Hovenia dulcis Thunb. (Rhamnaceae) invasion in the riparian zone alters the dynamics and decomposition of organic matter in subtropical streams, but not of associated invertebrate assemblages

摘要

Stream functioning is affected by allochthonous and autochthonous energy sources, organic matter decomposition and the structure and composition of the aquatic community. The presence of non-native tree species in the riparian zone may affect stream functioning. Thus, we quantified the allochthonous organic matter input to streams from native tree species and Hovenia dulcis, a non-native species, over a year, and we evaluated litter colonization and decomposition by aquatic invertebrates. The input of native organic matter was greater in Winter and Spring. On the other hand, the input of H. dulcis was higher in Autumn. The annual contribution of native organic matter was twofold greater than that of H. dulcis and was correlated with rainfall. H. dulcis leaf litter had decomposition rates that were three- to fourfold greater than those of native leaf litter. The invertebrate abundance and richness, and functional feeding groups did not vary between native and non-native leaf litter. We conclude that the presence of H. dulcis in the riparian zone changed the input patterns of allochthonous organic matter into streams. Furthermore, H. dulcis litter broke down faster than that of native species and did not directly affect the associated invertebrate community. However, the dominance of this species in riparian zones causes homogenisation of environment, resulting in changes in the composition of other biological communities (e.g., fungi and fish).