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Seasonal variation of microbial biomass carbon and dissolved organic carbon in farmland soil and influencing factors

Lei Zhang

Field experiment, determining in-situ and laboratory simulated experiment were conducted to study the seasonal dynamics of soil respiration flux, soil microbial carbon (SMBC), and dissolved organic carbon (DOC) in agricultural soil. The impact factors such as temperature, precipitation, and biomass, were also analyzed. The results showed that soil respiration rate increased rapidly after May and reached the maximum in July to September. There was a significantly positive correlation between respiration rate and soil temperature (p<0.01). The seasonal variation of SMBC had greater coefficient variance, 27.1% and 18.7% for 2004 and 2005, respectively (p<0.001). SMBC content was lower in May, subsequently increased rapidly and SMBC content was 774-842 mg/kg in June to September. DOC content was highest in May, subsequently decreased, and declined to the lowest in July. FromAugust to September, the DOC content increased rapidly to the highest value (177. 2 mg/kg) in September, and declined subsequently. Correlation analysis showed that there were significantly negative correlation between DOC and SMBC, 5 cmsoil temperature and soil respiration. However, it correlated positively with biomass. There was significant negative correlation between SMBC content and 5 cm soil temperature