An inventory of global N2O emissions from the soils of natural terrestrial ecosystems

We develop an inventory of global N2O emissions from natural ecosystem soils using an artificial neural network approach and field observational data of N2O fluxes. We estimate that the global soil N2O source strength from natural ecosystems is 3.37 Tg (1 Tg = 10(12) g) N per year with an uncertainty ranging from 1.96 to 4.56 Tg N per year in 2000. While our global estimate is lower than other existing estimates, the spatial patterns of our simulated N2O emissions agree with other existing studies. There was a large spatial and seasonal variability in the soil N2O emissions due to the variation in soil type, vegetation and climate conditions. Consistent with other studies, we confirm that warm and moist tropical soils are the major source of atmospheric N2O. As a result of the low temperatures, the high latitude ecosystems have significantly low emission rates and contribute little (less than 0.10 Tg N per year) to the global N2O source. The simulated annual global N2O emissions are found to be most sensitive to variation in precipitation. This study uses the most current available data for N2O fluxes and their associated environmental variables to quantify the global N2O emissions, and provides an independent global inventory of this important trace gas, which will facilitate future studies of atmospheric chemistry and climate feedbacks at the global scale. (C) 2011 Elsevier Ltd. All rights reserved.