Abstract
Soil erosion has been progressing over a large area on the beech (Fagus crenata) forest floor with an understory impoverished by the feeding of deer (Cervus nippon) in Doudaira (located in East Tanzawa of Kanagawa Prefecture), and has a significant impact on the environment of the forest and streams. In previous studies at Doudaira, it is reported that the amount of washed soil is larger than the splashed soil, and washed soil is strongly affected by the overland flow. In this study, four erosion plots (2 m wide × 5 m long) with different understory cover percentage were installed on the beech forest slope in Doudaira. Throughfall, overland flow, forest floor cover percentage (the total values of understory cover percentage and litter cover percentage), soil erosion rate and other factors. were monitored during 2004∼2009, and the effect of forest floor cover percentage on the overland flow rate was examined. As a result, a significant negative correlation expressed by Rem = −18.9 ln (Cm) + 86.4 between the forest floor cover percentage (Cm) and the overland flow rate (Rem) was found. From the equation, when the forest floor cover percentage decreases, the overland flow rate increases. The overland flow rate changes seasonally; for example, such as in summer (Jul.∼Sep.) with less litter, the overland flow rate decreases compared to spring (Apr.∼Jun.) and autumn (Oct.∼Nov.) with a great deal of litter.
