Study On Risk Assessment Of Desertification Disaster In Xilin Gol Grassland

Desertification is one of the most important forms of land degradation in the Xilin Gol Grassland.It leads to the loss of available grassland resources and the reduction of biological production,which results in serious deterioration of the ecological environment.The predecessors have carried out desertification research for many years in the area,and most of the research results are to determine or evaluate desertification land types.However,the impact of desertification and its consequences are relatively few studied.Desertification disaster risk assessment refers to the possibility of the occurrence and development of desertification disasters and the possibility of loss.It not only emphasizes the natural intensity of disasters,but also considers the effects and harms of desertification,providing new ideas and directions for the quantitative study of desertification.Took Xilin Gol Grassland desertification was the object of study,from the perspectives of soil-vegetation-atmosphere-hydrological process and human activities,and guided by regional disaster system theory and natural disaster risk theory,desertification disaster risk assessment models was constructed by means of multi-source data,set pair analysis,grid GIS,optimal segmentation.Then,dynamic assessment and zonation of desertification disaster risk for the fourth phase of 1990,2000,2010 and 2015 in the study area was analysised,and the research division types and subregions were proposed.The aim is to provide scientific basis for the rational development and utilization of Xilin Gol Grassland and the implementation of anti-desertification measures in accordance with local conditions.(1)Characteristics of temporal and spatial evolution of desertification in Xilin Gol GrasslandUsing visual interpretation methods,Landsat TM images of 1990,2000,2010 and 2015 in the study area were respectively interpreted,and the area of desertified lands in four-phase and its transfer characteristics were calculated.The results show that Xilin Gol Grassland desertification experienced a process of development-reversion-slight reversion during the period of 1990-2015.The area of desertification accounted for more than 50% of the total area of the study area,and mainly dominanted by the slight desertified land.Spatially,the extent of desertification varies from high to low from southwest to northeast.(2)Effects of desertification on grassland soil and vegetationSoil and vegetation samples were collected at 13 sites in the Xilin Gol Grassland(including non-desertified lands and desertified lands in different degrees),and soil mechanical composition,pH,calcium carbonate and organic matter were measured in-house.The species diversity index,evenness index,and abundance index of vegetation communities were calculated using the statistics of abundance,coverage,and frequency in the vegetation plots.Finally,the above-ground vegetation biomass was statistically analyzed.The results showed that moderate and severe desertification resulted in an increase in soil sand content,powder and clay content,and moderate desertification only affects the content of soil sand;desertification will increase soil calcium carbonate content;the soil pH content in severe desertification land was higher,and mild and moderate desertification had no significant effect on soil pH;soil organic matter decreases with increasing degree of desertification;The diversity and abundance of vegetation species in severe desertified land was low,but the evenness of that was high;slight desertification only affected the single index of vegetation community characteristics;the above-ground biomass of moderate and severe desertified land has been reduced compared to the non-desertified land,and slight desertification has little effect on it.In short,the slight desertification has little effect on soil physical and chemical properties,vegetation community characteristics and biomass,and it occupies a dominant position in the desertification land in the study area.Effective management and prevention of desertification in the early stages of desertification can effectively suppress the occurrence and development of desertification and reduce the risk of desertification disaster.(3)Analysis on the factors of desertification disaster in Xilin Gol GrasslandBased on the regional disaster system theory and the formation mechanism of desertification disasters,this study identifies and analyzes the factors of desertification disasters in the Xilin Gol Grassland from three aspects: the disaster-causing factor,the disaster-bearing body and the disaster-breeding environment.The results show that the frequency and duration of drought in the study area increased significantly from the end of the 1990 s to 2017,and there was a serious trend of drought.and there was a serious trend of aridification;the number of sand driving windy days showed a downward trend;during the period of 1980-2000,both the livestock carrying capacity and the opening rate in the study area showed an increasing trend,and then began to decline;grassland is the most important land use method in the study area,accounting for more than 80% of the research area,followed by cultivated land;the population of Xilin Gol Grasslandshowed a linear increase,and the proportion of agricultural population was high;the economy is dominated by the secondary industry and the proportion of the primary industry is not high;the temperature in the study area showed a fluctuating upward trend,while the precipitation was contrary to it,but the magnitude of change of that is not significant.The western part of the study area is dominated by desertification grasslands,and the soil is mostly chestnut-calcium soil and semi-fixed sandy soil,which is prone to desertification.(4)Risk Assessment of desertification disaster in Xilin Gol GrasslandAccording to the theory of natural disaster risk,from the perspectives of the hazard of the disaster-causing factor,exposure and vulnerability of the disaster-bearing body,the risk assessment index system and evaluation model of desertification disaster in Xilin Gol Grassland was constructed by means of set pair analysis method,the entropy combined weighting method and grid GIS method and the fusion of meteorological data,remote sensing data,measured data,and socio-economic data.Then,the desertification disaster risk in 1990,2000,2010 and 2015 was dynamically evaluated and classified.The results show that the risk of desertification disasters in the study area experienced a process of increase-decrease-increase;spatially,the western part of the study area is prone to high and extremely high risks.The center of gravity of the extremely high risk level migrated from southern Zhengxiangbai banner to middle Sunite left flag banner.From the side,it was confirmed that the level of desertification disaster risk is increasing in the west.The extremely low and low risk level are mainly concentrated in the West Ujimqin banner,which also shows that the level of desertification disaster risk in the northeast part is relatively small.