Organic Carbon Mineralization And Microbial In Typical Karst Soil As A Response To The Exogenous Addition Of Calcium Carbonate And Organic Substrate

This paper focuses on terra fusca, rendzina and zonal red soil (control) from Karst area of Huanjiang Guangxi, to study the effects of addition of14C-labeled straw and the14C-labeled calcium carbonate [the addition manner:①Control (no addition, CK);②The addition of a14C-labeled organic substrate (S);③14C-labeled calcium carbonate (C);④the addition of a14C-labeled organic substrate and14C-labeled calcium carbonate (S+C’)] on SOC mineralization, and abundance and genetic polymorphism of soil microbial community, by incubation test with combination of14C isotope tracer techniques and molecular biotechnology. It build science and theory foundation to deepen the relationship between soil microorganism and SOC stabilization, and objective evaluation on the impact of inorganic carbonate on soil respiration. The main results are as follows:1. After a100days incubation test, both additions stimulate SOC mineralization of the three soils:the priming effects of SOC to the addition of14C-labeled straw and the14C-labeled calcium carbonate in the erra fusca, rendzina and red soil were28.7%,46.2%,15.5%and127.0%,175.3%,100.1%, respectively, and the contribution rates of14C-labeled calcium carbonate in "apparent mineralization accumulation" were40.40%,49.06%,19.72%, respectively. Rendzina was the most stable soil, which is helpful to accumulation of SOC.2. After14C-labeled straw and the14C-labeled calcium carbonate addition, total microbial biomass carbon in rendzina was significantly higher than that in erra fusca and red soil (p<0.05). The abundance of soil microbial community in the three soils after different processing was study using Real-time PCR. Result showed significant differences of soil microbial quantity in different treatments. Microbial quantity in rendzina was much larger than that in terra fusca and red soil, while no significant differences of fungi quantity appeared in three soils fungi quantity. For the same theatment, rDNA gene richness in Bacteria was significantly higher than that in fungi.3. The genetic polymorphism of soil microbial community in the three soils after four addition manner was study using PCR-DGGE, showed that obvious dominant species appeared in the three soils soil bacterial community and fungi community after exogenous addition.In terra fusca, rendzina and red soil, the comparability of bacterial communities were56.27%,51.07%and36.98%, and the comparability of fungal communities were27.54%,39.78%and49.75%, respectively. Soil type, exogenous addition and their interaction had significant effect on Shannon diversity of bacterial and fungal.All the analysis above shows that, soil type and14C-labeled straw and the14C-labeled calcium carbonate addition were significant influence on SOC mineralization and abundance and genetic polymorphism of soil microbial community. Moreover, inorganic carbonate involved the turnover of SOC by the action of soil microorganism. So inorganic carbonate should be considered when study SOC mineralization for the carbonated lime soil and evaluation its impact on atmospheric CO2.