Ecological Stoichiometric Characteristics Of Soil Carbon,Nitrogen And Phosphorus And Its Influencing Factors In Binggou River Basin

Soil carbon,nitrogen and phosphorus and their eco-stoichiometric ratio can reflect the cycle process of carbon,nitrogen and phosphorus in vegetation-soil,which is of great significance for the maintenance of soil quality.The Binggou River basin is a typical small watershed on the north slope of the eastern section of the Qilian Mountains.The spatial difference of meteorological and hydrological elements and steep elevation gradient lead to the high variability of vegetation and soil pattern.Therefore,it is of great significance for soil ecological conservation and ecological restoration to study the ecostoichiometric characteristics of soil carbon,nitrogen and phosphorus in Binggou River basin and to explore the influencing factors of soil carbon,nitrogen and phosphorus cycle.Based on this,this paper takes the Binggou River Basin on the north slope of the eastern section of the Qilian Mountains as the study area.And takes the contents of soil organic carbon(SOC),total nitrogen(STN)and total phosphorus(STP)collected in 2018 and 2019 vegetation growing season(May-October)as research data.Analyzes the temporal and spatial variation characteristics and influencing factors of SOC,STN,STP content and their eco-stoichiometric ratio,and mainly draws the following conclusions:(1)The change of SOC content showed the time variation characteristics of high in spring and autumn and low in summer,with the lowest value in July and the highest value in May;the change characteristics of STN content were different in different land types;the change of STP content was generally stable.Among the three land types,the change of SOC content in farmland was high in spring and autumn and low in summer,which was opposite to that of STP.The three indexes of grassland soil showed opposite characteristics at different sampling sites.The change characteristics of SOC and STN contents in woodland soil were consistent,both decreased at first and then increased.STP was stable in spring and summer and significantly decreased in autumn.(2)The C: N value of farmland soil is relatively stable,and the C: N value of grassland is higher in spring and autumn and lower in summer,while the change characteristics of woodland and grassland are opposite.The C: P values of the three land types are higher in spring and autumn and lower in summer.The change of N: P value of farmland soil was stable,the N: P value of grassland soil fluctuated,and the N: P value of woodland soil in autumn was significantly higher than that in spring and summer.(3)The spatial distribution characteristics of SOC,STN and STP in the Binggou River basin are different,and the spatial variability of SOC is the strongest,showing a decreasing trend from the upper reaches to the middle and lower reaches of the basin.The spatial variability of STN is strong,showing a decreasing trend from the upper reaches to the middle and lower reaches of the basin.The spatial variability of STP is weak,and there is no obvious difference between upstream and middle and downstream.The spatial variability of C: N and C: P is strong,and the difference between downstream and upper and middle reaches is significant,while the spatial variability of N: P is weak.(4)The contents of SOC and STN in different land types decreased with the increase of soil depth,and changed greatly in 0-30 cm soil layer,but stable in 30-60 cm soil layer.The change of STP content was not obvious with the increase of soil depth.Among the three types of land,the change of farmland soil is the most stable,while the change range of grassland and woodland is larger.From the perspective of eco-stoichiometric ratio,the vertical changes of C: N in the three land types are relatively stable.C: P showed a decreasing trend from the surface layer to the middle and lower layer,in which the change range of farmland was smaller,that of grassland was the second,and that of woodland was the largest.There was no significant vertical difference of N: P in farmland,but it decreased from the surface layer to the middle and lower layer of grassland soil,and the change characteristics of N: P in woodland soil were different.(5)The distribution characteristics of soil carbon,nitrogen and phosphorus are the result of the interaction of soil,vegetation,climatic conditions and surrounding environment.Different land use patterns determine the material sources of soil nutrients.Climatic conditions are an important guarantee of soil nutrient balance.Altitude gradient affects the change of soil nutrients by changing climate and vegetation types.Human activities also affect soil nutrient cycling to a certain extent.(6)Returning straw to field and applying organic fertilizer in farmland soil can maintain soil carbon source and increase grain yield.Moderate grazing in grassland soil and increasing grass species types can improve grassland productivity.In woodland soil,the utilization rate of soil nutrients can be improved by improving stand density and building mixed forest.For different elevations,riparian forests and shrubs can be planted on both sides of the river bank in areas below 2600 m,and grass types suitable for the local environment can be introduced far away from the river.In the area above 2600 m,shallow root and deep root vegetation can be planted reasonably,and appropriate water use strategy should be adopted for Qinghai spruce forest.