The Biological Landscape
The Southern Appalachian Mountains are among the most biologically diverse areas in the world outside of the tropics (Braun 1950). By some estimates, there are more than 100 tree species, 500 vertebrate species, and 2,000 higher plant species native to the Blue Ridge Mountains alone. The Great Smoky Mountains contain more tree species than the entire continent of Europe. Explanations for this diversity include the great age of these mountains and the fact that they were not covered by glaciers during the Pleistocene ice ages. One of the most important factors influencing this diversity is the topography of the area. Variations in elevation and topographic position (i.e., ridge, slope, or cove) creates a variety of climatic conditions, providing suitable habitat for a wide range of species.
Climates in the Southern Appalachian Mountains create environmental conditions associated with the temperate deciduous forest biomes and the northern coniferous forest biome. The temperate deciduous forests cover most of the Southern Appalachian range. Its natural communities are dominated by deciduous tree species, although pines are commonly mixed with hardwood species. This widespread biome is composed of several community types that are also influenced by the environmental gradients associated with changes in elevation and topography. Therefore, terrain influences the spatial arrangement of communities in mountain landscapes. The natural communities of the temperate deciduous forest include:
In contrast to the temperate forest types, which are widely distributed, northern coniferous forests in the Southern Appalachians are confined to the highest peaks . Due to high elevations, the climate on these peaks is cold and wet and similar to that of New England or Canada. These conditions are tolerated by two tree species: red spruce (Picea rubens) and Fraser fir (Abies fraseri). The primary community types at higher elevations are:
- Environmental Gradients : There are strong relationships between the location of natural communities and environmental gradients principally controlled by topography.
- Spruce-Fir Forests : Forests dominated by two conifer species, red spruce and Fraser fir, cap the tallest peaks of the southern Appalachians. Bordered by northern hardwood forest below, the spruce-fir forest begins at elevations above 4600-5500 ft (1400-1680 m).
- What are Biomes? : Regions of similar vegetation are called biomes and their geographic boundaries are largely determined by climate. The seasonal patterns of precipitation and temperature pose practical problems for survival and reproduction for the plants that live there.
- Spatial Arrangement
- Grassy and Heath Balds : Treeless shrub or grass-dominated ridges and peaks are collectively called "balds". There are two principal types: heath balds and grassy balds.
- Cove Forests
- Mixed Hardwoods : Mixed hardwood forests are widespread in mountain landscapes and occupy sites below 4000 ft elevation that are intermediate on gradients of fertility, moisture, and exposure to sun and wind.
- Xeric Oak-Pine : Xeric oak-pine forests occupy dry, exposed ridges at moderate to low elevations (<4000 ft). They can also occur on the upper portions of exposed, south- and west-facing slopes.
- Pine Heath
- Northern Hardwoods
Encyclopedia ID: p1519
