山火事が森林生態系における水・主要塩類の収支に及ぼす影響 : III.樹冠による降水遮断量

抄録

Precipitation, throughfall, stemflow and stream discharge were measured simultaneously throughout a year from middle April of 1981 till early April of 1982 in both a natural and burnt red pine forest on Etajima Island, Hiroshima Prefecture, west Japan, where a forest fire occurred in June of 1978. Little difference in precipitation between these two forests was found, however, throughfall in the burnt forest was always larger than that in the natural forest due to the loss of the canopy by fire, the annual ratio of throughfall to precipitation was estimated at 94.4% and 83.0%, respectively. There was no significant difference in stemflow between the two forests, because stemflow was promoted by smoothing out the thick and rugged bark by fire in spite of the loss of most of the canopy (leaves and fine branches). Consequently, the annual interception storage, which is estimated as the balance between precipitation and the sum of throughfall and stemflow, was 3.6% and 14.0% of the annual precipitation in the burnt and natural forests, respectively. The difference in interception storage between these two forests (10.4% of annual precipitation) corresponded closely to difference of stream discharge, especially that of the direct flow between them.