The effects of logs, stumps, and root throws on understory communities within 28-year-old aspen-dominated boreal forests

Abstract

This study examined the role of logs, stumps, and root throws on the understory composition of aspen-dominated boreal forests. Measures of microsite coverage and suitability, and vascular plant composition and abundance were taken from 28-year-old wildfire and harvest sites. Larger logs (>20 cm diameter) with soft surfaces were the most suitable for colonization by vascular plants. These logs covered more than five times the area of stumps or root throws in both harvest and wildfire sites. Detrended correspondence analysis revealed that logs and stumps were colonized by a significantly different assemblage of vascular plants than the forest floor of either disturbance type. Contrary to studies in other forest types, assemblages of plants on root throw pits and mounds were similar to those on the forest floor. Initial colonization patterns on logs and stumps in both wildfire and harvest sites were similar. However, on more decayed logs assemblages of vascular plants were more similar to their respective wildfire or harvest forest floor assemblages. Ordination of species suggested that tree seedlings and shade-tolerant herbs were disproportionately more abundant on logs and stumps.Key words: plant community assemblages, deadwood resources, coarse woody debris, root throws, logs, boreal forest.