average of 75.4 years (review by [159]). Western hemlock-Douglas-fir forests on the Olympic Peninsula have mostly long-interval, stand-replacement fires. These infrequent crown fires occur mostly in drought years, with fires returning about every 500 to 750 years [106].

Douglas-fir-dominated forests: Douglas-fir forests in mainland western British Columbia historically experienced mixed-severity fires, with a prevalence of even-aged stands suggesting a history of mostly stand-replacement fires. Fire-return intervals ranged from 35 to 256 years, averaging 107.5 years (review by [159]). A fire history study on Vancouver Island suggested a regime of mostly low-severity understory fires in a Douglas-fir-grand fir-bigleaf maple forest. The community occurred in a ravine. Most trees were 100 to 150 years old, and the oldest were 350 to 500 years old [142].

A fire history study on Orcas Island, Washington, showed a regime of frequent, low-severity understory fires in Douglas-fir forests with scattered bigleaf maples, western hemlocks, and shore pines (Pinus contorta var. contorta). Fire-return interval averaged 28.3 years from 1773 to 1893, with no fires since then. By the 1990s, stand structure had changed from a primarily open to a closed canopy on most sites. The authors predicted that because fire exclusion led to stand closure, the next fire is likely to be stand-replacing [161].

Along the McKenzie River on the western slope of the Cascade Range, Oregon, bigleaf maple is common in early-seral Douglas-fir-western hemlock-western redcedar forests. These forests had a fire rotation interval of about 162 years in the presettlement period, with at least 77% of the landscape burning from 1525 to 1575. Average fire-return interval during the settlement period (1850-1924) was 40 years [218]. Other fire studies in the southern Cascade Range found fire-return intervals from 18.6 to 26.3 years in Douglas-fir forests; fires were mostly low-severity surface fires (review by [184]). Skinner and Taylor [184] caution that actual fire-return intervals might have been shorter because many old Douglas-firs had fire scars that healed over after low-severity fires. These scars were not apparent until after the area was logged and entire stumps could be examined [184].

A fire history in southwestern Oregon showed bigleaf maple was associated with productive, low-elevation sites that were relatively close to old-growth stands (P=0.15). The area was on the Siouxon Creek Watershed in a Douglas-fir-western hemlock forest. It had experienced both large, "intense" and small, patchy fires. The oldest Douglas-firs in old-growth areas established around 1500. Numerous small, patchy fires occurred in the early 1800s, and a large, mostly stand-replacement fire occurred in 1902, with portions of the 1902 burn apparently reburning 2 or 3 times in the next 80 years. Between 1479 and 1938, 12 separate fires were detected on the 40,000-acre (16,000 ha) watershed [76].

Bigleaf maple has invaded formerly open areas where fire has been excluded in the Willamette Valley. Bigleaf maple, and to a larger extent, Douglas-fir, is encroaching into areas that were historically grasslands or Oregon oak woodlands [82]. Fires set by American Indians and then by European-American settlers maintained the Willamette Valley as grasslands and woodlands [30].

Mixed-evergreen forests: FIRE REGIMES in mixed-evergreen forests region are variable [2,134]. These forests often occupy steep slopes and have abrupt elevation changes and highly variable soils, so vegetation types can shift quickly. Mixed-evergreen forests in the Klamath-Siskiyou region have mostly mixed understory and stand-replacement fires that leave patches of unburned, underburned, and crown-fire burned areas across the landscape [5,76,77,134]. Fire-return intervals vary from 10 years or less for Oregon white oak and canyon live oak woodlands to about 15 years for low-elevation (≤4,000 feet (1,000 m)) Douglas-fir/hardwood forests and about 160 or more years for midelevation (4,000-6,000 feet (1,000-2,000 m)) white fir forests.

The Big Bar (1999) and Quartz (2001) wildfires in the Klamath-Siskiyou region of southern Oregon were mostly low- to moderate-severity understory fires at high elevations and north slopes, especially on sites with large-diameter trees. Low-elevation sites, south-facing slopes, and sites with small-diameter trees and/or ladder fuels were most likely to experience stand-replacement fires. The plant communities that burned were Douglas-fir-tanoak-ponderosa pine at low elevations and white fir at high elevations; elevations ranged from 2,580 to 6,043 feet (785-1,842 m). Bigleaf maple was described as a dominant hardwood in these communities [5].

Fire studies in riparian zones within mixed-evergreen forests are rare (review by [67]). Limited studies show median fire-return intervals of 16 to 42 years in black cottonwood sites near Lake Shasta (Skinner 2000 cited in [67]) and 12 to 19 years in riparian Douglas-fir forests on the Klamath National Forest. From 1627 to 1992, the average area burned in riparian Douglas-fir forests was 860 acres (350 ha), with 16 fires larger than 1,200 acres (500 ha) [201]. Fires burned mostly in midsummer or early fall [202].

Bigleaf maple communities: Bigleaf maple-dominated stands embedded within mixed-evergreen forests comprise a very small portion of the mixed-evergreen ecosystem, and little information is available on fire behavior in these stands. With the Biscuit Wildfire in southwestern Oregon, 82% of the hardwood forest types that burned experienced very low- to low-severity fire. Hardwood forest types were classified as nonstocked (<10% commercial timber species). In contrast, 84% of other nonstocked forest types experienced moderate- to high-severity fire. The bigleaf maple type comprised about 2% of hardwood-dominated stands; tanoak comprised about 63% [16].

Bigleaf maple stands may occur on sites that are too moist to burn in most years. A 1961 to 1962 inventory of the Tillamook Burn found that the bigleaf maple-red alder association was the only type that did not burn during the initial, 1933 wildfire. The association occurred in mesic stream bottomlands. Red alder showed fire scars from the 1939 and 1945 fires, but bigleaf maple was apparently not damaged. At the time of the study, the bigleaf maple overstory was about 90 feet (30 m) tall, with bigleaf maple cover ranging from 1% to 70% [17].

Chaparral: Low-elevation [124] chaparral communities have almost exclusively stand-replacement fires, about every 50 to 125 years. Coastal sage scrub communities also have stand-replacement fires but with a wider range of fire-return intervals, from 20 to 150 years [126]. Montane chaparral communities, which border mixed-conifer ecosystems of the Sierra Nevada, experience both mixed-severity and stand-replacement fires that average 50 and 95 years, respectively [125].

Fire may skip over hardwood communities in ravines and mesic canyons that are surrounded by chaparral. In the Santa Monica Mountains, bigleaf maple-California bay-white alder communities in deep canyons escaped wildfires that burned in adjacent chamise (Adenostoma fasciculatum) or mixed-chaparral communities [178].

More info for the terms: adventitious, basal area, crown fire, density, forest, hardwood, prescribed fire, root crown, seed, stand-replacement fire, succession, top-kill, tree, wildfire

Fire adaptations: Adventitious buds on the root crown enable bigleaf maple to sprout after most fires [146].

Plant response to fire: Bigleaf maple sprouts from the root crown after top-kill by fire [59,61,94,120,146,151,164,171,184,184,195,195,214,214].

As of 2011, there were no reports of postfire seedling establishment by bigleaf maple, although few studies reported whether bigleaf maple's postfire regeneration was from root crown sprouts or seeds. Given bigleaf maple's ability to establish from seed after logging (see Seedling establishment and Successional Status), bigleaf maple seedlings may establish on new burns if surrounding vegetation is not dense enough to interfere with bigleaf maple seedling establishment and growth. Trees that survive or are missed by fire may provide on-site seed. Because wind readily disperses bigleaf maple seed, off-site trees may provide additional bigleaf maple seed. Since bigleaf maple has only a transient seed bank, it is unlikely that viable seeds remain in the soil after the fire season. However, bigleaf maple disperses seed after the fire season, through late fall and winter, so if a seed source is available, bigleaf maple seedlings may emerge on new burns in the first winter or spring (see Seasonal Development) after fire.

Fire generally favors bigleaf maple [12]. Studies in Washington [3,61], Oregon [136,169], and northern California [95,171] showed postfire establishment of bigleaf maple, even after a severe fire [61].

Red alder and bigleaf maple often dominate early stages of postfire succession in Douglas-fir forests of the Pacific Northwest [12]. Two months after the lightning-ignited Hoh Fire in Olympic National Park, all bigleaf maples on burned plots were top-killed or killed. Before fire, bigleaf maple grew on well-drained, stable terraces above the Hoh River. The forest type on these low-level terraces was Sitka spruce, with a western hemlock-Douglas-fir forest type on upland sites. The wildfire was patchy, with some crown fire, some crown scorch, and some unburned areas; most crowning occurred on upland sites. The fire often extinguished when it reached moist Sitka spruce/bigleaf maple terraces. Bigleaf maple was a minor component in most riparian communities, although after the fire it showed the greatest relative loss of live basal area compared to the dominant conifers [3].

