Changes Of Plant Ecological Stoichiometry And Its Relationships With Soil Nutrients In Degraded Leymus Chinensis Steppe

The ecological stoichiometry reveals the process of ecosystems through analyzing the ecological stoichiometry characteristics of C,N and P elements and their ratios in both plant and soil.In this study,C content,N content,P content of vegetation and soil data were obtained by field observations in Leymus chinensis steppe of Xilin River Basin in Inner Mongolia.Characteristics of ecological stoichiometry on three levels,i.e.community,functional groups,and key species,were illustrated under different degradation stages by means of ecological stoichiometry theory and methodology.Responses of plant ecological stoichiometry to soil nutrients were explored.And then,the relationship between plant and soil nutrient was revealed.Finally,nutrient elements limiting plant growth were determined.The main conclusions showed that:1.The observational data of 69 plots were divided into four different degradation stages:?,L.chinensis + forbs(22 plots);?,L.chinensis + Stipa(S.grandis + S.krylovii)(18 plots);?,L.chinensis +Cleistogenes squarrosa(21 plots);?,L.chinensis + Artemisia frigida(8 plots).2.There was lack of soil nutrient available,and grassland soil fertility in the low level in this study region.The soil nutrient content decreased with the grassland degradation process,such as total nitrogen,total phosphorus and available nitrogen were significant.3.No matter community,functional groups and species,the most N content and P content were positively correlated with soil available nitrogen and available phosphorus.Plant C:N and C:P were negatively correlated with soil available nitrogen and available phosphorus respectively.Grassland degradation led to reduce content of soil nutrient,and changed the plant nutrient content and the characteristic of ecological stoichiometry.4.Except for the C:N of annual plant,the C:N of plant community,functional groups and species decreased with the grassland degradation process.It was indicated that plant response to changed environment by improving growth rate.5.Except for the N:P of annual plant,the N:P of plant community,functional groups and species increased with the grassland degradation process,which indicated that the growth of plant may be limited by N element transform to P element.This study highlights the dynamic of plant ecological stoichiometry in grassland degradation processes,and reveals relationships between plant ecological stoichiometry and soil nutrient.These results enrich knowledge about ecological stoichiometry of the grassland ecosystems.It is also helpful to promote grassland resources restoration and protection.