Increased soil emissions of potent greenhouse gases under increased atmospheric CO_2

摘要

Increasing concentrations of atmospheric carbon dioxide (CO_2) can affect biotic and abiotic conditions in soil, such as microbial activity and water content1'2. In turn, these changes might be expected to alter the production and consumption of the important greenhouse gases nitrous oxide (N_2O) and methane (CH_4) (refs 2,3). However, studies on fluxes of N_2O and CH_4 from soil under increased atmospheric CO_2 have not been quantitatively synthesized. Here we show, using meta-analysis, that increased CO_2 (ranging from 463 to 780 parts per million by volume) stimulates both N_2O emissions from upland soils and CH_4 emissions from rice paddies and natural wetlands. Because enhanced greenhouse-gas emissions add to the radiative forcing of terrestrial ecosystems, these emissions are expected to negate at least 16.6 per cent of the climate change mitigation potential previously predicted from an increase in the terrestrial carbon sink under increased atmospheric CO_2 concentrations4. Our results therefore suggest that the capacity of land ecosystems to slow climate warming has been overestimated.