Effect Of Exogenous Calcium Carbonate On The Mineralization Of Organic Carbon In Typical Soils In Guizhou

This study took Guizhou typical yellow soil and lime soil as the research object,set to add exogenous Ca¹³CO₃（30 g/kg dry soil）and sterilized treatment,through a100-day indoor culture test,combined with high-throughput sequencing technology,to study exogenous calcium carbonate The effect on soil CO₂release,soil active organic carbon and soil microbial community,reveals the contribution of calcium carbonate to the typical soil CO₂release in the area and the priming effect on SOC mineralization,and explores its microbiological mechanism.The main results are as follows:（1）The release rate of total CO₂and ¹³C-CO₂in the soil both reached their peak on the first day of culture,and then decreased rapidly,and then leveled off after the15th and 10th days,respectively.At the end of the cultivation,the contribution rate of Ca¹³CO₃to the total CO₂release of yellow soil and lime soil was 25.47%and 20.76%,respectively,indicating that calcium carbonate has a considerable contribution to the release of CO₂from the soil-atmosphere system in Guizhou karst area.The change of soil original organic carbon mineralization rate with incubation time is consistent with the total CO₂release rate.After adding Ca¹³CO₃,the cumulative mineralization of organic carbon in yellow soil and lime soil decreased by 76.05%and 45.14%,respectively,indicating that exogenous Ca¹³CO₃had a negative priming effect on the organic carbon mineralization of yellow soil and lime soil,and it had a negative excitation on yellow soil.The degree is higher than that of lime soil.The results of analysis of variance showed that the interaction between soil type and calcium carbonate has a significant effect on the increase rate of soil organic carbon accumulation and mineralization.（2）The DOC content of yellow soil was higher than that of lime soil at the same incubation time.After adding Ca¹³CO₃,the soluble organic carbon（DOC）content of yellow soil and lime soil increased significantly,indicating that calcium carbonate can increase soil DOC content,and yellow soil DOC content increased more than Lime soil is large.After adding Ca¹³CO₃,the MBC content of yellow soil and lime soil significantly decreased by 69.71%and 28.61%on the first day of culture,and the MBC content of yellow soil increased significantly from day 5 to 100,but the increase of lime soil was not obvious.After adding Ca¹³CO₃,the mass ratio of¹³C-MBC/Ca¹³CO₃in yellow soil and lime soil reached the maximum on the 5th day,which were 0.26%and 0.18%,respectively,indicating that soil microorganisms participated in the metabolism of ¹³C.（3）In yellow soil and lime soil,Actinobacteria,Proteobacteria,Chlorocurve and Acidobacteria are the dominant bacteria;Ascomycota is the dominant fungus.The addition of Ca¹³CO₃can reduce the diversity and richness of soil microbial community to a certain extent,but has no obvious effect on the structure of microbial community.The community structure at the level of yellow soil bacteria is affected by DOC,MBC,SOC mineralization and CO₂cumulative release,while the fungal community is mainly affected by DOC,and the calcareous bacteria and fungi communities are more affected by MBC.The soil organic carbon mineralization rate and soil DOC after sterilization were higher than those of unsterilized soil.The sterilization reduced the diversity and richness of the microbial community,and at the same time changed the composition of the soil microbial community.The dominant groups of soil microorganisms after sterilization mainly include the Proteobacteria and Actinomycetes,and the dominant fungi is the Ascomycota.Sterilized yellow soil is unique to Armored Bacteria and Rumelibacteria,and sterilized lime soil is unique to Delftia.