Ecosystem water use efficiency in a young plantation in Northern China and its relationship to drought
Ecosystem water use efficiency in a young plantation in Northern China and its relationship to drought
复制标题
中国北方幼林生态系统水分利用效率及其与干旱的关系
DOI：
10.1016/j.agrformet.2019.05.004
复制
发表时间：
2019-09-15
影响因子：
6.2
通讯作者：
Zhou, Caixian
中科院分区：
文献类型：
--
作者：
Ma, Jingyong;Jia, Xin;Zhou, Caixian
气候模型预测，中国北部的气候变异性很大，干旱会更频繁、更持久。然而，很少有研究研究中国北部易受干旱影响的幼龄人工林水分利用效率(WUE)的季节和年际变化。这里，在几个时间尺度的6年期间(2012-2017)，在北京的一个幼龄人工林中研究了WUE的变化。这项研究是通过检验总生态系统生产量(GEP)和蒸散量(ET)的涡动协方差测量进行的。结果表明，该幼龄人工林的多年平均水分利用效率为1.71+/-0.22g C/kg H2O。干旱使水分利用效率在夏季降低，秋季升高，春季影响不明显。长期干旱通常比短期干旱对年度GEP、ET和WUE的影响更大。严重干旱对生态系统的GEP、ET和WUE有约3年的长期遗留影响。月水分利用效率与生长季归一化植被指数(NDVI)和土壤体积含水率(VWC)呈显著正相关。水分利用效率的季节变化主要受控制GEP的生物物理因素的影响。相反，WUE的年际变化在更大程度上受植被覆盖(即NDVI)的控制，而植被覆盖又对VWC的变化做出响应。这些结果清楚地表明了干旱的时间和持续时间在控制生态系统WUE中的重要性。总体而言，水分利用效率受到影响碳吸收的因素的影响比受水消耗的影响更大。我们的发现表明，未来的干旱，再加上气候变异性的增加，灌溉支持规划和选择合适的树种应该是中国北部植树造林计划的核心。
Climate models predict large climatic variability and more frequent, prolonged droughts in northern China. Still, few studies have examined the seasonal and interannual variation in water use efficiency (WUE) in northern China's young plantations predisposed to drought. Here, variation in WUE was examined in a young plantation in Beijing over a 6-year period (2012-2017) at several timescales. The study was conducted by examining eddy-covariance measurements of gross ecosystem production (GEP) and evapotranspiration (ET). Results showed that the multi-year mean WUE for this young plantation was 1.71 +/- 0.22 g C per kg H2O. Drought reduced WUE in summer, but increased it in autumn, with no apparent effect in spring. Long-term droughts usually had a greater effect on the annual GEP, ET and WUE than short-term droughts. Intense drought was observed to have a long-term legacy effect on ecosystem GEP, ET and WUE of about 3 years. Monthly WUE had a strong positive linear relationship with normalized difference vegetation index (NDVI) and soil volumetric water content (VWC) during the growing season. Seasonal variation in WUE was mainly regulated by the biophysical factors controlling GEP. In contrast, interannual variation in WUE was controlled to a greater extent by vegetation cover (i.e., NDVI), which in turn responded to variation in VWC. These results clearly show the importance of timing and duration of drought in controlling ecosystem WUE. Collectively, WUE was more strongly affected by factors affecting carbon uptake than water consumption. Our findings suggest that future drought, when coupled with increased climate variability, irrigation-support planning and selection of appropriate tree species should be central to afforestation programs in northern China.