| The study of soil organic carbon in karst areas plays an important role in the global carbon cycle.Due to the special geological background and complex topographic features of karst areas,the content of soil organic carbon shows obvious spatial heterogeneity.The content is also significantly affected by the physical and chemical properties of the soil and human activities.The study of soil organic carbon is not only an important link of carbon migration between the soil environment and the atmospheric environment and the cave environment,but also an important way to understand the carbon cycle of the ecosystem.In-depth exploration of the coupling relationship between soil physical and chemical properties and soil organic carbon content will help us improve our understanding of the influence mechanism of soil organic carbon content,regional soil evolution,and the biogeochemical cycle of soil organic matter during soil erosion.To clarify the laws of the occurrence,development and change of the soil,to provide a reference for the further study of the soil as a carbon source or a carbon sink in the region.Based on the overlying soil in this area is an important link in the study of the key karst zone,from January 2020 to January 2021,6 different types of land were selected in the two important branch tunnels of the Shuanghe cave system,the wind tunnel and the Mahuang tunnel.Use the grid method to excavate soil profiles,which are abandoned land,converted farmland to woodland,forested land,dry land,shrubland,corresponding to SH1#,SH2#,SH3#,SH4#,SH5#,SH6# in turn,Collect soil samples according to the surface layer,20 cm,40cm,and 60 cm layer,combined with indoor experiments and analysis,systematically study the spatial distribution characteristics and influencing factors of soil organic carbon in the study area,and apply correlation analysis and principal component analysis methods to explore the impact The dominant factor of soil organic carbon content in this area.It has important theoretical and practical significance for promoting the development and rational utilization of Shuanghe National Geopark and the restoration and reconstruction of karst ecosystem.The main conclusions are as follows:(1)Soil organic carbon shows the characteristics of high content and strong variability.The content of soil organic carbon generally showed a change pattern of summer>winter.(2)Spatially,the content of soil organic carbon has a significant decreasing trend with the increase of soil depth,and the overall appearance is surface layer>bottom layer.The main storage space of soil organic carbon is in the surface layer of soil,which has obvious surface accumulation.(3)The change law of soil organic carbon content of different land use types is: forest land(23286mg/kg)> returning farmland to woodland(18334mg/kg)> shrub land(18017 mg/kg)> dry land(14132 mg/kg)> irrigation Grassland(13885mg/kg)>abandoned land(11040mg/kg),and both reached the level of significant difference(p<0.05).The variation coefficients of soil organic carbon content in different soil layers ranged from 55.87-76.28%,showing moderate variability with obvious variability.(4)Correlation analysis shows that the profile of soil organic carbon content is significantly positively correlated with soil water content,soil temperature,soil bulk density,and soil CO2,and significantly negatively correlated with soil ph and soil porosity.The results of principal component analysis showed that the main factor affecting the changes in soil organic carbon content in the study area was soil water content(41.268%),followed by soil temperature(28.038%),and both accounted for 70% of the variation.(5)Soil bulk density and soil porosity are used as the main indicator information of the first principal component,and soil temperature and soil moisture content are used as the main indicator information of the second principal component.From this analysis,it can be concluded that soil bulk density and soil porosity are the main factors affecting the organic carbon of the overlying soil of Shuanghe Cave,followed by soil temperature and soil water content. |
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