Effects Of Grazing Intensity On Vegetation Community Characteristics And Soil Physical And Chemical Properties Of Typical Steppe

Excessive grazing has become one of the essential factors that cause the degradation of typical steppe in Inner Mongolia.In this regard,determining the appropriate grazing intensity of typical steppe has become an urgent research focus.This study was conducted to determine the effects of different grazing intensities on plant community characteristics,soil physical and chemical properties of the typical steppe in Xilingol,Inner Mongolia.The grazing intensities include no grazing(CK),light grazing(GI170),moderate grazing(GI340),heavy grazing(GI510)and extreme heavy grazing(GI680).Data was collected on species composition,quantitative characteristics,biomass and vegetation diversity,soil bulk density,soil porosity,soil water holding capacity and nutrients across the designated treatments.The relationship between vegetation and soil physical and chemical properties was investigated using correlation analysis.The study identified the appropriate grazing intensity that could help reverse degradation and enhance the productivity and health of Xilingol grasslands in the typical steppe of Inner Mongolia.The theoretical basis for the reasonable application of the appropriate grazing intensity in the typical steppe is provided.The main results are as follow:1.With increased grazing intensity,the dominant species changed from perennial grasses such as Leymus chinensis and Stipa grandis to annuals and biennials such as Eragrostis Pilosa and Chenopodium acuminatum.Grazing significantly reduced the total vegetation cover,height,and biomass(P<0.05).Community density was higher in the heavy grazing treatment compared to other treatments.The species and functional groups in the community responded differently to grazing intensity.Moderate grazing increased the important value and coverage of Stipa grandis,while the important values,height,and coverage of Leymus chinensis and Stipa grandis were significantly reduced under heavy grazing.In contrast,heavy grazing increased the important values and biomass of species such as Eragrostis pilosa and Chenopodium acuminatum.The highest species richness and evenness index of the community was recorded under moderate grazing compared to other treatments,which indicated the stability of the community structure.2.Medium grazing increased soil porosity,soil water content and soil water holding capacity,and significantly decreased soil bulk density.The soil aeration was best under moderate grazing,which was good for improving soil structure.However,the lowest bulk density in the deeper soil layer was observed for the extreme heavy grazing treatment.In addition,moderate grazing increased the total carbon,total nitrogen,and total phosphorus contents in the topsoil,but decreased in soil nutrients at the deeper soil layer.Grazing intensity had no significant effect on soil pH.3.Correlation analysis showed a negative association between soil bulk density,aeration,porosity and community quantity characteristics.However,soil moisture content,non-capillary porosity,and soil nutrients had positive correlations with community characteristics.There was no significant correlation between water holding capacity and community characteristics.Soil water content,bulk density,and soil nutrients were related to vegetation growth and distribution.Soil carbon and phosphorus play an important role in species growth and distribution.4.It was concluded that moderate grazing(GI340,340 SSU·d/hm~2·y)in typical grasslands of Inner Mongolia is a reasonable grazing intensity that could help reverse grassland degradation while promoting the productivity and health of the natural resource base.