Study On Soil And Water Process In Different Governance Modes Of Typical Karst Peak-Cluster Depression In Guangxi

The research on ecological restoration and management mode of typical landforms is beneficial to improving ecological service function and providing beneficial basis for controlling water and soil losses.Deposition rate and dynamic process of nutrient elements under different vegetation cover types and restoration degree of different modes are important research contents of water and soil process.In this paper,the typical depression of Xitang,Yangshuo,Guilin is selected as the research area,and the soil physical and chemical properties under the ecological management mode of economic fruit forest,artificial economic forest management mode and natural forest management mode are studied by ring knife method.In addition,the soil erosion rate and amount were estimated in 4 sample areas of different vegetation cover types in the study area by using dual-nuclide tracer method,including sugar orange,summer orange fruit,arbor,shrub and forest land,weed grassland,and the correlation between organic matter and soil erosion was discussed,and the influencing factors on different types of soil were analyzed.The main results are as follows:（1）The maximum water holding capacity of fissures in the study area ranges from 12%to 28%.The change of land use mode and the type of vegetation cover are the important influencing factors of field water holding capacity.The maximum water holding capacity of Arbor-shrub Forest land is 5%-10%higher than other modes.The field water holding capacity of Arbor-shrub Forest is relatively high.High vegetation coverage is beneficial to water and soil conservation and can effectively reduce water and soil loss.The water holding capacity of typical cracks with closed section differs significantly between different treatment modes.（2）The background value of ¹³⁷Cs(854.35 Bq·m^-2)is less than ²¹⁰Pbex(9837.06 Bq·m^-2).Annual soil deposition thickness of different land types estimated by the ¹³⁷Cs method was summer orange fruits land(0.228 mm·a^-1)>weed grassland(0.144 mm a^-1)>natural recovery forest(0.106 mm a^-1)>sugar orange fruits land(0.026 mm·a^-1).The annual soil deposition thickness estimated by the ²¹⁰Pbex method was naturally restored forest(0.777 mm a^-1)>weed grassland(0.574 mm a^-1)>sugar orange fruit land(0.316 mm a^-1)>summer orange fruit land(0.189 mm a^-1).The average soil deposition rate for this study area was 203.60 t·km^-2·a^-1for ¹³⁷Cs method and 747.01 t·km^-2·a^-1for ²¹⁰Pbex method soils.（3）The distribution of ¹³⁷Cs,²¹⁰Pbex,SOC and SON has similar distribution patterns in space and profile,with tree and irrigation forests being more conducive to the accumulation of SOC and SON,and the distribution characteristics of ¹³⁷Cs and ²¹⁰Pbex being significantly and positively correlated with SOC.²¹⁰Pbex can replace ¹³⁷Cs to better quantify the effect of soil erosion on the spatial and temporal distribution of SOC.The abundance values ofδ¹³C andδ¹⁵N were closely correlated with SOC and SON content,and showed a similar pattern to the nuclide distribution in depth distribution.（4）Measures to mitigate soil erosion are taken according to local conditions and in conjunction with the topography of the area,through the models of"sedimentation ponds+rainwater collection on roads+artificial construction of water storage cabinets"and"water collection and diversion pipes on slopes+water collection ponds",to regulate slope runoff and control soil erosion in mountainous orchards.The project aims to achieve the full collection and use of water resources in water-scarce areas.The application of soil erosion control techniques in mountainous areas of fruit forests,such as"sugar orange+inter-planting grafted summer orange",can effectively improve the structure of the vegetation community,and the increased root system can optimize the soil retention effect of the fruit forest,ultimately reducing the rate of soil erosion and achieving the purpose of erosion control.