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 c_a 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.

中文翻译：

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清晰，气象和生理因素对日本北部卡马布奇实验流域蒸散量的影响

本实验研究清楚切割的（效果和森林蒸散的气象和生理因素ET），通过使用在Kamabuchi实验水预算方法分水岭（KMB; 38°56'21“N，140°15'58 ” E）在日本北部。使用1939年无雪期（从6月到10月）收集的气象和排放数据比较了三个子流域的ET：三个未受干扰的小流域；第二和第三流域；明确修剪后种植日本柳杉的地方。配对分水岭实验表明，截割导致ET下降约100 mm yr ^-1，即使种下了粳稻，这种减少也持续了20多年。在所有流域中，ET的波动都类似，无论是否进行明确砍伐或种植。这种波动主要是由太阳辐射和温度引起的。固有水分利用效率（IWUE），使用计算出的δ ¹³ Ç在树轮纤维素的蚕蛾增加，由于升高的大气CO ₂浓度。我们将单棵树上的年度碳固定量估计为年度净光合作用（A）。随后，根据iWUE与水之间的关系计算出蒸腾量（E）一。结果表明，每棵树的A和E随着树的长大而增加；然而，树木对增加c _a的反应抑制了ET的增加。此外，在观测期间，来自流域的ET的波动比P的波动小，这是因为E的增加和减少与拦截损失是相辅相成的。