Community composition and diversity of riparian forests regulate decomposition of leaf litter in stream ecosystems

Riparian forest plantings are a well-established restoration technique commonly used to stabilize banks and intercept nutrient flow from adjacent agricultural fields. Tree species planted for these efforts may not reflect mature forest communities within the same region. Given contemporary research on links between biodiversity and ecosystem functioning, we conducted a leaf-litter decomposition study to investigate how mixing of detrital resources that reflect forest community composition would regulate in-stream leaf litter. Leaf litter bags containing material from a mature forest (Liriodendron tulipifera, Acer rubrum, Quercus rubra, full factorial treatments = 7) and a restored riparian forest (Cornus sericea, Fraxinus pennsylvanica, Platanus occidentalis, full factorial treatments = 7) were deployed in a stream reach that experienced riparian reforestation in 2004. Litter from the restored riparian community had less mass remaining (45.28 +/- 2.27%) than that from the mature riparian community (54.95 +/- 2.19%) after 5 weeks. In addition, mixed litter treatments in the restored riparian community had less mass remaining (40.54 +/- 2.37%) than single-species treatments (51.80 +/- 4.05%), a pattern not observed in the mature forest community. Results highlight the importance of planting mixed-species assemblages as this structure may regulate processes such as decomposition and food-web structure, processes often not targeted in the restoration plans.