Precipitation and carbon-water coupling jointly control the interannual variability of global land gross primary production.
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Carbon uptake by terrestrial ecosystems is increasing along with the rising of atmospheric CO2concentration. Embedded in this trend, recent studies suggested that the interannual variability (IAV) of global carbon fluxes may be dominated by semi-arid ecosystems, but the underlying mechanisms of this high variability in these specific regions are not well known. Here we derive an ensemble of gross primary production (GPP) estimates using the average of three data-driven models and eleven process-based models. These models are weighted by their spatial representativeness of the satellite-based solar-induced chlorophyll fluorescence (SIF). We then use this weighted GPP ensemble to investigate the GPP variability for different aridity regimes. We show that semi-arid regions contribute to 57% of the detrended IAV of global GPP. Moreover, in regions with higher GPP variability, GPP fluctuations are mostly controlled by precipitation and strongly coupled with evapotranspiration (ET). This higher GPP IAV in semi-arid regions is co-limited by supply (precipitation)-induced ET variability and GPP-ET coupling strength. Our results demonstrate the importance of semi-arid regions to the global terrestrial carbon cycle and posit that there will be larger GPP and ET variations in the future with changes in precipitation patterns and dryland expansion.
We thank the Numerical Terradynamic Simulation Group at the University of Montana for providing the improved MOD17 GPP and MOD16 ET datasets. We thank the TRENDY-v4 modelers for contributing model outputs. We thank Dr. Kaiyu Guan for discussion on the early version of the manuscript. This study by Y.Z., X.X., X.W., and J.D. is partially supported by a research grant (Project No. 2013-69002) through the USDA National Institute for Food and Agriculture (NIFA)‘s Agriculture and Food Research Initiative (AFRI), Regional Approaches for Adaptation to and Mitigation of Climate Variability and Change, and a research grant (IIA-1301789) from the National Science Foundation EPSCoR. We thank Ms. Sarah Xiao at Yale University for the English editing of the manuscript.
This is the author accepted manuscript. The final version is freely available from Nature Publishing Group via the DOI in this record.
Vol. 6, pp. 39748 -
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