Soil Erosion Dynamics Induced By Natural And Anthropogenic Forcings And Its Regionalization Application

Soil erosion is the result of both natural forces and anthropogenic factors, soil erosion regionalization is the key to soil erosion prevention. The soil erosion regionalization and prevention have been based on natural forces for a long time, ignoring the impacts of the differences in human activities. Particularly, with the fast socioeconomic development in China, human activities, compared with natural forces, affect soil erosion faster, more frequently, and more intensively in a short period, and can no longer be ignored. Therefore, it is vital to characterize regional soil erosion and the driving forces, quantify the relationship between soil erosion and natural forces and human activities, evaluate the extent and the direction of the impacts of human activities on soil erosion, and provide measures to regionalize and prevent soil erosion based on the extent and the direction of the impacts of natural forces and human activities on soil erosion.This research evaluated the combining effect of environmental and socioeconomic factors at large scale, and established a set of basic indicators to soil erosion at regional scale. The driving factors for soil erosion were selected using the Partial Least Square (PLS) regression models. Furthermore, this research quantified the relationship between soil erosion and the impact factors, and analyzed the variations and the spatial patterns of soil erosion and the impact factors. This research, conducted in Hubei province, aims to analyze the impacts of spatial and temporal change of man-induced disturbance on soil erosion and apply results to regionalization and prevention of soil erosion, in order to provide scientific evidence for characterizing and controlling soil erosion at regional scale. Below are the conclusions from this research.1. The spatial distribution of soil erosion in Hubei province was in agreement with topography, with serious soil erosion in mountainous area, less serious soil erosion in hilly area, and least soil erosion in plains. Overall, in2006and2000, the area suffered from moderate and serious soil erosion significantly decreased in comparison with the soil erosion area in1995. The area of mild soil erosion decreased in2006, but the area of serious soil erosion increased by588km2. The spatial distribution of soil erosion was variable. Overall, the area of soil erosion decreased by5-20%in the western and eastern Hubei province, and the intensity decreased as well. However, the soil erosion in hilly areas was deteriorated, and the area of soil erosion increased by5-20%in some areas, and average modulus increased1000t/(km2-a) above.2. The regional topography was a long-term and stable factor for soil erosion, but the impacts of human activities on soil erosion was increasing. Socioeconomic activities and soil erosion were restricted by topography, and thus demonstrated an agreement with the spatial distribution of topography. The PLS model for the impact factors of soil erosion was based on the topographic, hydrologic, and precipitation factors and the human factor, which was the combination of multiple socioeconomic indicators. The factors related with soil erosion were evaluated for each time period. The spatial auto-correlation and hotspot analysis revealed that these socioeconomic factors were affected by topography, agreed well with the spatial distribution of topography and soil erosion. Although topography is a primary factor for soil erosion, the impact of human activities is increasing. Compared with2000, the importance of topography was decreasing in2006, but the impact of human activities was increasing.3. Human activity is the driving force for the change of soil erosion in a short time period due to the national macro-control policy.The number of human-activity indicators increased, and different factors demonstrated different spatial distribution. With the impact of human activities, in a short time period, soil erosion deteriorated faster in mountainous area with higher slopes than in hilly areas. During studying period, industrial structure (proportion of the primary industry), economic development (the gross income of rural residents), soil and water conservation, and road construction had strong impacts on the change of soil erosion.4. Hubei province was divided into six primary sub-regions according to topography and precipitation. Based on the properties of soil erosion and the driving forces in primary sub-regions, the sixteen secondary sub-regions were developed. Based on regional natural conditions and the change of socioeconomic characteristics on soil erosion, optimal situations and possible strategies for ecological restoration for the targeting area were proposed. The characteristics of soil erosion dynamics in sub-regions were analyzed, and the driving force model was built for each sub-region. I found that the accuracy of simulation of sub-regional model was better than the model for the whole Hubei province, and the driving factors were strongly correlated with regional economic development, industrial structure, and policies. Factors that can reduce soil erosion include soil and water conservation, afforestation, improvement of living standards and energy structure in rural area, while the inappropriate utilization of resources, construction, and urbanization can accelerate soil erosion. The deterioration of soil erosion in Qingba Mountainis was mainly caused by industrial development. In ErYu Mountainis area, the increase in cultivation of agricultural products and the construction of infrastructure accelerated soil erosion, In Nanyang Basin and Dahong Mountain area, growing agricultural products in Nanyang basin reduced soil erosion, but in Dahong Mountain area farmland cultivation accelerated soil erosion. What worth noticing is that the urbanization and industrial development caused the serious soil erosion in Jianghan Plain area. In Tongbo Mountain area, human disturbances, such as the increase in cultivation of animals and agricultural products as well as the increase in the income of rural residents, accelerated the soil erosion in this area.In Dabie Mountain, the increase in population and infrastructure construction accelerated soil erosion. In Mufo Jiulin Mountain area, the measures taken to control soil erosion were effective, but the soil erosion in areas with large industry and agriculture proportions might be deteriorated without effective soil and water conservation.The highlights of this research include:1. this study analyzed the impact of human activity dynamics on soil erosion at large scale and based on the combination of multiple socioeconomic indicators, and applied results to regionalization and prevention.2. PLS model quantified the relationships among the soil erosion indicators, environmental factors, and socioeconomic factors. This method not only overcomes the shortcomings of traditional regression analysis, but also is more objective and general than the expert scoring.3. Primary factors were selected using PLS model, and the differences in spatial distribution of soil erosion and the impact factors were illustrated using local analysis advantages of GWR.