Decomposition of Bauhinia purpurea leaf litter in a polluted and unpolluted Hong Kong waterway

Decomposition of Bauhinia purpurea leaves in litter bags submerged in the Tai Po Kau Forest Stream (TPKFS) and the Lam Tsuen River (LTR) was investigated. In winter, the organically enriched LTR was categorized as polluted based on BOD₅, turbidity, and heterotrophic bacteria counts. The TPKFS was always relatively clean. Weight loss of leaf litter at both sites was very rapid when compared with published values and exhibited a distinct seasonal pattern. The decomposition rate of leaf litter varied linearly with mean water temperature. Carbon content of the leaf litter decreased during decomposition and was negatively correlated with the percent ash content. Except in the first 2 wks, the nitrogen content of decomposing leaf litter decreased with time at a rate correlated with the abundance of heterotrophic bacteria in winter leaf litter. Based on the results of the winter study only, the decomposition of leaf litter seems to be suppressed in the polluted river. -from Authors