Characterization of farmland soil respiration and modeling analysis of contribution of root respiration

Daily and seasonal variation of soil CO2 emission fluxes were measured using close chamber method in typical crop fields in Huang-huai-hai Plain, the impacts of soil temperature and moisture on soil CO2 emission flux were analyzed respectively, and the contribution of root respiration by using the DNDC ( DeNitrification – DeComposition ) model was also discussed. The results indicate that seasonal variations of CO2 emissions from cotton, fallow and winter wheat–summer corn rotation field are all remarkable. The emission of CO2 is relatively higher in summer and lower in other seasons, and it is consistent with the variation of air temperature. The maximum values of CO2 emission fluxes are 2324 mg?m-2?h-1 in winter wheat–summer corn rotation fields, 1111.9 mg?m-2?h-1 in cotton fields and 436.07 mg?m-2?h-1 in fallow fields. Analyses show that the CO2 emission is exponentially correlated with the soil temperature at 5 cm, but there is no significant correlation between soil respiration and soil moisture. The fields under the same crop with higher soil organic matter content can emit more CO2. According to the DNDC simulated results, the contribution of maize root respiration to soil respiration at the whole growth stage varied from 91% to 93%, while the contributions of cotton and wheat root respiration were 70% and 80%, respectively. Soil N-application did not only influence the soil microbial respiration but also the root respiration.