Contributory factors of the secular trends to changes in ecosystem water-use efficiency in China
Contributory factors of the secular trends to changes in ecosystem water-use efficiency in China
复制标题
中国生态系统水分利用效率变化长期趋势的影响因素
DOI：
10.1016/j.jhydrol.2022.128690
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发表时间：
2022-11-21
影响因子：
6.4
通讯作者：
Wang, Kelin
中科院分区：
文献类型：
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作者：
Jiao, Fusheng;Xu, Xiaojuan;Wang, Kelin
生态系统水分利用效率（WUE）是反映生态系统功能的有效指标，广泛用于表征陆地碳与水循环之间的耦合关系。虽然WUE的线性趋势已经得到了很好的报道，但WUE长期趋势的非线性及其对总体变化的相对贡献仍然很少。在这项研究中，我们使用集合经验模式分解（EEMD）提取的长期趋势的WUE和它们的相对贡献（RC）的WUE的变化，在中国，代表生态系统功能的稳定性。我们发现，虽然增加的趋势占主导地位的长期趋势的WUE，近一半的研究领域经历了趋势转变。除落叶林和混交林以趋势变化为主外，大部分土地覆盖类型以增加趋势为主。RC沿海拔梯度沿着呈双峰型，峰值在20 m和5000 m处。同样，RC在东部和南部方面最高，西部和北部方面最低。相比之下，钢筋混凝土表现出一个U形图案的斜率，并在80度是最低的。在单调递增和先降后升的变化趋势中，高RC主要出现在华北平原和黄土高原，表明生态系统的改善和较强的稳定性。同时，中国东北部和西南部的生态系统改善程度较低，这表明生态系统的改善是不可持续的。在递增递减趋势和单调递减趋势下，RC值始终很低，表明生态系统稳定性较低，改善的可能性很大。温度和大气CO2浓度是影响WUE变化的主要气候因子。影响生态系统稳定性的是气候的平均状态，而不是气候的变率。本研究的结果突出了长期趋势对WUE变化的相对贡献，并提供了一个更好的理解生态系统功能的结构和稳定性。
Ecosystem water-use efficiency (WUE) is an effective indicator of ecosystem functioning, which is widely used to characterize the coupling relationship between terrestrial carbon and the water cycle. Although the linear trends in WUE have been well reported, the nonlinearity of the secular trends in WUE and their relative contribution to the overall changes were still poorly investigated. In this study, we used ensemble empirical mode decomposition (EEMD) to extract the secular trends of the WUE and their relative contribution (RC) to the WUE changes in China, which represents the stability of the ecosystem functioning. We found that although increasing trends dominated the secular trends of the WUE, nearly half of the study areas had experienced trend shifts. Except that deciduous forests and mixed forests were dominated by trend shifts, most of the land cover types were dominated by increasing trends. The RC exhibited a bimodal pattern along the elevation gradient, with peaks at 20 m and 5000 m. Similarly, the RC peaked at the east and south aspects, and was the lowest for the west and north as-pects. In comparison, the RC exhibited a U-shaped pattern with the slope, and was the lowest at 80 degrees. For the monotonically increasing trends and decreasing-to-increasing trends, the high RC mainly occurred on the North China Plain and Loess Plateau, indicating ecosystem improvement and strong stability. Meanwhile, it was low in northeastern China and southwestern China, indicating unsustainable ecosystem improvement. The RC was al-ways very low for increasing-to-decreasing trends and monotonically decreasing trends, indicating low ecosystem stability with a high possibility for improvement. Temperature and the atmospheric carbon dioxide (CO2) concentration were the two main climatic factors driving the WUE changes. The climatic mean state rather than the climatic variability affected the ecosystem stability. The results of this study highlight the relative contribution of the secular trends to WUE changes and provide a better understanding of the structure and the stability of ecosystem functioning.