Decomposition of stump and root systems of Norway spruce in Sweden—A modelling approach

The demand for quantifying the biomass of stumps and roots and the carbon stored therein is related to aspects of biodiversity, site productivity, atmospheric carbon cycling issues, and the demand for bioenergy. This, in turn, creates a need to develop high-quality tools for estimating biomass and carbon-equivalents in the ground. The objective of this study was to develop decomposition functions for quantifying the remaining dry weight of the biomass of individual stumps and their associated roots in Norway spruce (Picea abies (L.) Karst.). The negative exponential model was chosen for this purpose, combined with a chronosequence approach, involving 99 stumps and their roots from three sites in Sweden. The results showed a relative decay rate of 4.6% annually for stump and root systems. Based on this rate, the time required for the loss of 50% (t0.5) and 95% (t0.95) of the wood is 15 and 64 years, respectively. Although there are many variables that affect decomposition, residual studies indicated that the remaining biomass could be predicted fairly accurately on the basis of the independent variables stump diameter and time.