Effects of alternative conifer release treatments on a soil seed bank in a boreal spruce plantation

Abstract

Evaluates the effects of 5 alternative conifer release treatments : cutting with brushsaws and a mechanical cleaning machine, applying herbicides (Release triclopyr and Vision glyphosate) by helicopter, and, untreated control on environmental components in a young spruce plantation. Documents the effects of clearcutting. Study site: Fallingsnow Ecosystem Project near Thunder Bay, Ontario.

This soil seed bank study was carried out as part of the Fallingsnow Ecosystem Project, located near Thunder Bay, Ontario. The project is an operational scale, integrated, multi-disciplinary study that was established in 1993. It evaluates the effects o f 5 alternative conifer release treatments (cutting with brushsaws and a mechanical cleaning machine; applying herbicides (Release [a.e. triclopyr] and Vision ® [a.e. glyphosate]) by helicopter and untreated control) on environmental components in a young spruce plantation. In addition, the project documents the effects of clear cutting on the environmental components by comparing post-harvest changes with changes in adjacent unharvested forests. This study compares the treatment effects on the soil seed bank. Samples o f the soil seed bank were collected in 1996 and green house grown during the winter of 1997. The resulting germinants were identified and quantified by species and treatment. Thirty-four species were identified, two of which were tree species: White birch (Betula papyrifera Marsh.) and trembling aspen (Populus tremuloides Michx ). Species richness, abundance and evenness indices clearly show that there was a treatment effect on the seed bank. Analysis further shows a significant difference in richness (number of species) between treatments. Species abundance curves were completed and are typical for the Northern Hemisphere. Orthogonal comparisons also show significant differences in species abundance between the forest and the cutover, the brushsaw treatment compared to the Silvana Selective treatment, and the treated cutover (brushsaw, Silvana Selective, Release®, Vision® in comparison to the untreated cutover and the forest combined. These seed bank germination differences resulting from applied silvicultural treatments could play a role in future forest management practices that strive to emulate forest fire effects.