When you have successfully completed this section you will:

1.  Be able to identify the major forest biomes and cover types which occur in North America.

2.  Know the most important species which occur in each forest biome.

 

Biomes are a means of classifying vegetation into distinct groups, at a very broad scale.  North America is comprised of 11 very different biomes, including...

Arctic Tundra
Desert
Broad Sclerophyll,
Pinyon-Juniper,
Temperate Grasslands
Mountain Complex
Subtropical
Tropical
Northern Coniferous Forest
Moist Temperate Coniferous Forest
Temperate Deciduous Forest

Reprinted From: College of Agriculture, Department of Forestry, University of Illinois, Urbana, 1974.

 NORTHERN CONIFEROUS FOREST BIOME - BOREAL FOREST
The northern coniferous forest biome occupies a vast area below the tundra, extending completely across Canada and into interior Alaska.  The biome is also referred to as the boreal forest or taiga.

Compared to the arctic tundra, the climate of the boreal forest is characterized by a longer and warmer growing season.  Precipitation averages 20 inches per year, but ranges from 40 inches in the eastern regions to 10 inches in interior Alaska.  Available soil moisture is high as a result of cool temperature and low evapotranspiration rates.  Mineral soils are generally thin and poorly drained.  Large expanses of land are covered with thick deposits of peat and organic soils, ranging in depth from several feet to nearly a hundred.  These soils have very high moisture holding capacities and are often completely saturated.

NORTHERN CONIFEROUS FOREST BIOME - BOREAL FOREST
A broad belt of forest-tundra transition lies along the northern edges of the boreal forest.  Here, forest trees are interspersed with tundra plants, the former occupying more stable soils not subject to movement or heaving due to cyclic freezes and thaws.

NORTHERN CONIFEROUS FOREST BIOME - BOREAL FOREST
The diversity of tree species in the boreal forest is quite low, with black spruce (Picea mariana), larch or tamarack (Larix laricina), and white spruce (P. glauca) the most common species.  The former two species generally occupy wet sites with poorly drained mineral or organic soils, while white spruce is the climatic climax species on sites that are drier and higher in nutrient content.  Balsam fir (Abies balsamea) is a dominant tree species in the eastern half of the biome.  This species is very tolerant of understory conditions (more so than the spruces which are also relatively tolerant) and competes well with tolerant hardwoods.  Balsam fir is, however, susceptible to injury by insects, fungi, fire, and ice.  Like the above species, it is also shallow-rooted and subject to wind throw.

NORTHERN CONIFEROUS FOREST BIOME - BOREAL FOREST
Red spruce replaces white spruce as a dominant south of the St. Lawrence Valley and into the northern Appalachians.  Still further south in the high Appalachians, Fraser fir (Abies fraseri) replaces balsam fir and forms a high altitude association with red spruce as far south as the Carolinas and Tennessee.  In the northwestern part of the biome, balsam fir is replaced by subalpine fir (A. lasiocarpa), in association with white spruce.

NORTHERN CONIFEROUS FOREST BIOME - BOGS
Much of the northern coniferous forest biome is covered with lakes, which eventually fill with mineral and organic matter to form bogs.  A succession of plant communities is associated with the change in substrate and microenvironment.  Thus, floating and submerged aquatic plants occupy the shallow waters near the shore, slowly accumulating wind-blown soil and decaying organic matter.  This initial stage is replaced by invading sedges and grasses and in turn by shrubs, including Labrador tea (Ledum groenlandicum), leather leaf (Chamaedaphne calyculata), sweet gale (Myrica gale), alder (Alnus spp.), and various species of blueberry (Vaccinium spp.).  Tamarack, with a high tolerance for wet, cold, highly acid and highly organic substrates, is the first tree species to invade bogs.  It is gradually replaced by black spruce, the edaphic climax on wet, boggy sites in the biome.

NORTHERN CONIFEROUS FOREST BIOME - WHITE PINE-RED PINE ASSOCIATION
Surrounding the Great Lakes in both the U.S. and Canada is the white pine-red pine association, which is included in both the northern coniferous forest and temperate deciduous forest biomes (northern hardwoods association) by various authors.  The original extensive stands of eastern white pine (Pinus strobus) that once covered this area have largely been destroyed by improper logging practices and white pine blister rust; most of these stands have been replaced by northern hardwooods or jack pine (P. banksiana).  Eastern white pine can be considered an edaphic climax species or a sub-climax species of long duration (300-500 years). It reaches its maximum development on sandy loam soils.  Moist sites in the Lake States often supported pure stands of white pine, while drier sites were more often occupied by mixed stands of red pine (P. resinosa) and jack pine, with jack pine occupying the most extreme of dry sandy sites.  On heavier (i.e., clayey) soils, none of the pines were able to compete favorably with the northern hardwoods.

