Convergence of community composition during secondary succession on Zokor rodent mounds on the Tibetan Plateau

Aims The community succession theory is much debated in ecology.We studied succession on Zokor rodent mounds on the Tibetan Plateau to address several fundamental questions,among them:(i)During secondary succession,does the community composition converge towards one community state or multiple states depending on the initial colonization?(ii)Do mound communities located in different background communities exhibit different assembly trajectories?Methods In a sub-alpine meadow,we investigated a total of 80 mound com-munities at several successional stages in three different background communities resulting from different management histories and compared their changes in species composition.The distribution of plant communities over time was analyzed with quantitative clas-sification and ordination methods.The co-occurrence patterns of species were evaluated at each successional stage,and the degree of convergence/divergence among communities was obtained by calculating two beta-diversity indices.Important Findings During secondary succession,species richness of mound com-munities changed over time,and this change was dependent on the background community.Five life-form groups exhibited different dynamic patterns in species richness and plant cover.Community composition and the degree of species co-occur-rence between communities increased over time since disturb-ance.There was much variation in species composition at earlier stages of succession,but communities on older mounds became more similar to each other and to their surrounding vegetation over the course of secondary succession.Post-disturbance suc-cession of Zokor mound communities transitioned from‘multiple alternative states’to‘background-based deterministic commu-nity assembly’over time.Tradeoffs between competition and colonization,as well as the characteristics of different life-forms and mass effects within a limited species pool are the mecha-nisms responsible for convergence of mound communities.