Estimating N2O emissions from soils under natural vegetation in China

BackgroundNatural and managed soils have been identified as the largest sources of atmospheric nitrous oxide (N2O). However, the quantification of N2O emissions from soils under natural vegetation in China and their possible responses to changing climate and atmospheric nitrogen deposition remains uncertain. In particular, information regarding N2O emissions from Chinese shrublands is lacking.MethodThis study used 28 sets of N2O field measurements in China to validate a process-based dynamic nitrogen cycle model (DyN-LPJ), which was then used to investigate the N2O fluxes from soils under natural vegetation in China from 1970 to 2009.ResultsN(2)O emissions from Chinese forests, grasslands, and shrublands in the 2000s were estimated to be 0.100.06 Tg N yr.(-1), 0.09 +/- 0.09, Tg N yr.(-1) and 0.14 +/- 0.07 Tg N yr.(-1), respectively. Monthly N2O fluxes were linearly correlated with precipitation, and exponentially (Q(10)=3) with air temperature. The total N2O fluxes from natural terrestrial ecosystems in China increased from 0.28 +/- 0.03 Tg N yr.(-1) in the 1970s to 0.46 +/- 0.03 Tg N yr.(-1) in the 2000s. Warming and atmospheric nitrogen deposition accounted for 37% (or 0.07 +/- 0.03 Tg N) and 63% (0.11 +/- 0.01 Tg N) of this increase respectively.Conclusions Our results indicate that when compared to grassland ecosystems, N2O emissions from forest and shrubland ecosystems contain larger uncertainties due to either their uncertain areal extent or their emission rates. Long-term and continuous field measurements should be conducted to obtain more representative data in order to better constrain shrubland N2O emissions.