NORTHERN CONIFEROUS FOREST BIOME - JACK PINE
Jack pine, with its serotinous cone habit, is a prime example of a "fire species," commonly occurring in pure stands on recently burned areas. On all but the driest of these sites, jack pine is replaced by white and red pine.  Quaking aspen (Populus tremuloides), balsam poplar (Populus balsamifera), and paper birch (Betula papyrifera), are all short-lived, intolerant pioneer species which quickly invade the richer or moister sites that have been denuded by fire or logging.  All are good invaders with their large crops of lightweight, wind-dispersed seeds; the aspens and poplars are further enhanced in this regard by their prolific sprouting ability.  In the northernmost part of the biome, black spruce (also with serotinous cones) replaces jack pine as the fire-related invader species.

 MOIST TEMPERATE CONIFEROUS FOREST BIOME - CLIMATE
The moist temperate coniferous forest of the Pacific Northwest includes the area from the coastal ranges of northern California (below 5000 ft. elevation) to the southern coast of Alaska (below 2000 ft.).  Because of its proximity to the Pacific Ocean, the climate is mild and without temperature extremes.  Precipitation varies from 50 inches per year in the southern portion of the biome, where relatively dry summers prevail, to 200 inches on the mountain slopes of Washington and southern British Columbia.

Mixed stand of douglas-fir, Pacific siver fir and grand fir in southwest Oregon.

MOIST TEMPERATE CONIFEROUS FOREST BIOME - FOGBELT
The fogbelt, comprising the southern part of the biome from San Francisco to southern Oregon, is dominated by redwoods (Sequoia sempervirens).  Stands are situated on moist river flats and in sheltered valleys, where evapotranspirational losses are minimized.  New and higher roots are produced in reaction to continued deposition of alluvial material at the bases of the tall trunks, which often surpass 250 feet in height. The thick bark, which affords protection against insects, pathogens, and fire, is thought to contribute to the great longevity (1,000-2,000 years) of individuals.

MOIST TEMPERATE CONIFEROUS FOREST BIOME - NORTH OF THE FOGBELT
To the north of the redwoods in Oregon and southern Washington, where the soil is well drained and precipitation is slightly lower, grow extensive, pure stands of the subclimax species, Douglas-fir (Pseudotsuga menziesii).  On the Olympic Peninsula, where it reaches its maximum development (often approaching 10 feet in diameter and 300 feet in height), Douglas-fir is found in association with Sitka spruce (Picea sitchensis), western redcedar (Thuja plicata), and western hemlock  (Tsuga heterophylla).  In the south it mixes with sugar pine (Pinus lambertiana), incense cedar (Libocedrus decurrens), and ponderosa pine (Pinus ponderosa).

Managed Douglas-fir stands are common on the Olympic Peninsula.

This smaller western recedar germinated and is growing on an older redcedar stump.

MOIST TEMPERATE CONIFEROUS FOREST BIOME - BOTTOMS
The sandy and gravelly soils along rivers and streams of this biome are frequently lined with narrow groves of red alder (Alnus rubra), black cottonwood (Populus trichocarpa), and bigleaf maple (Acer macrophyllum).  Both bigleaf maple and red alder (a nitrogen fixer) are also pioneer tree species on recently burned and heavily logged areas in the region.

Red alder (white stems) and bigleaf maple (dark stems) on a stream bottom.

MOIST TEMPERATE CONIFEROUS FOREST BIOME - OLYMPIC PENINSULA
Northward in the Puget Sound area (and in particular the Olympic Peninsula), a climax forest of western hemlock, western redcedar, and Pacific silver fir (Abies amabilis) dominates the landscape.  Sitka spruce, Alaska-cedar (Chamaecyparis nootkatensis), and mountain hemlock (Tsuga mertensiana) are common associates.  At higher altitudes, these species are joined by grand fir (A. grandis), and on drier sites by Douglas-fir.  The dense canopy of these forests precludes the growth of all but a few species in the herb and shrub layers where cover is sparse.  Due to the prevailing moisture-laden winds, there is a partial extension of this forest association into the western slopes of the Rocky Mountains in Idaho and British Columbia.  Western larch (Larix occidentalis) and western white pine (Pinus monticola) are important successional species in this eastern extension.

