| China is one of the countries suffering from the serious aeolian desertification in the world. Especially, the Northern China is the key area for research and prevention of the aeolian desertification. Although the government of China has been conducting too much research and taking many measures on aeolian desertification over half a century, it is still in a situation of local rehabilitation and overall deterioration. Furthermore, it is developing continuously and rapidly.Currently, research on desertification mainly concentrated on the determination or evaluation of the natural strength of desertification process and land desertification types. In these studies, the interactive relationship between the environmental hazards of desertification and the improvement of social and economic was not considered. On the other hand, there is lack of studies on the losses of ecological environment and human society which were resulted from aeolian desertification. Aeolian desertification is a typical disaster risk event derived from uncoordinated man-land relationship. Hence, research on ecological risk assessment provides new ideas and research methods to research on desertification.Horqin sandy land, the farming pastoral ecotone, is one of the most serious desertification zone and fragile ecological environment in Northern China. In this paper, a typical desertification area of Naiman Banner in Horqin sandy land is taken as the study area.The main conclusions of the study as follows:(1) Spatiotemporal evolution characteristics of the aeolian desertification in Naiman BannerWe interpreted of Landsat TM remote sensing images of 1980, 1990, 2000 and 2013 of Naiman Banner and obtained the different degrees of desertified land area in different times.The results show that the aeolian desertification in Naiman Banner experienced a process of reversion-development-reversion during 1980-2013. In 1980-1990, the aeolian desertification reversed, the area of desertified land reduced 207.58 km2. In 1990-2000, the aeolian desertification developed, the area of desertified land increased 60.25 km2. In 1990-2000, the desertification shows apparently reversal, increased by a total of 671.62 km2. In the space,aeolian desertification expanded to the northwest, and the land distributed in central and the middle-east of study area began to develop into desertified land during 1980-1990. In1990-2000, aeolian desertification in northern begun to reverse, but in the central region, the desertified land begun to increase. And in 2000-2013, the desertified area in central region reversed to the non-desertified land, and most of the land is converted to low-grade.(2) Desertification disaster risk assessment of Naiman BannerAccording to the natural disaster risk forming principle and the formation mechanism of desertification disaster risk, this paper established the desertification disaster risk conceptual framework. Based on the remote sensing images, meteorological data, laboratory data and socio-economic data, under the support of entropy weight method, fuzzy comprehensive evaluation method, comprehensive evaluation weighted method, grid GIS method and the optimal segmentation method, the assessment model of desertification disaster risk was established from the aspects of hazard, exposure, vulnerability and restorability. Then, the desertification disaster risk was assessed for Naiman Banner. The results show that the ratio of high risk is the highest, accounting for 28% of the study area, distributed with "S" shape. The moderate risk region accounted for 23% of the study area, which has the "S" shape distribution in the study area as well. Low disaster risk region accounts for 21% of the study area, mainly distributed in the mid-west and southwestern. Very high risk region is up to 18%of the study area and distributed in the northeast part. Very low risk region accounts for 10%of the study area and mainly distributed in the mid-west and southwest part.(3) Desertification ecological risk assessment of Naiman BannerAccording to the regional disaster system theory, natural disaster risk theory and landscape ecology theory, took field sampling, laboratory experiment and "3S" technology,fusion multi-source data of "space-based, ground-based and aero-based data", the principle of the DPSIR model and the mechanism of the influence factors of aeolian desertification, this paper establiashed conceptual model for aeolian desertification ecological risk and selected the indicators of desertification ecological risk. Then, factors of desertification ecological risk of Naiman Banner were evaluated by means of mutation progression method. With the help of comprehensive weighted evaluation method, the desertification ecological risk of Naiman Banner was evaluated as well. The results showed that and the single factors of driving force,pressure, state and response trends upward and the impact factors trends downward during1980-2013. Desertification ecological risk showed a decreasing trend, the area of the very high ecological risk zone reduced from 457.96 km2 to 48.31 km2, high risk zone dropped from2724.59 km2 to 780.04 km2, and it was indicated that ecological environment management of Naiman banner has achieved initial success over 30 years. Spatial distribution of gavity changes of aeolian desertification ecological risk in Naiman Banner shows that the desertification ecological risk increased from east to west, followed by the ranking of low risk,middle risk, very low risk, high risk and very high risk. What is more, it presents a convergence effect with the spatial distribution of aeolian desertification of Naiman Banner.(4) In the study, we deeply realiazed that field sampling survey method is needed to improve the basic data and more perfect space distribution model is required for the refinement of the socioeconomic data. Dynamic mechanism within the system must also be considered in the study of formation mechanism of regional desertification. If the perfectdisaster loss data is adopted in the process of empirical study, the scientific and credibility of the model can be improved, which may also improve the outcome of the study guide. |
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