典型南方岩溶稻田土壤腐殖质、微生物和土壤呼吸的耦合关系研究

稻田土壤微生物固碳研究是当前全球气候变化下的前沿课题。岩溶土壤中腐殖质易与高含量钙镁结合成稳定的复合物，能够降低微生物的可利用性。但是我们发现，岩溶土壤中微生物的碳源代谢活性显著高于非岩溶区。因此，我们提出如下假设：在高含量的矿物腐殖质复合物的驱动下，细菌的碳源利用效率提高，真菌丰度降低，土壤呼吸下降，促进土壤有机积碳的积累和稳定。本项目以毛村岩溶试验场和会仙岩溶湿地的定位研究为基础，测定腐殖质组分及其结构，明晰岩溶土壤有机质的稳定特征；采用高通量测序法和比色测定法分析稻田土壤及其团聚体颗粒组中微生物群落结构和土壤酶活性特征；采用原位测定和微生物抑制呼吸技术明晰不同微生物群落对土壤呼吸的贡献；通过室内培养结合同位素示踪法验证土壤腐殖质、微生物群落及其呼吸活性之间的耦合关系，探讨岩溶稻田土壤微生物的固碳过程和机制，丰富土壤固碳理论。

The microbial carbon-sequestration in paddy soil is a subject in the forefront of research under the global climate change. In calcareous influenced soil of karst ecosystem, humus is easily stabilized by metals (Ca and Mg) bridges, reducing its bioavailability of microorganisms. However, we found that the carbon source metabolism activity of microbes in karst soil was significantly higher than that in nonkarst soil. Therefore, we hypothesize that the high content of mineral-humus complex represses the soil repartition through increasing bacterial carbon source utilization and deceasing fungi abundance, which promotes the accumulation and stabilization of soil organic matter. In this study, the follow subjects will be carried on based on the positioning trial in both Maocun karst experimental site and Huixian karst wetland. The component and structure of humus will be measured to recognize the stable characteristics of karst soil organic matter. The microbial community structure and soil enzyme activity in paddy soil and in its different aggregate groups will be analyzed by using high-throughput sequencing and colorimetric method. The soil respiration will be determined in situ and the contributions of different microbial communities to soil respiration will be verified by using respiration inhibition technology. The coupling relationship among humus, microbial community and soil respiration will be analyzed by incubation experiment together with the stable isotope tracer technique. The above results will help us to understand the process and mechanism of microbial carbon-sequestration in karst paddy soil and enrich the theory of soil carbon-sequestration.