Hydrological characteristics under deciduous broadleaf and evergreen coniferous forests in central Japan

Abstract

In Japan, many natural or secondary forests of the deciduous forest type have been converted to evergreen coniferous forests for plantation agriculture. This conversion should have an influence on the hydrological conditions. Thus, in order to reveal the difference in hydrological characteristics between deciduous broadleaf and evergreen coniferous forests, a 10-year hydrological observation was conducted at two small paired catchments. The results show that the annual discharge from the deciduous forest was higher than that from the coniferous forest. However, the peak discharge, the direct runoff during rainfall events and the runoff coefficient were higher in the coniferous forest than in the deciduous forest. In addition, the snow depth in the deciduous forest was higher than that in the evergreen coniferous forest due to the difference in canopy interception between the two forests. The forest canopy and the floor vegetation might be the most important factors in determining all of these hydrological characteristics. This research confirms that deciduous broadleaf forests are better able to foster water resources and control flooding than evergreen coniferous forests.