Low and contrasting impacts of vegetation CO 2 fertilization on global terrestrial runoff over 1982–2010: accounting for aboveground and belowground vegetation–CO 2 effects

Yang, Yuting; McVicar, Tim R.; Yang, Dawen; Zhang, Yongqiang; Piao, Shilong; Peng, Shushi; Beck, Hylke E.

Elevation in atmospheric carbon dioxide concentration (eCOinline-formula2) affects vegetation water use, with consequent impacts on terrestrial runoff (inline-formulaQ). However, the sign and magnitude of the eCOinline-formula2 effect on inline-formulaQ are still contentious. This is partly due to eCOinline-formula2-induced changes in vegetation water use having opposing responses at the leaf scale (i.e., water-saving 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 eCOinline-formula2-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 eCOinline-formula2 on plant leaf, canopy density, and rooting characteristics to attribute changes in inline-formulaQ and to detect the eCOinline-formula2 signal on inline-formulaQ via vegetation feedbacks over 1982–2010. Globally, we detect a very small decrease of inline-formulaQ induced by eCOinline-formula2 during 1982–2010 (inline-formula−1.7 %). Locally, we find a small positive trend (inline-formulapinline-formula< 0.01) in the inline-formulaQ–eCOinline-formula2 response along a resource availability (inline-formulaβ) gradient. Specifically, the inline-formulaQ–eCOinline-formula2 response is found to be negative (i.e., eCOinline-formula2 reduces inline-formulaQ) in low-inline-formulaβ regions (typically dry and/or cold) and gradually changes to a small positive response (i.e., eCOinline-formula2 increases inline-formulaQ) in high-inline-formulaβ areas (typically warm and humid). Our findings suggest a minor role of eCOinline-formula2 on changes in global inline-formulaQ over 1982–2010, yet we highlight that a negative inline-formulaQ–eCOinline-formula2 response in semiarid and arid regions may further reduce the limited water resource there.



Yang, Yuting / McVicar, Tim R. / Yang, Dawen / et al: Low and contrasting impacts of vegetation CO2 fertilization on global terrestrial runoff over 1982–2010: accounting for aboveground and belowground vegetation–CO2 effects. 2021. Copernicus Publications.


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