半湿润区雨养玉米农田水分利用效率对环境因子的响应

Responses of water use efficiency of rain-fed maize to environmental factors in sub-humid area of Liaoning,Northeast China

水分利用效率（WUE）能够反映碳水循环的耦合状况，同时也是评价陆地植被对气候变化响应的一个有效特征量。本研究以水分控制试验（2008--2009年，锦州）和大田作物试验（1990--2010年，朝阳）为基础，分析了玉米叶片水平的水分利用效率（WUE．）对光合有效辐射、叶片表面CO2浓度、气温和土壤湿度的瞬时响应以及玉米产量水平的水分利用效率（WUE。）随温度和降水的变化特征。结果表明，随着叶片表面CO2浓度的升高（350～800μm01．mol-1），玉米的光合速率升高，气孔导度和蒸腾速率降低，WUE。增加。气温和土壤体积含水量升高，叶片蒸腾速率的增加幅度大于光合速率，导致WUE。显著降低。产量水平的水分利用效率与ET呈显著的二次曲线关系，当ET为400～450mm时，该区玉米产量和WUE，达到最大值，此时生长季的ET则为最佳经济蒸散量。播种至成熟期间的平均气温与WUE，无明显关系。可见，该地区的WUE，主要受到水分的影响，温度不起主导作用。

Water use efficiency （WUE） can reflect the coupling status of carbon and water cy- cles, and is an effective integral trait for assessing the responses of terrestrial vegetations to cli-mate change. In this paper, a moisture control experiment in Jinzhou during 2008-2009 and a field crop trial in Chaoyang during 1990-2010 were conducted, respectively, aimed to examine the instantaneous responses of maize leaf WUE （WUEl ） to the changes of photosynthetically available radiation, leaf surface CO2 concentration, air temperature and soil humidity as well as the variation characteristics of the WUE at grain yield level （WUEg） with air temperature and precipitation. The results showed that with the increase of leaf surface CO2 concentration from 350 to 800 Ixmol ~ mo1-1 , the leaf photosynthesis increased, while the stomatal conductance and evaportranspiration （ET） decreased, resulting in the increase of WUE1. The increase of ambient temperature from 26 to 40 ℃ and of soil moisture content from 12% to 26% made the increment of leaf transpiration rate （ Tr） be larger than that of net photosynthesis （ P. ）, causing a signifi cant reduction of WUE1. The analysis of the effects of ET on the grain yield over the 20 years of monitoring ET. When showed that there was a significant quadratic-curve relationship between the the ET was 400-450 mm, the rain yield and WUE were the maximum. WUEg and and the ETin the growth season was the optimal economical evapotranspiration. No obvious relationship was observed between the mean air temperature from sowing to maturing stage, suggesting that the WUE of maize in the study areas was mainly affected by soil moisture condition, but less affected by air temperature.