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| DOI：10.13522/j.cnki.ggps.20170034 |
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| Water Use Efficiency of Maize Agroecosystem in Longzhong Region under Different Weathers |
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KAN Fei， YUE Ning， DING Linkai， LI Ling， WEI Guoxiao
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School of Earth and Environmental Science, Lanzhou University， Lanzhou 730000, China
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| Abstract: |
| 【Objective】 Agricultural production and ecosystem functions depend on weather. The purpose of this paper is to put some insight into the water use of a semi-arid maize agroecosystem in Longzhong region. 【Method】 Carbon and water fluxes measured from the eddy covariance were applied to estimate the water use efficiency (WUE) and inherent water use efficiency (IWUE) of the agroecosystem. The responses of WUE and IWUE to different weathers were analyzed. 【Result】 The relationship between gross ecosystem productivity (GEP) and evapotranspiration (ET) was not as strong as the relationship between GPP·VPD and ET, because the nonlinear effect of the vapor pressure deficit (VPD) on ET in the latter was taken into account. The time lag between GEP and ET resulted in a hysteresis curve, and IWUE reduced the effect of this hysteresis. Photosynthetically active radiation (PAR), VPD, flow rate and ET can be fitted into a single-peak curve for both sunny and cloudy days, with the associated values in sunny days larger than that in cloudy days. The variation of the net ecosystem CO2 exchange (NEE) was similar in sunny and cloudy days, and the water use efficiency was in a U-shaped curve with the corresponding value for cloudy days larger than that for sunny days. 【Conclusion】 The dependence of WUE on VPD and the flow rate in cloudy days are not as good as that in sunny day because of the disturbance of vapor. IWUE can improve the correlation coefficient. Compared to WUE, IWUE is more appropriate to describe water and carbon interaction in this area. |
| Key words: Longzhong; agroecosystem; water use efficiency; inherent water use efficiency |
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