Effects Of Litter From Three Dominant Plants On Ecosystem Stability And Multifunctionality In An Alpine Meadow

Through physical and chemical processes like decomposition and leaching of plant metabolites,plant litter traits（type or mass）can affect ecosystem functions.Previous research has mostly focused on the effects of litter on belowground factors such as soil temperature,moisture,and nutrient cycling.Little attention,however,has been paid to litter impacts on ecosystem structure,stability,and function.Therefore,this study investigated the impact of litter from three plant species（Kobresia setchwanensis,Elymus nutans,and Ligularia virgaurea）that are dominant in three successional stages of alpine meadows on the QTP.The experiment included five litter mass levels(0,100,200,400 and 600 g m^-2)for each litter species.It systematically studied the regulatory mechanisms of litter addition on ecosystem stability and multifunctionality.The main research observations are as follows:（1）Litter mass greater than 200 g m^-2 significantly reduced species richness and the functional group dominance index of plant communities.The species evenness index was highest at 400 g m^-2.The impact of litter mass onβ_simp andβ_diss diversity varied with litter type.The plant communityβ_jacc diversity was lowest at 200 g m^-2 litter mass.L.virgaurea litter significantly decreased species richness,functional dominance index andβsimp diversity index of plant community,and significantly increasedβ_jaccdiversity index.Litter mass regulated theαdiversity of the plant community by changing plant functional group composition and plant canopy structure（coverage and height）.Changes to the plant community’sβdiversity under litter manipulation were driven by litter impacts on plant community coverage,species richness,and functional group niche breadth.（2）Litter manipulation of greater than 200 g m^-2 reduced the aboveground biomass of alpine meadow plant communities.The responses of aboveground biomass of grass and sedges to litter mass were not significant.The aboveground biomass of legumes was highest at 400 g m^-2,whereas for forbs,aboveground biomass showed a downward trend with increasing litter mass.Litter of L.virgaurea significantly reduced the plant aboveground biomass.Litter mass significantly impacted the grassland plant community productivity by changing the canopy structure,functional group composition,and diversity of grassland plant communities.（3）After an extreme rainfall event,the temporal stability and resilience of plant communities to extreme rainfall disturbances showed a hump-like response to the litter mass manipulations,with the highest response observed at 200 and 400 g m^-2.After the end of extreme rainfall,the resistance of plant communities increased with increasing litter mass.Litter manipulation below 400 g m^-2 reduced the resistance,recovery,and resilience of grasses,but improved its temporal stability.Litter mass directly influenced the biomass of plant functional groups,thereby regulating asynchronous of plant functional group.This indirect regulation of functional groups’ecological stability by litter mass ultimately drives the ecological stability of plant communities.Furthermore,species richness and coverage also played crucial roles as regulatory factors for the ecological stability of plant communities.（4）Manipulation of high litter mass levels(>200 g m^-2)reduced soil temperature,available phosphorus,and ammonium nitrogen,and increased nitrate nitrogen and soil pH.The minimum soil moisture content was detected under 200 g m^-2.The soil moisture content in the K.sichuanensis litter treatment was significantly lower than that in the L.virgaurea litter treatment.The soil temperature under the litter treatment of L.virgaurea was significantly higher than that of K.sichuanensis and E.nutans.However,the content of available phosphorus and nitrate nitrogen in the soil was opposite.Soil ammonium nitrogen was significantly lower in the litters of K.sichuanensis and L.virgaurea than in the litters of E.nutans.The K.sichuanensis and L.virgaurea litter had a significant impact on soil bacterial composition and the spatial variability of the bacterial community.Soil bacterialαdiversity was not impacted by litter manipulation.The composition and spatial variability of soil bacteria were driven by plant litter through indirect effects of the physical and chemical properties of the soil on the plant community.（5）The ecosystem multifunctionality of alpine meadow declined as litter mass manipulation increased.A critical threshold for regulating ecosystem multifunctionality was observed at 200 g m^-2 litter mass,with a significantly higher response to L.virgaurea litter compared to E.nutans litter.Soil pH and soil temperature responses to litter manipulation were the key driving factors for ecosystem multifunctionality.In addition,the responses of plant community coverage and aboveground biomass of sedges and legumes to litter manipulation were crucial regulating factors for the ecosystem multifunctionality of an alpine meadow.In conclusion,maintaining an optimal level of litter mass(≤200 g m^-2)can support species richness and aboveground biomass of the plant community,leading to enhanced temporal stability and a high level of ecosystem multifunctionality.Therefore,optimizing management measures for alpine meadows and effectively regulating litter accumulation are of great significance for maintaining greater ecosystem stability and multifunctionality.This study has made a valuable contribution by providing important data for exploring the potential role of litter in regulating grassland ecological functions and structural stability,and provided a theoretical basis for formulating sustainable grassland management strategies.