Koichiro Kuraji, Mie Gomyo, Anand Nainar
Received 2019/05/17, Accepted 2019/08/05, Published 2019/09/11

Koichiro Kuraji1), Mie Gomyo2), Anand Nainar2)

1) Executive Office, The University of Tokyo Forests, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Japan
2) Ecohydrology Research Institute, The University of Tokyo Forests, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Japan

Changes in runoff caused by forest management practices such as thinning need to be better understood for effective water resource management. We established matched (20° slope) 62%-thinning treatment and grassland control lysimeter plots in a 22-year-old cypress plantation in the Inuyama Research Forest of the Ecohydrology Research Institute, Japan. Runoff (surface and subsurface) was directed into a collection tank with a 90° v-notch weir outlet. Measurements were made before and after the thinning treatment and were compared with grassland control. Monthly manual measurements of subsurface runoff (March 2011–December 2014) performed via a measuring cylinder and stopwatch yielded 18 pre-thinning and 24 post-thinning observations. In addition, 26 pre-thinning and 24 post-thinning sets of storm-event measurements were continuously recorded via a water level data logger. Following thinning, subsurface runoff and peak storm-runoff changed by up to +133% and –80% respectively. By controlling the geology, soil characteristics and hydrological pathways, we were able to attribute these outcomes to reduced transpiration and increased ground resistance from felled logs respectively, suggesting that well-managed high-intensity thinning may be beneficial for increasing water supply and controlling floods. However, this is only achievable if felled logs are aligned along contour lines on the hillslopes.

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Copyright (c) 2019 The Author(s) CC-BY 4.0