The effect of land-use change on soil CH4 and N2O fluxes: a global meta-analysis: effect of land-use change on soil CH4 and N2O fluxes

Abstract

Land-use change is a prominent feature of the Anthropocene. Transitions between natural and human-managed ecosystems affect biogeochemical cycles in many ways, but soil processes are amongst the least understood. We used a global meta-analysis (62 studies, 1670 paired comparisons) to examine effects of land conversion on soil-atmosphere fluxes of methane (CH4) and nitrous oxide (N2O) from upland soils, and explored what soil and environmental factors influenced these effects. Conversion from a natural ecosystem to any anthropogenic land use increased soil CH4 and N2O fluxes by 234 kg CO2-equivalents ha-1 y-1, on average. Reverting to natural ecosystems did not fully reverse those effects, even after 80 years (except for CH4 fluxes by –12 µg m-2 h-1). In general, neither the type of natural ecosystem that was converted, nor the type of anthropogenic land use it was converted to, affected the magnitude of increase in soil emissions. The exception to this is when natural ecosystems were converted to pastures or croplands (emissions increased by +23 and +5 µg CH4 m-2 h-1). A complex suite of variables interacted to influencing CH4 and N2O fluxes, but availability of soil inorganic nitrogen (i.e. extractable ammonium and nitrate), texture, pH, and microclimate were the strongest mediators of effects of land-use change. Land-use changes in wetter ecosystems resulted in greater CH4 fluxes, and effects of land-use change on soil nitrate, total organic C, and pH emerged as the greatest drivers of changes in CH4 fluxes. Effects of land-use change on N2O fluxes decreased in wetter ecosystems, and the land-use change effect was regulated primarily via changes in soil inorganic N and water content. Understanding the complicated effects of land-use changes on soil-atmosphere CH4 and N2O fluxes, and the mechanisms underpinning such emissions, could inform land management actions to mitigate increased greenhouse gas emissions after changing land uses.

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ORCID for Marc Dumont: orcid.org/0000-0002-7347-8668

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