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.