Response Of Soil Ecoenzymatic Stoichiometry To Carbon,Nitrogen And Phosphorus In Soil-Plant System Following Returning Farmland Toforests (abandon Land)

The stoichiometric ratio of soil ecological enzymes is an important basis for revealing the balance and limitation of ecosystem elements,and it is also one of the hotspots in the current ecological research field,but the evolution characteristics of soil ecological enzymes in vegetation restoration and its relationship within vegetation-soil system is still unclear.Based on this,this study intends to analyze soil carbon by three typical returning forests(Abandon land)(Robiniapseudoacacia,Caraganakorshinskii,and abandoned grassland)and four recovery years(10 years,18 years,28 years,43 years)in the loess hilly region.Carbon convertase(?-glucosidase;BG),two nitrogen convertase(?-1,4-N-acetylglucosaminidase: NAG;leucine aminopeptidase: LAP),and phosphorus conversion(acid phosphatase: AP)activities and their stoichiometry,combined with plant(leaf)-soil-microbial carbon(C)nitrogen(N)phosphorus(P)content and measurement characteristics and correlation,the system reveals the characteristics of soil eco-enzymes and its response to vegetation-soil C,N,P,which can provide a scientific basis for further understanding the element balance and resource status in the process of vegetation restoration in the loess hilly region.Below are key research findings(1)During the process of vegetation restoration,the activities of four enzymes related to soil carbon,nitrogen and phosphorus transformation increased significantly,but there were differences in different vegetation types and recovery years.The EC,EN and EP activities of artificial Robiniapseudoacacia reached the maximum at 28 years,and then decreased.The EC,EN and EP activities of the abandoned grassland increased with the recovery years,while the three enzyme activities of artificial Caragana showed fluctuations..In addition,soil ecoenzymes C:N(ECN),C:P(ECP),and N:P(ENP)are also affected by vegetation types and recovery years,in which artificial E.and ENP and ENP are gradually decreasing,while Caragana ECP and ENP are first increased and then decreased.(2)During the vegetation restoration process,the vegetation(leaf)-soil-microbial C,N,P content and measurement ratio differed in different vegetation types and recovery years,and the C:P and N:P ratios were the most sensitive.Among the three vegetation types(Hedgehog,Caragana,and abandoned grassland),the leaf C was the highest,the leaf N was the highest,and the leaf P was the highest.With the increase of recovery years,the soil microbial and soluble C,N contents of artificial hedgehog and Caraganakorshinskii forest increased first and then decreased,reaching the maximum at 28 years,and the microbial P gradually increased;while the grassland microbes C,N,P is in an increasing trend during the recovery process.In addition,in the process of vegetation restoration,soil C:N ratio,microbial C:N ratio and available nutrient C:N ratio are relatively stable,while C:P and N:P ratio are different in soil,microbe and available nutrient system,among which The soil C:P and N:P ratios showed an increasing trend,while the microbial C:P and N:P increased first and then decreased in the hedgehog and caragana,and there was no significant change in the grassland.The available nutrients C:P and N:P increase first and then decrease in the hedgehog and gradually increase in the grass.The leaves C:P and N:P increased first and then decreased in the hedgehog and caragana,and showed a gradual decreasing trend in the grass.(3)Plant nutrient balance is closely related to enzyme stoichiometry,and C:P can participate in the regulation of plant-soil nutrient balance.The results showed that the soil ecological enzyme ratio(EC,EN and EP)was significantly positively correlated with soil,microbe,available nutrient C,N,P content and leaf N:P;soil and available nutrients C: P,N: P and ECP There was a significant negative correlation between ENP ratio.The studies implied that when soil lacked P,microbes would secreted AP to increase the contents P in available nutrient and microbial biomass and leaf P,which could satisfy the nutrient demand of microbes and plant.This study showed LCP could relate plant,soil and microbes.Studies have also shown that soil C:P,soil N:P ratio is a key environmental factor for regulating enzyme stoichiometry.