Recruitment of wood to streams in old-growth and second-growth redwood forests, northern California, U.S.A.

Abstract

From an ecological perspective, one aim of forest management is to supply wood to streams to protect and enhance aquatic habitats. An analysis was made of the mass balance of in-stream wood along 9 km of channels in old-growth and 50-year-old second-growth redwood (Sequoia sempervirens (D. Don) Endl.) forests in northern California, U.S.A. High volumes of wood storage in streams in old-growth forests were due primarily to streamside landsliding and bank erosion. Logging-related debris and high forest mortality rates in conifer and deciduous forests contributed to high wood storage in second-growth forests. Volumes of in-stream wood in second-growth forests were similar to volumes in one old-growth system and less than another. Diameters of wood were significantly greater in older forests. Wood recruitment from forest mortality in old-growth forests was low compared with second-growth sites, driven by differences in conifer mortality rates of approximately 0.04 and 0.9%·year–1, respectively. Contrasting old-growth redwood mortality with values reported for unmanaged Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) forests in Washington State (0.5%·year–1) and unmanaged Sitka spruce (Picea stichensis (Bong.) Carrière) forests in southeastern Alaska (1.2%·year–1) point to a strong latitudinal gradient of forest mortality reflected in tree size. The mass balance analysis of in-stream wood also allowed an estimation of bank erosion along large channels and soil creep along small, steep streams.