Acer grandidentatum

Bigtooth maple

Sapindaceae

The Basics

Taxonomy: Kingdom - Plantae (plants). Subkingdom - Tracheobionta (vascular plants). Superdivision - Spermatophyta (seed plants). Division - Magnoliophyta ( Flowering plants). Class - Magnoliopsida. Order - Sapindales. Family - Sapindaceae (Maple family). Genus -Acer L. Species - Acer grandidentatum Nutt.

Ecology: Bigtooth maple is a deciduous, small tree or shrub of variable size. Its life form is dependent upon the moisture regime. In canyon bottoms and along streams it grows as a tree with single or multiple trunks reaching 15 m tall and 30 cm in diameter, while on dry canyon slopes it grows as a shrub with 2 or more stems reaching 8 m tall. Bigtooth maple leaves are palmately lobed, 2.5-10 cm wide, and pubescent beneath.

Bigtooth maple has a broad ecological amplitude. It occurs on a wide range of sites with different aspects, soil types, and soil moisture conditions. Throughout its range it is most often located on cool, moist sites in canyons, ravines, along mountain streams, and on lower slopes...When bigtooth maple grows together with Gambel oak, it occupies ravines while Gambel oak occupies the slopes.

Bigtooth maple is an early- to late-successional species. It is abundant in late successional riparian communities in Zion National Park, Utah. Seedlings are shade tolerant and grow under the canopy of mature big sagebrush (Artemisia tridentata) and Gambel oak...Bigtooth maple commonly invades Gambel oak stands in Utah and northern Arizona...Because bigtooth maple leafs and flowers earlier and grows faster in stem and crown diameter than Gambel oak, it becomes more important in the canopy over time. On some sites, it may eventually replace Gambel oak. Bigtooth maple is the dominant climax species in many maple-oak woodlands from north-central Utah to south-central Idaho.

Identification

Bigtooth maple is a deciduous, small tree or shrub of variable size. Its life form is dependent upon the moisture regime. In canyon bottoms and along streams it grows as a tree with single or multiple trunks reaching 15 m tall and 30 cm in diameter, while on dry canyon slopes it grows as a shrub with 2 or more stems reaching 8 m tall.

Bigtooth maple leaves are palmately lobed, 2.5-10 cm wide, and pubescent beneath. Plants usually flower every 2 or 3 years. Flowers are umbellate or corymbose and have no petals. The fruit is a dry, indehiscent, double-winged samara, each side with 1 small seed. The ovary and young fruit have long, straight hairs. Twigs are glabrous and the bark is thin and smooth or flaky. Bigtooth maple has both lateral surface roots and a deep tap root. An extensive root system develops during the first growing season. Reproduction by layering of the lower branches extends the root system radially.

Threats

Bigtooth maple is generally tolerant of fire. Plants sprout from the root crown when stems are burned. Sprouting after fire is dependent upon tree age and fire severity. Sprouting is most likely to occur from young stems growing on moist sites where high moisture content in fuels results in low severity burns. A severe burn is likely to damage the sprouting response.

Although bigtooth maple may be top-killed by fire, plants can survive by sprouting from the root crown. In a severe burn, bigtooth maple would likely be killed. Smaller-diameter stems are more likely to be killed by fire, clearing areas for new tree seedlings and sprouts from surviving larger diameter trees.

Fire does not significantly change the species composition in bigtooth maple and Gambel oak stands in the oakbrush vegetation type in Utah. Burned stands "return quickly" to prefire species composition. Bigtooth maple may become more important in the canopy after fire. A severe fire can spread quickly through Gambel oak and bigtooth maple canopy during dry, windy weather and on steep terrain. After a stand- replacing fire, sprouts of Gambel oak and bigtooth maple appear within a few weeks.

Reproduction

Bigtooth maple reproduces sexually and vegetatively. Reproduction by seed is important for establishment of bigtooth maple in new areas. Layering is common in older plants and is a more effective method of reproduction in the mountain brush zone in central Utah. Bigtooth maple also sprouts from the root crown.

Seed dispersal - Flowers are either male or female. Plants may bear male flowers only or produce both male and female flowers on the same inflorescence...Bigtooth maple flowers are wind pollinated...Bigtooth maple seeds are dispersed by wind and gravity. Wind dispersed samaras are important for successful establishment of bigtooth maple in new areas, particularly on shady sites.

Seedling establishment/growth - Bigtooth maple samaras exhibit better establishment in new areas than under parent trees where layering is more common. Herbaceous vegetation beneath Gambel oak is often less dense than under bigtooth maple, allowing for easier establishment of bigtooth maple seedlings. Seedling growth in bigtooth maple is slow, especially during the first few growing seasons.

Vegetative regeneration - Bigtooth maple reproduces vegetatively by layering or by sprouting from the root crown when stems are broken off by flooding, beavers, fire, or other disturbances. Layering is the most effective means of reproduction in bigtooth maple in the mountain brush zone of central Utah.

Species Distribution

Citation

USDA Plants Database
USDA, NRCS. 2016. The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA.

USFS Plant Database
Habeck, R. J. 1992. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory.