The decomposition rate of non-stem components of coarse woody debris (CWD) in European boreal forests mainly depends on site moisture and tree species

Abstract

The decomposition rate of CWD is a key missing link for a quantitative understanding of forest ecosystem functioning. We examined factors influencing decomposition rates of bark, roots and branches from aspen (Populus tremula), birch (Betula pendula, B. pubescens), fir (Abies sibirica), spruce (Picea abies, P. obovata), Scots pine (Pinus sylvestris) and Siberian pine (Pinus sibirica) CWD in three primeval European boreal forests. The chronosequence approach with estimates of single exponential decomposition rate (k) based on calculation of mass loss was used. The k of non-stem parts increased in the order: branches (0.006 year−1 for P. sibirica and 0.020 year−1 for other species), roots in poorly drained sites (0.025 year−1), roots in well-drained sites (0.034 year−1) and bark (0.110 and 0.138 year−1 and 0.147 and 0.255 year−1 under poorly and well-drained conditions and from 1 to 3 m and >3 m above the root collar, respectively). Our results predict that the rate of decomposition of whole CWD pieces in European boreal forests is a function of vegetation zone, site conditions, tree species and size.