Response Of C,N,P Eco-Stoichiometry Of Typical Mountain Soils To Changes In Land Use Patterns

In recent years,due to natural factors and the influence of human production and life,the mountain erosion and soil erosion in Chongqing have become more serious,and the soil quality and water conservation capacity have been decreasing year by year.The loss of soil nutrients and the reduction of production capacity have become obstacles that seriously endanger the ecological sustainable development of the region and hinder social and economic development.Improving soil nutrients in Chongqing's mountainous areas,improving soil physical and chemical properties,slowing soil erosion,coordinating ecological civilization and economic construction in the area,and adopting a land use method that suits local conditions are no longer urgent.The study area is located in Tianfu Town,Beibei District,Chongqing.Due to the differential dissolution of limestone at the axis of the anticline,it takes the form of “one mountain,two troughs and three mountains” in the southwestern mountainous region.Tianfu Town was once famous for its rich mineral resources,especially coal resources.The long-term mining has led to nearly exhausted coal resources in Tianfu Town,which has become a serious mined-out area with a bad ecological environment.During the "Eleventh Five-Year Plan" period,Tianfu Town began a large-scale ecological management project of returning farmland to forest.Adopting a land use method adapted to local conditions and gradually recovering degraded soil with suitable vegetation is an effective measure to alleviate the ecological deterioration in the area.Based on the restoration of the ecological environment of the region,this study selected 4 types of mountain tea gardens(TP)without management,forest land(FL)that grows naturally after returning farmland to forest(FL),slope farmland(CL),and manually managed mulberry land(MP).The land use method is the research object.Soil samples of 3~0cm,10~20cm,20~30cm are collected respectively.Through field investigations,laboratory tests and analysis,the eco-stoichiometric characteristics of different landuse methods are discussed.Identifying the best land use method provides detailed theoretical support for the prevention and control of soil erosion and ecosystem restoration in the area,and is of great practical significance for revealing and evaluating the potential of carbon fixation(C)and nitrogen fixation(N)in mountainous soils in Chongqing.The results show:(1)The sequence of the pH value of the soil in Chongqing mountainous region is: CL> MP> TP> FL.Affected by the soil layer and land use pattern,in general,the content of C,N and P in the Chongqing mountainous region decreases with the increase of soil depth.The order of C content of different soil layers in different land use types is: TP> CL> MP> FL;N and P content are: CL> MP> TP> FL.Different land use methods have different effects on soil C/N,C/P and N/P values.Soil C/N value is TP> CL> FL> MP,C/P value is TP> FL> MP> CL,and N/P value is FL> TP> MP> CL.The difference between different soil layers is relatively stable.C/P and N/P are the restrictive indicators of soil nutrient content in the study area.Humans affect the soil C,N,P content and their eco-stoichiometric characteristics of the active area through different land use methods.Therefore,in the actual land use process,adjusting measures according to local conditions and selecting scientific and reasonable methods are effective measures to reduce the loss of soil nutrients.The results of the difference analysis show that there are no differences between the different soil layers of the four land use methods(TP,CL,FL,MP)of the Chongqing mountainous region,and the difference between C and N between TP and MP is significant(p <0.05).There are very significant linear function fitting relationships between N and P,N and pH,P and pH,C/N and C/P,and they are all positively correlated;between N and C/P,N/P and pH There is a significant power function fitting relationship,C/P and pH have a very significant power function fitting relationship,and both are negatively correlated;C/P and N/P have a very significant power function fitting relationship,which is a positive correlation.(2)Under different land use methods,the soil bulk density(BD)increases with the depth of the soil layer,and has a significant effect on the soil bulk density of the 0-10 cm soil layer.The ranking of each use mode is FL> MP> CL> TP.The soil BD of FL is the maximum at the same depth in the top layer(0-10cm)and the deepest layer(20-30cm).The soil porosity(Porosity)under different land use methods,except for TP,the other three land use methods increased slightly with depth,the order is TP> CL> MP> FL,which is the opposite of soil BD.The soil water retention capacity(WHC)under different land use methods,except for TP,shows that as the depth of the profile increases,it generally increases,and the smallest average value is MP.Through regression analysis,it is found that soil BD has a very significant linear functional relationship with WHC and Porosity.Soil WHC and Porosity have both a very significant linear functional relationship and a power function relationship.In addition,all three are negatively correlated.The relationship between chemical properties and physical properties is: there is a significant linear function relationship between soil C and BD,which is a negative correlation,and C and Porosity have a significant power function relationship,which is a positive correlation.(3)Gray correlation analysis results show that the improvement order of soil physical properties and nutrient content by different land-use methods is as follows: MP> FL> TP> CL in 0-10 cm soil layer;FL> TP in 10-20 cm soil layer > CL> MP;FL> MP> CL> TP in 20-30 cm soil layer.This study starts from the perspective of restoring and improving the niche of the goaf in Tianfu Town,Beibei District,Chongqing City,and believes that in the fragile ecological environment of the mountainous region of Chongqing,soil restoration and improvement should start with suitable land use methods.To slow down and weaken the destruction process of Chongqing's mountain ecological environment,it is necessary to select the dominant plants suitable for local growth according to local conditions,improve the surface vegetation coverage,improve the soil and water conservation capacity and soil fertility quality,and prevent soil erosion.Taken together,the soil quality of CL with greater human activity intensity is relatively worse than that of land use methods such as FL and TP,indicating that ecological restoration measures have a better potential for improving soil quality.