Responses Of Plant Functional Traits And Community Assembly To Different Disturbances In Alpine Meadow

Recently,the degeneration of alpine meadow in large areas posed grave threats to the ecological safety and economic development of the Qinghai-Tibet Plateau,so accelerating the development of recovery technique for degraded grassland and studying the mechanism of the recovery process had become an urgent issue to the local ecological construction and livestock development.Basing on the features of soil nutrients under different grassland recovery measure as the environment variables,this paper studied the plant photosynthetic functional traits(height,specific leaf area and leaf allocation),nutrient functional traits(leaf carbon nitrogen phosphorus concentration and their ratio with each other),reproduction functional traits(reproductive allocation)and stress resistance functional traits(leaf dry matter content)of degraded alpine meadow located in the east of the Qinghai-Tibet Plateau.With the analyses of distribution regulation of plant functional traits and the relationship with plant important value,we tried to reveal the process and mechanism of community assembly under the environment filtering.The main conclusions are as followed:(1)The result of principal component analysis showed that,the levels of soil comprehensive fertility under different disturbance measure was graze(PCA value:-2.31)<reseeding(-0.83)<enclosure(-0.15)<scarification(1.30)<fertilization(1.98).Along the increased soil comprehensive fertility gradient,above-ground biomass and sedge group biomass of plant community increased significantly,the species diversity decreased while similarity index between communities showed little change,which means that along the soil comprehensive fertility gradient,the change of species abundance was the main reason to alter the community structure of alpine meadow.(2)The variation of plant leaf dry matter content and leaf allocation was mainly effected by the species category while the variation of the other 9 plant functional traits was affected significantly by the species category the different measure and the interaction between them.In addition,plant nutrient functional traits and photosynthetic functional traits increased along the soil fertility gradient while reproduction functional traits performed to decrease gradually,and the relationship between reproduction functional traits and nutrient functional traits,photosynthetic functional traits was negative.Then we can conclude that,under the suitable habitat environment,alpine meadow plants prioritized the nutritional growth while plants will focus on the sexual propagation in order to maintain the survival of species population under harsh conditions.(3)Among the 5 plant functional traits which were sensitive to the change of soil nutrient,the trait range of plant height,leaf nitrogen phosphorus concentration and specific leaf area kept in low level under graze and fertilization,while the trait range of reproductive allocation also remained low under graze measure,indicating that the above plant functional traits will subjected strong environment filtering under both poor and rich soil nutrient conditions.(4)Plant nutrient functional traits performed to divergence under low soil fertility condition and convergence under high soil fertility condition,indicating that community species nutrient functional traits will tend to similar under rich soil fertility gradient.Photosynthetic functional traits and stress resistance functional traits behave in the opposite way indicating that community species photosynthetic functional traits and stress resistance functional traits will tend to difference under rich soil ferrtility gradient.While reproduction functional traits performed to divergence under both ends of soil fertility condition and performed to convergence under medium gradient.(5)Along soil fertility gradient,the relationships between plant functional traits and plant important value didn't show unify regularity.Plant leaf phosphorus concentration,leaf C:N,eaf C:P and leaf dry matter content performed significantly relationship with plant important value under all the measures,while there were large differences in the change of the slope under each treatment.Besides,when contacted to the distribution regulation of plant functional traits along the soil fertility gradient,the characteristics above won't appear an obvious corresponding relation.