Study On Drought Disaster Monitoring And Risk Assessment In Xilingol Grassland

In order to further improve the drought disaster monitoring and disaster prevention and mitigation capacity of Xilingol grassland, 3S technology combined with the methods of field investigation, mathematical modeling, social and economic statistical data analysis and natural disaster risk assessment were used in the thesis to study on drought disaster monitoring and risk assessment of Xilingol grassland. Research results showed that:(1) In recent 54 years(1961~2014), the annual precipitation of Xilingol grassland was decreased, the rate of climate change was-1.46mm/10 a, the precipitation of summer, July and August all showed downward trends. Summer accounted for 66.4% of the whole year, July and August accounted for 50.0% of the whole year, the decline of the annual and summer precipitation were mainly caused by the downward of July and August. In the space, 200 mm precipitation line was fluctuated in the east and west in different ages. The annual, seasonal and monthly temperature all showed upward trends, the rate of climate change was 0.41°C/10 a, the area of the annual average temperature above 2°C was increased gradually, 2°C temperature line was advanced toward the northeast with small amplitude.(2) In recent 15 years(2000~2014), the annual dynamics of evapotranspiration(ET) showed that ET of meadow steppe fluctuated in 250 mm, ET of typical steppe, sandy vegetation and the whole were fluctuated in 200 mm, and ET of desert steppe fluctuated in 150 mm. From seasonal dynamics, ET of meadow steppe, typical steppe, sandy vegetation and the whole were summer and autumn > winter and spring, but desert steppe was autumn and winter > spring and summer. From monthly dynamics, ET of meadow steppe, typical steppe, sandy vegetation and the whole were the highest in July and August, while the desert steppe was the highest in November and January, and the lowest ET of all types of grassland appeared in May.(3) Soil volumetric moisture was highly correlated with evapotranspiration deficit index(ETDI) which calculated from the actual ET and potential evapotranspiration(PET), based on the correlation analysis result, the soil volumetric moisture(SVM) inversion model was established: SVM=-48.851×ETDI+54.669(R2=0.62, RMSE=2.75%), the validation accuracy was RMSE=3.27%, the model has reached the application level of the rapid inversion of soil volumetric moisture in the region.(4) In recent 15 years(2000~2014), the annual drought dynamics in Xilingol grassland showed that meadow steppe was basically no drought, typical steppe, sandy vegetation and the whole grassland were basically light drought, and desert steppe was basically severe drought. No drought area and severe drought area showed increasing trends in recent 15 years. On month scale, during the regreening stage of April and May especially in May, the drought of meadow steppe, typical steppe, desert steppe and sandy vegetation were more serious, basically were moderate or severe drought. The drought of meadow steppe, typical steppe and sandy vegetation were mitigated in June, and almost no drought or light drought during the period of exuberance of July and August, and the drought further mitigated during the period of withering of September and October. Desert steppe was almost moderate or severe drought from April to October. Severe drought area of April and May showed upward trends in recent 15 years,so Xilingol grassland needed to pay more attention and strengthen the prevention of drought during regreening stage.(5) Main community changes analysis showed that, Gramineae dominance was significantly increased, Compositae dominance and the relative weight of Legumes showed decreasing trends in meadow and typical steppe.Gramineae species aggregation degree increased and the number of individual plants was uneven in the community in meadow steppe and typical steppe.Gramineae and Compositae dominance were decreased while other species dominance increased in desert steppe. The species richness and the number of plant families, generas and species were decreased in typical and desert steppe. Species vary greatly with low similarity in different types of grassland.(6) The difference of the drought disaster risk was large in banners, among them the drought disaster risk was extremely high in Erenhot city, and high in Sunite right banner, Sunite left banner and Xianghuang banner, and moderate in Abag banner, Xilinhot city and Zhengxiangbai banner, and low in East Ujimqin banner, West Ujimqin banner and Zhenglan banner, and extremely low in Duolun county and Taibus banner. In recent 11 years(2003~2013), drought disaster risk decreased in East Ujimqin banner, West Ujimqin banner, Abag banner and Xilinhot city, and increased in other banners, counties and cities.