| Soil erosion has become a hot discussed question which our country government and the populace faces, and also is one of hot topics which the international front field. Because of the special geology background and precipitation of karst region, the result is that many places suffer from serious soil erosion and a deteriorated ecological balance and many people living in poverty.In karst region, rock types mainly on limestone and dolostone, they're among carbonate. This kind of rock has the characteristics of hard and strong weather resistance, the existence of such features determines that soil environment of karst region, combined with slope is high and steep and soil formation rate is very low, these caused some problems such as soil infertile and vegetation growth difficulties, Therefore, the quality of the soil have a mutation mainly by soil erosion and creates serious impact and destruction for agriculture ecological environment and agriculture productivity, and they are becoming the dominant factors which restrict the development of agricultural in karst region. So, by knowing the conditions and rules of soil erosion will have very important scientific guidance value for controling soil erosion, degradation and the improvement of ecological environment in karst region, therefore, how to correctly estimate and evaluation soil erosion situation has important significance on the evaluation of soil erosion and land productivity, the implementation of small watershed water and soil conservation planning and identifying the key factors of soil erosion.But,the government and relevant departments didn't given enough attention to water and soil loss in karst region for a long time. Mainly it is because in the past research, people often use soil and water loss evaluation standard of non-karst region, due to soil erosion modulus generally low in karst region, so that obtain homologous conclusion that soil erosion is a slight in karst region.This is a longstanding myth. According to soil erosion classification classification standard issuedby Ministry of Water Resources(SL190-2007) in 2007, the lower limit of indicators of light erosion is different from region to region due to differences of the amount of soil erosion in the different types of soil erosion, the total was now 500 t km-2 year-1 in karst region. From the current research results we can know that the average soil erosion modulus in the karst region is generally below1000 t km-2 year-1, if we judged according to the unification of the above indicators can be discovered that the level of soil erosion is within the mild erosion level, but according to field investigation and research, Soil erosion has done great harm to local ecological environment and agricultural production, Such as: The problem of rocky desertification. Rocky desertification make the area easy to incur flash floods, landslides and debris flow, combined with karst development, it is more likely to initiate the disters of water and drought often occurs and cause a series of eco-environment problems, because of soil erosion caused by desertification problem, not only bring about a loss of productivity, but also formed the vicious circle, these created a range of issues such as: Montgomery Monty, less and less water, the decline of forest and poor soil and barren land, some areas reached a stage that no soil loss, and severely restricted the regional social and economic sustainable development, it raised a red flag about the environment people live in. So, accurate and reliable value seems to be very urgent and important to correct recognized process and mechanism of rocky desertification, identified the severity of rocky desertification of karst mountain and determine the soil erosion in karst region.In this study, we address the characteristics of the spatial and temporal evolution of soil erosion in karstic mountainous area of Houzhai River Basin of southwest China. The study uses GIS, erodibility test results, actual surveys of soil types, a revised universal soil loss equation for estimating soil erosion in 1973, 1990, 2002, and 2013, and an analysis of the spatial and temporal distribution of the evolution law of soil erosion for almost 40 years. Results show the following:(1) The soil erosion modulus of the Houzhai River Basin exhibits a decrease from 222.72 t km-2year-1 in 1973 to 103.82 t km-2 year-1 in 2013.(2) The intensity level of soil erosion changes across space. The most active area is mainly concentrated in the upstream peak cluster depression.Areas with a slope of 8 ° –25 ° account for 40.81% of the total erosion contribution rate,indicating that these are the main areas where erosion occurs.(3) The average soil erosion modulus in the basin is generally low(i.e., below1000 t km-2 year-1), the average soil between micro erosion and light erosion. On the whole, nearly 40 years, the condition of moderate erosionand intensive erosion still turn to worse continuously in Houzhai watershed, the amount of soil erosion increasing quickly. Therefore, under the premise that intensive erosion and very intensive erosion could be maintained without increasing, the area of moderate intensit erosion are priority areas for the relevant departments and the government need to prevention and strengthen soil erosion and make relevant plan of water and soil conservation. |
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