Herb cover effects on tree seedling patterns in a mature hemlock-hardwood forest [Prunus serotia, Acer rubrum, Tsuga canadensis, Betula, Dennstaedtia, Mitchella, Lycopodium, Oxalis, West Virginia]

The role of herbs in affecting tree seedling patterns was investigated in an old-growth hemlock-hardwood forest in Cathedral State Park, West Virginia. Herb species cover, tree seedling density, and overhead foliage were sampled along with midsummer soil pH, soil moisture, and light intensity in 20 selected herb patches and 440 30 x 30 cm plots. Analyses of the patch data showed significant correlations of seedlings of major tree species: Prunus serotina, Acer rubrum, Tsuga canadensis, and Betula spp., with leading herb species (Dennstaedtia, Mitchella, Lycopodium, and Oxalis). Each tree species had few seedlings in some herb species patches, but was independent of or concentrated in other patches. Herb species were spatially related to other herb species, but showed little correspondence to soil pH, soil moisture, and light intensity patterns. Analyses of plot samples supported each of the above results. In addition, total tree seedling density was inversely correlated with total herb cover, but neither total seedling density nor number of seedlings of leading tree species was correlated with the abiotic factors. Seedling density and herb cover varied with the height and composition of the overhead canopy foliage. Based on the data from the two sampling approaches in this old mesic woods, we conclude that herb patches play a major role in determining the density and distribution of seedlings of leading tree species, and that the distribution of herb patches is significantly affected by both tree canopy foliage and other herb patches. Dynamic models of forest growth, species diversity, and composition must include herbs.