Characteristics And Coupling Relationship Of Plant-Soil-Microbe Stoichiometry During Vegetation Restoration In The Middle Of Qinling Mountains,China

Vegetation restoration is an effective measure to improve the degraded ecosystem.The mechanism of vegetation restoration on ecosystem components has been studied widely,however the characteristics of plant-soil-microbial changes and their coupling relationships during vegetation restoration are unclear.Using the Pearson’s correlation,redundancy analysis,principal component analysis and random forest test,we investigated the plant diversity and the nutrient stoichiometry of the plant,soil,microbial biomass and extracellular enzyme as well as their interactions along a natural vegetation restoration chronosequence(1,8,16,31,and 50 years)following farmland abandonment in Qinling Mountains,China.Our study provides important insights into community dynamics and the relationships of above-and under-ground and provides a theoretical basis for improving the management and quality of forest stand after natural restoration of abandoned land in the middle of Qinling Mountains.The main conclusions are as follows:(1)In the late stage of restoration,the community structure tended to be complex and the stability improved.The Patrick index,Simpson index,Shannon-Wiener and Pielou index of plant community decreased initially and then increased with the vegetation restoration.Moreover,during the vegetation restoration,plant C and N contents were fluctuated changes.The plant P content significantly decreased,whereas the plant N:P ratio increased over the time.The nitrogen limitation of plant community alleviated significantly and thereafter began to shift to phosphorus limitation in 50 years after restoration.(2)The vegetation restoration improved the soil physicochemical properties.The vegetation restoration increased the contents of soil SOC,TN and available N,whereas decreased the available P of soil.After the farmland abandonment,microbial biomass C,N and P increased significantly whereas the microbial biomass C:N and N:P ratio increased initially and then decreased.These findings suggested that the soil microbes might be limited strongly by the phosphorus in the later stage of restoration.(3)The vegetation restoration significantly changed the soil enzyme stoichiometry and microbial metabolic limitation.The activities of C-acquiring enzyme,N-acquiring enzyme and P-acquiring enzyme as well as enzyme C:P ratio increased initially and then decreased.The enzyme C:N ratio decreased significantly whereas the enzyme N:P ratio increased over the time.Moreover,in the early stage of vegetation restoration,the microbial community were limited by nitrogen.The nitrogen limitation of microbial community alleviated significantly and thereafter began to shift to phosphorus limitation in 31 years after restoration.(4)The vegetation restoration varied the soil environment and soil moisture and phosphorus element strongly affected the plant and microbial nutrient stoichiometry,respectively.However,the microbial C,N and P stoichiometry and plant C:N ratio could remain strict homeostasis.Moreover,the changes in plant nutrient limitation were the consistent of those in microbial nutrient limitation,but soil microbes were limited by phosphorus earlier than plants.Soil C:N ratio explained more variations for changes in plant and microbial nutrient limitation,which might suggested that the imbalanced of soil C:N ratio may determine the soil microbial metabolic limitation and further mediate the variation in plant nutrient limitation during natural vegetation restoration.