Effects Of Grazing Types On The Community-weighted Mean Functional Traits And Ecosystem Functions In A Typical Steppe

The relationship between functional traits and ecosystem functions is a hot topic of ecological research.Community level traits are the bridge connecting individual plant functional traits and ecosystem functions.In grassland grazing ecosystem,how different grazing types affect community-weighted mean(CWM)functional traits,community composition,ecosystem functions and their relationships are still controversial.In this paper,four grazing experiments of no grazing,sheep grazing,cattle grazing and mixed grazing of cattle and sheep were used in Maodeng pasture of typical steppe in Inner Mongolia.In 2019 and 2020,21 individual traits of five dominant species and five ecosystem functions including above-ground biomass,below-ground biomass,Net ecosystem CO2 exchange(NEE),ecosystem respiration(ER)and gross ecosystem productivity(GEP)were measured.The responses of CWM traits,functional diversity and ecosystem functions to grazing types were analyzed,and the relationships between CWM traits and functional diversity and ecosystem functions were discussed.The main results and conclusions are as follows:1.Community-weighted mean functional traits had obvious responses to grazing.After grazing,CWM height decreased,specific leaf area increased,leaf dry matter content decreased,and nitrogen and phosphorus content increased.2.Grazing significantly decreased species diversity index,above-ground biomass and ecosystem carbon sequestration capacity.The underground biomass showed an increasing trend after grazing in 2019,and the increase of single grazing cattle was the largest(increase 602.91 g/m~2).However,the underground biomass decreased significantly after grazing in 2020,and the sheep grazing was the least(884.98 g/m~2).3.After Sheep grazing,the community-weighted mean height,carbon content,carbon nitrogen ratio,and above-ground biomass,carbon sequestration capacity of the ecosystem were significantly reduced,as well as the species in the community occupied more niche space after sheep grazing.Sheep grazing has a greater negative impact on the grassland.4.After grazing cattle(cattle grazing and mixed grazing by sheep and cattle),the community-weighted mean nitrogen and phosphorus content is significantly increased,which is conducive to the nutrient cycle of the grassland.The relationship between community-weighted mean traits and ecosystem functions was closer after grazing cattle(CG and MG).This potentially changes the regulatory role of community-weighted mean traits on ecosystem functions.The results of this study indicate that appropriate reduction of sheep grazing and increase of cattle grazing in typical grassland ecosystems can help maintain ecosystem versatility.This study can provide scientific basis for sustainable grassland management.