MOIST TEMPERATE CONIFEROUS FOREST BIOME - MOUNTAIN COMPLEX
The mountain complex biome refers to the totality of vegetation types and associated animals which occupy the mountains and high plateaus of western North America.  Elevational transects extending over several thousand feet may exhibit vegetation ranging from desert to alpine tundra. The type of plant community which will dominate a given altitude is dependent on three interrelated factors of the physical environment:

1. steepness and orientation of slope with respect to incoming solar radiation;
2. composition of the soil; and
3. amount of available moisture.

MOIST TEMPERATE CONIFEROUS FOREST BIOME - CLIMATE
On a more regional basis, precipitation and temperature vary considerably, depending on latitude and the location and orientation of mountain masses relative to the prevailing westerlies and relative to other mountain masses.  Thus, we see that timberline decreases in altitude with increasing latitude in both the Rockies and Pacific Coast mountains, but that at a given latitude timberline is lower in the coastal mountains than in the Rockies.  The effects of orographic precipitation are seen in the dramatic shifts in vegetation from the windward to leeward sides of mountain masses.

MOIST TEMPERATE CONIFEROUS FOREST BIOME - SOUTHERN ROCKIES
The mountain complex of the southern Rockies is exemplified in the vegetation of the San Francisco Mountains of northern Arizona, which reach altitudes in excess of 12,000 feet.  The zonation of flora ranges from desert species at the lowest elevations (where rainfall is low and evapotranspiration rates are high), through Douglas-fir and spruce-fir forests at the middle elevations (where moisture from orographic precipitation is high), to alpine vegetation at the highest points (where low temperatures becomes a limiting factor).

MOIST TEMPERATE CONIFEROUS FOREST BIOME - CREOSOTE BUSH-GREASEWOOD
The creosote bush-greasewood association (Larcea divaricata and Sarcobatus vermiculatus, respectively) occupies the hot, dry lower slopes below 6000 feet.  Once desert grassland, this area was severely overgrazed by sheep and cattle.

Obviously delusional in the high heat your instructor insists he sees a lake not far away.

MOIST TEMPERATE CONIFEROUS FOREST BIOME - PINYON-JUNIPER
The range between 5000 and 7000 feet is occupied by the pinyon-juniper association.  The area is characterized by an environment of alkaline soils, low rainfall and humidity, high wind movement, intense sunlight and high evapotranspiration rates.  The stands of slow growing, sparsely spaced trees range from pure pinyon (Pinus cembroides) to pure juniper (Juniperus spp.), probably depending upon available seed source as much as on geographical location and local environmental conditions.

MOIST TEMPERATE CONIFEROUS FOREST BIOME - PONDEROSA PINE
The ponderosa pine (Pinus ponderosa) zone is found from 6000-8000 feet.  Here it forms a well-adapted fire-related association with the easily combustible grasses found in the understory and having general park-like appearance.

MOIST TEMPERATE CONIFEROUS FOREST BIOME - DOUGLAS-FIR
The Douglas-fir zone is situated in the 7500-9000 feet elevational range.  The area of overlap of the ponderosa pine and Douglas-fir zones is commonly referred to as the lower montane forest.  Compared to lower zones, daily temperature fluctuations in the Douglas-fir zone are smaller, the average temperature is somewhat lower, and humidity is significantly higher.  The Rocky Mountain variety of Douglas-fir (Pseudotsuga menziesii var. glauca) encountered here is much smaller (and more tolerant in the understory) than its relative in the Pacific Northwest (P. m. var. menziesii) and usually occurs in mixed stands rather than in pure stands. Common associates include white fir (Abies concolor) and blue spruce (Picea pungens) on moist sites, and ponderosa pine and lodgepole pine (Pinus contorta) on drier sites.  The dry exposed ridges of this zone are commonly occupied by limber pine (Pinus flexilis) and bristlecone pine (P. aristata).

MOIST TEMPERATE CONIFEROUS FOREST BIOME - SPRUCE-FIR ZONE
In the cold, humid environment above the Douglas-fir zone, between 8,500 and 11,500 feet, is the spruce-fir zone, dominated by Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa).  In the lower and middle parts of the range, subalpine fir occupies sites too wet, too dry or too low in nutrients for Engelmann spruce to grow.  At higher elevations it is not uncommon to find pure stands of Engelmann spruce.  As in the lower montane forest, limber and bristlecone pines occupy the dry, exposed, south-facing ridges and slopes.  Many of the bristlecone pines are over 4000 years old.

MOIST TEMPERATE CONIFEROUS FOREST BIOME - KRUMMHOLZ
Krummholz is the name given to the dwarfed and stunted trees that occupy the transition zone between the spruce-fire zone and alpine tundra. The environment is characterized by intense solar radiation, high winds and large diurnal temperature fluctuations.

