Soil erosion and overland flow in Japanese cypress plantations: spatio-temporal variations and a sampling strategy |
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| Authors: | Takanori Sato Nobuaki Tanaka Anand Nainar Koichiro Kuraji Mie Gomyo Haruhiko Suzuki |
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| Institution: | 1. Ecohydrology Research Institute, the University of Tokyo Forests, Graduate School of Agricultural and Life Sciences, The University of Tokyo , Seto, Japan satot@g.ecc.u-tokyo.ac.jp;3. Ecohydrology Research Institute, the University of Tokyo Forests, Graduate School of Agricultural and Life Sciences, The University of Tokyo , Seto, Japan;4. Executive Office, the University of Tokyo Forests, Graduate School of Agricultural and Life Sciences, The University of Tokyo , Tokyo, Japan;5. Industrial Affairs Department, Forestry Division , Toyota, Japan |
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| Abstract: | ABSTRACT Many studies have focused on soil erosion in unmanaged Japanese cypress plantations because the sparse understory vegetation and litter covering the forest ground enhance soil erosion. In this study, soil erosion, litter, and overland flow measurements were conducted over 14 months to identify the spatio-temporal variation and examine the optimal sample size. Fifteen traps (each 0.25 m wide) were installed in line along the bottom of a 15-m-wide slope. Soil erosion and overland flow had large spatial variations as compared to litter. The temporal coefficient of variation of soil erosion and overland flow was highest during dry seasons, while smaller during wet seasons. The random sampling analysis showed that the rate of decrease in spatio-temporal variation became moderate as the sample size increased beyond six. This result indicated that the optimal sample size was five, the total width of which was equivalent to about 8% of the monitored slope width. |
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| Keywords: | Japanese cypress plantation soil erosion overland flow small-sized trap random sampling |
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