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| Relationship Among Soil Organic Carbon, Enzyme Activities and Microbial Numbers in Typical Karst Ecosystem: A Case Study of Yaji Karst Experimental Site, China |
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| KeyWord:karst depression; soil organic carbon; enzyme activity; microbial number |
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| Abstract: |
| The soil organic carbon（SOC） as one of the largest and most important reservoirs of carbon（C） in the global C-cycle produces the correlated response which plays an important role in the karst region. Moreover, the relationship between SOC and microbe numbers and soil enzyme activity in karst region was evaluated to partition the soil organic carbon（SOC） accumulation mechanism. Soil samples from three karst types（saddle, depression and slop） at 0~10 cm, 10~20 cm and 20~30 cm layers in the Yaji Karst Experimental Site were collected to appraise their function and relationship. SOC contents and microbial community population were analyzed using sulfate digestion method with potassium dichromate and dilute plate incubation counting respectively. Microbial activity was valuated using soil enzyme assays as well. It could be seen that the SOC decreased from the topsoil to the fundus at three karst forms. In the 0~10 cm layer, the SOC was 40.10 g·kg-1 in depression compared to 38.28 g·kg-1 in saddle and 24.42 g·kg-1 in slop. Bacterial numbers in depression from the topsoil to the fundus were 3.26×106, 2.73×106 CFU·g-1 and 1.15×106 CFU·g-1 respectively, which are higher than that in saddle and slop. Moreover, at topsoil of 0~10 cm, urea activity was 1.92 mg·（g·24 h）-1 in depression compared to 1.12 mg·（g·24 h）-1 in saddle and 0.77 mg·（g·24 h）-1 in slop. Alkaline phosphatase activities at different layers were all higher in depression than that in same depths of addle and slop. According to the statistical analysis, the bacterial number, urea activity, normalized overall microbial number and normalized overall enzyme activity plus SOC contents had a significant positive correlation. Moreover, it could be confirmed that the soil microbial number and soil enzyme activity were improved with the accumulation of soil organic carbon. Therefore, the bacterial number, normalized overall microbial number and normalized enzyme activity could be used to indicate the soil functioning in karst region. |
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