[Stream ecosystem health assessment based on the measurement of leaf litter breakdown: a case study in Hengshishui River of Guangdong Province].

Based on the Gessner' s model of leaf litter breakdown, the functional integrity and ecosystem health of Hengshishui River in Guangdong Province were assessed, and the breakdown rates of Castanopsis fissa and Schima superba leaf litters at the sites unpolluted and polluted by acid mine drainage were compared. The leaf litters of the two tree species had a significantly lower breakdown rate at polluted than at unpolluted sites (P < 0.05). According the Gessner's model, all polluted sites had an ecosystem health score 0, while all unpolluted sites had a score 2, indicating that the health status of polluted river reaches were severely damaged. The biological assessment of stream ecosystem health was consistent with the results of water quality analysis, indicating that the leaf litter breakdown model was a suitable index of stream status.