Coarse woody debris biomass in successional and primary temperate forests in Chiloé Island, Chile

Coarse woody residues (snags and logs) are a massive and functionally important component of high-latitude forest ecosystems, both natural and managed. Decaying logs and snags provide habitat for many organisms and participate in biogeochemical element fluxes within the forest ecosystem. Because of their large mass and slow decay rates, they may also play a significant role in the global carbon cycle. For these reasons, it is important to understand the dynamics of coarse woody debris (CWD) during forest succession. Here, we estimated the biomass of CWD (defined as logs or snags >10 cm stem diameter) in nine forest stands, both primary and secondary, on Chiloé Island (42°S), southern Chile. The stands represented a successional chronosequence following non-catastrophic human disturbance by fire and logging. We characterized logs in terms of their decay class, total carbon content, moisture content, volume, and dry biomass. CWD biomass ranged from 18 to 413 Mg ha −1, with a recently disturbed and old-growth forests having the largest values. Early- and mid-successional stands had the lowest values. Decay classes of logs differed in density, moisture contents and total carbon content. Carbon stored in logs and snags was nearly 10 times higher in old-growth and primary forests than in young-successional forests. CWD biomass is substantially reduced in young growing stands with disrupting effects on ecological functions and biodiversity.