GLOBAL PATTERNS OF CARBON-DIOXIDE EMISSIONS FROM SOILS

We use semi-mechanistic, empirically based statistical models to predi ct the spatial and temporal patterns of global carbon dioxide emission s from terrestrial soils. Emissions include the respiration of both so il organisms and plant roots. At the global scale, rates of soil CO2 e fflux 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 predi cted CO2 emissions by only about 1%. The estimated annual flux of CO2 from soils to the atmosphere is estimated to be 76.5 Pg C yr(-1) 1-9 P g greater than previous global estimates, and 30-60 greater than terre strial net primary productivity. Historic land cover changes are estim ated to have reduced current annual soil CO2 emissions by 0.2-2.0 Pg C yr(-1) in comparison with an undisturbed vegetation cover. Soil CO2 f luxes have a pronounced seasonal pattern in most locations, with maxim um emissions coinciding with periods of active plant growth. Our model s suggest that soils produce CO2 throughout the year and thereby contr ibute to the observed wintertime increases in atmospheric CO2 concentr ations. Our derivation of statistically based estimates of soil CO2 em issions at a 0.5 degrees latitude by longitude spatial and monthly tem poral resolution represents the best-resolved estimate to date of glob al CO2 fluxes from soils and should facilitate investigations of net c arbon exchanges between the atmosphere and terrestrial biosphere.