Biological Features

Forests at Coweeta were traditionally classified as belonging to the oak-chestnut association. However, with the loss of chestnut (Castanea dentata) as the dominant canopy species, the area is more appropriately included in the oak-hickory or Appalachian oak association. The plant communities in the Coweeta Basin are distributed in a reasonably predictable mosaic over the highly varied topography in relation to complex moisture and elevational gradients (Bolstad et al. 1998). Generally, deciduous oak species are the dominant canopy species with an abundant evergreen understory component composed primarily of Rhododendron maximum and Kalmia latifolia. Four major forest types are recognized: (1) northern hardwoods, (2) cove hardwoods, (3) oak (-chestnut), and (4) oak-pine. These forest types exhibit successional change in response to historical disturbances (logging, fire, windstorm, drought, and chestnut blight). Generally, species that were co-dominants with chestnut at the time of the blight have increased in basal area. More opportunistic species, such as yellow birch, yellow poplar, and red maple, have also increased in relative basal area since the blight. The evergreen under-story species, Rhododendron and Kalmia, have also increased in importance since the 1930s.

In addition to the variety of watershed experiments previously discussed are forest stands in a range of successional status and vegetation types within the Coweeta Basin. Two watersheds (WS 1 and WS 17) have 46-year-old eastern white pine (Pinus strobus) plantations (dating from 1957). Past treatments in other experimental watersheds in the basin have included light selection cutting, clearcutting without roads or products removed, commercial clearcutting with and without cable yarding, whole tree harvesting, a combination of thinning and clearcutting, and clearcutting followed by grass planting and then applying herbicide. These treatments have produced naturally regenerating forests ranging in age from 6 to 100 years, thus providing a unique opportunity to assess both the extent of ecosystem alteration following treatment and the patterns, rates, and mechanisms of post-treatment recovery. Superimposed on the environmental gradient in the Coweeta Basin are disturbed ecosystems that contain a wide range of biotic diversity.

Paralleling the diversity of forest ecosystems within the Coweeta Basin is a comparable diversity of stream ecosystems with a variety of bottom substrate types. These diverse headwater streams are characterized both by distinct biotic assemblages, particularly with reference to benthic invertebrates, and by distinct functional processes (e.g., organic matter processing).

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