MOIST TEMPERATE CONIFEROUS FOREST BIOME - ALPINE TUNDRA
The alpine tundra zone occurs above timberline where climate is even more severe than that in the Krummholz.  Short grasses (Poa spp., Festuca spp.), sedges (Carex spp.), tiny alpine flowers, and rocky outcrops dominate the landscape.

Above the tundra lie the mountain tops, a land of perpetual ice and snow. The complete lack of soil and the severe environmental conditions combine to make colonization by even the hardiest invaders an impossibility.

MOIST TEMPERATE CONIFEROUS FOREST BIOME - ALPINE MEADOWS
Above the tundra lie the mountain tops, a land of perpetual ice and snow.  The complete lack of soil and the severe environmental conditions combine to make colonization by even the hardiest invaders an impossibility.

Alpine meadows occur in depressions sheltered by hills or open areas surrounded by trees. Large amounts of snow accumulate and with the mositure provided by the "spring" melt (late June-early July) showy wildflowers come to dominate the landscape.

MOIST TEMPERATE CONIFEROUS FOREST BIOME - LODGEPOLE PINE
Lodgepole pine, a prolific seeder with serotinous cones, and quaking aspen, a prolific seeder and sprouter, are particularly well-adapted to fire, and are among the first to successfully invade a burn, almost regardless of altitude or latitude.  Aspen is also common in areas of major soil disturbances, such as ravines swept by avalanches.  Narrow leaf cottonwood (Populus angustifolia) is commonly found along the stream banks of this region and the lower plains.

MOIST TEMPERATE CONIFEROUS FOREST BIOME - NORTHERN ROCKIES
In the northern U.S., timberline decreases in altitude, as do the various accompanying vegetational zones.  There is also a major change in species in some of the higher zones due to a wind corridor through the Cascades.  This corridor allows moisture bearing winds from the Pacific to reach the western slopes of the Rockies, resulting in a wetter, milder climate than would normally be expected.  Because of this, mountain hemlock (Tsuga mertensiana) is found growing with Engelmann spruce and subalpine fir (Abies lasiocarpa) in the higher altitudes. Western hemlock , western redcedar, and grand fir are found in the Douglas-fir zone.  Western larch and western white pine (Pinus monticola) are the two principal successional species of the latter zone, both germinating and growing well on mineral seedbeds prepared by fire and other major disturbances.

MOIST TEMPERATE CONIFEROUS FOREST BIOME - NORTHERN ROCKIES DRY RIDGES
Whitebark pine (Pinus albicaulis) is characteristic of the dry ridges and exposed areas of high altitudes.  Its flexible branches allow it to withstand heavy snow loads but often the snow, coupled with extreme wind and cold, force the whitebark into its familiar, prostrate, ground-hugging form.  The cones of the whitebark, unlike the other pines, fall from the trees and disintegrate, forming a fertile oasis among the thin, bare soils of the mountain top in which its seeds can germinate.

MOIST TEMPERATE CONIFEROUS FOREST BIOME - CANADIAN ROCKIES SUBALPINE ZONE
In the Canadian Rockies the subalpine zone is by far the most extensive, covering nearly all of the mountains.  In the northern part of this range, white spruce of the northern forest is commonly found in association with subalpine fir.

MOIST TEMPERATE CONIFEROUS FOREST BIOME - SIERRA NEVADAS
Physically, the Sierra Nevada Mountains range from northern to southern California, but floristically vegetation extends into the Cascade range of southern Oregon.  The Sierras are oriented in a north-south direction, perpendicular to the prevailing westerly winds, and thus show distinct patterns of orographic precipitation.  The west slopes of the Sierras rise gradually from the Great Valley, receiving very little precipitation; heavy rains fall near mid-slope as a result of condensation of cool moist air.  The abrupt drop to the Great Basin on the east slope is very dry as the moisture-depleted air provides little precipitation.

MOIST TEMPERATE CONIFEROUS FOREST BIOME - DRY FOOTHILLS
The foothills of the west slopes form an open woodland between 500-2500 feet.  Blue oak (Quercus douglasii) is the dominant tree, but is often found in association with digger pine (Pinus sabiniana).

