Effects Of Grazing By Herbivores On Vegetation And Soil Characteristics Of Stipa Grandis Steppe In Xilinguole

Grassland ecosystem is an important part of terrestrial ecosystem and an key base for animal husbandry.In China,the grassland is not only the foundation of economic activities and human survival,but also the green barrier which can adjust the climate,prevent soil erosion and desertification.However,in recent decades,due to the unreasonable development and climate change,grassland degradation become an increasingly serious environmental problem.Grassland desertification and sandstorm which are attributed to overgrazing,severely impact grassland ecosystem health and the sustainable development of grassland animal husbandry.As an important pathway to utilize and manage the grassland,herbivores grazing can affect the structure and function of grassland ecosystem through foraging behaviors,trampling,feces and urine,etc.Nowadays,people often focus on the effects of grazing intensity on different grassland types,but few studies are conducted on the response of grassland ecosystem to different grazing pattern.It is of great theoretical and practical significance to research the differences and mechanisms for the impacts of different large herbivores on grassland ecosystem.The study was conducted in Stipa grandis Steppe in Xilinguole,and aimed to reveal the effects of grazing pattern on plant aboveground biomass,species diversity,and the soil characteristics.The main conclusions are as follows:(1)Different grazing treatments had different impact on the aboveground biomass and species diversity.The grazing significantly decreased the aboveground biomass,and there was no remarkable difference between different grazing treatments.The grazing treatments also decreased the Shannon-Weiner index and the Simpsion index and the Pielou index in the experimental sites,the Shannon-Weiner index and the Simpsion index in the sheep grazing plots decreased significantly;the Pielou index is lowest in the cattle grazing plots.This suggests that the single grazing has a negative influence on the vegetarians in Stipa grandis Steppe,but the effect of mixed grazing is minimal.(2)Soil properties had different response degree of different grazing treatments.Soil moisture of no grazing,the cattle grazing and sheep grazing treatments decrease significantly,except the mixed grazing treatment.There were no significant difference in the soil moisture between no gazing,the cattle grazing and the sheep grazing,but all of them were significantly lower than that of the mixed grazing experimental sites.This showed that the mixed grazing can maintain the soil water content in Stipa grandis Steppe better.The CO2 flux of no grazing and the sheep grazing reduced significantly,but it didn'tdecreased significantlyin the cattle grazing and the mixed grazing.Additionally,the CO2 flux in the grazing were significantly higher than that of no grazing.The soil organic carbon content and soil total nitrogen content and soil carbon/nitrogen ratio in all plots had no significant change.The soil organic carbon content increased the most for the mixed grazing treatment,in the cattle grazing and sheep grazing experimental plots,the soil total nitrogen content had a tendency to reduce,whereas it increased in the mixed grazing plots.The soil organic carbon content and the soil total nitrogen content and the soil carbon/nitrogen ratio have no obvious difference between all grazing treatments.This indicates that the grazing benefit the soil carbon cycle of Stipa grandis Steppe,and the effects of the cattle and sheep mixed grazing is best;the cattle grazing is against the increase of soil total nitrogen content,and the mixed grazing will promote the accumulation of soil total nitrogen content.The soil available nitrogen content had significantly increased in all grazing treatments.There is no obvious difference of soil available nitrogen content between grazing treatments.But in the short time,the increase is not significantly in no grazing,the cattle grazing and mixed grazing,except sheep grazing.This shows that the grazing has little influence on soil available nitrogen in Stipa grandis Steppe,but in the short time,the soil available nitrogen content is much influenced by the sheep single grazing.(3)There are certain interaction relationships between soil character factors,but there are no significant linear relations between vegetation and soil characteristics.Soil total nitrogen content increases with the increase of soil organic carbon content;soil CO2 flux is remarkably correlated linearly with soil available nitrogen and soil nitrate nitrogen;the linear relations between soil available nitrogen and soil nitrate nitrogen is also remarkable.In conclusion,grazing influences the grassland vegetation and soil,and this effect is relatedwith grazing pattern.The grassland vegetation and soil properties have different responses to grazing pattern,and some characteristic factors interact in grazing.thereby,different grazing pattern have different influences on grassland ecosystem structure and function.The experiment by studying the influence of different grazing pattern on Stipa grandis Steppe,and reveals that the single grazing and mixed grazing played an important role in maintaining the stability of grassland ecosystem structure and function,and enriches the research of the grassland ecology theory.The experimental conclusions also point out in Stipa grandis Steppe,the mixed grazing may realize the sustainable utilization and stable development of grassland,and provided evidence-based strategies for managing the adaptability of grassland.