Understorey plant communities in boreal cutblocks with different sizes and numbers of residual tree patches

Abstract

The influence of residual tree patch size after harvest on understorey plant communities was investigated in aspen and pine – black spruce forests in boreal Alberta, Canada. Three different patch size treatments were created in both study areas; patches amounted to 3% residual merchantable timber in each cutblock. In the aspen study area, species richness was higher in cutover matrix than in preharvest forests and large residual patches. Species richness was larger in small residual patches and the cutovers than in the preharvest forests. In contrast, in pine – black spruce stands, species richness did not differ between the preharvest forests, the large and small residual patches, and the cutover matrix; however, lower richness was observed in medium-sized residual patches than in the cutover matrix. In both study areas, significant differences between understorey plant communities in the preharvest forests and those in large, medium-sized, and small residual patches were observed. In addition, large and medium-sized residual patches had understorey plant communities that differed from those in the cutover matrix. If forest managers expect to maintain preharvest understorey plant communities within cutblock boundaries, residual patches need to be larger than those tested.