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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 l)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 g)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(350~800μmol·mol-1),玉米的光合速率升高,气孔导度和蒸腾速率降低,WUE l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 l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400~450 mm时,该区玉米产量和WUE g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 g无明显关系。可见,该地区的WUE g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 of carbon cycle and is also an effective feature to evaluate the response of terrestrial vegetation to climate change. Based on the water control experiments (Jinzhou 2008-2009) and field trials (1990-2010, Chaoyang), the effects of water use efficiency (WUE l) at maize leaf level on photosynthetically active radiation, leaf surface CO2 Instantaneous response of temperature and soil moisture, as well as the change of WUE g with temperature and precipitation. The results showed that with the increase of CO2 concentration on the leaf surface (350 ~ 800μmol · mol-1), the photosynthetic rate of maize increased while the stomatal conductance and transpiration rate decreased and the WUE l increased. The increase of temperature and volume of soil water content, the increase of leaf transpiration rate was greater than that of photosynthesis, resulting in a significant decrease of WUE l. The water use efficiency at the yield level showed a significant quadratic relationship with ET. When the ET was 400-450 mm, the yield and WUE g of maize reached the maximum, and the ET in the growing season was the optimal economic evapotranspiration. The average temperature during sowing to maturity was not significantly related to WUE g. It can be seen that the WUE g in this area is mainly affected by the moisture, and the temperature can not play a leading role.