Greater effect of canopy conductance in regulating the energy 冠层导度变化对地表能量分配起关键作用.pdfVIP

HYDROLOGICAL PROCESSES Hydrol. Process. (2012) Published online in Wiley Online Library () DOI: 10.1002/hyp.9413 Greater effect of canopy conductance in regulating the energy partition above the maize field in arid northwest China Sien Li,1 Shaozhong Kang,1* Lu Zhang,2 Fusheng Li,3 Taisheng Du,1 Ling Tong,1 Shufen Wang1 and Hongna Lu1 1 Center for Agricultural Water Research in China, China Agricultural University, Beijing 100083, China 2 CSIRO Land and Water, GPO Box 1666, Canberra, ACT, 2601, Australia 3 College of Agriculture, Guangxi University, Nanning, Guangxi, 530005, China Abstract: The partition of available energy into evapotranspiration affected by environmental and physiological factors is critical in understanding the water cycle and optimizing the water management in the field. Our study attempted to accurately quantify the environmental and physiological control on variability in evaporative fraction (EF) based on the Penman–Monteith model. The eddy covariance method was used to measure water flux over a canopy and then calculate the EF above a maize field in northwest China in 2007. Results indicate that the EF was lower in other growth stages than in the heading stage, so the EF value in the heading stage was taken as the standard value. The decreases in EF caused by canopy conductance and environmental factors were 0.176 and 0.026, accounting for 117% and 17% of the total difference in EF, respectively. Such results were mainly due to the following: (1) the variation of maize canopy conductance was greater than that of the environmental factors, such as air temperature, air humidity, wind speed and radiation; (2) the EF of the maize was more sensitive t