Variation of Soil Respiration from Different Land Uses in Subtropical Agricultural Soils, Central China

In order to better understand the limiting factors and substrate affecting soil CO₂ flux, we measured total organic carbon, microbial biomass carbon, microbial biomass nitrogen, dissolved organic carbon, and dissolved organic nitrogen from seven sites of four land use types of subtropical agriculture soils. Objectives were to (1) evaluate the relationship of MBC, MBN, DOC, and DON with soil CO₂ flux, in addition to the relationship obtained by usually used environmental variables (soil temperature and moisture), and (2) investigate the seasonal and annual CO₂ fluxes from different land uses. Annual CO₂ fluxes ranged from 5.4 to 9.5 Mg CO₂ ha^-1 yr^-1. Vegetable field had the highest CO₂ emission, while pine forest had significantly lower CO₂ emission than cultivated land uses. Different quantities of MBC, MBN and DOC significantly regulated the CO₂ emission among different land uses. Our results indicate that microbial biomass and dissolve organic substances must be considered in a warming future as these can explain a major part of temporal variation of soil CO₂ fluxes.