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Contrasting responses of woody and grassland ecosystems to increased CO2 as water supply varies

Nature Ecology & Evolution volume 6, pages 315–323 (2022)Cite this article

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Abstract

Experiments show that elevated atmospheric CO2 (eCO2) 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 eCO2 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 eCO2 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 eCO2 impacts on the productivity of terrestrial ecosystems.

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Fig. 1: Relationships between eCO2 enhancement of ANPP and iPPT.
Fig. 2: Mean responses of EAPPAV to MAP across multiple ecosystems.
Fig. 3: The relationship between EAPP and ELAI.

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Data availability

Data collated and used for analyses, figures and tables of this study are available for access (https://doi.org/10.2737/RDS-2021-0093). The processed data underlying Figs. 1–3 and Extended Data Figs. 1–4 are available in the Source Data files. Full description of the original datasets is provided in Supplementary Tables 1–4. Source data are provided with this paper.

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Acknowledgements

The authors acknowledge the FACE experiments, scientists’ investigations and publications that provide data for this study. 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. The lead author is grateful to J. Morgan and J. Nösberger for valuable comments and insights contributed to earlier drafts of the manuscript. This study was originally inspired by a synthesis study published in 2004 by Nowak et al.16.

Author information

Authors and Affiliations

  1. USDA Forest Service, Northern Research Station, Durham, NH, USA

    Yude Pan & David Y. Hollinger

  2. The Woods Institute for the Environment and at the Precourt Institute for Energy, Stanford University, Stanford, CA, USA

    Robert B. Jackson

  3. University of Leeds, School of Geography, Leeds, UK

    Oliver L. Phillips

  4. Department of Natural Resources and Environmental Science, University of Nevada, Reno, NV, USA

    Robert S. Nowak

  5. Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN, USA

    Richard J. Norby

  6. Nicholas School of the Environment and Pratt School of Engineering, Duke University, Durham, NC, USA

    Ram Oren

  7. Department of Forest Science, University of Helsinki, Helsinki, Finland

    Ram Oren

  8. Department of Forest Resources, University of Minnesota, St Paul, MN, USA

    Peter B. Reich

  9. Institute for Global Change Biology and School for the Environment and Sustainability, University of Michigan, Ann Arbor, MI, USA

    Peter B. Reich

  10. Western Sydney University, Penrith, New South Wales, Australia

    Peter B. Reich

  11. ETH Zurich, Institute of Agricultural Science, Zurich, Switzerland

    Andreas Lüscher

  12. Agroscope, Forage Production and Grassland Systems, Zurich, Switzerland

    Andreas Lüscher

  13. Biological, Geological and Environmental Sciences, Cleveland State University, Cleveland, OH, USA

    Kevin E. Mueller

  14. Department of Agronomy, Throckmorton Plant Sciences Center, Kansas State University, Manhattan, KS, USA

    Clenton Owensby

  15. Woodwell Climate Research Center, Falmouth, MA, USA

    Richard Birdsey

  16. Department of Plant and Soil Sciences, University of Delaware, Newark, DE, USA

    John Hom

  17. Center for Ecosystem Science and Society, Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ, USA

    Yiqi Luo

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  1. Yude Pan
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Contributions

Y.P. assembled and analysed the data and wrote the manuscript; R.B.J., D.Y.H., O.L.P. and R.S.N. provided concepts and substantial editing of the manuscript; R.J.N., R.O., P.B.R., A.L., K.E.M. and C.O. were the major investigators for the eCO2 experiments, providing the data, insightful comments and editing; R.B., J.H. and Y.L. edited and provided comments on the manuscript.

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Correspondence to Yude Pan.

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Extended data

Extended Data Fig. 1 Responses of C3 and C4 grasses to eCO2.

(a) EAPP responses of C3 and C4 grasses to annual precipitation (iPPT); (b) the Z-score analysis for C3 grasses, and a linear regression; and (c) the Z-scores analysis for C4 grasses; there is not an obvious relationship between EAPP and iPPT.

Source data

Extended Data Fig. 2 Sensitivity of ANPP enhancement to annual precipitation (slopes of the linear functions (Supplementary Table 5).

(a) Across woody and across (b) grassland ecosystems. A positive slope means EAPP increasing with increasing iPPT at a given site; a negative slope EAPP decreasing with increasing iPPT. Error bars are the standard errors (SEs) for slopes and MAP, respectively. The symbol ‘*’ is used for sites with a linear regression at *p = 0.1. Arrows show MAP levels when slopes approach zero in woody and grassland ecosystems.

Source data

Extended Data Fig. 3 Mean ANPP enhancements affected by eCO2 levels.

(a) Mean values of EAPP for all sampling years and all sites (EAPPAVE) of woody (solid symbols) and grassland (open symbols) ecosystems; EAPP responses to iPPT are not significantly different between woody and grassland ecosystems (t-test: p = 0.055); (b) EAPPAVE of woody and grassland ecosystems after adjusting higher eCO2 concentrations used in experiments to 550 ppm based on the Farquhar model (Extended Data Fig. 4); EAPP responses to iPPT are significantly different between woody and grassland ecosystems (t-test: p = 0.011). Error bars represent standard deviations (SDs).

Source data

Extended Data Fig. 4 Effects of CO2 levels on canopy photosynthetic rates illustrated by the Farquhar model.

Y-axis shows the impact (scalar) of intercellular CO2 levels on canopy photosynthesis rates, given an assumption of optimal intercellular CO2 level being close to the atmospheric level. Relatively higher CO2 concentrations were used in 6 enrichment experiments (600–720 ppm) compared to the CO2 concentration (~550 ppm) used in forest ecosystems.

Source data

Supplementary information

Supplementary Information

Supplementary Discussion, Tables 1–9 and Figs. 1–3.

Reporting Summary

Source data

Source Data Fig. 1

Experimental years, annual precipitation, aboveground NPP CO2 enhancement ratios (EAPP) derived from 14 CO2 experiments of woody and grassland ecosystems, Z scores of EAPP and annual precipitations of experimental data.

Source Data Fig. 2

Mean annual precipitation and mean ecosystem EAPP of experimental sites.

Source Data Fig. 3

The enhancement ratios of leaf area index (ELAI) and enhancement ratios of aboveground NPP (EAPP) from experimental sites.

Source Data Extended Data Fig. 1

Annual precipitation and CO2 enhancement ratios (EAPP) of C3 and C4 plants; Z scores of annual precipitation, Z scores of EAPP of C3 and C4 plants, respectively.

Source Data Extended Data Fig. 2

Mean site annual precipitation (MAP) and slopes of linear functions of CO2 enhancement ratios.

Source Data Extended Data Fig. 3

Annual precipitation, aboveground NPP enhancement ratios (EAPP) under different CO2 levels used in the experimental sites; annual precipitation and EAPP after adjusting CO2 levels to 550 ppm.

Source Data Extended Data Fig. 4

Results of Farquhar models and values for adjusting CO2 levels.

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Pan, Y., Jackson, R.B., Hollinger, D.Y. et al. Contrasting responses of woody and grassland ecosystems to increased CO2 as water supply varies. Nat Ecol Evol 6, 315–323 (2022). https://doi.org/10.1038/s41559-021-01642-6

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