Effects of clear-cutting,meteorological, and physiological factors on evapotranspiration in the Kamabuchi experimental watershed in northern Japan |
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Authors: | Tayoko Kubota Akira Kagawa Toshio Abe Ikuhiro Hosoda |
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Affiliation: | 1. Department of Disaster Prevention, Meteorology and Hydrology, Forestry and Forest Products Research Institute, Tsukuba, Japan;2. Department of Wood Properties and Processing, Forestry and Forest Products Research Institute, Tsukuba, Japan;3. Tohoku Research Center, Forestry and Forest Products Research Institute, Morioka, Japan;4. Kansai Research Center, Forestry and Forest Products Research Institute, Kyoto, Japan |
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Abstract: | This study investigated the effects of clear-cutting and the meteorological and physiological factors on forest evapotranspiration (ET), by using the water-budget method in the Kamabuchi experimental watershed (KMB; 38° 56′ 21″ N, 140° 15′ 58″ E) in northern Japan. Meteorological and discharge data collected during no-snow periods (from June to October) from 1939 were used to compare ET in three sub-watersheds: No. 1, where the forest had been left undisturbed, and No. 2 and No. 3, where Cryptomeria japonica was planted after clear-cutting. Paired watershed experiments revealed that clear-cutting caused ET to decrease by approximately 100 mm yr−1, and this reduction continued for more than 20 years, even after C. japonica was planted. ET fluctuated similarly across all watersheds, regardless of clear-cutting or planting. This fluctuation is mainly caused by solar radiation and temperature. Intrinsic water-use efficiency (iWUE) calculated using δ13C of tree-ring cellulose in C. japonica increased due to elevated atmospheric CO2 concentration. We estimated annual carbon fixation in a single tree as the annual net photosynthesis (A). Subsequently, transpiration (E) was calculated from the relationship between iWUE and A. The results showed that A and E per tree increased as the tree grew older; however, the trees' responses to increasing ca suppress the increase in ET. Moreover, the fluctuation of ET from the watershed was small compared to the fluctuation of P during the observation periods because the increase and decrease in E and interception loss complemented each other. |
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Keywords: | clear-cutting evapotranspiration global warming intrinsic water-use efficiency paired watershed experiment tree-ring cellulose δ13C δ18O |
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