Document: MAR-3-69-17

Four-year response of the herbaceous layer to harvesting in a mixed coniferous-deciduous forest.

ROBERTS, M.R.*

University of New Brunswick, Fredericton, NB, Canada ¹

Abstract:
Information concerning the effects of different harvesting systems on the herbaceous layer is scarce. Using 169 5m² permanent plots established before harvesting, we compared changes in the herbaceous layer (vascular plants <1m tall) in two operational clearcutting treatments (CS = with mechanical site preparation and planting followed by herbicide application in year 3; C = without site preparation, planting or herbicide) to an adjacent uncut control (UC) in a 56-ha watershed in southeastern New Brunswick, Canada. Preharvest tree composition included Betula papyrifera, Acer rubrum, Populus spp., Picea spp. and Abies balsamea. Sixteen species were lost and 35 new species colonized the CS treatment by the fourth year after harvest, compared to 5 and 30 species, respectively, for the C treatment. Richness of forest-dependent species decreased in all three treatments, with the greatest decrease in the CS treatment where higher levels of forest floor disturbance and herbicide occurred. Shannon-Wiener diversity (H') for forest-dependent species decreased over four years after harvest in the CS treatment but increased in the UC and C treatments. Total species richness and H' increased over the four years in all treatments. Unique habitats in the harvest block, including a seepage spring, contained unusual species and high plant diversity. Our results suggest that species diversity of the herbaceous layer could be maintained by minimizing forest floor disturbance, protecting unique habitats and leaving uncut patches within cut blocks.

Keywords: Clearcutting, disturbance, forest harvesting, forest understory, herbaceous layer, species diversity, vascular plants

This abstract is being presented at: 2:30 PM in session:
Oral Session #51: Disturbance Ecology: Harvesting, Grazing and Roads.