Global patterns of carbon dioxide emissions from soils

TLDR

Emissions include the respiration of both soil organisms and plant roots. The study aims to produce the highest‑resolution statistical estimates of global soil CO₂ emissions to aid investigations of net carbon exchanges between the atmosphere and terrestrial biosphere. The authors employ semi‑mechanistic, empirically based statistical models to predict spatial and temporal patterns of global soil CO₂ emissions. The models show that global soil CO₂ efflux is strongly linked to temperature and precipitation, with an annual flux of 76.5 Pg C yr⁻¹—1–9 Pg higher than prior estimates and 30–60 % above net primary productivity—while wetlands reduce emissions by only ~1 %, historic land‑cover changes have lowered emissions by 0.2–2.0 Pg yr⁻¹, and seasonal dynamics with year‑round production explain wintertime CO₂ increases.

Abstract

We use semi‐mechanistic, empirically based statistical models to predict the spatial and temporal patterns of global carbon dioxide emissions from terrestrial soils. Emissions include the respiration of both soil organisms and plant roots. At the global scale, rates of soil CO 2 efflux correlate significantly with temperature and precipitation; they do not correlate well with soil carbon pools, soil nitrogen pools, or soil C:N. Wetlands cover about 3% of the land area but diminish predicted CO 2 emissions by only about 1%. The estimated annual flux of CO 2 from soils to the atmosphere is estimated to be 76.5 Pg C yr −1 , 1–9 Pg greater than previous global estimates, and 30–60% greater than terrestrial net primary productivity. Historic land cover changes are estimated to have reduced current annual soil CO 2 emissions by 0.2–2.0 Pg C yr −1 in comparison with an undisturbed vegetation cover. Soil CO 2 fluxes have a pronounced seasonal pattern in most locations, with maximum emissions coinciding with periods of active plant growth. Our models suggest that soils produce CO 2 throughout the year and thereby contribute to the observed wintertime increases in atmospheric CO 2 concentrations. Our derivation of statistically based estimates of soil CO 2 emissions at a 0.5° latitude by longitude spatial and monthly temporal resolution represents the best‐resolved estimate to date of global CO 2 fluxes from soils and should facilitate investigations of net carbon exchanges between the atmosphere and terrestrial biosphere.