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 litters were studied over a 3.5-year period in a sub-alpine coniferous forest in 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 extractives, 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. Lignin underwent less decomposition in both litters compared with extractives and holocellulose. After a 3.5-year period of decomposition, the concentrations of extractives, holocellulose, and lignin were similar between the two litters. Over a 3.5-year period of decomposition, the sugar compositions reached similar levels between the two Litter types at the later decomposition stage. Dendrogram analysis of sugar dynamics indicated two groups, the first group included galactose, xylose, glucose and rhamnose and the second group included mannose. A convergence in concentrations of organic components between two litter types was demonstrated at two levels, i.e. first level: major fractions such as extractives, holocellulose and lignin; and the second level: sugars, such as arabinose, rhamnose, glucose, galactose, xylose and mannose. (C) 2000 Editions scientifiques et medicales Elsevier SAS.