Characteristics Of Soil Carbon Transfer In Carbonate Area On The Southern Slope Of The Qilian Mountains And Influencing Factors

The dissolution of carbonate rocks plays an important role in storing CO₂and slowing the rise of atmospheric CO₂ concentration.The south slope of Qilian Mountains province is an important water conservation area on the northeastern Tibetan Plateau and in Hexi Corridor,it is an ideal area to study carbonate rock dissolution and soil carbon transfer in qinghai-tibet plateau.However,there are few reports in this field.In this study,the carbonate area on the south slope of Qilian Mountains Qilian Mountains was selected as the research area To estimate the dissolution rate of carbonate rocks on the south slope of Qilian Mountains,and to monitor the soil physical and chemical properties,soil microorganisms and soil enzymes by field surveys and laboratory studies,the carbon isotope technique was used to study the fixed CO₂ and carbon transfer in the soil during the formation of secondary carbonate The least squares,redundancy and path analysis were used to explore the main controlling factors of soil carbon transfer.The main findings are as follows:（1）Based on the field investigation,the main types of surface cover ecosystems in the carbonate region on the south slope of Qilian Mountains are shrub and grassland.The annual rainfall,annual mean temperature and evapotranspiration in the carbonate rock region as a whole show an upward trend,the annual rainfall（25.14 mm/10a）and annual mean temperature（0.22℃/10a）were lower than those on Non-carbonate rock area on the southern slope of Qilian Mountain（27.60 mm/10a,0.23℃/10a）,the evapotranspiration（62.26 mm/10a）slope was higher than that of Non-carbonate rock area on the southern slope of Qilian Mountain（58 mm/10a）.（2）Soil organic carbon(103.94 g·kg^-1),soil CO₂（4680.15 ppm）,soil CO₂¹³C（-18.89‰）and soil inorganic carbon¹³C（-5.15‰）in grassland were higher than those in shrub,the contents of inorganic carbon(1.87 g·kg^-1)and soil organic carbon¹³C（-23.94‰）in shrub soil were higher than those in grassland.The contents of soil organic carbon(101.63 g·kg^-1)and Soil CO₂¹³C（-18.84‰）in limestone area were higher than those in dolomite area,the contents of Soil Organic Carbon¹³C（-24.41‰）,soil inorganic carbon(2.20 g·kg^-1),soil CO₂（5753.40 ppm）and soil inorganic carbon¹³C（4.69‰）in the dolomite area were higher than those in the limestone area.（3）There were significant differences in soil microbial groups between shrub and grassland,dolomite and limestone areas.Among the bacteria,Gammaprteobacteria,Blastocatellia,Vicinamilbacteria and ALphaproteobacteria were the dominant flora,among the fungi,Agaricomycetes,Unclassified,Leotiomycetes and p＿Ascomycota＿Unclassified were the dominant ones,and most of the soil bacteria（>75%）and fungi（about 45%）were common.（4）The activities of soil phosphatase(4.76 mg·g^-1·d^-1),soil urease(1.84 mg·g^-1·d^-1),soil cellulase(5.53 mg·g^-1·d^-1)and soil Catalase(4.95 mg·g^-1·d^-1)in grassland were higher than those in shrub,the activity of sucrase(71.02 mg·g^-1·d^-1)in shrub soil was higher than that in grassland;Soil phosphatase(5.28 mg·g^-1·d^-1),soil urease(2.09mg·g^-1·d^-1)and soil cellulase(6.61 mg·g^-1·d^-1)in limestone area,soil sucrase activity(70.28 mg·g^-1·d^-1)and soil Catalase activity(4.87 mg·g^-1·d^-1)were higher than those in dolomite area,and soil enzyme activity decreased with the increase of soil depth.（5）The amount of secondary carbonate in shrub soil(1.15 g·kg^-1)was higher than that in grassland(0.84 g·kg^-1),and that in limestone soil(0.87 g·kg^-1)was lower than that in dolomite soil(1.11 g·kg^-1),in the process of secondary carbonate formation,the amount of CO₂(0.25 g·kg^-1)in shrub-fixed soil was higher than that in grassland(0.18g·kg^-1),the content of CO₂ in fixed soil(0.19 g·kg^-1)in limestone area was lower than that in dolomite area(0.24 g·kg^-1),and the content of carbon transfer in shrub soil(0.09g·kg^-1)was higher than that in grassland(0.08 g·kg^-1),the amount of soil carbon transfer in limestone area(0.07 g·kg^-1)was less than that in dolomite area（0.10 g·kg^-1）.（6）The effects of soil physical and chemical properties on soil carbon transfer were studied by least squares method.Three principal components were proposed,with an interpretation rate of 0.98 and a prediction ability of 0.97 for soil carbon transfer,respectively,soil bulk density,soil porosity,Soil Moisture Content,soil inorganic carbon and soil CO₂ had the greatest influence on soil carbon transfer.The effects of soil microorganisms on soil carbon transfer in carbonate rocks were analyzed by RDA,and the results showed that soil carbon transfer was mainly influenced by Verrucomicrobiota and Methylomirabilota,and Basidiomycota and Glomeromycota.The direct effects of soil cellulase,soil phosphatase and soil Catalase on soil carbon transfer were found to be relatively small through path analysis,soil sucrase had indirect positive effect on soil carbon transfer,while soil sucrase and soil urease had direct effect.