Effects Of Different Land Use Types And Fertilization On Soil Organic Carbon Storages In Alpine Meadows

Soil is the largest organic carbon(C)pool in terrestrial ecosystems.Different land use types and fertilizations can affect soil organic C(SOC)storages by altering a dynamic equilibrium between C input and output.Minor changes in SOC storages will have a great influence on global climate.In this paper,we studied how different land use types and fertilization changed plant and soil physicochemical properties and then changed SOC storages in alpine meadows on the Qinghai – Tibetan Plateau.The objective was to provide theoretical basis for choosing proper land use types and fertilization treatments to improve plant productivity and maintain soil function as C pool.We chose typical land use types(fenced meadow,moderately grazed meadow,tilled cropland and abandoned croplands)and fertilization practices(control treatment and different rates of single nitrogen(N)fertilization,single phosphorus(P)fertilization and both N and P fertilization respectively).We investigated plant biomass and C,N and P,soil C fractions,N,P and soil physical and chemical properties in top profile under different land use types and fertilization treatments.Results showed that:1)Tillage significantly decreased soil bulk density and p H;single N fertilization increased soil bulk density,but reduced p H.2)Among four land use types,above-ground C storages took up 0.7%-1.7% of total organic C storages,with the highest at fenced meadow and proportions of root C storages ranged from 2.5% to 4.3%,with the highest at moderately grazed meadow;the percentages of C storages are 0.6%-2.4% in above-ground and 2.0%-3.9% in root,with the highest at medium rate of single N fertilization.3)Moderately grazing notably increased soil microbial biomass C(MBC)while tillage and abandonment decreased MBC;moderately grazing,tillage and abandonment all lowered soil cumulative C mineralization;fertilization decreased soil MBC and cumulative C mineralization.4)Tillage reduced SOC storages;medium and high rate of single N fertilization and medium rate of single P fertilization increased 3.9%,2.3% and 0.5% of SOC storages as compared to the control treatment respectively,while other treatments decreased 0.7%-6.6%.5)Abandonment decreased above-ground C/N,but increased root C/N,plant and soil N/P;low rate of single N fertilization and high rate of NP fertilization notably decreased root and soil C/N;single N fertilization significantly increased plant N/P,while P fertilization lowered plant N/P;fertilization reduced soil N/P.To sum up,in alpine meadow,different land use types and fertilization treatment altered plant productivity,C concentration,C/N,N/P and soil physico-chemical and microbial characteristics,and resulted in higher SOC storage in moderately grazing,abandonment,medium and high rate of single N fertilization,while tillage and P fertilization lowered SOC storage.These results could provide theoretical basis for choosing proper land use types and fertilization treatments to guarantee plant productivity and recover and maintain SOC sequestration function.