| Inner Mongolia grassland,as a sensitive and fragile area to global change,can be easily degraded due to the co-interference of natural and human factors.As the carrier of comprehensively understanding the nomadic civilization,grassland cultural heritage relic areas,whose regional ecological environment has been severely damaged due to the climate change and human activities,are facing serious threats.Therefore,it is urgent to establish and improve the ecological risk assessment techniques and methods in grassland cultural heritage relic areas,and then to assess the ecological risks in the historical period of grassland cultural heritage relics,predict the ecological risks of the future under different emission scenarios,explore the impact of climate warming on ecological environment,and ultimately reveal the influence mechanism of multiple risk sources on the regional ecological environment in grassland cultural heritage relic areas.In this dissertation,the author adopted NDVI to characterize the ecological environment in grassland cultural heritage relic areas,carried out quantitative attribution analysis on the natural factors that affected NDVI(including precipitation,the average temperature,the maximum temperature and the minimum temperature)and the human activities(represented by LUCC)influence on ecological environment,and ultimately revealed the relationship of regional ecological environment,climate and Land-Use and Land-Cover Change(LUCC).With the combination of “3S” technology(i.e.,Remote Sensing,Geography Information Systems,Global Positioning Systems),this dissertation has constructed the regional ecological risk evaluation index system based on the regional ecological risk assessment theory,and adopted the multi-stage comprehensive fuzzy mathematical model to perform the risk evaluation for the ecological environments in the Genghis Khan Mausoleum,Xanadu of Yuan dynasty(1271 A.D.-1368 A.D.)and Ganzhuer Temple relic areas during the period of 1990-2015 so as to analyze the risk change reasons,put forward the corresponding management and control suggestions and countermeasures according to the regional risk differences.Combined with the global climate model,the ecological risks of these relic areas in the period of 2020-2045 under different emission scenarios have been estimated to explore the reasons of risk changes in the future,so as to provide scientific references for the regional sustainable development.The main conclusions were as follows:(1)The NDVIs of the Genghis Khan Mausoleum,Xanadu of Yuan dynasty and Ganzhuer Temple relic areas during the period of 1982-2016 all showed a trend of significant increase both on the annual and seasonal scale.This dissertation quantitatively distinguished the influences of climate elements and LUCC on the ecological environment in the relic areas on the annual scale,and found that the precipitation and the minimum temperature were the dominant climate factors affecting NDVI,while LUCC was the dominant human factor that affected the regional ecological environment through changing the underlying surface.On the annual scale,precipitation played a decisive role in the NDVI;while on the seasonal scale different climate elements had their respective optimum ranges for vegetation growth,and the growth of vegetation was controlled by both the precipitation and the temperature,and changed accordingly.(2)From 1990 to 2015,there were ecological risks in the above cultural heritage relic areas.And the ecological risk increased in the Genghis Khan Mausoleum and Ganzhuer Temple relic areas,while the ecological risk decreased in Xanadu relic area of Yuan dynasty.The warming and drying of climate,the decrease of soil moisture content and the increase of precipitation concentration resulted in the occurrence and aggravation of ecological risks in the Genghis Khan Mausoleum.In addition,the development of local tourism,mining and transportation industries had intensified the negative impact on the ecological environment.In Xanadu relic area of Yuan dynasty,the warming and drying climate changed the evapotranspiration there,and,meanwhile,overgrazing and grassland reclamation and other factors was accelerating the local degradation of grassland.In Ganzhuer Temple relic area,the warming and drying trend of climate had increased the vegetation's dependence on water and affected the stability of grassland ecosystem.The booming development of tourism and transportation industries,and overgrazing had damaged the ecological environment of the grassland.After 2000,Inner Mongolia implemented the ecological restoration measures,which,to a certain extent,mitigated the negative impact of human activities on the environment in the Genghis Khan Mausoleum and Ganzhuer Temple relic areas,thus reducing the ecological risk of some local areas,but the overall ecological risk was still at a high level.The restoration measures in Xanadu relic area of Yuan dynasty had improved the local ecological environment.And the increase of air temperature prolonged the vegetation growth season and reduced the occurrence frequency of low-temperature freezing injury.The ecological risk was reduced under the synergistic effect of these two factors.(3)Based on CDF-t method,the author has carried out the statistical downscaling for the 14 climate modes of CMIP5 and analyzed the climate changing trends of the above three cultural heritage relic areas under different RCP scenarios in the future.Under the RCP2.6,RCP4.5 and RCP8.5 scenarios,the overall changing rate of precipitation will show an increasing trend in the Genghis Khan Mausoleum,Xanadu of Yuan dynasty and Ganzhuer Temple relic areas from 2020 to 2045.All the temperature increasing rates of the average temperature,maximum temperature and minimum temperature can be more than 0.5°C per 10 years in these three relic areas under the RCP2.6,RCP4.5 and RCP8.5 scenarios.According to the constructed regional ecological risk prediction index system and the established evaluation model,the ecological risks in the three relic areas have been estimated under different RCP scenarios in the future,and all these three relic areas will be in severe risks under different scenarios in the future.The reason is that the precipitation concentration of these three areas will become larger in the future,and the temperature will rise by more than 0.5°C.The synergistic effects of extreme events and soil drying acceleration caused by the above factors can contribute to the intensification of local climate warming,thus making the damage to ecosystem continue to strengthen.The research achievements in this dissertation have enriched the ecological risk assessment methods and technical models for the grassland cultural heritage relic areas,and realized the long-term regional ecological risk prediction for the future in combination with the climate model,which can provide scientific basis and technical support for the protection and supervision of grassland ecological environment.It is of great scientific significance and practical value in understanding the causes of regional ecological risk,as well as its estimation and prediction. |
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