Study On The Dynamic Relationships Between Ecosystem Multifunctionality And Functional Diversity Of Different Trophic Groups Driven By Grassland Management

Global threats of land-use intensification to biodiversity have motivated considerable research directed towards understanding the relationship between biodiversity and ecosystem functioning（BEF）.Most previous BEF studies focus on the classical biodiversity measurements（species richness or the diversity indices such as Shannon-Weiner）and one or a few ecosystem functions,such as productivity,litter decomposition or soil nutrient cycling.However,there is growing evidence that functional diversity（FD）is often more important to ecosystem functions than species diversity measures,and that ecosystems are valued for multiple ecological functions that they provide simultaneously（i.e.,multifunctionality）.Additionally,most tests of the BEF relationship have been conducted in highly controlled plant communities,while the terrestrial animal communities are less known and the combined effects of above and below-ground biodiversity on ecosystem multifunctionality are largely unexplored.Therefore,based on a long-term grassland experiment in the typical steppe region of Inner Mongolia,this paper examined the variations of taxonomic diversity（TD）,functional traits（CWMs）and functional diversity（FD）of both plant and arthropod communities and ecosystem multifunctionality,across four land management types（all growing-season grazing,spring&summer grazing,mowing and enclosure）,and explored the interrelations among plant and arthropod diversity,soil factors and grassland productivity,and the relative importance of direct and indirect（through mediating plant and arthropod diversity）effects of land-use and precipitation inter-annual variation on plant and arthropod productivity.The results showed that:1.Moderate grazing increased plant diversity and ecosystem multifunctionality,but decreased arthropod diversity and community productivity,whereas fall mowing provided a viable management strategy for conservation of both trophic levels and ecosystem functions.2.Ecosystem multifunctionality was positively related to plant diversity,and plant and soil microbial diversity combined explained a much greater（62.5%）proportion of variance in multifunctionality than that did either component alone（40.2%for plant,7.6%for bacterial,and 0.4%for fungal diversity）,across all management types.3.Grassland productivity was positively interrelated with plant FD,but not plant TD;and was negatively interrelated with arthropod TD,but not arthropod FD across different management types.The respective positive versus negative bi-directional relationships of productivity with plant diversity versus arthropod diversity,were majorly a consequence of divergent grazing/mowing effects on plant versus arthropod diversity.4.Moderate grazing and plant growing-season precipitation（PGP）enhanced plant productivity mainly via indirectly increasing plant functional dispersion（FD）and decreasing plant nitrogen concentration(CWM_NC)associated with the shift in dominant species,but reduced arthropod productivity majorly by direct grazing damage and less importantly by indirect mediation of arthropod body size(CWM_BS).Meawhile,management and precipitation-induced changes in functional traits and diversity,not species richness,were crucial predictors for their effects on plant and arthropod productivity.These results provide new evidences and insights into the effects of land-use changes on biodiversity and ecosystem functions and their interelations,and deepen our understading of the mechanisms underlying the ecosystem changes.The results also indicate it critically important to incorporate functional trait changes in multiple trophic groups in conservation and sustainable management of grasslands.