Acer macrophyllum

Acer macrophyllum
Angilbas at English Wikipedia · Public domain · source
Name	Bigleaf maple
Genus	Acer
Species	macrophyllum
Authority	Pursh

Acer macrophyllum is a large deciduous maple native to the Pacific Northwest of North America, notable for its exceptionally large leaves and ecological importance in temperate rainforests. The species is valued for timber, cultural uses by Indigenous peoples, and as a component of mixed-species forest stands in coastal regions. It is a conspicuous element of landscapes from southern British Columbia to central California and figures in conservation, forestry, and urban planting discussions.

Description

Acer macrophyllum is a tall tree reaching 20–35 m (occasionally over 45 m) with a broad crown and a trunk often exceeding 2 m in diameter in mature specimens. Its opposite, palmate leaves typically measure 15–30 cm across, sometimes larger, and have 5 deep lobes; leaves turn yellow to orange in autumn in many localities. The species produces panicles of small, greenish-yellow flowers in spring followed by paired samaras that aid wind dispersal. Bark on mature trees is usually dark brown to gray and furrowed, providing habitat structures used by cavity-nesting species.

Distribution and habitat

Acer macrophyllum occurs along the Pacific Coast from the Olympic Peninsula and southwestern British Columbia through Washington (state), Oregon, and into coastal California, with disjunct inland populations in the Cascade Range rainshadow. It favors moist, humid sites including riparian corridors, lowland alluvial terraces, coastal mixed-conifer forests, and montane valleys where precipitation and fog create temperate rainforest conditions. Elevational range varies regionally, extending from near sea level to several hundred meters in northern portions and higher elevations in southern populations near the Sierra Nevada foothills.

Ecology and wildlife interactions

Bigleaf maple functions as a mid- to late-successional tree within stands dominated by species such as Douglas fir, Western hemlock, and Sitka spruce. Its leaf litter contributes to soil nutrient cycles and supports mycorrhizal networks involving genera such as Rhizopogon and Laccaria in coniferous understories. The tree provides forage and habitat resources: browse and seeds are used seasonally by mammals like black-tailed deer and American black bear; cavity-rich trunks host nesting by birds including northern flicker and pileated woodpecker; and its sap and epiphytic microhabitats support invertebrates, bryophytes, and lichens associated with coastal forests. Flowering structures offer nectar and pollen to native bumblebee species and other pollinators, while samaras are dispersed by wind and occasionally secondarily moved by corvids such as Steller's jay.

Uses and cultivation

Acer macrophyllum timber is moderately heavy and prized for furniture, veneer, and specialty woodcraft, comparable in use-context to woods marketed by companies and artisans in regions such as Vancouver and Portland, Oregon. Indigenous peoples of the Pacific Northwest, including the Coast Salish and Makah, historically used inner bark fibers for cordage and baskets and consumed sap in seasonal practices. In horticulture, the species is planted in parks and large gardens for shade and specimen value in cities such as Seattle and Victoria, British Columbia, though its large size limits use in small yards. Cultivation requires moist soil and space; it tolerates coastal fog and maritime climates but can suffer drought stress inland. Silvicultural systems and restoration projects often incorporate bigleaf maple to increase structural diversity and accelerate understory development in degraded riparian zones.

Conservation and threats

While Acer macrophyllum maintains broad distribution and is not currently listed as globally threatened, local populations face pressures from timber harvest, urban development, and changes in disturbance regimes driven by fire suppression and altered hydrology. Invasive pathogens and pests affecting maples elsewhere, as well as climate-driven shifts in precipitation and increased drought frequency in parts of its range, pose emerging risks that can compound susceptibility to secondary pests and windthrow. Conservation actions emphasize protection of old-growth stands, restoration of riparian corridors, incorporation in urban tree inventories used by municipalities such as Vancouver, British Columbia and San Francisco, and research coordinated among institutions including state and provincial forestry agencies and botanical gardens. Monitoring of genetic diversity and propagation efforts by arboreta and tribal forestry programs support resilience against future environmental change.

macrophyllum