Influence of exogenous cadmium on respiratory intensity and microbial community of dark brown soil

Through laboratory simulation, the influence of exogenous cadmium on respiratory intensity and microbial community of dark brown soil were studied by adding different concentration of heavy metal cadmium. The results indicated that:the soil respiration had a significant weakening trend in the same culture days with exogenous cadmium content increasing; the soil respiration intensity decreased obviously with the increase of culture time, especially after 14 days when the soil exogenous cadmium content was in the range of 0.5~3.0 mg/kg, While the soil respiration had not obvious variation with the increase of culture time when the exogenous cadmium content was in the range of 5.0~10.0 mg/kg. The soil microbial community decreased significantly and were much lower than that of the control treatment in the same culture days with the increase of soil exogenous cadmium content, the soil microbial community declined significantly with culture time increasing for all exogenous cadmium treatment. Comparing with the control, the number of soil microbial community were only 46.43%, 32.26%, 28.74%, 27.39% and 24.62% of that of the controls in the culture days of 7, 14, 21, 28 and 42, respectively at 10 mg/kg of exogenous cadmium content. It indicated that higher concentration of cadmium in dark brown soil had a significant inhibitory effect on soil microbial growth.