Microbial Decomposition of Tree and Shrub Leaf Litter. 1. Weight Loss and Chemical Composition of Decomposing Litter

Leaves of various tree and shrub species, treated with X-rays to kill animals, were allowed to decompose (usually for two years) in field conditions in openended glass tubes containing soil. Hazel, ash, oak, and birch, were each studied for three two-year periods: 1966-68, 1967-69, 1968-70. Apart from hazel, no litter showed significant within-species differences in weight loss with time. Where the curves of percentage of original weight remaining against time showed no significant differences for the same species in different years, the data were pooled. Throughout, an asymptotic regression fitted the data better than an exponential regression. Each litter showed an initially rapid weight loss for up to 20 days. In some cases, even the asymptotic regression did not fit the data well during this period. Chemical analyses (C, H, N, LOI) suggested that no significant change of composition of the leaves with time could be clearly detected because of the variability of the composition of the litters. However, oak, hazel, elm, and lime showed marked fluctuations in nitrogen content with time. In some cases there were quite large gains in nitrogen. Carbon/nitrogen ratios showed a clear decrease with time.