Bigleaf maple basal area (m²/ha) 3 months after the Hoh Fire in Olympic National Park [3]   Burned plots Unburned plots Live stems 0 1.7 Dead stems 0.9 0

Bigleaf maple sprouted after a severe wildfire near Bellingham, Washington. A gas pipeline near Whatcom Creek leaked, exploded, and burned a black cottonwood-red alder-bigleaf maple forest. The burned area was surveyed in postfire year 1. Seventy-two bigleaf maples grew in the area before the fire. Of these, 59 trees (82%) survived. Eighteen of the surviving trees retained a live crown, and 41 were top-killed and sprouted. Bigleaf maples with surviving crowns, and those that died, ranged from 4 to 24 inches (10-60 cm) in diameter. Sprouting trees were 4 to 12 inches (10-30 cm) in diameter [61].

A 38-year study on the H. J. Andrews Experimental Forest showed bigleaf maple abundance peaked in early seral stages following clearcutting and slash burning. Bigleaf maple density peaked in posttreatment years 18 to 21, at around 200 stems/ha. Posttreatment mortality was partially attributed to successional replacement (26.3%) and mechanical damage such as windthrow (13.6%); most mortality was due to unknown causes (58.4%) [136].

On the Oregon Coast Ranges, bigleaf maples had mixed responses to hardwood thinning, spraying, and prescribed fire. Some trees were killed by the treatments, while others were only top-killed and sprouted. Treatments were initiated to reduce hardwood dominance on brushfields that developed after the Sitka spruce-western hemlock-Douglas-fir overstory was logged. Large hardwoods were logged in March and April 1974; 2, 4, 5-T was sprayed on 2 June 1974; and the site was burned on 9 August 1974. The fire was "intense", and most of the site burned [169].

Bigleaf maple sprouts were noted on broadcast-burned, pile-burned, and unburned sites following clearcutting in Douglas-fir-ponderosa pine forests on the Klamath National Forest, California. Across sites, sprouts reached up to 16 feet (5 m) by postfire year 6 [95].

Hardwood sprouts grew rapidly after wildfire or logging in northern California. The Three Creeks Wildfire in Humboldt County, California, started in heavy slash left after a mixed-evergreen forest was logged. The mostly stand-replacement fire burned in August, 1951. Among bigleaf maple, Pacific madrone, Oregon white oak, tanoak, and Pacific dogwood (the 5 most common sprouting hardwoods), bigleaf maple had produced the greatest number of sprouts/root crown by postfire year 2, and its sprouts were the tallest. Bigleaf maple also showed a strong sprouting response after a mixed-evergreen forest in Trinity County, California, was logged. Among the same 5 sprouting hardwoods, bigleaf maple showed the strongest tendency for the numbers of sprouts produced/clump to increase with diameter of the top-killed tree. Height of bigleaf maple sprouts also increased with tree diameter, although this response was greater for Pacific madrone and Oregon white oak than for bigleaf maple. Pooled data, collected from burned or logged sites, for growth of bigleaf maple are shown below [171].

Pooled growth responses of bigleaf maple on wildfire or logged sites in northern California. n=10 bigleaf maple sprout clumps [171]. Variable 2nd growing season 3rd growing season mean range mean range Height of tallest sprout in clump (feet) 9.8 6.8-13.1 12.8 7.5-17.1 Crown diameter of sprout clump (feet) 11.5 6.8-15.5 14.7 10.4-21.5 Sprouts/clump 78 14-143 37 8-67

More info for the terms: forest, fuel, litter, mesic, tree

The moist to mesic sites bigleaf maple favors often accrue heavy fuel loads quickly. Because it is a large tree with extremely large leaves, bigleaf maple's contribution to total fuel load can be considerable. Its litter may decay faster than that of associated conifers, however. In the Pacific Northwest, annual litterfall of bigleaf maple averaged 1,319 lbs/acre (dry weight) [200]. A study on the H. J. Andrews Experimental Forest found bigleaf maple litter had a slightly faster rate of decay than most associated hardwoods, but it decayed slowly than litter of ponderosa pine, Douglas-fir, and western redcedar (P≤0.05) [213]. In the Klamath-Siskiyou region of southwestern Oregon, litter loads in tanoak-Douglas-fir communities with bigleaf maple increased with the relative amount of Douglas-fir present [15].

An energy value of about 8,400 BTUs/pound (oven-dry) is reported for bigleaf maple wood ([222], review by [110]).

Several studies provide site-specific information on fuel structure or loads that may apply to similar sites elsewhere. Fierke and others [57] describe stand structure for black cottonwood communities with bigleaf maple. Their data were collected in stands by the Willamette River, Oregon [57,57]. Spies and Franklin [189] provide a description of forest floor, coarse woody debris, litter, and stand structure characteristics of Douglas-fir forests of the Pacific Northwest. Their information is based on 196 sample sites across the Cascade Range in Washington and Oregon, the Northern Coast Ranges of Oregon, and the Siskiyou Mountains of Oregon. Young (<80 years), mature (80-195 years), and old-growth (>195 years) stands were sampled; bigleaf maple was among the dominant deciduous trees in these stands [189]. Rickard [167] gives measurements of litterfall in a 2nd-growth Douglas-fir forest with scattered bigleaf maples and Oregon white oaks. Data were collected on the west bank of the Columbia River [167].

The following citations provide models that help predict fuel loads in plant communities where bigleaf maple is important:

• to calculate aboveground biomass of bigleaf maple and other trees in the Pacific Northwest, see these sources: [19,57,79,203]
• for height-diameter equations for bigleaf maple and other overstory species, see: [19] for the Olympic Peninsula of Washington; [70] for western Oregon in general; and [216] for the Willamette Valley
• for crown widths of bigleaf maple and other overstory trees of western Oregon, see [87]; for crown area equations developed from sites across northern California and coastal southern Oregon, see [212]
• for predicting bigleaf maple tree height and crown dimensions by trunk diameter, see [118]

More info for the terms: forest, stratification, tree

Bigleaf maple seeds overwinter in the soil, germinating at low winter [151,199] or spring [13] temperatures. They require 60 to 120 days of cold stratification [152,225]. Germination occurs on mineral or organic substrates [83,84,151]. In the Pacific Northwest, Arno [13] observed that in spring, "countless seeds from the previous year's crop" germinate on the forest floor. Seeds that overwinter on the tree may begin germinating before they disperse [225]. Germination rates of 30% to 90% are reported in the laboratory [151,152].

More info on this topic.

More info for the term: phanerophyte

Raunkiaer [165] life form:
Phanerophyte

Bigleaf maple is relatively thin-barked [146], so it is not fire-resistant [48,151,164]. Fire top-kills bigleaf maple in most size classes [83,184,195,214], although large, mature trees that have developed thick bark may survive [47] moderate-severity fires. Severe fire kills most bigleaf maples ([61,94], review by [162]), but a few may survive severe fire ([61], review by [162]).

More info for the terms: cover, density, hardwood, litter, reburn, tree

Many wildlife species use bigleaf maple for food and cover [112,157,162]. Livestock browse it [49,96,177]. Honeybees and other insects feed on the nectar [13].

Mule deer [151,170], elk [24,151], mountain beavers [45,151], other rodents [151,162], and invertebrates browse bigleaf maple foliage [151]. Mountain beavers on the Tillamook Burn used bigleaf maple as a winter food [151]. Various animals, including Douglas's squirrels [13,32], northern flying squirrels [33], finches, and evening grosbeaks [13] eat the seeds, especially during winter when other foods are scarce [13,32]. In the spring, deer mice were observed eating germinating bigleaf maple seeds in the Sierra Nevada [111].

Early-seral, riparian communities with bigleaf maples are habitat for many small animals. A survey of riparian zones on the Oregon Coast Ranges found that some rodent and amphibian species preferred seral red alder-bigleaf maple brushfields that developed after the Douglas-fir overstory was logged. Numbers of creeping voles, Townsend's chipmunks, western redbacked salamanders, and Pacific giant salamanders captured were greater the year after logging compared to before logging [39]. McComb and McGarigal [141] provide site descriptions and lists of small mammals and amphibians that use Douglas-fir-red alder riparian communities with bigleaf maple as habitat in Lincoln County, Oregon.

Many bird species use riparian habitats in which bigleaf maple is prominent [107]; some depend on a component of deciduous trees in general [107] or are associated with bigleaf maple in particular. Gleaning birds such as brown creepers forage on large bigleaf maples [140]. In studies on the western slope of the Cascade Range in Oregon, dusky and Hammond's flycatchers were positively associated with small- (0.4-4 inches (1-10 cm)) and medium- (4-20 inches (10-50 cm)) diameter bigleaf maples (P<0.04) [71]. Barred owls prefer uneven-aged mosaics of bigleaf maple and other early-successional tree species over mature conifer forests. Allen [6] speculates that increased numbers of barred owls in the Pacific Northwest are partially due to establishment and growth of bigleaf maple and other early-successional trees after logging.

Downed bigleaf maple branches are a component of channel-floodplain woody debris and log jams [41,108]. Such debris slows stream channel flow [68,208], and retained organic matter enhances habitat quality for many aquatic animals [68,122]. Retained debris enhances steelhead [204] and other fisheries [181,204]. In the Pacific Northwest, hardwoods such as bigleaf maple are associated with high biomass of aquatic macroinvertebrates (Piccolo and Wipfli 2002 cited in [117]). In the Queets River, large woody debris of bigleaf maple and other large hardwoods appeared to decay more rapidly than that of Sitka spruce and other conifers [108], so organic matter from decaying hardwoods was likely more readily available to aquatic detritus feeders than organic matter from conifers.

