open access

https://hdl.handle.net/2115/43008

Watershed controls on the export of large wood from stream corridors

英語

Watershed hydrology

2010-04-15

Elsevier B.V.

Geomorphology

117(1-2)

33-43

Large wood maintains in-channel and floodplain habitats by influencing the biophysical character of the river corridor. Large wood dynamics in a river corridor are a product of both watershed-wide processes but also of local recruitment, transport, and storage. This complexity of scales added to the logistical constraints in taking measurements limits our understanding of large wood dynamics through the watershed. To begin to unravel this issue, we compiled a dataset of the volume of large wood deposited annually into 131 reservoirs across Japan, and compared large wood export to both flow discharge and watershed characteristics (watershed size, latitude, channel slope, percent forest, and forest type). We found that large wood was predominately transported during peak flow events. Large wood export increased logarithmically with watershed area. The decreasing export rate of large wood per watershed area is interpreted as a combination of annual export variability in upper watersheds, a non-significant increase in large wood recruitment along the longitudinal gradient (potentially human influenced), the increase in long-term storage on adjacent large floodplains, and significant decay/fragmentation downstream. Watersheds <10-20 km2 had a highly variable large wood export pattern, conforming generally to previously published work that suggest transport limitation in smaller watersheds. The data suggest that there is an export threshold (∼75 km2) where large wood export is no longer related to watershed size. Export across all watershed sizes was controlled by watershed characteristics (slope, percent forested, etc.) and peak discharge events. The connection with upstream watersheds and laterally with the floodplain increases the net flux of large wood through downstream transport and retransport of buried logs. Identifying rates of large wood transport due to watershed connectivity as a potential key input process will improve our basic understanding of geomorphic and ecological patterns within the watershed. These results highlight the importance of understanding both the local and watershed scale dynamics of large wood in creating and maintaining more heterogeneous riparian and aquatic habitat along the river corridor.

学術雑誌論文

Accepted Manuscript

0169-555X