2018 Volume 60 Issue 2 Pages 55-61
We added “dwarf-bamboo-dominant type” to the conventional types of undergrowth in planted Japanese cypress (Chamaecyparis obtusa) forests (“fern-dominant type”, “herbaceous type”, “shrub type”, and “poor vegetation type”), as classified from an examination of the coverage and dominant species in southern Gifu Prefecture. We also reordered the undergrowth types in terms of their ability to deter surface soil erosion. The dwarf-bamboo-dominant type appeared at higher altitudes than the fern-dominant type, and the dwarf-bamboo-dominant type could appear on forest floors where there was poor light. Its greater vegetation cover led to a reduction in the soil erosion susceptibility index, which is an indicator of the relative risk of surface soil erosion. The index of the dwarf-bamboo-dominant type was lower than those of the herbaceous type and the shrub type, but the vegetation cover of the dwarf-bamboo-dominant type was similar to those of these two types. The dwarf-bamboo-dominant type had a deterrent effect on surface soil erosion because of the greater vegetation cover of its herbaceous layer and the multilayered vegetation and litter cover. Consequently, adding the dwarf-bamboo-dominant type to the types of undergrowth in Japanese cypress stands is effective in estimating the surface-soil-erosion deterrence of undergrowth. Among these undergrowth types, the soil erosion susceptibility index increases in the order of fern-dominant type, dwarf-bamboo-dominant type, herbaceous type, shrub type, and poor vegetation type. This result should help to improve the versatility of methods used to estimate the surface-soil-erosion deterrence of different types of undergrowth.