Palatability and nutritional value: Sampson and Jesperson [177] rate the palatability of bigleaf maple foliage as good to poor for mule deer, fair to poor for domestic goats, and poor for domestic sheep, cattle, and horses. Palatability is rated good for Roosevelt elk [42].

Bigleaf maple foliage collected in the Pacific Northwest was fairly high in nitrogen and calcium content. See Tarant and others [200] for a nutritional analysis of bigleaf maple foliage. Bigleaf maple bark is also high in calcium. This probably accounts for the unusually high load of epiphytes that bigleaf maple typically carries [121]. Valachovic and others [213] provide nutritional analyses of bigleaf maple litter.

Cover value: Wild ungulates, rodents, birds, and insects use bigleaf maple as cover, nesting, and/or foraging habitat.

Mule deer select bigleaf maple communities as habitat. On the Tillamook Burn, their density averaged 54 deer/mile² in bigleaf maple/creeping snowberry the community, the highest among 5 communities studied. Mule deer populations were surveyed from 1964 to 1969 [101]; this was 13 to 18 years after the last reburn. Mule deer probably used the bigleaf maple/creeping snowberry community for foraging and bedding in winter because the open slopes were relatively warm. They avoided the community in summer [100]. A 1964 study on the Tillamook Burn found mule deer sightings in bigleaf maple/creeping snowberry communities were high in late winter (15% of total sightings), declined from March to May (2.2%-4.6%), increased through summer (12%), and peaked in October (17.8%). In contrast to the earlier study, mule deer preferred these communities for summer bedding [145].

On the Olympic Peninsula, Roosevelt elk used mature hardwood forests in the Queets River valley floor as spring, summer, and fall habitat. Red alder, black cottonwood, and bigleaf maple dominated these forests [180].

Dusky-footed woodrats may build nests in bigleaf maple [56].

Many bird species nest in bigleaf maple [13], including harlequin ducks [35] and pileated woodpeckers [91,92]. Pileated woodpeckers on Vancouver Island excavated cavities in large bigleaf maples for nesting, although they also selected other large trees (x = 32 inches (82 cm)) DBH) for cavity nesting. Regardless of the tree species selected for nesting, areas around active cavity trees had greater numbers of bigleaf maple than areas without active cavity trees (P=0.05) [92].

Bald eagles use bigleaf maples as roost trees [190].

Many insects use the furrowed, scaly bark of large bigleaf maples as habitat [140].

More info for the term: tree

Tree

More info for the terms: epiphyte, forest, litter, tree

Peterson and Peterson's [162] review provides many suggestions for managing bigleaf maple, as well as an overview of bigleaf maple ecology.

Bigleaf maple can interfere with the establishment and growth of commercial conifer species [83,84,131,164,164] because its sprouts usually grow faster than conifer seedlings [83]. These sources provide information controlling bigleaf maple with herbicides: [44,58,120,131,131,151,155,162,198,215]. Norris and others [154] provide a guide for using and some effects of herbicides in riparian zones.

Bigleaf maple can also have positive effects on conifer growth. Litter and debris from bigleaf maple trees and sprout clumps can increase forest floor and soil nutrients and accelerate nutrient and litter turnover in Douglas-fir and western hemlock forests [209]. In western Oregon, soil nitrogen and potassium levels were greater under bigleaf maples than under Douglas-firs. Nutrient content (N, K, P, Ca, Mg) and turnover rate of litter was significantly greater under bigleaf maples, as were turnover rates for forest floor nutrients (P<0.05) [64,66]. Fried [64] concluded that complete removal of bigleaf maple from Douglas-fir plantations could reduce overall nutrient availability. Bigleaf maple may be a nurse tree for western redcedar, which often establishes in the humus layer beneath bigleaf maple [121].

Bigleaf maple is among the many native species that are alternate, non-oak hosts of Phytophthora ramorum, the pathogen causing sudden oak death disease [69,168].

Bigleaf maples burdened with heavy epiphyte loads are more susceptible to windthrow than unencumbered trees [151].

More info for the term: hardwood

Bigleaf maple is a commercial sawtimber hardwood [151,210]. The wood is used for lumber and to make furniture, flooring, and veneer [151]. It is also planted as an ornamental [22,146].

The sap can be rendered into maple syrup [174], although the yield is less than that of sugar maple (Acer saccharum) [151].

American Indians historically harvested bigleaf maple branches and twigs. They used its bark for making rope, the wood for utensils and canoe paddles [13], and the shoots for baskets [10,11,36]. Selected bigleaf maples were burned or pruned frequently to force sprouting [11].

More info on this topic.

More info for the term: tree

Bigleaf maple germinates, and trees resume growth, early in the year. Flowers bloom before or with leave emergence [105,146,164].

Phenology of bigleaf maple Area Event Period California, southern flowers late March Oregon, Coast Ranges germination complete April-May [151] Pacific Northwest flowers and leaves emerge late April-early May [13] Northern parts of range, high elevations flowers June [151] Across range germination starts late January-February [151,199] seeds ripe August-October [151,225] seeds disperse October-January [13,151,225]; some seeds remain on tree until March [151,225]

More info for the terms: monoecious, seed

Insects pollinate bigleaf maple [13,83,113,151]; these pollinators include bees, flies, and beetles (Julian-Gordon 1993 personal observation [113]).

Bigleaf maple is heterdichogamous. This mating system is rare; plant species employing it bear 2 types of flowers on individual trees: 1) those that are functionally female but structurally also have vestigial male flower parts and 2) those that are functionally and structurally male [73,113]. Within and among populations, trees may produce female flowers before male flowers (protogynous) or the reverse (protandrous). The ratio of female:male flowers is apparently about 1:1 [113]. Functionally, this mating system is similar to that of monoecious species, and some authors have labeled bigleaf maple as monoecious [99,138].

Genetic tests of 2 populations in western British Columbia showed bigleaf maple was mostly outcrossing, with low levels of population differentiation. This is consistent with a species with wind-dispersed pollen and seed [109] and a heterdichogamous mating system [113].

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

POSTFIRE REGENERATION STRATEGY [194]:
Tree with a sprouting root crown
Crown residual colonizer (on site, initial community)
Initial off-site colonizer (off site, initial community)
Secondary colonizer (on- or off-site seed sources)

More info for the terms: breeding system, seed

• Pollination and breeding system
• Seed production
• Seed dispersal
• Seed banking
• Germination
• Seedling establishment and plant growth
• Vegetative regeneration

Bigleaf maple regenerates from seed and by sprouting. Sprouting is apparently more common, although fewer field studies have been conducted on bigleaf maple seedling establishment than on sprouting, so rates of seedling establishment may be underreported.

More info for the terms: forest, fresh, seed

Seeds do not live more than one winter under field conditions [83,151], so bigleaf maple's seed bank is only transient. In the laboratory, bigleaf maple seed viability dropped from about 88% for fresh seed to about 15% after 1 year in storage at 34 °F (1 °C) [226]. In southwestern British Columbia, viable bigleaf maple seeds were most common in undisturbed forest soils and least common in highly disturbed soils. Soil samples were collected from forest floor to 20-inch (5 cm) depths beneath a Douglas-fir/creambush oceanspray (Holodiscus discolor) forest, then germinated in either the greenhouse or the field [144].

More info for the term: seed

Bigleaf maple seed on gravel.

Wind disperses bigleaf maple seed [78,109]. The samaras "descend like little helicopters, which greatly increases their dispersal" [164].

More info for the term: seed

Bigleaf maple first produces seed when about 10 years old [13,83,84,151]. Arno [13] describes bigleaf maple as a "prolific seed producer"; production is abundant in most years [151]. Open-grown trees may produce a good seed crop every year, but shade-grown trees may have sporadic seed production [40].

More info for the terms: forest, habitat type, mesic, tree, vine

Bigleaf maple may establish on a variety of sites but generally, seedlings survive only if taproots reach moist soil before the dry season [40,151]. On the Coast Ranges and Klamath Mountains of Oregon, bigleaf maple seedling establishment was better on mesic valley floors than on low hillslopes (42% vs. 29% of total tree seedling composition, respectively) [158]. Most report best establishment occurs on clearcuts or other open sites [13,40,83,84], including canopy gaps (review by [83]). In Douglas-fir plantations in western Oregon, bigleaf maple seedlings established best in open canopies [64,65]. There are a few reports of bigleaf maple establishing best under closed canopies [151]. Some suggest that bigleaf maple is a "seedling banker", maintaining stunted seedlings that persist and grow slowly beneath a closed canopy but that grow rapidly once released (review by [83]).

