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中国科学院千烟洲红壤丘陵试验站地处亚热带季风气候区,其植被类型主要为人工针叶林．研究采用涡度相关技术观测结果计算了2003年和2004年的植被水分利用效率(WUE)季节变化．适逢2003年极端干旱,降雨量远远低于多年(1985～2002)平均水平,其中7月份降水量仅是多年平均值的2．8％,气温却高于平均水平3℃,而2004年的气象条件与多年平均水平接近。这为研究WUE的环境控制作用提供了天然的条件．经研究发现千烟洲试验站的降水多集中于春季。而夏季则存在明显的季节性干旱现象,从而导致了该区域特殊的植被WUE季节变化模式．WUE的季节变化与冠层蒸发散(Fw)和总初级生产力(GPP)的季节动态大致相反,在夏季达到最小值,而在冬季则达到最大值．在冬季GPP和凡随气温和大气饱和水汽压差(VPD)的增加而增加,且GPP和凡的增加速率比较接近;而在干旱的夏季,GPP和凡却随气温和VPD的增加而降低。并且GPP随气温和VPD变化而降低的速率要远远大于凡,这破坏了GPP和凡的平衡关系,并进一步改变了WUE的保守性,最终导致夏季WUE的降低．夏季干旱期土壤水分的亏缺和高强度的辐射也都是造成该生态系统WUE降低的原因．在冬季该生态系统植被的光合和蒸腾作用主要受控于环境因素,而受植被本身气孔行为的控制作用相对较弱．在夏季植被的Fw主要受植被本身气孔行为的限制作用,而植被的GPP则受环境因素和植被本身气孔行为的双重限制．
Chinese Academy of Sciences Qianyanzhou red soil hills Experimental Station is located in the subtropical monsoon climate zone, the vegetation types are mainly artificial coniferous forest. In this study, the seasonal variations of WUE in 2003 and 2004 were calculated using the results of eddy covariance techniques. The extreme drought in 2003 coincides with the rainfall below the average of many years (1985-2002), of which the precipitation in July was only 2.8% of the average for many years and the temperature was above the average of 3 ℃ in 2004 Meteorological conditions and the multi-year average close to. This provides a natural condition for studying the role of WUE in environmental control. The study found that precipitation at Qianyanzhou experimental station is mostly concentrated in the spring. In summer, however, there was a clear seasonal drought, which led to the seasonal WUE pattern of vegetation in this region. The seasonal variation of WUE is roughly the opposite of the seasonal dynamics of canopy evapotranspiration (Fw) and total primary productivity (GPP), reaching the minimum in summer and reaching the maximum in winter. In the winter, the GPP increased with the increase of VPD, and the increase rate of GPP was similar to that of GPP. In the arid summer, the GPP and GPP decreased with the increase of air temperature and VPD. And the rate of GPP decrease with temperature and VPD is much faster than that of GPP, which undermines the balance between GPP and vancomycin and further changes the conservativeness of WUE, leading to the decrease of summer WUE. The shortage of soil moisture and the high intensity of radiation during the summer drought are also the reasons for the decrease of WUE in this ecosystem. In winter, the photosynthesis and transpiration of the ecosystem vegetation are mainly controlled by environmental factors, while the control by stomata behavior of the vegetation itself is relatively weak. The vegetation Fw in summer is mainly limited by the stomatal behavior of the vegetation itself, while the vegetation GPP is limited by the environmental factors and stomatal behavior of the vegetation itself.