Successional changes in plant species diversity and composition after clearcutting a Southern Appalachian watershed
Watershed 7, a southwest-facing watershed in the Coweeta Basin, western North Carolina, USA, was clearcut in 1977. Twenty-four permanent plots were inventoried in 1974 before cutting and in 1977, 1979, 1984, and 1993 after clearcutting. This study evaluates changes in species diversity during early succesion after clearcutting and differences in overstory tree and ground flora response to disturbance by clearcutting and their interaction with previous disturbances and subsequent stand development. To quantify species diversity, we computed Shannon-Weaver's index of divexsity (H') and Pielou's everness index (J'). Woody species diversity remained relatively stable; however, woody species richness increased in the cove-hardwoods and hardwood-pines, but remained relatively constant in the mixed-hardwoods. Although revegetation was rapid, forest composition has changed through succession. opportunistic species, such as Liriodendron tulipifera, Robinia pseudoacacia, and Acer rubrum, increased in abundance, whereas Quercus veluntina, Carya spp., and Q. rubra decreased. Ground flora diversity declined in the cove-hardwoods and mixed-oak hardwoods communities, but the decrease in the hardwood-pines was not significant. The abundance (g biomass m-2 of ground flora was much lower in 1993 than in 1984; 79% less in the cove-hardwoods, 90% less in the mixed-oak hazdwoods, and 79% less in the hardwood-pines. Watershed 7 is apparently in a transition state between early and late successional species abundance.Early successional shade-intolerant species, such as Erechtites, Solidago, Eupatorium, Panicum, and Aster, have declined, whereas late successional, shade-tolerant species, such as Viola, Galium, Sanguinaria, Uvularia, and Veratrum are not yet well established.