Effects Of Exogenous Calcium Carbonate On Mineralization Of Organic Carbon In Lime Soil With Different Ratios Of Nitrogen To Phosphorous In Karst Area

In order to grasp the conversion law of soil organic carbon in karst area and the r elationship between organic carbon and inorganic carbon,to enhance the understandin g of the microbial mechanism of carbon cycle in karst ecosystem.In this study,the ty pical lime soil in the Karst area of Puding County,Guizhou Province was used as the t est soil,and three nitrogen-to-phosphorus ratios?N/P were 28,10,and 5?were set,an d the treatment without adding ¹³C-CaCO₃?NP₁,NP₂,and NP₃?As a control,three add itional ¹³C-CaCO₃ treatments?NP₁C,NP₂C,and NP₃C?were set,for a total of six trea tments.After 100 days of cultivation under indoor simulated culture conditions,the ef fects of exogenous calcium carbonate on the mineralization of organic carbon in limes tone soil with different nitrogen to phosphorus ratios and microbial mechanism were s tudied using ¹³C isotope tracing technology,chloroform fumigation and Miseq high-th roughput sequencing methods.The following main conclusions are obtained:?1?After adding ¹³C-CaCO₃ for 100 days,the CO₂ production rate showed a rap id decline in 1-10 days,a slow decline in 10-15 days and a slow decline in 15-100 day s.At the end of the 100-day cultivation,the cumulative mineralization amount and cu mulative mineralization rate of each treatment organic carbon are better to treat NP3C;the stimulation effect of the addition of ¹³C-CaCO₃ on the organic carbon mineralizat ion of each treatment is 8.84%,16.20%and 25.48%,The mineralization of soil organi c carbon was inhibited within 1 to 5 days,which showed a negative excitation effect,and 5 to 100 days showed a positive excitation.In the treatment with ¹³C-CaCO₃?NP₁C,NP2C and NP3C?,the“apparent cumulative mineralization amount”of the soil was15.14%,19.67%and 28.62%of carbon from ¹³C-CaCO₃.The addition of calcium car bonate can change the mineralization of organic carbon in the soil,and lime soil with high nitrogen and phosphorus has a strong ability to accumulate organic carbon.?2?After adding ¹³C-CaCO₃,the soil microbial biomass carbon in different treat ments showed NP3C>NP₂C>NP₁C.¹³C-CaCO₃ aggravated the mineralization of low-nitrogen-phosphorus limestone organic carbon and reduced the soil microbial biomass carbon content Lime soil organic carbon with high nitrogen to phosphorus ratio is mo re stable.?3?The addition of ¹³C-CaCO₃ increases the diversity of soil bacteria and fungi.Cluster analysis and bi-clustering heat maps at the genus level indicate that the additi on of ¹³C-CaCO₃ has a significant effect on the community structure of soil bacteria a nd fungi.The main dominant class of bacteria is Actinobacteria?Actinomycetes?,and the main dominant class of fungi is Ascomycota?Ascomycota?.Cluster analysis of en vironmental factors showed that different ratios of nitrogen and phosphorus had a sign ificant effect on bacterial and fungal communities.Actinobacteria?acid bacteria phylu m?had a very significant negative correlation with the ratio of nitrogen to phosphorus,Basidiomycota?basidiomycota?and SMBC had a very significant positive correlation,Ascomycota?Ascomycota?was significantly positively correlated with the ratio of ni trogen to phosphorus.In summary,the addition of ¹³C-CaCO₃ will inhibit the mineralization of soil organic carbon,and the lime soil with higher nitrogen and phosphorus is more stable.After adding ¹³C-CaCO_3,NP₃C treatment has a significant effect on soil microbial community structure.Soil fungi are greatly affected by the ratio of nitrogen to phosphorus,and fungi play an important role in regulating the carbon cycle.