| 英文摘要： |
Elevation in atmospheric carbon dioxide concentration (eCO(2)) affects vegetation water use, with consequent impacts on terrestrial runoff (Q). However, the sign and magnitude of the eCO(2) effect on Q are still contentious. This is partly due to eCO(2)-induced changes in vegetation water use having opposing responses at the leaf scale (i.e., watersaving effect caused by partially stomatal closure) and the canopy scale (i.e., water-consuming induced by foliage cover increase), leading to highly debated conclusions among existing studies. In addition, none of the existing studies explicitly account for eCO(2)-induced changes to plant rooting depth that is overwhelmingly found in experimental observations. Here we develop an analytical ecohydrological framework that includes the effects of eCO(2) on plant leaf, canopy density, and rooting characteristics to attribute changes in Q and to detect the eCO(2) signal on Q via vegetation feedbacks over 1982-2010. Globally, we detect a very small decrease of Q induced by eCO(2) during 1982-2010 (-1.7 %). Locally, we find a small positive trend (p < 0.01) in the Q-eCO(2) response along a resource availability (beta) gradient. Specifically, the Q-eCO(2) response is found to be negative (i.e., eCO(2) reduces Q) in low-beta regions (typically dry and/or cold) and gradually changes to a small positive response (i.e., eCO(2) increases Q) in high-beta areas (typically warm and humid). Our findings suggest a minor role of eCO(2) on changes in global Q over 1982-2010, yet we highlight that a negative Q-eCO(2) response in semiarid and arid regions may further reduce the limited water resource there. |
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