Examining the Influence of Burned Snags on Post-Fire Microsite Conditions and Forest Regeneration

Abstract

After a wildfire, standing dead trees (snags) are often left behind. While salvage logging can recover economic value, snags also contribute to post-fire recovery by altering microsite conditions that influence seedling performance. This study tested how different snag arrangements affect seedling growth and growing conditions. We planted trembling aspen (Populus tremuloides) seedlings in 18 burned subalpine forest plots in Alberta, Canada, across treatments that varied in snag density (dense clusters versus isolated snags), canopy openness, and whether stemflow (the water channeled down tree trunks during rain) was naturally delivered or redirected away from the root zone. We monitored stemflow, throughfall, soil moisture, and seedling growth throughout the growing season. Seedlings planted near isolated snags with natural stemflow access grew up to 3.5 times taller than those in open areas or dense clusters. Redirecting stemflow reduced growth, especially around individual snags. Although dense plots retained more soil moisture, they did not support better seedling growth, suggesting that water availability alone does not explain observed patterns. These findings show that microsite differences, including snag proximity and water delivery, strongly influence regeneration. To support seedling success, managers should consider selectively removing dense snag clusters while retaining scattered snags to balance moisture retention with favorable microsite conditions and to retain economic value of burned forests.