Björn Berg

Abstract

Aim. The aim behind this work is: (i) to review the work on Scots pine needle litter in order to construct a model for thedecomposition process, from litterfall until a stable fraction is left, (ii) suggest a simple regulating mechanism for itssequestration of carbon. Focus will be on foliar litter of Scots pine and the genus Pinus.Discussion. The chemical composition of newly shed pine litter is in part determined by climate, e.g. mean annual temperature(MAT). Thus concentrations of nitrogen (N) are higher – and those of manganese (Mn) lower – with higher MAT.This may also influence the decomposition process. Mass loss of newly shed pine needle litter is positively influenced byclimate (e.g. MAT), as well as by N and phosphorus (P) concentrations. In the late stage (above c. 30% accumulated massloss) the influence of climate fades and those of lignin (Acid Unhydrolyzable Residue – AUR), N, and Mn are regulatingthe decomposition process. As the degradation of AUR dominates the decomposition process important parameters arethose that influence the degradation of AUR, thus N and Mn. In the humus-near organic matter limit values have beenrelated to litter Mn concentration over a wide climate gradient. Thus, the higher the Mn concentration, the further theprocess goes and the smaller the stable fraction.Conclusions. It appears that factors regulating the size of the stable litter fraction may be used as a tool on a largergeographical scale to predict carbon sequestration rates in pine forests.

Keywords: Scots pine, decomposition, limit value, nitrogen, manganese, lignin, AUR

Björn Berg, University of Helsinki Department of Forest Sciences P.O. Box 27, FIN-00014 Helsinki: Finland