Study On Metabolic Limitation Mechanism Of Soil Microbial At Slope Scale On Loess Plateau

The ecological environment of Loess Plateau is fragile,the slope area is extensive,and soil erosion is serious,and vegetation restoration is an important way of ecological restoration on Loess Plateau.Due to water scarcity,soil water content has become a key limiting factor for vegetation restoration and reestablishment on the Loess Plateau,and has an important impact on the nutrient cycling process of the Loess Plateau ecosystem.However,systematic studies on soil nutrient cycling and microbial metabolism mechanisms driven by soil water content during vegetation restoration are still lacking.In this study,the soil microbial metabolic limitations of different slope positions,different soil layers,rhizosphere and bulk soils and different vegetation restoration types on the slope were studied to elucidate the soil microbial metabolic characteristics and driving mechanisms at the slope scale of the Loess Plateau,providing some scientific basis for the restoration of the Loess Plateau ecological environment.The main research results are as follows.(1)Soil microbial metabolic activities on the slope were mainly limited by carbon(C)and phosphorus(P),and the microbial metabolic limitation differed in different soil layers,with higher microbial C and P limitation in 0-20 cm than in 20-40 cm and 40-80 cm layers.Microbial metabolic limitation in 0-80 cm soil layer was regulated by soil water content(SWC)and nutrients.In the 0-20 cm soil layer,the total effect of nutrient stoichiometry ratio and total nutrients on C limitation was greatest,and the total effect of microbial biomass,nutrient stoichiometry ratio and SWC on P limitation was greatest;in the 20-40 cm soil layer,the total effect of total nutrients on C limitation was greatest and the total effect of SWC on P limitation was greatest;in the 40-80 cm soil layer,nutrient stoichiometry ratio had the largest total effect C limitation and SWC had the greatest effect on P limitation.(2)Microbial metabolic limitation of both the rhizosphere and bulk soils was limited by C and P.C and P limitation of rhizosphere soils were higher than that bulk soils;C limitation of soils on upper slopes was higher than that on lower slopes,and P limitation of both the rhizosphere and bulk soils gradually increased with slope length;carbon use efficiency(CUE)was not significantly different between the rhizosphere and bulk soils and on different slopes;organic carbon: total phosphorus(SOC: TP),soil available phosphorus(Olsen-P)and total phosphorus(TP)had significant effects on microbial metabolic limitation and CUE.(3)Microbial metabolism in slope grassland and Robinia Linn was mainly limited by C and P.There were no significant differences in microbial limitation at different slope positions,and microbial P limitation in Robinia Linn was significantly higher than that in grassland at mid-slope and downslope positions.The results of redundancy analysis(RDA)and partial least squares pathway modeling(PLS-PM)analysis showed that soil nutrients and nutrient stoichiometry were key factors driving vegetation restoration on slopes.