MOIST TEMPERATE CONIFEROUS FOREST BIOME - MONTANE FOREST
The montane forest ranges from 2000-6000 feet in the southern Cascades and from 5000-8000 feet in the southern Sierras.  There are six primary species in this zone, occurring either in pure stands or in various combinations.  White fir is the dominant species at the higher altitudes in the zone where winters are long and snows are heavy; it is seldom found in pure stands.  Pure stands of incense cedar (Libocedrus decurrens) dominate the richest sites in the lower sections of the zone.  Ponderosa pine tends to dominate the lower margins of the zone since it is the most drought resistant of the six species.  Jeffrey pine (Pinus jeffreyi), a close relative of ponderosa pine, has a higher tolerance for cold and frost and thus is commonly found in depressions and flats where cold air tends to gather, and at the upper extremes of the ponderosa pine zone where temperatures are much colder.  Sugar pine reaches its maximum development in the middle of the montane zone where the climate is less extreme.

MOIST TEMPERATE CONIFEROUS FOREST BIOME - DOUGLAS-FIR
Douglas-fir (Pseudotsuga menziesii var. menziesii) tends to dominate the more moist, northern regions.  A less common but more famous associate of these central montane species is the giant sequoia (Sequoiadendron giganteum).  The species occurs in scattered clumps throughout central California where annual precipitation is relatively high (40-60 inches) and soils are well drained.  Until recently, the primary danger of these "sentinels of the Sierras" (many of 30 feet in diameter and 250 feet in height) was soil compaction resulting from tourism.  The limited aeration destroyed the fibrous root system of the tree and altered water-holding properties of the soil, resulting in decreased vigor. Chaparral species commonly invade drier sites in the zone following fires.

MOIST TEMPERATE CONIFEROUS FOREST BIOME - SUBALPINE ZONE
The subalpine zone extends approximately 2000 feet above the upper montane limit.  The climate consists of long winters with heavy snows and short, dry summers with cool temperatures.  Red fir (Abies magnifica) is the major climax species here, often occurring in pure, even-aged stands. At the upper end of the subalpine zone red fir mixes with Jeffrey, western white and lodgepole pines.  The latter is an important fire-related successional species. White fir and mountain hemlock are less common associates.

MOIST TEMPERATE CONIFEROUS FOREST BIOME - TIMBER LINE
Near the timber line, whitebark, limber and foxtail pines are the dominant species, often occurring in scattered clumps interspersed by alpine meadows.  These are all small tree species, rarely surpassing 30 feet in height, limited by the severe environment and poor soil conditions.

The subalpine zone of the east slope is comprised mainly of timber line species of the western slope - whitebark, limber and foxtail pines. Lodgepole pine grows quite extensively on these eastern slopes, as it does throughout most of the West.  Red fir occurs only in scattered areas.

Jeffrey pine is the dominant species in the montane zone of the east slopes.  Here it forms open park-like stands, similar to, but in place of, the ponderosa pine of the western Sierras.

MOIST TEMPERATE CONIFEROUS FOREST BIOME - CASCADES
The Cascades extend from southern Oregon to British Columbia.  The western slopes are generally considered to be part of the moist temperate coniferous forest biome, with which they were included and discussed in this treatment of biomes.  However, above 5000 feet there exists a subalpine forest of mountain hemlock, noble fir (Abies procera), subalpine fir, and pacific silver fir (A. amabilis).  Timber line here occurs near 6000 feet, much lower than at the same latitude in the Rockies. This is attributed primarily to the heavier snow loads experienced in the Cascades.

MOIST TEMPERATE CONIFEROUS FOREST BIOME - CASCADES EASTERN SLOPES
The eastern slopes of the Cascades are drier than the west and have species similar to those of the northern Rockies.  The subalpine forest is much the same as on the western slopes.  The upper montane forest consists of Douglas-fir, western hemlock, and western redcedar.  Western larch and western white pine are the common successional species following fire.

MOIST TEMPERATE CONIFEROUS FOREST BIOME - CASCADES LOWER EASTERN SLOPES
The lower slopes of the eastern Cascades are especially dry, with rainfall ranging from 10-40 inches per year, and a long dry summer dominating the climate.  In this area, ponderosa pine thrives in vast, pure stands.  This tree has a long, fast-growing tap root that allows it to reach a more constant water supply than that available to most plants. Regeneration of ponderosa pine is also particularly successful because the seedlings are able to withstand prolonged drought by obtaining moisture from the night dew.

Ponderosa pine seedling growing on a very dry rock.

MOIST TEMPERATE CONIFEROUS FOREST BIOME - INTERIOR BRITISH COLUMBIA
In the interior of British Columbia, the Pacific Coast mountains and the Rockies merge. Here the land takes the shape of a high, rolling plateau that is covered by a forest of white spruce, Douglas-fir, lodgepole pine and aspen.  Farther to the north these species are replaced by an association of lodgepole pine, subalpine fir, and Englemann spruce.  In northern British Columbia, the Yukon, and Alaska the forest changes to white spruce and subalpine fir.  White spruce is the primary successional species on the nutrient rich sites, while black spruce (Picea mariana) forms an edaphic climax on the bogs.

