Increased intrinsic water-use efficiency during a period with persistent decreased tree radial growth in northwestern China: Causes and implications
Increased intrinsic water-use efficiency during a period with persistent decreased tree radial growth in northwestern China: Causes and implications
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DOI：
10.1016/j.foreco.2012.02.027
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发表时间：
2012-07
影响因子：
3.7
通讯作者：
Wenzhi Wang;Xiaohong Liu;W. An;Guobao Xu;Xiaomin Zeng
中科院分区：
文献类型：
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作者：
Wenzhi Wang;Xiaohong Liu;W. An;Guobao Xu;Xiaomin Zeng
为了了解干旱和半干旱地区树木生长如何应对大气二氧化碳浓度（[CO2]）上升和气候变化，确定天然林中的树木如何进行生理调整以适应不断变化的大气环境非常重要。在这里，我们对中国西北东部兴隆山脉的主要天然云杉（Picea crassifolia）树从1800年至2009年建立了年分辨率的树木年轮稳定碳同位素（δ13C）年表。树木年轮δ13C残差中记录的气候响应表明，去年秋季和当前生长季节的水分不足是主要的气候因素。 控制半干旱兴隆山树木年轮碳同位素辨别。结合树木年轮δ13C、大气[CO2](Ca)和年轮宽度数据，计算叶细胞间[CO2](Ci)及其比值(Ci/Ca)、内在水分利用效率(iWUE)和断面积增量(BAI)的变化，发现Ci/C在上个世纪基本保持不变，而Ci和iWUE则有所增加 显著地。到研究期结束时，iWUE 总计增加了约 40%。然而，1998 年之后，树木对大气 [CO2] 升高从主动响应转变为被动响应，导致 iWUE 相对稳定。自 1800 年以来，树木径向生长并不总是与 iWUE 的增长平行；在干旱时期，特别是1923年至1934年以及近十年发生的严重干旱期间，树木生长速度下降。这一应对措施是当前气候变化背景下未来森林管理和保护的关注点。
To understand how tree growth responds to rising atmospheric CO2concentration ([CO2]) and climate change in arid and semi-arid regions, it is important to determine how trees in natural forests adjust physiologically to the changing atmospheric environment. Here, we developed an annual-resolution tree-ring stable carbon isotope (δ13C) chronology from the dominant natural spruce (Picea crassifolia) trees in the Xinglong Mountains, in the eastern part of northwestern China, from 1800 to 2009. The climate response recorded in the tree-ring δ13C residuals indicated that insufficient moisture during the previous autumn and the current growing season was the dominant climatic factor that controlled tree-ring carbon isotope discrimination in the semi-arid Xinglong Mountains. By combining the tree-ring δ13C, the atmospheric [CO2] (Ca), and ring width data, and by calculating the variations in leaf intercellular [CO2] (Ci), their ratio (Ci/Ca), intrinsic water-use efficiency (iWUE), and basal area increment (BAI), we found that the Ci/Caremained mostly constant during the last century whereas Ciand iWUE increased significantly. The increase in iWUE totaled about 40% by the end of the study period. However, after 1998, the trees switched from an active to a passive response to elevated atmospheric [CO2], leading to relatively stable iWUE. Since 1800, tree radial growth did not always parallel the increase in iWUE; the tree growth rate declined during drought periods, and especially during the severe droughts that occurred from 1923 to 1934 and recent decade. This response is a concern for future forest management and conservation under the current climate change scenario.