Forest-Watershed Experiment and proposal for future experiments

About 40% of the forest in Japan is specified for the protection forest, and protection forest for headwater conservation and recharge improvement accounts for 73.1% of that percentage. The necessity of conducting the hydrological research related to forest management has increased, and the role that the forest hydrology plays has become increasingly important. We selected six experimental watershed sites (Kamikawa Experimental Watershed in Hokkaido: HKW, Kamabuchi Experimental Watershed in Yamagata: YKW, Takaragawa Experimental Watershed in Gunma: GTW, Hitachi Ohta Experimental Watershed in Ibaraki: IHW, Tatsunokuchi-yama Experimental Watershed in Okayama: OTW, Sankawa Experimental Watershed in Miyazaki: MSW) which run by Forestry and Forest Products Research Institute. Then, we summarized current status of knowledge on influence of vegetation changes including forest management (HKW: selective logging, influence of damage by wind, YKW: clear cutting, partial deforestation, establishment of terrace work, GTW: selective cutting, strip cutting, IHW: clear cutting, tractor logging, OTW: selective cutting, influence of pine withering and forest fire, MSW: clear cutting, partial deforestation). There are various methods of the forest management in forestry. In addition, because we must clarify the function for water and soil conservation based on the forest watershed experiment in different climate regions (i.e. snowy and cold region; a little precipitation region; heavy rainfall region), it is not accurate to use only one forest experimental watershed in order to evaluate the changes in the function for all forests. We proposed that the further forest watershed experiments should be conducted for the following research topics: 1) the hydrological observations for a long term; 2) a comparison of hydrological studies in different climate regions; 3) hydrological process studies; 4) evaluation of hydrological studies in large catchments; and 5) joint research with scientists in other fields such as forest ecology, forestry machine, and social economics.