 TEMPERATE DECIDUOUS FOREST BIOME - CLIMATE
The temperate deciduous forest biome occupies most of the eastern part of the United States and a small strip of southern Ontario.  Precipitation varies from 28 inches per year in the northwestern section of the biome to 60 inches per year in the southeastern part; in most areas the precipitation is distributed evenly throughout the year.  Frost occurs throughout the biome, and summer and winter are distinct seasons.  The dominant plant species of the biome are broad-leaved deciduous trees.  Because the biome covers such a large geographical area, large differences have led to the recognition of eight major forest regions within the biome, each dominated by a different species or association of species.  These are:  mixed mesophytic,  Appalachian oak,  hemlock-white pine-northern hardwoods, oak-hickory, maple-basswood,  beech-maple, oak-pine, and southern pine.

TEMPERATE DECIDUOUS FOREST BIOME - MIXED MESOPHYTIC FOREST
The mixed mesophytic forest region is in the centrally located and topographically diverse Appalachian and Cumberland Plateaus.  Geologically, it is the oldest region in the biome and is the most complex and highly developed biotically.  Nearly all the dominant species in the entire biome are found here, and many reach their maximum development here.  The mixed mesophytic region is thought to be the center of dispersal from which the other forest regions in the biome were formed.  In all, there are about 30 tree species which assume dominance in the region; however, in most areas dominance is shared by two or three of these species, depending on differences in microclimate and other factors.  Yellow buckeye (Aesculus octandra) and white basswood (Tilia heterophylla) are the most constant dominants and are considered the indicator species for the region.  Other common dominants include yellow-poplar (Liriodendron tulipifera), American beech (Fagus grandifolia), cucumber magnolia (Magnolia acuminata), sugar maple (Acer saccharum), white oak (Quercus alba), and eastern hemlock (Tsuga canadensis).

yellow buckeye sprout clump

TEMPERATE DECIDUOUS FOREST BIOME - APPALACHIAN OAKS
The Appalachian oak forest region lies to the east, north, and southeast of the mixed mesophytic forest.  Geologically, it is characterized by a system of parallel valleys and ridges. Northern red oak (Quercus rubra) and white oak are the two major species in the region.

TEMPERATE DECIDUOUS FOREST BIOME - APPALACHIAN OAKS
In the Appalachian oak forest White oak reaches its maximum development on deep, rich soils of coves and high bottomlands, but grows well on all but the driest and wettest sites in the region.  The success of white oak is attributed to its ability to survive for long periods as an understory species, its quick and vigorous response to release from this suppression, and its great longevity (often reaching 400-600 years).  The ecologically similar red oak occupies sites which are usually slightly drier or wetter than those dominated by white oak.  Chestnut oak (Q. prinus) is a third important species of the region and forms an edaphic climax with post oak (Q. stellata) and blackjack oak (Q. marilandica) on rocky, dry ridges.  The American chestnut (Castanea dentata) was another important dominant in the region until eliminated by a bark fungus in the early 1900's.  Sugar maple is the climax species on very rich sites, while American beech dominates the cove forests too moist for white oak and tulip-poplar.  Pitch pine (Pinus rigida) is a common successional species.

TEMPERATE DECIDUOUS FOREST BIOME - NORTHERN HARDWOODS
The hemlock-white pine-northern hardwood region is situated along the northern edge of the biome, bordering the northern coniferous forest. Eastern hemlock (Tsuga canadensis) is one of the most tolerant of all trees and survives under very low light conditions.  Eastern white pine is varied in its occurrence with other species and in its ecological role in the region.  In the Lake States it often forms extensive pure stands of on drier sites mixes with red pine and jack pine.  On heavier soils characteristic of the East, it occurs mainly as scattered individuals amongst a predominantly hardwood forest.  Sugar maple, American beech, white ash (Fraxinus americana) and yellow birch (Betula alleghaniensis) are the most common hardwoods in the region.  Paper birch (B. papyrifera) is a common early successional species in the eastern part of the region, while aspen (Populus tremuloides and P. grandidentata) and jack pine assume this role in the Lake States (along with paper birch).

