The Adirondack region is comprised of a variety of forest communities. Many factors influence plant community composition, including temperature, precipitation, bedrock geology, elevation, topography, aspect, soil features, drainage, and disturbance history. As a result, it is difficult to characterize patterns for the entire region.A typical pattern of forest community distribution along an elevational gradient in the central Adirondacks might look similar to that shown below.
This lowland coniferous community is associated with wet, seasonally saturated, humic soils, typical of bogs and poorly drained areas. Water levels and drainage are the primary factors influencing this forest community together with soil depth and nutrient status. The density of trees can be quite variable. At some sites trees are so closely spaced it is difficult to walk between them. At other locations individual trees, or small groups of trees, are widely separated with intervening openings occupied by a variety of characteristic bog shrubs and sphagnum moss. Black spruce and tamarack are the dominant species on the saturated acid-peat soils or floating mats surrounding the open water area of bogs. Northern white cedar may occur in isolated, small groups, or nearly pure stands where soils are not saturated year-round. Red spruce and white pine are commonly found on small hummocks or slightly elevated areas associated with the coniferous swamp. Speckled alder is a common associate of the fringes of this forest community. Growth and development of trees on these sites is usually extremely slow. Coniferous swamps typically are distinguished by the presence of sphagnum moss covering the ground.
The lowland conifer community is dominated by balsam fir and red spruce. Scattered white pine and paper birch are frequently found in association with this forest community. Lowland conifer types occupy imperfectly drained flats, low ridges, and knolls surrounding lakes, streams, swamps, and bogs; generally occurring on glacial outwash soils often of limited depth and low fertility, and frequently very stony. The ground is usually devoid of vegetation except for pockets of spagnum and other mosses and scattered seedlings of shade-tolerant tree species. The forest floor can be covered by a deep mat of spruce and fir needles. Frequently very subtle elevational changes (of just a few feet) can alter species composition in favor of white pine and paper birch on hummock and higher areas. As a result of the wet, shallow, rocky soil conditions, trees on these sites are very susceptible to windthrow. Many of these stands exhibit an even-aged character, with the shorter-lived balsam fir fading out as the stand matures, leaving the longer-lived red spruce as the dominant tree species.
This forest represents a transition between the lowland conifer and the northern hardwood communities. Soils are generally deeper than in the spruce flat, but are still very rocky, moist and less productive than those of the northern hardwood community. Dominant species include red spruce, balsam fir, eastern hemlock, red maple, and yellow birch. The percentage of spruce and fir is greatest at lower elevations, with red maple and yellow birch increasing on better drained areas. Eastern white pine may appear sporadically or in small groups. The upper limit of the mixedwood forest is marked by the disappearance of balsam fir and its replacement by American beech. Understory vegetation is abundant with witchhobble, honeysuckle, striped maple, American beech, and red spruce seedlings, together with common wood sorrel, bunchberry, yellow clintonia, ferns and mosses distributed throughout these sites. Decomposition is slow in the damp, acidic conditions found on the forest floor. An accumulation of needles and other organic materials is common.
The northern hardwood forest community occupies the richest, most productive areas of the lower and middle-elevation slopes in the central Adirondack region (up to 2500 feet). Best development occurs on moist, deep, well-drained, fertile, loamy soils. This forest community is by far the most common in the Adirondack region occupying over 50% of the forested land. Sugar maple, American beech, and yellow birch are the predominant tree species. Yellow birch occurs most frequently at the lower limits of this community. Lesser amounts of red spruce, white pine, white ash, eastern hemlock, black cherry and red maple may be present. Presence of these species depends on the age of the stand; old-growth stands generally lack these species while in second-growth stands these species are common. The ground is usually covered by leaf litter. Understory vegetation is likely to include a variety of tree and shrub species. Sugar maple seedlings, root suckers of American beech, and witchhobble are most common. Shade intolerant species are generally lacking due to the dense canopy. Ground cover plants typically include ferns, clubmosses, and a variety of spring-flowering herbaceous plants.
A forest community not typically recognized in most descriptions of Adirondack vegetation is the upper slope hardwood-conifer forest. This community is very similar to the mixedwood type except red maple is lacking and sugar maple and American beech are more common than in the lower slope hardwood-conifer type. Red spruce and eastern hemlock, together with sugar maple, yellow birch, and American beech are the dominant species, with scattered white pine also represented. This community occurs on steeper slopes within the normal elevational range occupied by the northern hardwood community and at or near the tops of many of the smaller (2500-2800 feet) mountains throughout the central Adirondack region. It is again, a transition forest, this time between the northern hardwood and the mountain conifer communities, reflecting the trend toward shallower soils, rock ledges and outcrops typically associated with higher elevations.
This forest community, sometimes called the mountain boreal forest, is comprised largely of conifer tree species. This forest is found at elevations above 2800-3000 feet on steep mountain slopes,growing on a fragile layer of often saturated soil comprised of organic duff over an acidic, nutrient-poor humus and a very thin layer of mineral soil. In the lower portion of the mountain conifer zone, red spruce and balsam fir are both common. However, with increasing elevation, balsam fir tends to dominate. Near timberline, black spruce joins with balsam in a dwarfed and contorted forest know as the Krummholz. Paper birch, yellow birch, and American mountain-ash are found along with the spruce and fir at the lower elevations. These hardwood species tend not to persist in the forest canopy for long periods of time, but re-invade after fire, windthrow, or snow damage. Beneath the deep shade of the boreal conifers, the forest floor is cold, dark, and damp. The ground cover varies from bare patches of partially decayed conifer needles and debris to a profusion of mosses and lichens. Herbaceous plant species are limited, with wood sorrel, bunchberry, clintonia, and spinulose woodfern among the most prevalent. A wide variety of mosses and lichens cover many of the exposed rock surfaces in this severe mountaintop environment.
Non-forest alpine plant communities exist on 11 of the Adirondack’s highest peaks, comprising a total of only 85 acres. Here, scattered amongst exposed rock surfaces encrusted with a wide variety of lichens and mosses, are found several unique plants typical of regions much farther to the north. These hardy pioneers include gold-colored deer’s hair, alpine bilberry, lapland rosebay, bearberry willow, mountain sandwort, and alpine holygrass, among others. The alpine plant community of the High Peaks region is truly a rare and limited Adirondack resource.