Dynamics of organic-chemical components in leaf litters during a 3.5-year decomposition

Changes in organic-chemical components of Abies needle and Betula leaf litt ers were studied over a 3.5-year period in a sub-alpine coniferous forest i n Japan. During the 3.5-year incubation, mass loss of litters was 56 and 78 % for Abies needle and Betula leaf, respectively. Decomposition of carbon components were expressed by Olson's constant Oc). Decomposition rates of e xtractives, holocellulose and lignin were 0.569, 0.274 and 0.143 for Abies needle and 0.547, 0.572 and 0.253 respectively for Betula leaf litter. Lign in underwent less decomposition in both litters compared with extractives a nd holocellulose. After a 3.5-year period of decomposition, the concentrati ons of extractives, holocellulose, and lignin were similar between the two litters. Over a 3.5-year period of decomposition, the sugar compositions re ached similar levels between the two Litter types at the later decompositio n stage. Dendrogram analysis of sugar dynamics indicated two groups, the fi rst group included galactose, xylose, glucose and rhamnose and the second g roup included mannose. A convergence in concentrations of organic component s between two litter types was demonstrated at two levels, i.e. first level : major fractions such as extractives, holocellulose and lignin; and the se cond level: sugars, such as arabinose, rhamnose, glucose, galactose, xylose and mannose. (C) 2000 Editions scientifiques et medicales Elsevier SAS.