Influence of alternative vegetation management treatments on plant community attributes : abundance, species diversity, and structural diversity

This study was designed to test the hypothesis that alternative vegetation management treatments (manual cutting and cut-stump applications of glyphosate herbicide), applied to young plantations, would decrease plant community abundance (crown volume index), species diversity, and structural diversity. The experimental design consisted of nine operational-sized plantations stratified on the basis of location and elevation into 3 blocks (i.e., 1 control, 1 manual, and 1 cut-stump plantation per block), and with 5 permanent strip-transects to sample vegetation within each plantation. Vegetation management treatments did not significantly (P > 0.10) affect the crown volume index of the herb, shrub, or coniferous tree layers. However, both manual and cut-stump treatments significantly reduced the crown volume index of deciduous trees in the first posttreatment year (P = 0.05 and P < 0.01, respectively). Due to prolific growth of stump sprouts, the manual treatment effect did not extend past the first post-treatment year. In contrast, the cut-stump treatment impeded sprouting and, relative to control and manual treatments, significantly suppressed deciduous growth for at least four years (P < 0.05). Species richness, diversity, and turnover of the herb, shrub, and tree layers were not significantly (P > 0.10) different between treatments and control. Similarly, the structural diversity of herb, shrub, and tree layers were also not significantly (P > 0.10) different between treatments and control. By opening the canopy and decreasing the dominance of the deciduous tree layer, both manual and cut-stump treatments showed greater total structural diversity (herb, shrub, and tree layers combined) relative to the control. However, differences in total structural diversity between treatments and control were, for the most part, not significant (P > 0.10). Therefore, the vegetation management treatments used in this study decreased only the volume of the targeted deciduous tree layer and did not adversely affect the species richness, diversity, turnover, or structural diversity of the plant community.Forestry, Faculty ofGraduat