In general, bigleaf maple seedlings may show better initial establishment than some associated species because of bigleaf maple's relatively large seeds. Many factors, including browsing, may impede this initial success, however. In a planting experiment in a western hemlock habitat type on the McDonald-Dunn Research Forest, Oregon, bigleaf maple and vine maple (Acer circinatum)—both large-seeded species—had higher rates of seedling emergence and survival than the smaller-seeded, associated species salmonberry (Rubus spectabilis) and salal (Gaultheria shallon) on sites protected from browsing. However, browsing pressure on the maples was high on unprotected sites, with maple seedling emergence ranging from only 0% to 4%. This was significantly less than emergence rates of salmonberry and salal on unprotected sites (P<0.001). Three years after sowing, bigleaf maple seedling growth (averaged across sites) was fastest on thinned sites, with seedlings averaging 6.3 inches (16 cm) tall. Growth averaged 4.7 inches (12 cm) on clearcuts and 2.4 inches (6 cm) on unthinned sites [199].

Open-grown seedlings in moist soils may grow 3.3 to 6.6 feet (1-2 m) in one growing season; typically, this growth rate is faster than that of bigleaf maple's conifer associates. Bigleaf maple's growth rate may be cut in half on sites with dense vegetation [151].

Growth generally slows at the pole and sawtimber stages [151]. On the southern coast of British Columbia, bigleaf maple grew most rapidly when 5 to 15 years old. On productive sites, 5-year-old trees averaged 4.5 feet (1.4 m) in height. At 100 years old, trees ranged from 40 to 120 feet (10-40 m) tall [186].

Heavy grazing can slow or stop bigleaf maple growth. A study of historical records describing vegetation at Olympic National Park, Washington, from the mid-1800s through the late 1900s revealed few bigleaf maples and black cottonwoods had grown above browse line after a hunting ban was implemented in 1905 and gray wolves became extirpated around 1920. The authors attributed bigleaf maple's lack of growth to intense browsing by elk herds that are increasing in size without population controls [24].

See Hann and Larsen [88,129] for equations to predict diameter growth of bigleaf maple and other overstory trees of southwestern Oregon.

More info for the terms: association, basal area, codominant, cover, fire regime, forest, frequency, hardwood, lichen, mesic, organic soils, reburn, succession, ultramafic soils, xeric

Site characteristics: Moist woods, forests, and canyons are bigleaf maple's most common habitats throughout much of its distribution [99,138]. Bigleaf maple is apparently limited by cold climate to the north of its distribution and by drought to the south [83,151]. Its frost tolerance is low, and it does not grow where deep soil freezes occur before snowfall ([121], review by [83]).

Moisture regime: Bigleaf maple prefers moist to mesic habitats and is described as "moisture demanding" [40]. In the Siskiyou Mountains of southern Oregon and northern California, bigleaf maple frequency increased with increasing soil moisture [219]. Bigleaf maple is most common in upland riparian zones [1] but also grows in low riparian zones and in mesic upland forests of the Pacific Northwest. In riparian habitats, it is often found on upper terraces of 5th- and 6th-order streams [1,219], although it also grows near smaller streams [158,214]. Franklin and Dyrness [63] consider bigleaf maple characteristic of old land surfaces—particularly upper riparian terraces—of the Olympic rain forest. Bigleaf maple is confined to riparian zones, moist canyons [13,81], and other sites with permanent water [151] in central and southern California [20,81,173]. It is occasionally reported on dry sites. It is a minor species, for example, on the Dead Indian Plateau of southwestern Oregon. The site has hot, dry summers, late spring frosts, and is a notoriously difficult site on which to regenerate commercial conifer species [149,193].

Soils: Bigleaf maple often grows in alluvial soils [40,93,105], but it is occasionally found on dry upland soils [17]. Soils supporting bigleaf maple are commonly coarse or gravelly in texture [105,151], although it also grows in fine-textured soils [139]. On the Gulf Islands of British Columbia, bigleaf maple grows on alluvial floodplains, outwash sandy loams, eroded rocky shores, shallow to deep glacial tills, poorly drained marine clays, and wet organic soils [54,55]. In the Pacific Northwest, bigleaf maple thrives in moist gravels [151]. In Sitka spruce-western hemlock (Picea sitchensis-Tsuga heterophylla) forests of Washington and Oregon, shallow, stony soils support bigleaf maple groves [63]. A bigleaf maple/California hazelnut (Corylus cornuta subsp. californica) community on the Suislaw National Forest, Oregon, occurs on loams and silt loams [139]. On the Willamette National Forest, Oregon, bigleaf maple grows in a rock garden community. This community is situated on exposed ridges with patches of shallow soil lodged in rock. The community is highly diverse, with no clear species dominants [97]. Bigleaf maple dominates some talus slopes in the Coast Ranges of Oregon and Washington [63]. On the Tillamook Burn of Oregon, the bigleaf maple/creeping snowberry (Symphoricarpos mollis) vegetation type occurs on steep talus slopes and basalt cliff faces [17,100]. Elevations range from 1,000 to 1,600 feet (300-500 m), and most sites exceed 100% slope. In contrast to bigleaf maple's usual habitat, these sites are xeric [17]. Thirteen years following the last reburn in 1945, groundlayer vegetation in this type was sparse, and soil was still eroding [100].

Quartz diorite is the parent material of soils supporting bigleaf maple in the Siskiyou Mountains [219], and gabbro is the parent material in the Pine Hills of El Dorado County, California [221]. Bigleaf maple grows in ultramafic soils in Port-Orford cedar (Chamaecyparis lawsoniana) riparian forests of the Klamath-Siskiyou region of Oregon and California [156].

Bigleaf maple is not nutrient-demanding [151], although best growth occurs on rich bottomland soils [13].

In the Pacific Northwest, soil pH beneath bigleaf maple averaged 5.5 [200].

Elevation and topography: Bigleaf maple is found from sea level to about 3,000 feet (900 m) in Washington and Oregon [13]. It does not grow much above 1,150 feet (350 m) in British Columbia [83,130,151]. In the Siskiyou Mountains, bigleaf maple frequency was greatest at 1,500 to 2,500 feet (460-760 m) elevation. It decreased with increasing elevation, and bigleaf maple was not found above 5,500 feet (1,700 m) [219]. Bigleaf maple's elevational range extends to about 6,000 feet (1,800 m) in most of California [40,99,138]. It may be found up to 7,000 feet (2,000 m) in southern California [28,151], often growing near montane headwater streams [28].

Topography where bigleaf maple grows is highly variable. Bigleaf maple frequently grows in flat, interior valleys in Washington and Oregon but is also found on steep, rocky slopes and cliffs on the Coast Ranges of southwestern Oregon [151]. In a survey of unmanaged riparian forests in western Oregon, bigleaf maple cover was greatest on floodplains, moderate on stream terraces, and least on low hillslopes on the Coast Ranges. In the Klamath Mountains, it was not found on floodplains, and it had greater cover on terraces than on lower hillslopes [158]. In a study of watersheds near Coos Bay, Oregon, bigleaf maple made up less than 10% of stands near 0-order (headwater) streams. On these sites, its basal area was greatest on downstream slopes, moderate at headwaters, and least in valleys (4.2, 3.5, and 3.1 m²/ha, respectively) [183]. In the Columbia River Gorge, bigleaf maple is associated with south slopes and ravines [223].

Plant communities: Bigleaf maple is common in some conifer, mixed-evergreen, and hardwood communities and in seral brushfields. These communities are often diverse in species composition and structure [162]. Bigleaf maple is associated with Pacific madrone (Arbutus menziesii), Pacific dogwood (Cornus nuttallii), and prince's-pine (Chimaphila) throughout most of its range [151]. Chapters within Barbour and others [21] provide details of other over- and understory species commonly associated with bigleaf maple. In addition to the many vascular plant species with which bigleaf maple is associated [21], many arboreal moss and lichen species use bigleaf maple as a substrate ([105,164], review by [117]). The table below lists plant communities in which bigleaf maple is most common. Among these, bigleaf maple reaches greatest frequency in mixed-evergreen forests of southwestern Oregon and northern California [13,206]. Descriptions of these and other plant communities with bigleaf maple follow. See the Fire Regime Table for further information about these plant communities.

Plant communities in which bigleaf maple is important Community type Area Conifer coast Douglas-fir (Pseudotsuga menziesii var. menziesii) British Columbia, Pacific Northwest, California [4,53,62,63,105,133,151,166,220] grand fir (Abies grandis) Pacific Northwest [29,133,207] mixed-conifer forests southern Oregon and California [20] mixed-evergreen forests Washington, Oregon, and northern California [206] Pacific ponderosa pine (Pinus ponderosa var. ponderosa) southern Oregon and California [4,143,151,179] Port-Orford cedar (Chamaecyparis lawsoniana) Oregon, northern California [151,191] redwood California [151,172,206] Sitka spruce British Columbia, Pacific Northwest [63,90] western hemlock British Columbia, Pacific Northwest [62,105,133,150,151,166] white fir (Abies concolor) southern Oregon and northern California [151] western redcedar (Thuja plicata) Washington, Oregon [62,105,151,151] Hardwood black cottonwood (Populus balsamifera subsp. trichocarpa) Pacific Northwest, California [20,62,93,105,117,151] California bay (Umbellularia californica) Oregon, California [176] coast live oak (Q. agrifolia) California [103] Oregon white oak (Quercus garryana) Oregon, northern California [63,151,176,192] red alder (Alnus rubra) Pacific Northwest, California [20,93,117,147] white alder (A. rhombifolia) California [103]

Conifer communities: Bigleaf maple often occurs in scattered patches within or on the streamside edges of conifer-dominated riparian communities [117]. In surveys near rivers of the Puget Sound area of Washington, bigleaf maple was most important in areas just adjacent to waterways, while western redcedar and Douglas-fir tended to dominate upland riparian zones [41]. Within western hemlock-Sitka spruce forests, bigleaf maple grows mostly as scattered individuals or in groves of large trees (≥30 inches (76 cm) DBH) within the conifer forest matrix. It is not restricted to riparian sites in these mesic forest types [63]. Bigleaf maple is a minor species in Pacific silver fir (Abies amabilis) forests of the Olympic National Forest, Washington [98], and in bristlecone fir (A. bracteata) forests of California [20]. In Monterey County, California, the redwood-bigleaf maple/California polypody (Polypodium californicum) community occurs on gently sloping alluvial terraces near streams with boulder or very rocky substrates [139]. It is a rare type within the area's redwood ecosystem [27]. In the Santa Ana [26] and San Gabriel [86] mountains of southern California, bigleaf maple grows in bigcone Douglas-fir (Pseudotsuga macrocarpa) communities.

