Lu Wei Wei, Yu Xin Xiao, Jia Guo Dong, Li Han Zhi, Liu Zi Qiang
College of Water and Soil Conservation, Beijing Forestry University/Key Laboratory of Soil and Water Conservation and Desertification Combating, Ministry of Education, Beijing 100083, China.
Ying Yong Sheng Tai Xue Bao. 2017 Jul 18;28(7):2128-2134. doi: 10.13287/j.1001-9332.201707.013.
Water use efficiency (WUE) is different among species and regions. Few literatures have been reviewed related to long-term WUE of Platycladus orientalis in mountainous areas of Beijing, China. Tree-ring δC of P. orientalis was used to determine the long-term variation of annual intrinsic water use efficiency (WUE) and its response to environmental change. Combining with quantification of tree-ring width, the relationship between net carbon sequestration and WUE of P. orientalis was eventually explored. The results showed that mean annual temperature increased with the increase of time from 1918 to 2013, whereas annual precipitation fiercely fluctuated. Tree-ring δC decreased and WUE increased over time. WUE was positively related and more sensitive to air temperature increasing than temperature decreasing. Correlation between WUE and fluctuated annualprecipitation was ambiguous, which indicated the precipitation was not the main factor affecting WUE. The de-trend tree-ring width of P. orientalis increased initially and then decreased, especially in recent 20 years. According to the correlation between WUE and environmental factors, temperature resulted in stomatal conductance (g) decreasing, which caused a reduction in evapotranspiration and an increase in respiratory loss, leading to the increase of WUE and a down trend in net carbon sequestration and tree growth.
水分利用效率（WUE）在不同物种和地区之间存在差异。关于中国北京山区侧柏长期水分利用效率的相关文献较少。利用侧柏的树轮δC来确定年内在水分利用效率（WUE）的长期变化及其对环境变化的响应。结合树轮宽度的量化，最终探讨了侧柏净碳固存与水分利用效率之间的关系。结果表明，1918年至2013年期间，年平均气温随时间增加而升高，而年降水量波动剧烈。树轮δC随时间下降，水分利用效率上升。水分利用效率呈正相关，且对气温升高比对气温降低更敏感。水分利用效率与波动的年降水量之间的相关性不明确，这表明降水不是影响水分利用效率的主要因素。侧柏去趋势化的树轮宽度最初增加，然后下降，尤其是在最近20年。根据水分利用效率与环境因素之间的相关性，温度导致气孔导度（g）降低，这导致蒸散减少和呼吸损失增加，从而导致水分利用效率增加以及净碳固存和树木生长呈下降趋势。
