Trade-off Analyses Of Grassland Ecosystem Services And Functions With Different Grazing Intensity

The Inner Mongolia Steppe plays an important role in livestock production,and it is one of the green ecological shelters for Northern China.Grazing is one of the most important management regimes in the Inner Mongolia Steppe.Enhancing some ecosystem services(provisioning services)may cause a reduction in other ecosystem services such as regulating and supporting services.There is lack of knowledge about how grazing intensity influence these trade-offs.Therefore,we conducted an experiment with four grazing intensities which include no grazing(CK),light grazing(grazing 3 days/month),moderate grazing(gazing 6 days/month)and heavy grazing(gazing 12 days/month)in the Inner Mongolia Steppe.The aims of this study are 1)to investigate the effects of grazing intensity on grassland ecosystem functions and services,including grassland aboveground biomass,plant growth biomass during the growing season,biodiversity index,hydrological cycle(soil water content and plant evapotranspiration rate)and carbon sequestration(soil organic carbon content,root biomass,soil respiration rate and net photosynthetic rate);2)to find out the optimized grazing regimes based on the multiple grassland ecosystem functions and services.The main results are as following:1.Grazing intensity significantly affected the provisioning servicesand functions.The community biomass and the dominant species biomass decreased with increasing grazing intensity.However,grazing intensity has different effects on plant growth biomass.For community net plant growth biomass and Stipagrandis growth biomass,light grazing could increase the plant biomass which exceed the biomass consumed by livestock,while moderate grazing could compensate these lost biomasses.However,for other species,such as Leymuschinensis andCleistogenessquarrosa,grazing could compensate the biomass loss in all kind of grazing intensities.2.Grazing intensity had significant effects on grassland regulation andsupporting services and functions.The diversity index and soil water contentdramatically decreased with increasing grazing intensity.On the country,evapotranspiration rate enhanced with increasing grazing intensity,but it is also affected by annual precipitation.There is no significant effect on root biomass and soil organic carbon.The soil respiration rate and the net photosynthetic rate varied greatly during grazing season and between different years.Precipitation and grazing interactions significantly influenced the soil respiration rate and the net photosynthetic rate.3.The three types of relationships(synergies,trade-offs and no relationship)between different ecosystem services all exist in this study.Such as the soil respiration rate wih net plant growth biomass,biodiversity with net photosynthetic rate acted as trade-offs relationship.Net plant growth biomass with soil water content,net photosynthetic rate,grassland evapotranspiration rate and biodiversity were synergistic respctiively.And the content of soil organic carbon was not related to other ecosystem services and functions.Grazing could weaken the conflicts between different ecosystem services.These conflicts vanished with the moderating grazing intensity.