Mossy bigleaf maples along the Quinault River. Photo courtesy of City Pictures.

Mixed-evergreen forests: Bigleaf maple is particularly abundant in mixed-evergreen forests, which are dominated by a mix of Douglas-fir and the evergreen broadleaved species tanoak (Lithocarpus densiflorus), California bay, and/or Pacific madrone. Bigleaf maple is very common in tanoak-Douglas-fir communities in the Klamath-Siskiyou region [15,25]. In southern Oregon and northern California, Oregon white oak or other deciduous species may codominate in mixed-evergreen forests [206].

Hardwood communities: Bigleaf maple is an important to dominant component of many riparian hardwood and some upland oak (Quercus spp.) communities. It occurs in a few other, minor hardwood communities; these are typically in upland wetlands.

Bigleaf maple dominates small stretches of some streams and is associated with many riparian hardwood species. Black cottonwood, red alder, and/or white alder are bigleaf maple's most common associates or codominants in hardwood riparian systems. In coastal California, black cottonwood-bigleaf maple-California bay woodlands are interspersed with mixed-oak, redwood, and Douglas-fir forests [217]. An inventory on the Tillamook Burn revealed a bigleaf maple-red alder association that occurred at 700 to 900 feet (200-275 m) elevation on flat bottomlands of large streams [17]. See the Bigleaf maple communities section of FIRE REGIMES for more information on this community. Bigleaf maple is a characteristic species in sycamore (Platanus racemosa) riparian forests of the Central Coast Ranges of California [103]. Quaking aspen (Populus tremuloides) often codominates with bigleaf maple near streams in the Sierra Nevada [20]. On the Blodgett Forest Research Station, California, bigleaf maple dominated a few riparian sites. Incense-cedar (Calocedrus decurrens) dominated most riparian areas surveyed [23].

In central and southern California, bigleaf maple occurs only in riparian woodlands or sheltered, mesic sites such as canyon bottoms [148,160]. Codominant or associated species may include boxelder (Acer negundo), Fremont cottonwood (Populus fremontii), and/or white alder [80,86,206]. In the San Gabriel Mountains, a white alder-bigleaf maple vegetation type occupied <5% of the landscape surveyed [196].

Bigleaf maple is a codominant or common component of several hardwood communities that are not exclusively riparian. It occurs in California bay [176], Oregon white oak [176], and canyon live oak (Q. chrysolepis) [43,137] woodlands of the Pacific Northwest and California. Bigleaf maple occurs in canyon live oak-Coulter pine (Pinus coulteri) woodlands of the San Bernardino Mountains [20]. Bigleaf maple is sometimes codominant in California hazelnut communities of the Willamette Valley, Oregon. Bigleaf maple-California hazelnut communities may be successional to western hemlock, but some occur on cobbly floodplains that flood frequently enough to prevent further succession [139].

In southern California, bigleaf maple may dominate or occur in hardwood communities in canyons, other mesic sites, or riparian areas that are surrounded by montane chaparral or coastal sage scrub. California bay and white alder often codominate in these sheltered communities [178]. In Orange County, bigleaf maple dominates shaded aspects of Coal Canyon amidst a mosaic of mixed chaparral, stands of bigcone Douglas-fir, and stands of the northernmost population of Tecate cypress (Cupressus forbesii) [187]. In the San Bernardino Mountains, bigleaf maple-coast live oak-California bay communities are a minor riparian type within the coastal sage scrub matrix [104]. On Santa Cruz Island, bigleaf maple stands occur below 1,510 feet (460 m) on the north side of the island and in Diablo Canyon. Coastal sage scrub predominates across the island [114].

Bigleaf maple is important in a few minor woodlands on year-round springs. In the East Bay Area of California, it is important (17% cover) in California bay-coast live oak/poison-oak (Toxicodendron diversilobum) communities on hillside springs [8]. Bigleaf maple dominates some spring-fed communities in Contra Costa and Alameda counties. California bay, willows (Salix spp.), and/or white alder codominate [7].

Brushfields: In seral brushfields of southern Oregon and northern California, bigleaf maple typically associates or is codominant with red alder; less often, it is the seral dominant [51,52,169]. These brushfields typically persist for a few decades, then succeed to Douglas-fir or mixed-evergreen forests. See Successional Status for more information.

More info on this topic.

More info for the terms: codominant, cover, eruption, fire exclusion, forest, frequency, mesic, natural, seed, stand-replacement fire, succession, tree, woodland

Bigleaf maple tolerates both sun and shade [13,22], although it prefers open, seral stands to late-successional, closed stands [119]. It is generally rated as moderately shade tolerant [20]. One shade tolerance rating placed it 2nd, or "tolerant" on a scale of 1 to 5 (greatest to least) [18]. Seedlings may establish under young conifer stands, but their shade tolerance apparently decreases with age (review by [83]). In the laboratory, bigleaf maple seedlings showed maximum photosynthetic efficiency on microsites that mimicked gap centers or forest edges, indicating a preference for open conditions. Photosynthesis was less efficient on microsites with dimmer light [132].

Bigleaf maple occurs in all stages of succession, being most common in seral forests. It is considered an indicator of young-seral forests of coastal British Columbia [119]. It is sometimes common in late-seral forests of the Pacific Northwest, however [38]. In surveys along the Tahsish and Artlish rivers on Vancouver Island, bigleaf maple occurred mostly in young-seral Douglas-fir forests, although a few bigleaf maples were noted in mature forests [37]. On the Coast Ranges, bigleaf maple may be a seral dominant in western hemlock vegetation types [63]. The often clumped distribution of bigleaf maple trees in Douglas-fir forests suggests that canopy-gap dynamics may be important in bigleaf maple succession [162], but little information was available on bigleaf maple succession in canopy gaps as of 2011.

Early and midseral stages: Bigleaf maple is common in primary succession on riverine sites, and it may establish on other new substrates as well. Bigleaf maple is described as a primary-successional dominant on fragmented, colluvial soils in coastal British Columbia [119]. Bigleaf maple seedlings were noted, at 8% mean frequency, in primary succession on mudflows the year following the 1980 eruption of Mount St Helens [85].

Periodic disturbances such as flooding, fire, or logging apparently help retain bigleaf maple as an important member of seral plant communities. Riparian zones experience flooding frequently [1]. Bigleaf maple grows on both lower and upper stream terraces (see Site characteristics). The upper terraces, where bigleaf maple is common, may experience fire or wind disturbances more frequently than lower terraces. Even so, in most years, upland riparian plant communities are more protected from flooding, fire, and wind than plant communities outside the riparian zone [1]. In the Stehekin Valley of Washington, Douglas-fir-bigleaf maple and Douglas-fir-ponderosa pine/bigleaf maple forests experienced small- to large-scale wildfires, logging, or both every 30 to 375 years [130].

In riparian communities, bigleaf maple often follows red alder and willows successionally. On upland sites, it may replace Pacific madrone and oaks [151]. Along the Hoh River in Washington, Agee [1] reports that bigleaf maple is a midseral species that occupies midlevel terraces. Red alder and Scouler willow (Salix scouleriana) colonize gravel bars, while red alder dominates 1st-level, 80- to 100-year-old terraces. Bigleaf maple, Sitka spruce, and black cottonwood dominate the next-oldest and higher, 2nd terrace. Sitka spruce-western hemlock and western hemlock, respectively, dominate the successively older, 3rd and 4th terraces [1]. Another survey along the Hoh River had similar findings, with red alders dominating floodplains, bigleaf maple dominating communities on 1st and 2nd terraces, and western hemlock dominating uppermost, 3rd terraces [60].

Conifers may replace bigleaf maple successionally in riparian zones. A Sitka spruce-black cottonwood-bigleaf maple forest may replace riparian hardwoods on the Olympic Peninsula (review by [63]). On banks of the Queets River in Olympic National Park, bigleaf maple and black cottonwood occur in midsuccession, after red alder. In turn, they are eventually replaced by Sitka spruce. Turnover rate from red alder to bigleaf maple and black cottonwood dominance ranges from 60 to 80 years; bigleaf maple and Sitka spruce may remain codominant "for centuries" before Sitka spruce overtops the hardwoods [19]. Incense-cedar and other shade-tolerant conifers may replace bigleaf maple in the Sierra Nevada (Fryer 2001 personal observation).

