| As one of the most significant factors of the loss of land resources,soil erosion has been an international ecology problem,which has already produced some adverse impacts on human life and society development.Li County was taken as an example,where with intense soil erosion because of its complex landform and high-frequency geological disasters.Its surface structure and vegetation were damaged more extensively in and after Wenchuan earthquake in 2008.Although Li County has been gradually reconstructed and developed in recent years,the violent soil erosion is still generating negative effects on the process of economic development,which would last for several years or longer.Therefore,it is necessary to do some quantitative research on soil erosion in this area.The soil erosion in Li County before and after the Wenchuan earthquake was simulated and predicted to provide a basis for soil protection in the future.Landsat satellite data in Li County was used as an important data source to complete the remote sensing image pre-processing process through radiation calibration,atmospheric correction and geometric correction.On the other hand,the object-oriented classification method was applied to extract land utilization data in the research area,and the vegetation management factor C was extracted through linear spectral hybrid analysis method combined with the remote sensing data.Furthermore,the RUSLE model was used to simulate the soil erosion in Li County in 2003,2008 and 2014.The spatial distribution of soil erosion was studied by combining the GIS analysis method,and the correlation analysis of influencing factors was carried out.Finally,the CA-Ann-Markov model was established to predict the future soil erosion and put forward some pertinent governance suggestions.Here are the main understandings of the study as follows:(1)The spatial distribution of soil erosion in Li County was almost similar from 2003 to 2014.The spatial distribution of soil erosion was strongly correlated with elevation,slope,distance from rivers and vegetation types.The most serious soil erosion occured at 30-40 degrees,2000-4000 m above sea level,less than 1 km away from the rivers and forest vegetation types.(2)The soil erosion in Li County changed extremely obviously from 2003 to 2014,and the total amount of soil erosion had been constantly increasing.The area of micro soil erosion decreased first and then remained basically unchanged,the area of mild erosion tended to decrease linearly,the area of moderate erosion shows the trend of linear growth,the area of intensity,extreme intensity and severe erosion all increased first and then decreased.(3)The earthquakes in 2008 caused mass destruction to the ecological environment of Li County.Shortly after the earthquake,soil erosion above the intensity level occurred dramatically.Also,geological hazards of various scales took place from time to time,which caused the continuous moderate soil erosion.Large-scale geological hazards generally occurred in the areas where soil erosion changed tremendously.(4)It can be shown from the simulation results that the trend of soil erosion in Li County from 2014 to 2020 is basically the same as that from 2008 to 2014.The total amount of soil erosion increases,the area of micro and mild erosion increases,and the area of intensity,extreme intensity and severe erosion decreases.(5)The spatial and temporal change of soil erosion in Li County is affected by many factors,such as earthquake,rainfall,slope,vegetation and so on.Therefore,the control needs to be adapted to local conditions.The areas with poor soil quality and the areas prone to geological disasters are the focus in the future. |
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