TEMPERATE DECIDUOUS FOREST BIOME - OAK-HICKORY FOREST
The oak-hickory forest region occupies drier areas to the west of the mixed mesophytic forest region.  Drought-resistant oaks and hickories are the most common trees species.  The principal oaks are white oak, northern red oak, and black oak (Q. velutina), while bur oak (Q. macrocarpa), blackjack oak, shingle oak (Q. imbricaria) and overcup oak (Q. lyrata) are also common.  The most important hickories are bitternut (Carya cordiformis) and shagbark (C. ovata), while shellbark (C. laciniosa), mockernut (C. tomentosa), and pignut (C. glabra) occur more frequently on the drier upland soils.  The trees commonly found scattered throughout the stream and river valleys of the region (and indeed nearly all regions in the biome) are American elm (Ulmus americana), American sycamore (Platanus occidentalis), hackberry (Celtis spp.), silver maple (Acer saccharinum), river birch (Betula nigra), and eastern cottonwood (Populus deltoides). These riparian trees are generally fast-growing, shallow-rooted, relatively large, and able to withstand repeated floodings throughout the year.  A savanna-like transition zone is formed along the western edge of the oak-hickory region where the temperate deciduous forest biome grades into the temperate grasslands biome.  Here bur oak, the most drought resistant of all (eastern) oaks, occurs as scattered trees amongst the grassy plains.

TEMPERATE DECIDUOUS FOREST BIOME - MAPLE-BASSWOOD FOREST
The maple-basswood forest region, encompassing lower Minnesota, northeastern Iowa, and western Wisconsin, comprises the northwestern corner of the temperate deciduous forest.  Sugar maple and American basswood (Tilia americana) are the major tree species within this region. Sugar maple is a prolific seeder, while basswood is a vigorous sprouter-properties which coupled with their understory tolerance, help account for the dominance of these species. Other important tree species in the region include boxelder (Acer negundo), blue ash (Fraxinus quadrangulata), and northern red oak.  Bur oak and bitternut hickory occupy sites lower in nutrients.

TEMPERATE DECIDUOUS FOREST BIOME - BEECH-MAPLE FOREST
The beech-maple forest region is found almost entirely within Indiana and northern Ohio. American beech, similar to the codominant sugar maple in shade tolerance and most environmental requirements, prefers slightly moister sites.  Because of its thin bark and shallow root system, beech is especially susceptible to fire injury, sunscald, and winter cracking. Other important species in the beech-maple region include black cherry (Prunus serotina), yellow birch, American ash, black walnut (Juglans nigra), tulip-poplar, red elm (Ulmus rubra), northern red oak, and, in the southern section, Ohio buckeye (Aesculus glabra).  Shagbark hickory and various oaks occupy dry sites throughout the region.

TEMPERATE DECIDUOUS FOREST BIOME - OAK-PINE FOREST
The oak-pine region occupies an area between the hardwoods of the Appalachians and the pure pines of the southlands.  Generally speaking, half of this forest is comprised of hardwoods, primarily upland oaks, while the other half is a mixture of loblolly, shortleaf and Virginia pines (P. taeda, P. echinata, and P. virginiana, respectively).  The dominant hardwoods are white oak, post oak, shagbark hickory, mockernut hickory, pignut hickory, and sweetgum.

TEMPERATE DECIDUOUS FOREST BIOME - SOUTHERN PINE REGION
The southern pine region occupies an area comprised of the Gulf and Atlantic Coastal Plains, plus the Piedmont of the eastern and southern Appalachians.  In spite of the dominance of pines, the natural climax vegetation is considered to be hardwoods.  Throughout much of the southern U.S., the lands now occupied by pines were abandoned after a period of intensive use (farming, surface mining, etc.) and allowed to revert back to natural conditions.  Most of these lands are highly eroded, with little of the A1 soil horizon remaining.  A typical successional sequence on such lands in the Piedmont might be:  (1) annual and perennial weedy forbs and grasses (crabgrass, goldenrod, asters, horseweed, ragweed and buttonweed); (2) broomsedge (a perennial grass); (3) woody invaders, eastern redcedar (Juniperus virginiana), sassafras (Sassafras albidum), winged elm (Ulmus alata), persimmon (Diospyros virginiana); (4) southern pines (primarily loblolly and shortleaf); (5) oaks and hickories.  This process of secondary succession may take several hundred years.

TEMPERATE DECIDUOUS FOREST BIOME - SOUTHERN PINE REGION
A great deal of the southern pine region is intensely managed for the production of pine pulp, poles and sawtimber.  Clearcuts, burns, replantings and young plantations are common scenes throughout the southeastern United States.

TEMPERATE DECIDUOUS FOREST BIOME - SOUTHERN PINE REGION
This loblolly pine plantation in north Georgia is in its fourth growing season.  It will likely be harvested in 18-20 years after several fertilizer applications, and - depending on objectives - thinnings.