After logging, bigleaf maple and other sprouting species [151,169] occupy clearings that succeed to conifers [63,105,169,224]. Bigleaf maple is common in 2nd-growth forests of southwestern British Columbia, but it is rarely dominant [163]. In western hemlock-Douglas-fir forests in coastal British Columbia, bigleaf maple frequency was 1% on a site logged 13 years previously, 4% on a site logged 42 years previously, and 8% on an unlogged site [116]. Such sites may convert to red alder-bigleaf maple or red alder brushfields if conifer seed sources are lacking [220].

Bigleaf maple increased in cover following logging and slash burning on the H. J. Andrews Experimental Forest in southern Oregon. Western hemlock dominated the overstory prior to logging. Bigleaf maple abundance was [51,52]:

Mean percent bigleaf maple cover (and frequency) before and after logging and slash burning on 3 sites on the H. J. Andrews Experimental Forest [51,52] Logging Before logging (1962) 0.2 (3.3) After logging (1963) 0.3 (3.3) Fire Postfire year 1 (1964) 1.1 (4.9) Postfire year 2 (1965) 1.3 (3.3) Postfire year 3 (1966) 2.1 (4.9) Postfire year 4 (1967) 2.2 (6.6) Postfire year 5 (1968) 2.3 (6.6)

Studies in the Cascade Range of southwestern Washington and western Oregon showed bigleaf maple was significantly more common in young and mature than in old-growth Douglas-fir forests (P≤ 0.5). However, on the Coast Ranges of Oregon, bigleaf maple was most common in old growth (P<0.1). All stands sampled originated after stand-replacing wildfires. Stand age classes were [188]:

<80 years = young
80 to 195 years = mature
>195 years = old growth

Bigleaf maple patches within a conifer matrix may shrink or wink out without disturbances such as fire or logging. A comparison of 1939 and 1993 landscapes on the Coast Ranges of Oregon showed early- to midsuccessional patches of bigleaf maple and/or red alder had declined in number, size, and total area. Declines were attributed to fire exclusion and reduced logging and grazing [117]. Two surveys made of the same areas in Yosemite Valley—one from 1932 to 1936 and the other from 1988 to 1999—indicated that large-diameter bigleaf maples (≥4 inches (10 cm) DBH) had declined over time, although differences in methods and inability to relocate the original plots made direct comparisons impossible [135].

Plant response to fire provides more information on bigleaf maple postfire succession and growth.

Late-seral and old-growth stages: Bigleaf maple may form part of the canopy in late succession, sometimes sharing dominance with conifers or other hardwoods. Bigleaf maple is a common component of old-growth, mixed-evergreen forests of southwestern Oregon and northern California [25,76,77]. It is the most common deciduous tree in old-growth Douglas-fir forests of Horse Rock Ridge Research Natural Area in Oregon [46]. It also occurs in old-growth redwood forests in California [72].

Bigleaf maple is noted as a late-seral species in the Willamette Valley [175]. Following stand-replacement fire, most vegetation succeeds from a grass stage to an oak woodland, then an oak forest, and last to a Douglas-fir-grand fir-bigleaf maple forest (Franklin and Dyrness 1973 cited in [50]). Comparing plant community composition of the European-American settlement period with that of the early 1960s, Habeck [82] found bigleaf maple was encroaching into Oregon white oak woodlands on mesic sites, while Douglas-fir was encroaching on both mesic and dry sites. Habeck suggested that eventually, bigleaf maple may replace both Oregon white oak and Douglas-fir successionally [82]. Another viewpoint is that Douglas-fir becomes the late-successional dominant on dry sites, while bigleaf maple codominates with Douglas-fir on moist sites (review by [63]).

Acer macrophyllum Pursh var. kimballi Harrar

Acer macrophyllum Pursh var. macrophyllum

Acer macrophyllum Pursh forma rubrum Murray [151]

The scientific name of bigleaf maple is Acer macrophyllum Pursh
(Aceraceae) [99,102,105,115,138].

More info for the term: litter

Bigleaf maple is useful for riparian revegetation [22,34,74]. It is a soil-building species. Its litter contains high levels of calcium, potassium, and other nutrients [151]. Cultivars are commercially available [211]. See these sources for propagation information: [211,225].

More info for the terms: forest, root crown, top-kill, tree

Bigleaf maple sprouts from the root crown or stump after top-kill by fire [59,120,151,164,171,184,195,214], cutting [40,58,120,131,151,164,171,198], or herbicide use [44,58,120,131,215]. Sprouts may attain 10 feet (3 m) in 1 year [58,164]. Three-year-old sprouts may reach 17 feet (5 m) tall and 21.5 feet (6.5 m) in crown diameter, with as many as 67 sprouts/root crown [151]. All age classes of bigleaf maple sprout, with sprouts of large trees growing more rapidly than sprouts of small trees [162]. Dale and others [48] developed a model to predict the rate of bigleaf maple sprouting. They predicted that trees from 4 to 20 inches (10-50 cm) in DBH will produce 10 to 50 sprouts/plant after top-kill. Their model was developed for bigleaf maples in the Pacific Northwest [47].

Sprouts grow most quickly on open sites, where they may reach 7 to 13 feet (2-4 m) in their first growing season [83,84]. Bigleaf maples growing under the canopy of old growth may die back and sprout repeatedly (Newton 1984 personal communication cited in [83]).

On the McDonald-Dunn Research Forest, clump size of bigleaf maple sprouts was positively correlated with parent tree stump diameter and negatively correlated with amount of bark removed from the parent during logging (P≤0.05). Mule deer browsing had no significant impact on clump size [198].

Characteristic trees, shrubs, and herbs associated with bigleaf maple in five portions of its native range are listed in table 2. Douglas-fir, Pacific madrone, Pacific dogwood, swordfern, and prince's-pine grow with bigleaf maple in most environments. Bigleaf maple communities often present on moist sites include willow-black cottonwood-bigleaf maple and red alder-bigleaf maple/salmonberry. The bigleaf maple/snowberry (Symphoricarpos albus) community is found on dry sites (5). Bigleaf maple is present but is not a dominant species in several other plant communities-western hemlock/western swordfern/ Oregon oxalis and Douglas-fir/oceanspray (western Washington and Oregon), Sitka spruce/devilsclubstink currant (Ribes bracteosum) (British Columbia), and white fir/Oregongrape (California), for example.

Bigleaf maple is present in the following forest cover types (3): Red Alder (Society of American Foresters Type 221), Black Cottonwood-Willow (222), Sitka Spruce (223), Western Hemlock-Sitka Spruce (225), Pacific Douglas-Fir (229), Douglas-Fir- Western Hemlock (230), Port-Orford-cedar (231), Redwood (232), Oregon White Oak (233), Douglas-Fir-Tanoak-Pacific Madrone (234), Pacific Ponderosa Pine-Douglas-Fir (244), and Pacific Ponderosa Pine (245).

Bigleaf maple supports several epiphytic plants in moist climates. This support is particularly evident in the "rain forest" on the west side of the Olympic Peninsula, where epiphytes weigh nearly four times as much as the leaves of host bigleaf maples (19). Some of those maples, heavily laden with rain-soaked epiphytes, are more susceptible to windthrow than trees with less luxuriant epiphytic growth (32). A club moss (Selaginella oregana) and the mosses Hylocomium splendens, Leucolepis menziesii, Isothecium stoloniferum, and Neckera menziesii are the most abundant epiphyte species, but lichens (Cladonia, Nephroma, and Crocynia spp.) and the licorice fern (Polypodiuni glycyrrhiza) are also common (5,32).

Bigleaf maple grows over a wide range of temperature and moisture conditions, from the cool, moist, marine climate of coastal British Columbia to the warm, dry, growing seasons of southern California (table 1). Springs, streams, and other permanent sources of water are often associated with bigleaf maple in southern California, but it also grows on eastern and northern slopes in California where more than 600 mm (24 in) of annual rainfall occurs (15). It receives abundant moisture in the coastal redwood region of northern California (36). Bigleaf maple is not, however, limited to moist sites in southwestern Oregon, where it is found from moist stream bottoms to dry hillsides. Nocturnal moisture stresses of more than 2.0 M Pa (20 bars) have been recorded on some of those hillsides in southwestern Oregon. This maple also grows on hot, dry sites in the central-western Cascade Range in Oregon and does not seem to be limited by moisture deficiencies there (40). Moisture deficiencies seldom occur in western valleys of the Olympic Peninsula or in coastal British Columbia (25,32). Temperature probably limits the northern distribution of bigleaf maple (29).

