Contrasting Responses of Woody and Grassland Ecosystems to Increased CO2 as Water Supply Varies

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Nature Ecology and Evolution


Experiments show that elevated atmospheric CO2 (eCO(2)) often enhances plant photosynthesis and productivity, yet this effect varies substantially and may be climate sensitive. Understanding if, where and how water supply regulates CO2 enhancement is critical for projecting terrestrial responses to increasing atmospheric CO2 and climate change. Here, using data from 14 long-term ecosystem-scale CO2 experiments, we show that the eCO(2) enhancement of annual aboveground net primary productivity is sensitive to annual precipitation and that this sensitivity differs between woody and grassland ecosystems. During wetter years, CO2 enhancement increases in woody ecosystems but declines in grass-dominated systems. Consistent with this difference, woody ecosystems can increase leaf area index in wetter years more effectively under eCO(2) than can grassland ecosystems. Overall, and across different precipitation regimes, woody systems had markedly stronger CO2 enhancement (24%) than grasslands (13%). We developed an empirical relationship to quantify aboveground net primary productivity enhancement on the basis of changes in leaf area index, providing a new approach for evaluating eCO(2) impacts on the productivity of terrestrial ecosystems.

The extent to which excess carbon dioxide causes a 'fertilization effect' varies across biomes and as a function of water supply, finds a study examining data from 14 CO2 experimental sites.


Y.P. acknowledges the support of Bullard Fellowship at Harvard University. O.L.P acknowledges support from the Royal Society and the European Research Council ERC (AdG grant 291585). R.S.N. and R.J.N acknowledge support from the US Department of Energy, Office of Science, Biological and Environmental Research Office. R.O. acknowledges support from Jane and Aatos Erkko 375th Anniversary Fund through the University of Helsinki. The contribution of P.B.R. was supported by the US NSF Biological Integration Institutes grant DBI-2021898.