Grassland gross carbon dioxide uptake based on an improved model tree ensemble approach considering human interventions: global estimation and covariation with climate

作者：Wei Liang, Yihe Lü, Weibin Zhang, Shuai Li, Zhao Jin, Philippe Ciais, Bojie Fu, Shuai Wang, Jianwu Yan, Junyi Li, Hui-Min Su · 发表于：Global Change Biology · 年份：2016 · DOI：10.1111/gcb.13592 · 被引用次数：38 · 研究领域：Atmospheric and Environmental Gas Dynamics、Science and Climate Studies、Plant Water Relations and Carbon Dynamics

Abstract Grassland ecosystems act as a crucial role in the global carbon cycle and provide vital ecosystem services for many species. However, these low‐productivity and water‐limited ecosystems are sensitive and vulnerable to climate perturbations and human intervention, the latter of which is often not considered due to lack of spatial information regarding the grassland management. Here by the application of a model tree ensemble ( MTE ‐ GRASS ) trained on local eddy covariance data and using as predictors gridded climate and management intensity field (grazing and cutting), we first provide an estimate of global grassland gross primary production ( GPP ). GPP from our study compares well (modeling efficiency NSE = 0.85 spatial; NSE between 0.69 and 0.94 interannual) with that from flux measurement. Global grassland GPP was on average 11 ± 0.31 Pg C yr −1 and exhibited significantly increasing trend at both annual and seasonal scales, with an annual increase of 0.023 Pg C (0.2%) from 1982 to 2011. Meanwhile, we found that at both annual and seasonal scale, the trend (except for northern summer) and interannual variability of the GPP are primarily driven by arid/semiarid ecosystems, the latter of which is due to the larger variation in precipitation. Grasslands in arid/semiarid regions have a stronger (33 g C m −2 yr −1 /100 mm) and faster (0‐ to 1‐month time lag) response to precipitation than those in other regions. Although globally spatial gradients (71%) and interannua...