Forest Site Classification

Mesophylic tree species

Mesophytic tree species growing on a moist lower slope.

A forest site is a small parcel of land, less than an acre, which has unique environmental characteristics of heat, moisture, and nutrients. The species composition and growth rate of forest vegetation are strongly dependent on the amount of those components, particularly moisture, which is available during an annual growing cycle. Sites of high quality have ample moisture and nutrients for continuous growth during the spring and summer, but low quality sites usually lack adequate moisture during the late summer. For example, yellow-poplar and northern red oak are often present on low elevation sites in moist coves and oaks usually dominate ridge sites, which are typically dry and infertile. Resource managers must determine the characteristics of forest sites when making decisions ranging from conservation to silviculture. Foresters often estimate site quality based on tree height at a certain age. Ecologists, however, need methods of determining the temperature, moisture, and fertility regimes of a site.

Our research shows:

  • Soil moisture availability during the growing season is a good predictor of species composition and growth.
  • Landform, the concave or convex surface shape of a site, is more important than aspect in determining site quality in the southern Appalachian Mountains.
  • Most mountain soils are strongly acidic and low in fertility.
  • Soils derived from amphibolite rock formations have higher fertility than soils formed from gneisses and schists.
  • Large ecosystems in the southern Appalachian Mountains can be grouped by elevation zones, each of which has unique ecological characteristics.
  • Forest ecosystems, consisting of trees, shrubs, and herbs can be mapped across landscapes using digital data sets and predictive models applied by computer.
  • An expert system based species composition is being developed to predict forest the moisture regime of a forest site.