Effects Of Grazing Disturbance On Biodiversity And Ecosystem Multifunctionality Of Alpine Meadow

The relationship between biodiversity and ecosystem multifunctionality is the core issue of ecology,The study on the change of biodiversity and ecosystem multifunctionality under different grazing intensity and the relationship between them will help to clarify the response mechanism of ecosystem multifunctionality to grazing intensity,and provide effective basis for the protection and rational utilization of alpine meadow.This study took the alpine meadow of Gannan as the research object,selected grasslands with no grazing,light grazing,moderate grazing and heavy grazing as the research sample,carried out field community investigation on the sample plots,collected plant leaves and soil samples,selected 7 functional traits sensitive to the changes of alpine meadow habitat and easy to measure,and calculated the weighted average value of community functional traits.Ecosystem multifunctionality was quantified by plant growth,organic carbon storage,water conservation and nutrient cycling,and the differences of species diversity,plant functional traits,functional diversity and ecosystem multifunctionality under different grazing intensities were compared.The relationship between biodiversity and ecosystem multifunctionality under different grazing intensity was analyzed based on species and plant functional traits.The main results are as follows:（1）When grazing intensity increased,Margalef index decreased,Simpson index,Shannon-Winener index and Pielou index increased first and then decreased,and the species diversity index was the lowest under heavy grazing intensity.Redundancy analysis results showed that Margalef index,Simpson index were positively correlated with soil organic carbon（SOC）,soil total phosphorus（STP）,soil water content（SWC）,and soil total nitrogen（STN）（P<0.05）.They were negatively correlated with soil bulk density（SBD）,electrical conductivity（EC）and soil p H（p H）（P<0.05）.SWC,SOC and STP were the main influencing factors of species diversity change under different grazing intensities.（2）Plant functional traits showed a significant response to grazing intensity.Plant height（PH）,leaf organic carbon content（LCC）and leaf total phosphorus content（LPC）showed a gradual decline when grazing intensity increased,while leaf dry matter content（LDMC）first decreased and then increased.The specific leaf area（SLA）and total nitrogen content（LNC）increased first and then decreased,while the leaf thickness（LT）increased with the increase of grazing intensity.Under grazing disturbance,PH,LCC,LPC,SLA and LNC were positively correlated（P<0.05）,while LT and LDMC were negatively correlated with PH,LCC,LPC,SLA and LNC（P<0.05）.Redundancy analysis of plant functional traits and soil physicochemical factors showed that LCC,SLA and PH were positively correlated with STN,SOC,STP and SWC,negatively correlated with EC,p H and SBD（P<0.05）,and LT was positively correlated with soil p H（P<0.05）.It was negatively correlated with STN,STP,SOC and SWC（P<0.05）.SWC,SBD and soil nutrient were the main factors affecting plant functional traits under grazing intensity change.（3）With the increase of grazing intensity,the functional diversity index of PH,SLA,LCC,LNC and LPC decreased,while the functional diversity index of LT and LDMC increased.The functional diversity of multiple traits decreased significantly with the increase of grazing intensity.The redundancy analysis of functional diversity and soil physical and chemical factors showed that functional diversity was positively correlated with STN,SWC,SOC and STP（P<0.05）,and negatively correlated with EC,p H and SBD（P<0.05）.Soil water content and soil nutrient were the main influencing factors of functional diversity under grazing interference.（4）With the increase of grazing intensity,plant growth function and organic carbon storage function increased first and then decreased,while water conservation function,nutrient cycling function and ecosystem multifunctionality decreased with the increase of grazing intensity.Based on species analysis of the relationship between species diversity and ecosystem single function and multifunctionality,the research results showed that species diversity was positively correlated with plant growth function,organic carbon storage function,water conservation function,nutrient cycling function and ecosystem multifunctionality（P<0.05）,and species richness had the higher explanatory rate for ecosystem multifunctionality.The relationship between weighted mean of community functional traits（CWM）,functional diversity and ecosystem single function and multifunctionality was analyzed based on plant functional traits.The results showed that the weighted mean of community functional traits was significantly correlated with plant growth function,organic carbon storage function,water conservation function,and nutrient cycling function（P<0.05）.PH_CWM,LCC_CWM and LPC_CWM were significantly positively correlated with ecosystem multifunctionality（P<0.05）,LDMC_CWM and LT_CWMwere significantly negatively correlated with ecosystem multifunctionality（P<0.05）.There was significant positive correlation between functional diversity and water conservation function,nutrient cycling function and ecosystem multifunctionality（P<0.05）.The variance decomposition analysis of species diversity,weighted mean of community functional traits,functional diversity and ecosystem multifunctionality showed that functional diversity had a higher independent explanation rate for ecosystem multifunctionality.The change of ecosystem multifunctionality under different grazing intensity was the result of the common influence of biodiversity.