Estimation of annual forest evapotranspiration from a coniferous plantation watershed in Japan (2): Comparison of eddy covariance, water budget and sap-flow plus interception loss

Takanori Shimizu, Tomo'omi Kumagai, Masahiro Kobayashi, Koji Tamai, Shin'ichi Iida, Naoki Kabeya, Reo Ikawa, Makiko Tateishi, Yoshiyuki Miyazawa, Akira Shimizu

研究成果: Contribution to journalArticle査読

17 被引用数 (Scopus)

抄録

Evapotranspiration (ET) was estimated from a planted coniferous forest in southwestern Japan by applying three methods: the eddy covariance method; the measurement of rainfall (P) and runoff (Q) in a small watershed; and a combination of rainfall interception loss (IC), upper canopy transpiration based on a sap-flux density measurement in Japanese cedar (Cryptomeria Japonica D. Don) stands (EUC), and modeled sub-canopy ET (ESC). After inverse multiplication of the energy imbalance ratio, ET by the eddy covariance method (ETEC) was 839.9mm in 2007 and 811.8mm in 2008. The yearly values of P-Q were partially affected by P in the previous autumn. After continuous data collection for more than 5years, P-Q became stable. The 9-year (2000-2008) average P-Q, which was considered most reliable in this study, was 897.5mmy-1. The cumulative ETEC during the daylight hours from the right stream bank, covered mainly with large Japanese cedars, was 894.1mm from April 2007 to March 2008. The value was almost the same as that calculated as the components sum (ETCOMP=IC+EUC+ESC: 911.4mm), and the comparison suggested that the annual totals of ETEC with an energy imbalance correction provide a reliable estimate of ET in a forest stand on a complex topography. Spatial variation in the watershed was likely caused by differences in soil water retention at each slope position. The slight difference in annual ETEC in 2007 compared with 2008 was attributed to differences in the radiative energy input. In the monthly-weekly analysis, ETCOMP was frequently higher than ETEC after heavy rainfall, while ETEC was higher under dry conditions and during active ET. Even under dry canopy conditions, daily ETEC was often higher than EUC+ESC. The results suggested a time-lag in evaporation from the ecosystem and/or under-estimated ETEC after rainfall.

本文言語英語
ページ(範囲)250-264
ページ数15
ジャーナルJournal of Hydrology
522
DOI
出版ステータス出版済み - 3 1 2015

All Science Journal Classification (ASJC) codes

  • Water Science and Technology

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