著者

マンフロイ オダイル ジョセ 鈴木 雅一 田中 のぶあき 諸岡 利幸 蔵治 こいちろ

出版者

日本森林学会

雑誌

日本林学会大会発表データベース

巻号頁・発行日

vol.115, pp.P4049, 2004

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In this analysis, we investigated effects of increase of number of raingauges, spatial variability, extent of zones of intense TF dripping and effect of wind speed on TF measured in a 10 X 10 m plot of a lowland tropical forest in Lambir, Sarawak, Malaysia. Daily TF catches by 20 fixed raingages in a 10 X 10 m plot, called fixed plot, was measured over two years. During this same two years, by using additional 20 relocating raingages, TF was also measured during a period of about one month in each of 23 different plots, of same size as the fixed plot, inside the limits of the 4 ha crane site biological plot. An intense daily TF measurement with 60 raingages for a period of about 2 months duration was carried out in the fixed plot. From this period, 15 single storms separated by 6 hours dry spell could be extracted. Analysis of the TF data were based on the TF ratio which is the percent TF catch of a gauge or gauges in a storm or period of time divided by total open rainfall in the same period. The main results were as follows. 1) General TF characteristics: Mean Total TF in the fixed plot was 82 % of the open rainfall in the first year and 87 % in the second year. Mean TF measured in the 23 relocating plots were in average 9% greater than TF measured in the fixed plot during a same period. 2) Intense TF measurement in the fixed plot:Interpolation of the percent TF ratio caught by the 60 gauges over all the 2 months period of intense measurement in this plot showed that zones of relatively intense dripping occupied less than 10 % of the area of the plot. Analyses of the 15 single rainfall storms selected from this period also showed the occurrence of zones of intense dripping in 11 of the storms but the pattern or place of occurrence of these zones were not constant. Mean catches by the 20 fixed set of TF gauges (gauges used to measure TF during the two years period) in 15 storms differed from 0.2 to 0.6 mm of the mean catches of all 60 gauges in the same storms. In addition, analysis of the TF ratio catches of the 60 gauges in each of the 15 single storms with empirical variograms suggested no spatial autocorrelation between gauges percent catches, and therefore TF catches by individual gauges within this plot can be regarded as independent and the TF process as random within plots of this size. Finally, the distribution of the 60 gauges TF ratio in the fixed plot resembled the distribution of the TF ratio measured in 520 different points in the 23 relocating plots inside the 4 ha plot. 3) Wind speed effect: In the present study site storms occurs both in the night, usually under calm wind condition and afternoon usually in active wind condition that make the separation of the wind speed effect alone in TF difficult. Despite of that, low mean TF in the fixed plot was associated with storms occurred under windy condition or afternoon. An increase in the total stemflow of the fixed plot for storms under windy condition was not found, and therefore rainfall interception loss calculated as the difference of rainfall and TF-plus-stemflow was higher for storms under windy condition.