Effects Of Grazing Intensity Regulation On Community Characteristics And Stability Of Stipa Breviflora Grassland After Rest Grazing

The Stipa breviflora desert steppe has the characteristics of transitional ecological geographical position,vulnerability and sensitivity to external disturbance.With the influence of grazing disturbance and global warming,the sustainable utilization of desert grassland has attracted extensive attention of researchers.The stability index of plant community is one of the important indicators to evaluate the sustainable use of grassland.Based on dominant populations,functional groups(life-form functional groups and grazing response functional groups),and plant communities,the relationship between their quantitative characteristics and stability index is discussed,respectively.It can not only reflect the degree of stability of plant communities in grazing grassland,but also reveal the degree of influence of dominant populations on the stability of plant communities.Meanwhile,it can analyze the influence of functional group differences of grassland plant communities on the stability of plant communities,and then systematically explain the multidimensional and complex of maintaining the stability of plant communities.Therefore,the research results provide a theoretical basis for the rational and sustainable utilization of desert grassland.This research was conducted on the field positioning observation platform of Inner Mongolia Agricultural University in the desert steppe of Stipa breviflora in Hadeng Hushu village,Hantala Town,West Sunite banner.A grazing experiment with a complete randomized block design with 3 treatments and 3 replicates,making a total of 9 plots,was established.The treatments were 3 levels of grazing: CK(control area),SA1(spring rest grazing + summer grazing + autumn suitable grazing)and SA2(spring rest grazing +summer suitable grazing + autumn grazing).In this study,all experimental data was measured in in the 2018 growing season and in July 2019 and 2020.The measured indicators include dominant populations(e.g.Stipa brevis/Stipa breviflora,Cleistogenes songorica,and Allium polyrhizum),functional groups,plant community height,coverage,density,aboveground stock(the species diversity of plant communities and the stability of each tissue level).Analysis of variance,factor analysis,canonical correlation analysis and other statistical analysis methods were used to study the effects of grazing intensity regulation after rest grazing on community characteristics and stability of Stipa breviflora steppe.The results were as follows:(1)Whether within the growing season or between years(2018-2020),the performance of dominant populations,functional groups,and plant community quantitative characteristics in the SA1 treatment is close to or even better than that in the CK treatment;Meanwhile,the interspecific compatibility between the dominant plant species in the SA1 treatment and the CK treatment is also relatively close;the position of dominant species in the community is still dominant,but the process of dominant community stability is not consistent.(2)Whether in the growing season or between years,the important values on the functional groups of perennial grasses play a vital role in the community;Shrubs and subshrubs functional groups are bridges and ties between the quantitative characteristics and stability of each functional group;Functional groups of annual or biennial plants may have special significance in combating grazing disturbances.(3)Under seasonal dynamics,the absolute dominant populations and grazing sensitive species have higher important values in CK treatment,while the absolute dominant species and grazing insensitive species occupy the dominant position in SA1 and SA2 treatment;Grazing is beneficial to plant communities in the SA1 treatment.Under the interannual change,the SA1 treatment can not only maintain the absolute dominant species importance value close to the CK treatment to the maximum extent,but also ensure that the grazing insensitivity species importance value is relatively stable between years.There was a high similarity in the affinity and stability between grazing response functional groups in the SA1 and SA2 treatments during grazing years and seasons.(4)The basic quantitative characteristics of plant communities in the SA1 treatment are superior to those in the SA2 treatment both in terms of seasonal dynamics and interannual changes.The number of species in the growing season and the Shannon Wiener species diversity index in the three treatment showed CK>SA1>SA2,while the Simpson dominance index and Pielous evenness index generally showed SA2>SA1>CK.The grazing and utilization patterns in the interannual SA1 treatment are conducive to the improvement of species diversity of grassland plant communities and the stability of interannual plant communities,and there is a high correlation between the ecological stability of plant communities and the Shannon Wiener diversity index.(5)During the growing season,the plant community is mainly composed of shrubs,semi-shrubs,and annual and biennial plant functional groups.The basic quantitative characteristics of each level of the plant community are related to their stability at each level;interannual plant communities can establish relationships through dominant populations,functional groups,and even the overall plant community,forming a complex network of basic quantitative characteristics at each level of plant community and their stability at each level;whether in the growing season or between years,the interspecific compatibility of plant communities in CK and SA1 treatment is close and stronger than that in SA2 treatment.In summary,the adoption of the grazing management types in the SA1 treatment(spring rest grazing+summer heavy grazing+autumn suitable grazing)for desert grasslands is beneficial to the quantitative characteristics of various organizational levels of plant communities and the maintenance of stability of plant communities.This way of maintaining stability is reflected in the dominant role of dominant populations and the species diversity insurance hypothesis.Therefore,the multi-dimensional mechanism for maintaining plant community stability in the SA1 treatment ensures the anti-interference and tolerance of the desert grassland,thereby ensuring the sustainable utilization of the grassland.