2024 Volume 106 Issue 10 Pages 285-289
We measured the surface soil (fine soil, gravel, and litter) movement under four types of undergrowth in a planted Japanese cypress (Chamaecyparis obtusa) forest. We also clarified the differences in surface soil erosion among the different types. The patches of undergrowth were all growing next to each other under the same conditions in the same stand on the same slope. The transport rate of fine soil per 1 mm precipitation increased in the order of the following types: fern (Diplopterygium glaucum) dominant, shrub with herbaceous layer, shrub without herbaceous layer, and poor vegetation. Greater cover of floor litter and undergrowth reduced the transport rate of fine soil. The fern-dominant and shrub-with-herbaceous-layer types therefore had a greater deterrent effect on surface soil erosion because of their multilayered cover of floor litter and herbaceous (≤30 cm) and shrub (>30 cm) layers. The shrub-without-herbaceous-layer type had a smaller deterrent effect than the former two types, because it had only a single shrub layer and lacked herbaceous and floor-litter layers. However, it had a greater deterrent effect than the poor vegetation type, which had no floor cover. These results suggest that we can improve surface-soil-erosion deterrence by controlling the type of undergrowth.
