Responses Of Rodent Dominant Populations To Different Grazing Disturbances And Nutrition Niche In Typical Steppe

With the excessive use on the grassland,the grassland has been degraded.Rodent as an important element of grassland ecosystem,the degradation of grassland contribute to the population of rodents increased gradually,and contributed to the occurrence of rodent pest.Therefore,studying response of rodent dominant populations to different grazing disturbances and nutrient niche of rodent is of great significance for protecting grassland ecosystem.An experiment adopted a randomized block design with 3 blocks and five treatments,including continuous grazing(CG),monthly grazing(MG),seasonal grazing(QG),over grazing(OG)and grazing exclusion(GE)was conducted in Xilin Gol typical steppe from 2014 to 2018.Rodent population under grazing exclusion and different grazing methods was investigated using live trapping.At the same time,the index of plant characteristics in each grazing area was investigated and analyzed by sample method.The stable isotope technique was used to study the nutritional niche of rodents.The results showed that:1.In all five grazing treatments,the capture rate of the Lasiopodomys brandtii was the highest(33.33%for OG,33.33%for CG,50.00%for QG,52.87%for MG,64.67%for GE);The population of Lasiopodomys brandtii increased significantly in 2017 and 2018,while the population of other rodents decreased.2.In all five grazing treatments,there was a significant positive correlation between the population of Lasiopodomys hrandtii and the density of vegetation.The population of Spermophilus dauricus was significantly negative correlated with vegetation density and aboveground biomass.The population of Cricetulus barabensis and Phodopus sungorus was mainly positively correlated with vegetation height and vegetation aboveground biomass.3.The nutrient niche of Cricetulus barabensis and Allactaga sibirica were overlap partially,and the other rodents showed a separation in nutrient niches.4.The nutritional niche of Lasiopodomys brandtii in different age groups were not separate.The content of δ13C in different tissues was different,the order from high to low was:bone tissue(δ13C Ⅱ=-22.591‰,δ13CⅢ=-22.196‰,δ13C Ⅳ=-22.455‰)>fur(δ13C Ⅱ=-23.053‰,δ13CⅢ=-22.882‰,δ13CⅣ=-23.163‰)>muscle tissue(δ13CⅡ=-23.842‰,δ13CⅢ=-22.572‰,δ13CⅣ=-24.252‰)>liver tissue(δ13CⅡ=-23.843‰,δ13CⅢ=-22.591‰,δ13CⅣ=-24.340‰);The order of the content of δ15N from high to low was:liver tissue(δ15N Ⅱ=6.247‰,δ15N Ⅲ=6.383‰,δ15N Ⅳ=6.193‰)>muscle tissue(δ15N Ⅱ=5.746‰,δ15N Ⅲ=5.498‰,δ15NⅣ=5.212‰)>fur(δ15Ⅱ=4.953‰,δ15NⅢ=4.892‰,δ15N Ⅳ=4.899‰)>bone tissue(δ15NⅡ=3.640‰,δ15NⅢ=3.861‰,δ15NⅣ=3.596‰).