Wetland CH4 emissions have been demonstrated to be more sensitive than wetland CO2 emissions to increasing temperatures, which may result in a greater relative contribution of CH4 to total GHG emissions under climate warming. However, it is not clear whether this greater sensitivity occurs globally across diverse hydrologic regimes. Here, we evaluate the temperature dependence of CO2 and CH4 emissions on water table depth using a global database and show similarities in the temperature dependence of CO2 and CH4 emissions. A lower water table is associated with a decrease in the temperature dependence of CH4 emissions and a higher water table has the opposite effect. Water table depth does not affect the temperature dependence of CO2 emissions. Our findings suggest the stimulatory effect of increasing temperature on wetland CH4 emissions may not always be stronger than that on CO2 emissions and depends on the wetland water table.
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The original data for this study will be publicly available at: https://doi.org/10.5281/zenodo.5113602.
The code used in this study is available from the corresponding author on reasonable request.
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We greatly appreciate the authors of the published studies who supported our data sources. We also thank J. Zou, Y. Zhang, M. Wang and other students for their contributions to the database. The National Science Foundation of China provided support for M.N. and H.C. (grant no. 91951112), B.L., M.N. and X.X. (grant no. 41630528) and C.F. and X.X. (grant no. 32030067).
The authors declare no competing interests.
Peer review information Nature Climate Change thanks Sophie Comer-Warner and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Some of the sites are very close to one another, and the corresponding symbols thus overlap to some extent.
Extended Data Fig. 2 The relationship between wetland CO2 (a, c) and CH4 (b, d) emission rates and temperature across 204 sites.
Regression lines represent the fitted efflux–temperature exponential (a, b) and linear (c, d) relationships.
Extended Data Fig. 3 Correlations of average site temperatures with average CO2 and CH4 emissions in globally distributed ecosystems.
The average site temperature is positively correlated with the average CO2 (a) and CH4 (b) emissions, ln\(\bar R\)(T), across 204 sites.
Extended Data Fig. 4 Influence of water table depth (WTD) on the temperature dependence of wetland CH4 and CO2 emissions.
Different letters denote significant differences (P < 0.01). The sample sizes by greenhouse gas type and water table depth interval are as follows: CO2, < −30 = 332; CO2, −30 to −5 = 675; CO2, > −5 = 592; CH4, < −30 = 331; CH4, −30 to −5 = 676; CH4, > −5 = 589. The data are represented as the mean and s.e. (the s.e. values among different water table depth intervals were obtained from the mixed-effects models).
Extended Data Fig. 5 Correlation of water table depth (WTD) with the temperature dependence of CO2 and CH4 emissions for wetland sites with relatively static water tables.
The apparent activation energy was used to reflect the temperature dependence of CO2 and CH4 emissions (more details in the Method).
The solid line represents a Gaussian distribution fitted to the frequency data for WTD. The distribution of site-level mean WTD values yields an average of −18 cm (represented by the dashed line).
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Chen, H., Xu, X., Fang, C. et al. Differences in the temperature dependence of wetland CO2 and CH4 emissions vary with water table depth. Nat. Clim. Chang. 11, 766–771 (2021). https://doi.org/10.1038/s41558-021-01108-4