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Energy exchange and evapotranspiration over irrigated seed maizeagroecosystems in a desert-oasis region, northwest China

2016-12-13 09:58:36 【 【打印】【关闭】

Energy exchange and evapotranspiration over irrigated seed maizeagroecosystems in a desert-oasis region, northwest China

 

Yongyong Zhanga,, Wenzhi Zhaoa, Jianhua Heb, Kun Zhangb

 

a Linze Inland River Basin Research Station, Key Laboratory of Eco-hydrology of Inland River Basin, Cold and Arid Regions Environmental and EngineeringResearch Institute, Chinese Academy of Sciences, Lanzhou 730000, China

b Key Laboratory of Western China’s Environmental Systems (Ministry of Education), College of Earth and Environmental Sciences, Lanzhou University,Lanzhou 730000, China

 

a b s t r a c t

Investigating the dynamics of energy and water vapor exchange in oasis agroecosystems is importantto improve scientific understanding of land surface processes in desert-oasis regions. In this study,water vapor and energy fluxes were obtained by using an eddy covariance technique for two similarirrigated seed maize fields at Yingke and Pingchuan, in northwest China. Seasonal variabilities of evap-otranspiration (ET) and relevant environmental and biophysical factors were explored. Results showedthat the energy balance closures were reasonable, with energy balance ratio of 0.99 and 0.79 for a half-hourly time scale at Yingke and Pingchuan, respectively. The seasonal changes in net radiation (Rn),latent heat flux (LE), and sensible heat flux (H) of Yingke and Pingchuan were similar. Net radiation was11.27 MJ m1day1during the growing season. Latent heat flux accounted for 67.5% of net radiation, sen-sible heat flux was 25.0%, and soil heat flux was 7.5%. A reverse seasonal change was found in partitioningenergy flux into LE and H. The seasonal variation in energy flux partitioning was significantly related tothe phenology of maize. During the growing season, ET was 467 and 545 mm, and mean daily ET 2.84 and3.35 mm day1at Pingchuan and Yingke, respectively. “Non-growing” season ET was 15% of the annual ETin the bare field (during October–March) and 85% of the annual ET for maize (during April–September).Daily ET was mainly controlled by net radiation and air temperature, and was significantly affected byleaf area index (<3.0 m2m2) and canopy conductance (<10 mm s1). Furthermore, irrigation promoteddaily ET greatly during the growing season. Accurate estimation of seed maize ET and determinationthe controlling factors helps to develop exact irrigation scheduling and improve water resource use indesert-oasis agroecosystems.