Remote Sensing Based Dynamic Monitoring And Evaluation Of Eco-environmental Change In Earthquake-striken Areas

The devastating Wenchuan Earthquake in May 12^th,2008 was rare around the world,which not only caused heavy damage to the national economy,people's lives and property,but also induced secondary geological disasters such as landslides,collapses,and mud-rock flows.These disaster processes resulted in the aggravation of regional water and soil erosion,reduction of biodiversity,incensement of resource consumption and the degradation of ecological functions,etc,which threatened the survival of humankind and the sustainable development of social economy.Due to the impact of earthquakes,secondary geological disasters and human activities,the recovery processes of damaged ecosystems are not synchronized in time and space.Therefore,under the guidance of new technologies,methods and concepts,the extraction of key parameters and quantitative retrieval of the ecological environment in the earthquake-stricken areas rapidly and effectively,establishing eco-environmental evaluation system for scientific evaluation of the study area and ascertaining the spatial characteristics and evolution laws of eco-environmental in earthquake-striken areas have practical and scientific significance to guide the dynamic monitoring of ecological environment in distress area and reconstruct scientific decision.The dynamic monitoring of ecological environment helps to select restoration measures rationally,to further adjust and improve restoration programs,and to provide scientific basis for the establishment of medium and long term ecological restoration measures.The dissertation chooses Beichuan County,a hard-hit area in the Wenchuan earthquake,as the research area.Based on the National Natural Science Foundation of China“Method of Remote Sensing Dynamic Monitoring of Vegetation Eco-water?layer?and Water Stress in the Western Sichuan Plateau”?grand No.41671432?and Sichuan Science and Technology Support Plan Project“Wenchuan Earthquake Disaster Recovery and Key Technologies for Ecological Restoration Research”?grand No.2011FZ0021?projects,together with field investigation of the ecological environment,with previous studies and with high generality,authenticity,systematicness and continuity of remote sensing images,this dissertation extracted and retrieved the key parameters of the ecological environment using the principles of3S technology,.In addition to eco-environmental evaluation,the eco-environment evolution in the research area is systematically studied.The main contents and innovation results of the dissertation are as follows:?1?According to the landmark features,combined with field surveys and thematic databases,the main land use?landscape?types in the study area are interpreted in detail using multi-temporal,multi-scale remote sensing data,,.Under the influence of earthquakes,secondary geological disasters,ecological restoration measures and socio-economic development,the land use of study area,the temporal and spatial changes of landscape pattern and mutual difference are studied.?2?In view of the importance of land surface ecological water?layer?to the restoration of ecological environment,the concept and theory of ecological water?layer?are introduced into the evaluation of ecological environment in earthquake-stricken areas.Based on the two-dimensional feature space method of Nir-Red,the measured soil moisture?W,thickness?and SMMRS linear regression models are constructed.A variety of spectral vegetation index and vegetation canopy water content?FMC?relationship models are established to select the best vegetation index?MSI?as the research data source,thus constructing a linear regression model of the measured equivalent canopy thickness?EWT_c?and MSI of the vegetation canopy.The dynamic changes of the ecological water conservation in the study area before the earthquake,the year during the earthquake and the recovery period are monitored quantitatively.?3?It is considered that ecological water conservation,soil erosion,vegetation coverage,land surface temperature,leaf area index and soil quality are the key parameters for the evaluation of eco-environmental in the research area.A P-S-R frame model was developed and improved based on the extraction of key parameters and quantitative retrieval of the ecological environment and combining with natural,social and economic data.An evaluation system of ecological environment in earthquake-stricken area was also established.Considering the interactions of the evaluation indicators,the internal circulation of hierarchical structures and the dependency and feedback between hierarchies,through the principle of ANP method,the Super Decisions model is constructed.The objective evaluation of eco-environmental in the research area conducted under GIS software,which provides a scientific basis for dynamic monitoring of ecological environment in earthquake-stricken areas and rapid understanding of eco-environmental status.?4?Regarding to the differences of Zone Type in the study area,the dissertation systematically studied the eco-environment changes of different units on the basis of eco-environmental evaluation,and further identified the changing relationship and influence mechanisms among natural factors,human activities,local conditions of ecological environment and the ecological environment.This dissertation also clarifies the main constraints that affected the restoration speed of the ecological environment,basically identified the key areas for dynamic monitoring and evaluation of the ecological environment in the earthquake-stricken areas in the future,and put forward the main recovery measures that should be taken in different restoration periods.From the perspective of ecological environment,this dissertation proposed a methodology of evaluation of ecological environment in earthquake-stricken areas with good results,which involved:the extraction of key parameters—data processing—quantitative retrieval of key parameters—the construction of index system—eco-environment evaluation.The results provide new ideas and methods for the dynamic monitoring and evaluation of eco-environmental in similar disaster areas,which provides a theoretical basis for the scientific and reasonable selection of rehabilitation measures,with great significance to the protection of ecological environment and the harmonious development of social economy after earthquake disaster.