Interactions between riparian forest restoration and tree biodiversity on litter breakdown in stream ecosystems

Reforestation of stream-side vegetation is a common practice performed by restoration scientists. Tree species used in riparian restoration projects are often planted in assemblages that deviate from patterns seen in natural communities. Because streams derive energy from leaf litter that originates in the riparian zone, planting species in non-natural assemblages with altered diversity may have consequences for aquatic ecosystem processes. This study investigated the influence of community composition and diversity of restored stream-side buffers on the ecosystem processes associated with organic matter breakdown. A leaf litter breakdown study and a laboratory feeding experiment were conducted to determine community and diversity effects. Significant differences in leaf litter breakdown between two forest communities were measured across three streams. Leaf packs composed of restored community leaf species lost significantly more mass than those composed of species representative of a pristine riparian community. However, invertebrate responses to different forest communities in the laboratory were not consistent with results from the field study. Diversity influences on mass loss were observed in the field but varied between sites, while all invertebrate treatments in the laboratory exhibited increased feeding activity on diverse resources. This work provides insight into how altering community composition and diversity of riparian forests through restoration practices affects a valuable ecosystem process, and may have implications for future management strategies.