Response And Resilience Of Plant Functional Traits On Meadow Steppe Under Different Grazing Intensities

The response of Plant Functional Traits(PFTs)to environmental changes and external disturbances reflects the phenotypic plasticity,survival strategies,and adaptability of plants.Numerous studies have shown that plant functional traits can predict plant response to grazing.The research on plant functional traits,the relationship between different functional traits,and the relationship between plant functional traits and diversity and environment are hot issues in plant ecology.The research on functional traits of grassland plants mainly focuses on the response of plant functional traits,the diversity of functional traits and their mechanisms of action on community structure formation under different interference conditions.However,there is still relatively little research on the resilience of plant functional traits and their diversity.The grassland ecosystem is the largest terrestrial ecosystem in China,and livestock grazing is one of the main ways of grassland utilization.With increasing grazing pressure,overgrazing has become a common grazing method,affecting the function of the grassland ecosystem.Researching functional traits is significantly important for improving ecosystem function and protecting ecosystem diversity.This study conducted a long-term grazing restoration experiment based on the National Field Observation and Research Station of the Hulunbuir Grassland Ecosystem in Inner Mongolia.The study investigated the effects of long-term different grazing intensities on the functional traits and diversity of leaves of 6 dominant plants and 8 main plant groups,as well as the resilience response of plant functional traits and diversity after stop-grazing.Explore the adaptive mechanisms and strategies of plant individuals and communities during grazing and stop-grazing processes.The main results and conclusions are as follows:(1)The six dominant plants showed plant miniaturization under long-term grazing with different intensities.As the grazing intensity increased,the leaves became smaller and thinner,and the nitrogen and phosphorus content in the leaves gradually increased,while the C/N of the leaves decreased.According to the growth rate theory,the organisms with higher growth rates had lower C/N.Along with the compensatory growth of plants,the growth rate of plants increases with the increase of grazing intensity,photosynthesis is strengthened,and the competition between species becomes greater,which is conducive to improving the productivity of the meadow steppe.After stop-grazing,the recovery of leaf functional traits of the six dominant plants under heavy grazing was better than that under light grazing,and the overall positive response was greater than the negative response,which promoted the recovery of meadow grassland plant functions.(2)With the increase of grazing intensity in the long term,the dry weight and leaf area of the eight main plant functional groups decreased gradually,while the water content of leaves increased,aand the morphological traits of most functional groups reached the maximum at moderate grazing,which supported the intermediate disturbance hypothesis.The content of nitrogen and phosphorus in leaves varies under different grazing intensities,and leaf C/N and leaf N/P gradually decrease with grazing intensity,enhanced plant regeneration capacity and competitiveness.After stop-grazing,the morphological traits of the eight main functional groups showed positive>negative effects and the overall positive effect of leaf N/P>negative responses.The nutrient characteristics of leaves,the responses of leaf nitrogen content and leaf C/N were different,and the overall positive response of leaf phosphorus content was<.Negative response,indicating that stop-grazing promoted the recovery of plant function,and the resilience effect was the best under moderate and heavy grazing.(3)At the community level,aboveground biomass significantly decreases with increasing grazing intensity,while average leaf dry weight,leaf area,leaf nitrogen content,leaf phosphorus content,and leaf N/P significantly decrease with increasing grazing intensity.Specific leaf area and leaf C/N significantly increase with increasing grazing intensity.Functional dispersion index FDiv and Rao secondary entropy index FD_Q were significantly different among the four grazing intensities and reached the maximum under heavy grazing.After stop-grazing,the aboveground biomass and functional diversity(CWM index)of individual traits showed positive responses on the whole,while the functional diversity(FD index)of species diversity and multiple traits showed negative responses on the whole,indicating that stop-grazing was beneficial to the restoration of meadow grassland and the effective utilization of natural resources,and increased the yield to some extent.The changes of plant functional traits and diversity with the increase of grazing intensity in Meadow Steppe under long-term grazing support the intermediate disturbance hypothesis and growth rate theory,indicating that reasonable grazing intensity can improve plant diversity and increase grassland productivity.After stopping grazing,the meadow grassland recovered well as the best under moderate and severe grazing intensity,indicating that the stopping grazing and recovery after high-intensity grazing is conducive to the effective utilization and protection of natural resources,and provides support for protecting the biodiversity of meadow grassland in Inner Mongolia and building a scientific management system.