Influence of alternative vegetation management treatments on conifer plantation attributes: abundance, species diversity, and structural diversity

摘要

This study was designed to test the hypothesis that alternative vegetation management treatments (manual cutting and cut-stump applications of glyphosate herbicide) would decrease plant community abundance, species diversity, and structural diversity of young mixed conifer plantations in southern British Columbia, Canada. The experimental design consisted of nine operational sized plantations, stratified into three blocks (1 control, 1 manual, and 1 cut-stump plantation per block), with five permanent strip-transects to sample vegetation within each plantation. Vegetation management treatments did not significantly (p>0.10) affect the crown volume index of herb, shrub, or coniferous tree layers. However, both manual and cut-stump treatments significantly reduced crown volume index of deciduous trees in the first post-treatment year (p=0.05 and p<0.01, respectively). Due to prolific regrowth of stump sprouts, the manual treatment effect did nor last beyond the first posttreatment year. In contrast, the cut-stump treatment impeded sprouting and, relative to control and manual treatments, continued to significantly suppress deciduous growth for at least 4 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, these vegetation management treatments affected 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. These results may be applicable to other temperate forest ecosystems where conifer release is practised in young plantations.