TEMPERATE DECIDUOUS FOREST BIOME - SOUTHERN PINE SUBREGIONS
Several "subregions" of the southern pine region can be defined on the basis of the dominant species.  The Virginia pine subregion occupies the northern Piedmont and Appalachian foothills.  Virginia pine, the most drought-resistant of the southern pines, is a pioneer species on impoverished soils.  It is often found in association with pitch pine (P. rigida).  The shortleaf-loblolly pine subregion occupies the Piedmont south of the oak-pine region.  The climate is humid, with long hot summers and mild winters; soils are predominantly sandy.

TEMPERATE DECIDUOUS FOREST BIOME - SOUTHERN PINE SUBREGIONS
Pure stands of loblolly pine are commonly found where drainage is poor; by contrast, shortleaf pine is found on soils which are better drained and of lower nutrient content.  The longleaf-slash pine subregion is found along the Gulf Coastal Plains and into central Florida. Over 50 percent of the forest stands in the subregion are comprised of these two species, generally with slash pine on the wet sites and long leaf pine on the drier sites.  Fire plays an important role in maintaining this seral pine stage, primarily by reducing hardwood competition and by controlling plant diseases.  This is particularly evident in longleaf pine, which may be held in the grass stage for prolonged periods in the absence of fire.

TEMPERATE DECIDUOUS FOREST BIOME - SOUTHERN PINE SUBREGIONS
The scrubland subregion is situated on white sands near the coast where soils are acidic, highly leached, very low in nutrients, and extremely droughty.  On undisturbed sites a scrub oak community, composed primarily of live, turkey, and blackjack oaks (Quercus virginia, Q. laevis, and Q. marilandica, respectively) forms the natural vegetation. Spanish bayonet (Yucca spp.), a monocot, is also common here.  In areas undisturbed by fire, lie thick forests of saw-palmetto (Serenoa repens), the most abundant of the native palms.  Pine stands of sand pine (Pinus clausa) are often found on sites extremely low in nutrients. This species closely resembles jack pine of the Lake States, with one of its varieties having serotinous cones typical of "fire species."  Southern magnolia (Magnolia grandiflora) is likely to be found on moist, well-drained sites in association with nearly all the southern oaks, tulip-poplar, sweetgum, the ashes, and the hickories.

TEMPERATE DECIDUOUS FOREST BIOME - WET LANDS
The oak-gum-cypress region of the lower Mississippi Valley cuts through the southern pine region and comprises the major wetlands vegetation here.  The characteristic trees of this area are baldcypress (Taxodium distichum), with its characteristic knees and heavily fluted trunk, and water tupelo (Nyssa aquatica), both often found in standing water.  Dispersal is via water-borne seed.

TEMPERATE DECIDUOUS FOREST BIOME - APPALACHIANS
The Appalachian Mountains, trending roughly north-south, traverse the eastern part of the biome.  The relatively high altitudes allow northern species to penetrate far more deeply into the South than would normally be possible.  There is also somewhat of an altitudinal zonation of plant associations in the southern Appalachians, with oak-hickory-pine occupying lower elevations and dry sites; mixed mesophytic forests occurring in moist, sheltered coves; northern hardwoods dominating the 3500-4500 ft. elevational range; and northern coniferous forests occupying the highest areas.  These same vegetation zones are progressively lower in elevation at higher latitudes, and some vegetation types (e.g. oak-hickory) virtually drop out.

Source: College of Agriculture, Department of Forestry, University of Illinois, Urbana, 1974.

 COVER TYPES
Forest trees in nature may be aggregated into sertain groupings or associations such as the beech-birch-maple forests of the northeastern United States and adjacent Canada, and the loblolly pine-shortleaf pine forests of the South; or they may occur in essentially pure stands such as lodgepole pine in the mountains of the West.  These aggregations and pure stands, called forest cover types, may be either stable or transitory.  Some have occupied the area for long periods.  Others are temporary occupants of disturbed sites and through ecological succession gradually give way to a more stable cover and ultimately, under stable conditions, to climax forest.

Forest cover types have been described in-depth by the Society of American Forests (see reference on previous page).  The classification is based on existing tree cover, with recognition of formational ecological factors.

These cover type descriptions are useful for conveying forest descriptions and management practices; they provide a common reference framework and aid in the development of mental pictures of the vegetation that exists in a given area.  In most descriptions, species that make up the majority of the growing stock, geographic distribution, ecological relationships, and variants and associated vegetation are described.

Reprinted From:  F.H. Eyre, Ed.  1980.  Forest Cover Types of the United States and Canada.  Society of American Foresters, Washington, D.C.  148 pp.