Density-dependent woody detritus accumulation in an even-aged, single-species forest

Deadwood in forests influences fire intensity, stores carbon and nutrients, and provides wildlife habitat. We used a 54-year-old density management experiment in Larix occidentalis Nutt. forests to evaluate density dependence of woody detritus accumulation. Based on self-thinning theory, we expected woody detritus produced by the current stand to increase with stand density. Density-dependent woody detritus accumulation was apparent for fine woody debris and snags and for all woody detritus pools combined. Clear size-density relationships were apparent for coarse woody debris (CWD) and snags; mean piece size decreased with increasing stand density. Legacy CWD that originated from the preharvest old-growth stands accounted for about 45% of total woody detritus biomass. Live trees were largest in the low-density thinning treatments. Greater woody detritus biomass in the high-density and unthinned treatments originates primarily from past self-thinning, with additional inputs from density-dependent top breakage due to snow and ice and branch self-pruning. Because our results were driven by self-thinning mortality, the general trend of increasing woody detritus accumulation with increasing stand density should hold for maturing even-aged stands in other cool temperate and boreal forests.