Effects Of Plant Diversity In Inner Mongolia Steppe And Simulated Soil Moisture On Ecosystem Functioning

Studying on the relationship between biodiversity and ecosystem function has become one of the main topics in the field of ecology due to the biodiversity loss in the context of global change.However,to date,how plant diversity at inter-and intraspecific levels interactively affect ecosystem functioning and how such effects are regulated by climatic factors remain unexplored.We conducted a three-factor microcosm experiment using typical grassland common species in Inner Mongolia as study materials to assess how soil moisture(drought and non-drought conditions),species diversity(2,4 and 7 species)and genotypic diversity(1,3 and 6 genotypes)of the constructive species Leymus chinensis affect ecosystem functioning directly or indirectly by regulating plant community functional structure [community weighted mean trait values(CWM)and functional dispersion(FDis)] and soil microbial diversity(Shannon-Wiener index).The main results were shown in the following.(1)The genotypic diversity of L.chinensis and species diversity interactively affected ecosystem functioning.The interaction of soil moisture,species diversity and genotypic diversity of L.chinensis had significant effects on soil acid phosphatase activity,soil N,P cycle,soil multifunctionality and soil microbial diversity.Soil moisture significantly affected soil total C,soil total N,soil ammonium nitrogen,soil nitrate nitrogen,soil available phosphorus,biomass,soil C cycle,CWM and soil microbial diversity.Species diversity significantly affects soil β-glucosidase activity,soil ammonium nitrogen,soil nitrate nitrogen,soil urease,soil acid phosphatase activity,soil N cycle,CWM and FDis.Genotypic diversity of L.chinensis significantly affected soil β-glucosidase activity,soil total N,soil available phosphorus,soil acid phosphatase activity,aboveground biomass,soil C,N,P cycle,soil multifunctionality and soil microbial diversity.(2)Community functional structure and soil microbial diversity regulated the indirect effects of plant diversity on ecosystem functioning.The cascading effect of genotypic diversity in L.chinensis and soil microbial diversity had a significant effect on underground biomass.CWM regulated the responses of all ecosystem functions observed in this study(except soil N cycle)to the changes in soil moisture and species diversity,which supports the mass ratio hypothesis as a dominant mechanism to explain the relationship between community functional structure and ecosystem functioning.This study demonstrates the importance of genotypic diversity of the constructive species L.chinensis in affecting belowground ecosystem functioning and soil microbial diversity,which has significance for grassland conservation and management.In addition,the results provide a new insight into the relationship between biodiversity and ecosystem functioning and mechanisms accordingly in arid and semi-arid grasslands in the context of global climate changes.