An analysis of summer evapotranspiration based on multi-year observations including extreme climatic conditions over a cool-temperate evergreen coniferous forest, Takayama, Japan

作者：Saitoh Taku M^*; Tamagawa Ichiro; Muraoka Hiroyuki; Kondo Hiroaki

来源：Hydrological Processes, 2013, 27(23): 3341-3349.

DOI：10.1002/hyp.9834

• decoupling coefficient
• eddy covariance
• evergreen coniferous forest
• evapotranspiration
• inter-annual variation
• surface conductance

Five years (2006-2010) of eddy-covariance data were used to investigate inter-annual variation of evapotranspiration (E) under dry canopy conditions (i.e. no rainfall in the previous 24h) in summer over a cool-temperate evergreen coniferous forest in Japan. The data included the warmest summer (June to September) in the past 50years (2010) and the coolest summer in the past 15years (2009). We found significant differences between 2009 and 2010 in gas exchange properties such as equilibrium evaporation (E-eq) and surface conductance (G(s)) in addition to meteorological variables such as air vapour pressure deficit (D-a) and net radiation. The values of E, however, were not significantly different in these two years. Furthermore, the inter-annual variation (coefficient of variance, CV) in E was relatively low (3.5%) as compared with higher values of inter-annual variation in gas exchange properties (4.2-10.0%) and meteorological factors (4.3-18.3%). The relatively steady E can be explained by (1) less effective atmospheric demand (i.e. less sensitive to E-eq) because of the low decoupling coefficient (0.07-0.15) at the study site and (2) the negative response of G(s) to D-a and a reduced sensitivity of E to high D-a values in relation to plant physiological regulation (i.e. stomatal control).

• 出版日期2013-11-15