Observation of canopy interception ratio in old-aged low-density Japanese cypress plantations in the Aso District, Southern Japan

Abstract

In 2014 and 2015, canopy interception ratios (the ratio of rainfall interception to gross rainfall) were observed in two plots established in old-aged Japanese cypress (Chamaecyparis obtusa Endl.) plantations (plot A, 89-years-old; plot B, 92-years-old; as of 2013) in the Aso district, Kumamoto Prefecture, southern Japan. These stands have been managed by regular thinning regimes. The stand densities were 522 trees ha-1 in plot A and 356 trees ha-1 in plot B, which was the lowest density among the previous studies on interception ratio of coniferous plantations in Japan. The interception ratios in 2014 and 2015 were 8.0 and 12.1% in plot A and 11.2 and 13.9% in plot B, respectively. The relationship between the stand density and the interception ratio of coniferous plantations in Japan was analyzed using the 49 data from previous studies and this study. The result demonstrated that the relationship was well expressed by an exponential function rather than a linear function. Our results will be effective when evaluating the effect of forest management on the water yield.