Table 1- Climatic variation in northern and southern portions of the native range of bigleaf maple

Areas Mean Temperature Frost-Free period Mean precipitation Annual Maximum Minimum
Annual Growing season (°C) (°C) (°C) (days) (mm) (mm) British Columbia¹ 8 to 10 18 to 26 12 to 2 140 to 270 700 to 6600 300 to 1170 California² 13 to 15 24 to 27 2 to 6 270 to 350 560 to 1470 50 to 130 (°F) (°F) (°F) (days) (in) (in) British Columbia 46 to 50 64 to 79 28 to 36 140 to 270 27 to 260 12 to 46 California 55 to 59 75 to 81 36 to 43 70 to 350 22 to 58 2 to 5 ¹Latitudes 49° to 51°N. (20).
²Latitudes 35° to 37° N. (29).

Fungi are responsible for much of the defect in bigleaf maple. Decay is seldom a serious problem in young undamaged trees, but stem and branch wounds are invaded by wood-rotting fungi such as Heterobasidion annosum, Fomitopsis pinicola, Polyporus berkeleyi, and Inonotus dryadeus that can reduce the tree to a hollow shell. Overmature bigleaf maples are often decayed by root rot (Armillaria spp.) and butt rots (Ganoderma applanatum and Oxyporus populinus). Verticillium wilt (Verticillium albo-atrum) occasionally kills forest trees, but it is most serious on ornamental bigleaf maples (14).

The carpenter worm (Prionoxystus robiniae) may seriously damage living maples. It attacks trees of all sizes, particularly those that are open-grown. The resulting larval tunnels degrade the lumber cut from affected stems. Dead trees and maple products are damaged by powderpost beetles (Hemicoelus, Melalgus, Polycaon, Ptilinus, Scobicia, and Xestobium spp.), and a roundheaded borer (Synaphaeta guexi) makes large burrows in dead or dying trees (8).

Bigleaf maple twigs and young stems are browsed by deer and elk. They are also clipped by mountain beavers. The roots are sometimes attacked by nematodes (Meloidogyne spp.) (14). A high percentage of seedling mortality also results from predation by rodents and grazing by slugs and other invertebrates (7).

Seed predation by small mammals is high, and it may be related to overstory condition. Seedling emergence on artificially seeded plots in the Oregon Coast Range is from 7 to 100 times greater on plots protected from birds and rodents than on unprotected plots. The highest rate of predation is in young (20- to 40-year-old) and old (80- to 250-year-old) stands with lower rates in clearcuts and in pole-size stands (40 to 80 years old) (7).

Bigleaf maple begins to produce seed at about 10 years of age and continues every year thereafter (23). It is polygamous, and both staminate and perfect flowers are mixed in the same dense, cylindrical racemes. Flowers are greenish yellow and scented, and they appear before the leaves-from March, at low elevations and in the southern part of the range, to June, at high elevations and in the north. Pollination by insects usually occurs within 2 to 4 weeks after the buds burst (29). Pubescent double samaras result, with 3.5- to 5-cm (1.4- to 2-in) wings that diverge at less than a 90° angle. They ripen in September and October.

The Kimball maple (Acer macrophyllum Pursh var. kimballi Harrar), a rare variety of bigleaf maple, occurs in the Washington counties of Snohomish, Cowlitz, and Pierce. It differs from Acer maerophyllum var. macrophyllum in having much more deeply lobed leaves, often tricarpellate flowers, and frequent triple samaras (12).

Acer macrophyllum Pursh forma rubrum Murray is an even rarer form of bigleaf maple. First noticed at Berkeley, CA, in 1968 and later found in the Coast Ranges north of San Francisco, it has red leaves (18). The young leaves of an early German cultivar, 'tricolor,' are also red. Tricolor leaves are rose-red, however, and they later become marked with white.

Rapid height growth of bigleaf maple continues through the sapling stage, but it slows as the trees grow from pole to sawtimber size. Diameter growth is proportional to leaf area, and trees with large crowns develop more sapwood than trees with small crowns (37). The volume of individual trees ranges from 0.11 m³ (4 ft³) at 15 cm (6 in) in d.b.h. to 6.5 m³ (230 ft³) at 91 cm (36 in) in d.b.h. (24). The largest bigleaf maple known in 1977 grew in western Oregon and had a circumference of 1064 cm (419 in) at breast height, a height of 30.8 m (101 ft), and a crown spread of 27.4 m (90 ft) (26). The oldest attain ages of 200 years or more (2).

Pure, 70-year-old stands of bigleaf maple have yielded about 315 m³/ha (4,500 ft³/acre). Under intensive management, rotations of 50 years or less could probably be used (16).

Rooting Habit- Bigleaf maple has a shallow, widespreading root system well suited to the shallow or saturated soils on which it often grows. It probably has a competitive advantage over deeper-rooted species under such conditions.

Bigleaf maple is not a pioneer species that rapidly invades disturbed areas; however, it is often present in undisturbed stands and is able to respond with vigorous sprout growth after disturbance. Maple seedling establishment is most likely to occur in Douglas-fir stands after the start of natural thinning and before the dense understory characteristic of older stands develops. Light or other factors related to stand density apparently limit establishment. Increases in light from 0 to 20 percent of that in the open result in increases of from 0 to 60 percent in survival, but additional increases in light are not beneficial. Seedlings often occur in clusters, with various age distributions, suggesting that conditions favoring establishment vary from year to year (7). The presence of bigleaf maple in undisturbed stands and its potential for rapid growth suggest that it can respond quickly to gap formation or overstory removal.

Maple seedlings often appear in intermediate or late seral communities. Bigleaf maple frequently follows willow (Salix spp.) or red alder in riparian seres (4,13), and sometimes it replaces oaks or Pacific madrone on upland sites.

Silviculture of bigleaf maple usually involves control rather than culture. Bigleaf maple does not aggressively invade clearcut units, but vigorous stump sprouting is a problem when it occurs in the harvested stand. Sprouting can be control!ed by applying water-soluble amines or potassium salts of phenoxy herbicides around the sapwood perimeter on freshly cut stumps (21). Girdling the uncut trees is ineffective, for girdled bigleaf maples survive for several years and sprout. Aerial spraying of herbicides and other foliar applications are also ineffective-herbicide translocation is inadequate and the roots are not killed (22). Basal bark treatments overcome this problem. They are effective when ester-in-oil formulations of the phenoxy herbicides are applied (21).

Dry sites with bigleaf maple overstories should not be clearcut if conversion to Douglas-fir is attempted. Seedling survival will be better if the Douglas-fir is underplanted, preferably after the overstory maples are killed with a basal spray of phenoxy ester in oil (20).

When bigleaf maple is harvested as a crop rather than killed as a weed, often only trees that will yield a minimum log size (3.7 m by 25 cm, or 12 ft by 10 in) are harvested (16). Merchantable trees are usually scattered, limbing is laborious, and logs are short. Felling, yarding, and milling costs therefore tend to be higher for bigleaf maple than for conifers. Mill waste is also high-as much as 30 percent in slabs, sawdust, trim, and defect (16).

Seeds are abundant almost every year, but production by individual trees and stands can vary from year to year (7). Although most of the seeds are dispersed by the wind between October and January, some seeds can be found on trees as late as March. Bigleaf maple seeds are large and generally triangular or oval. They are 4 to 12 mm (0.16 to 0.47 in) long and 4 to 9 mm (0.16 to 0.35 in) thick. At field moisture content, filled-seed weights range from 5,200 to 7,900 seeds/kg (2,400 to 3,600 seeds/lb) for individual trees in the Oregon Coast Range. Seed coat comprises 60 to 70 percent of the seed weight (39).

Seed moisture content reaches a minimum of 10 to 20 percent (dry weight basis) before the autumn rains begin in western Oregon. After the rains begin, seed moisture content varies among individual trees, but it increases by 140 to 200 percent. The pubescent seed coat appears to be effective in holding water and raising seed moisture content quickly. Seed collection and storage are best done when minimum moisture content is reached before the start of the autumn rains. Seeds in this condition can be stored without further drying for at least 1 year at 1° C (34° F) with only a slight loss in viability. Seeds collected after the moisture content has increased are usually killed by redrying, but they can be stored for up to 6 months at the field moisture content with a 30- to 40-percent reduction in viability Seeds stored in this way produce vigorous seedlings when planted in nursery beds (39).

Germination is epigeal. It begins in late January or early February under field conditions and is usually completed by April or May in the Oregon Coast Range. Seeds germinate completely at 1° C (34° F) under laboratory conditions, beginning at about 60 days and completing their germination after 90 to 120 days (39). Because of this low temperature threshold for germination, seeds germinate early under natural conditions if moisture is not limiting. Germination during stratification can be used as a means of screening seeds before sowing. If seeds are stratified for 60 days and then germinated, the optimum temperature for germination is 15° C (59° F) (10). Exogenous gibberellin, cytokinin, or ethylene do not overcome the stratification requirement (10). A small number of seeds have been found germinating on trees in December before dispersal (39).

Seed germination is excellent on mineral soil and organic substrates (7,25,39), and seedling establishment is best when those substrates do not dry excessively during the growing season. Bigleaf maple seedling emergence is not affected by Douglas-fir canopy density in coastal Oregon under conditions that vary from young-and-dense to old-and-open stands, but emergence is better under all of these stand conditions than it is in clearcut areas (7). An average 30 to 40 percent of the viable seeds germinate if they are protected from predators, and occasional seed lots attain 80 percent germination (7). All bigleaf maple seeds germinate during the late winter and spring after seed dispersal. Delayed germination does not occur in subsequent years (7).

Bigleaf maple seedlings have a high juvenile growth potential, exceeding that of Douglas-fir and other conifers (38,39). When open-grown under conditions of adequate moisture and nutrients, seedlings reach heights of 1 to 2 m (3.3 to 6.6 ft) in one growing season. Competition affects growth, however; and first-season height is reduced by more than 50 percent when seedling density is increased from 1 to about 600 seedlings/m² (0.1 to 55.7 seedlings/ft²). Seedling weight is even more sensitive to competition than seedling height, and an increase in density from 1 to 60 seedlings/m² (0.1 to 5.6 seedlings/ft²) can result in a 50-percent decrease in seedling dry weight (39).

The morphology of young seedlings is strongly influenced by density. At low density, branch development begins in the buds associated with the cotyledons and moves up the stem as height growth progresses. At high densities, branch development is suppressed and the few branches that develop soon die. Internode length is highly responsive to density, and the longest internodes are produced at intermediate densities during the first year of growth.

The growth potential of bigleaf maple is rarely achieved in the field under normal conditions of light, moisture, competition, and browsing intensity (7). A survey of bigleaf maple seedlings in western Oregon showed that the tallest seedlings were 5 m (16.4 ft) tall and 20 to 30 years old. The height distribution of all seedlings in a stand most commonly resembled an inverted J, with 0 to 25 cm (0 to 10 in) tall, 1- to 4-year-old seedlings, most numerous. Normal and bimodal height distributions were also observed in the western Oregon survey. Although these seedlings were all growing in the understories of Douglas-fir stands, shapes of the height-distribution curves did not seem to be associated with stand conditions. Few seedlings were found in clearcuts (7). Browsing by deer probably is the most important factor influencing the height and stem morphology of bigleaf maple seedlings (7).

Temporary flooding is common on riparian sites, and the seedlings are able to survive short periods of inundation. Bigleaf maple is not as tolerant of flooding as red alder, Oregon ash (Fraxinus latifolia), black cottonwood, Sitka spruce, and western red-cedar, however; flooding for 2 months during the growing season kills both maple seedlings and mature trees (35).

Well drained alluvial and colluvial soils are well suited to bigleaf maple. Abundant moisture and a deep, gravelly profile produce the best growth-usually on river terraces, flood plains, and seepage sites (25). Growth is poorer on shallow, rocky soils, but bigleaf maple is frequently found on such soils. In the Coast Ranges of Oregon and the north Cascade Range in Washington, it even grows on steep talus slopes (1,5).

Bigleaf maple is associated with many soil groups (5,25). On upland sites, these groups include the moist but well drained Brown Soils (Haplumbrepts and Dystrochrepts); Reddish Brown Lateritic soils (Haplohumults); Podzols (Haplorthods); both fine-and coarse-textured dry soils (Haploxerolls and Xeropsamments); and shallow, dry soils (Lithic Xerumbrepts). Soil groups associated with bigleaf maple in lowland areas include flood plain alluvium (Udifluvents); alluvial pumice deposits (Vitrandepts); wet, gley soils (Aqualfs); and cool, acid, well-drained soils (Boralfs). These soil great groups and suborders are found in the soil orders Inceptisols, Ultisols, Spodosols, Mollisols, Entisols, and Alfisols.

Bigleaf maple does not require high concentrations of soil nutrients (36), but it is very sensitive to toxic concentrations of soil boron (9). Litterfall weights are greater under bigleaf maple than under Douglas-fir, and bigleaf maple leaves and litter contain high concentrations of potassium, calcium, and other macro-and micro-nutrients (6,33). Bigleaf maple is a soil-building species that benefits the sites on which it grows.

Bigleaf maples grow at low elevations on the north side of Santa Cruz Island (27) but are usually found on riparian sites above 915 m (3,000 ft) in southern California, where the maximum elevation at which they grow is 2135 m (7,000 ft). Farther north in California, maximum elevations decrease to 1675 m (5,500 ft) in the Sierra Nevada and 1035 m (3,400 ft) in the Coast Ranges (29). In central and northern California, bigleaf maple becomes less riparian and more widely distributed (11), sometimes growing as shrubby clumps on the steepest north-facing canyon walls (15). This maple does not grow in the Central Valley of California (11). It is found above 310 m (1,017 ft) in steep-sided ravines and on mesic slopes in the Klamath Mountains (31) and at elevations of 1220 m (4,000 ft) on the Cascade Range in southern Oregon.

The topography occupied by bigleaf maple in Oregon and Washington includes flat interior valleys, gently sloping stream bottoms, and moderate to steep slopes. It grows on both moist, fertile stream bottoms and arid, precipitous, south-facing rock outcroppings with slopes greater than 100 percent in the Coast Ranges of northwestern Oregon (1). On the Olympic Peninsula in Washington, the maximum elevation at which it grows is 455 m (1,500 ft). Bigleaf maple is seldom found above 305 m (1,000 ft) in coastal British Columbia, but it has been observed above 350 m (1,150 ft) on the east coast of southern Vancouver Island (25).

Bigleaf maple is an excellent shade tree. Its wood is used in the furniture industry, but it is neither as hard nor as strong as the wood of sugar maple (Acer saccharum) (16). Like sugar maple, it has sweet sap that can be made into syrup. The flow of sap is adequate for syrup production in January and February, but the syrup is of a lower quality than that made from sugar maple (30).

Bigleaf maple is a preferred wood for piano frames. It is excellent for decorative face veneer and makes good container material but is not suitable for flooring (16). The amounts of bigleaf maple being marketed for fuelwood are increasing as the use of wood stoves increases. Bigleaf maple has about 70 percent of the fuel value of Oregon white oak and 115 percent of the fuel value of red alder wood.

Bigleaf maple is usually harvested in conifer stands along with the conifers. These trees generally originate from sprouts and are of poor quality. Higher quality trees could be produced by managing maple stands that originate from seed or planted seedlings.

Bigleaf maple sprouts profusely after being cut. The large stumps produce more and taller sprouts, but all sizes regenerate vigorously. Sprout clumps have achieved heights of 5 m (17 ft) and crown diameters of 6.5 m (21.5 ft) in 3 years, with as many as 67 sprouts around a single stump (28). This sprouting vigor probably could be used in reproducing pure stands of bigleaf maple by the coppice method. It creates undesirable competition for the conifers being managed on most sites. Unlike vine maple (Acer circinatum), bigleaf maple does not appear to reproduce by layering. It can, however, be propagated from stem cuttings.

Aceraceae -- Maple family

Don Minore and John C. Zasada

Bigleaf maple (Acer macrophyllum), also called broadleaf maple or Oregon maple, is one of the few commercial hardwood tree species on the Pacific Coast. It is small compared with its conifer associates. Most mature bigleaf maples are about 15 m (50 ft) tall and 50 cm (20 in) in d.b.h. (5). Large trees often reach heights of 30 m (100 ft) and diameters of 90 to 120 cm (36 to 48 in). True to its common name, bigleaf maple usually bears leaves up to 30.5 cm (12 in) across, and exceptionally large leaves may attain widths of 61 cm (24 in) (2). They are borne on rounded crowns supported by short, branching boles if open-grown, but trees growing in dense stands are often well formed and free of branches for half to two-thirds of their height. Bigleaf maple is an excellent shade tree. The wood is used for furniture, especially piano frames, and the sap can be made into syrup.

The native range of bigleaf maple extends from latitude 33° to 51° N., always within 300 km (186 mi) of the Pacific Ocean. This maple is not found in southeastern Alaska or on the Queen Charlotte Islands (34), but it does grow on Vancouver Island at least as far north as Port Hardy (25). On the mainland, the range is a continuous belt from near Sullivan Bay, BC, to within 16 km (10 mi) of San Francisco Bay, CA-a belt that includes the western slopes of the Coast Ranges of British Columbia, the Olympic Peninsula in Washington, the Coast Ranges of Oregon and California, and the western slopes of the Cascade Range in Oregon and Washington. The species is less common south of San Francisco Bay, but extensive stands are found in the Santa Cruz and Santa Lucia Mountains. Isolated groves are scattered along the southern California coast to San Diego County. Bigleaf maple is common on the western slopes of the Sierra Nevada north of the Yuba River and is present in less abundance as far south as Sequoia National Park (11).

Most of the estimated volume of standing sawtimber is found in Washington (about 19.6 million m³ or 3.43 billion fbm) and Oregon (about 18.0 million m³ or 3.16 billion fbm). Almost half this timber is in Lewis and Whatcom Counties in Washington and Douglas and Lane Counties in Oregon (17). The estimated 1.1 million m³ (200 million fbm) of bigleaf maple in British Columbia is found on the south coast and Vancouver Island (16).


-The native range of bigleaf maple.

Acer macrophyllum, the bigleaf maple or Oregon maple, is a large deciduous tree in the genus Acer.

It is native to western North America, mostly near the Pacific coast, from southernmost Alaska to southern California. Some stands are also found inland in the foothills of the Sierra Nevada of central California, and a tiny population occurs in central Idaho.

Large Acer macrophyllum leaf in Washington State