The Study On The Comprehensive Benefit Evaluation For Soil And Water Conservation Based On The Theory Of Ecosystem Services

As an important part of the ecological environment construction, soil and water conservation is a very practical activity in agricultural, forestry and water affairs. It is necessary to research the benefit evaluation of soil and water conservation for evaluating the implementation effect, conforming the purpose and significance or comparing and choosing the implementation plan of soil and water conservation. Due to various effects in ecological environment and socio-economic aspects, a single indicator cannot evaluate the overall impacts of soil and water conservation. Therefore, two methods often used to evaluate the comprehensive benefit of soil and water conservation. One is based on the theory of system engineering, the other is according to the theory of ecosystem services. The theory and methods of comprehensive benefit evaluation for soil and water conservation according to the theory of ecosystem services were mainly studied in this article. The evaluation index system was established by optimizing indexes for evaluation. The evaluation model was established, and basic parameters in the model were determined. Taking middle scale research and demonstration region of soil and water conservation and ecological environment construction in Yanhe River basin as empirical research object, the impacts of soil and water conservation on the function of ecosystem services in and outside the research region and the driving forces of the ecosystem services changing were evaluated. At the same time, the main problem in the further improvement of ecosystem services, and the strategy and methods of solving these issues were analyzed. It was shown in the study that the theory of ecosystem services has a certain significance to scientifically determine factors of comprehensive benefits, improve the evaluation index system for soil and water conservation.The index system of comprehensive benefit evaluation for soil and water conservation based on the theory of system engineering is a method of multi-objective evaluation, which needs to select and normalize the evaluation indexes from all impacts of soil and water conservation, determine the score value and weight of each index, and finally transform the impacts of soil and water conservation on various aspects to a final evaluation value by mathematical methods. But the evaluation value is only a relative value, does not have a real ecological or economic, sociological significance. There are some differences in the selection and normalization of evaluation indexes, the decision of weighting factors and so on in different index systems. So the evaluation results between different index systems cannot be directly compared. In this article, a number of evaluation index systems for soil and conservation proposed by national scholars in 1990s were statistical analyzed. According to the frequency of 67 evaluation indexes, 13 indexes were selected as common indicators.The comprehensive benefit evaluation for soil and water conservation according to the theory of ecosystem services is based on the theory of ecosystem services. The function of ecosystem services include the value and the use value, which could be assessed by ecosystem services valuation, ecological footprint, emergy and virtual water and other indicators to measure them. However, the current theory and methods of ecosystem services assessment were not perfect. In this paper, some new works in ecosystem services assessment have been done based on the former theories and practices. The stock and incremental value were distinct in ecosystem services valuation. The question of intermediate products and yield factor in the ecological footprint calculation were initially proposed and solved. Emergy was divided into the emergy for ecosystem services and the emergy for ecosystem to maintain energy and the energy value. Based on the relationship between emergy for ecosystem services and for ecosystem sustaining, ecological– social complex system was divided into four basic types. The "blue virtual water" and "green virtual water" in the calculation of virtual water were distinct. The initial evaluation system of the human activities on water use efficiency was established.According to the theory and models of ecosystem services assessment, the evaluation models of impacts on water, soil, biosphere, and atmosphere by soil and water conservation on the ecosystem services in and outside the research region were established by direct or indirect methods. According to these models, the comprehensive benefits for soil and water conservation were assessed by 4 indicators, which are ecosystem services valuation, ecological capacity, emergy and the virtual water. And the basic parameters in these models were initially determined through theoretical and experimental analysis.It could be known in this research: from 1997 to 2004, ecological services valuation per capita in the research region increased from 1966 yuan to 2384 yuan, in which internal ecological services valuation(agricultural added value)increased from 1300 yuan to 1487 yuan, external ecological services valuation(agricultural added value)increased from 666 yuan to 877 yuan; ecological capacity per capita increased from 2.03 hm2 to 2.28 hm2, in which internal capacity increased from 1.20 hm2 to 1.24 hm2, external capacity increased from 0.83 hm2 to 1.04 hm2; emergy for net ecological services per capita increased from 3024.6 Gsej to 3745.1 Gsej, in which internal emergy increased from 586.2 Gsej to 697.8 Gsej, external emergy increased from 2438.4 Gsej to 3047.3 Gsej; the available water resource increased by soil and water conservation per capita increased from 2435 m3 to 2884 m3, in which internal benefit increased from 898 m3 to 1084 m3, external benefit increased from 1537 m3 to 1800 m3. So the internal value of ecological services by soil and water conservation was higher than external value, but external use value was higher than internal value. At the same time, the ecological external services increased more rapidly than internal services.According to above 4 kinds of evaluation, the marginal ecological services of forest was higher than others, the following were terrace and orchard respectively, and the marginal ecological services of grassland was the lowest. The main service function of farmland and orchard were internal services and economic benefit. The main service function of forest and grassland were external services and ecological or social benefit.The indexes system to evaluate benefit of soil and water conservation based on the system theory showed that the degree of realization in the comprehensive control soil and water loss increased from 65.96% in 1997 to 72.90% in 2004. The degree of realization in social benefit is higher than others. The degree of realization in ecological benefit enhances fastest, especially the improvement of control degree and vegetation coverage was prominent. At present, basic farmland and grain per capita have achieved the target value, and control degree and vegetation coverage have achieved that 70%-90%t of the target value. However, the degree of realization of indexes such as soil erosion modulus, income per capita, labor productivity, land productivity yet was low, which would be emphases in the future work.There were some consistencies between the evaluation of comprehensive benefit in soil and water conservation based on the ecological services theory and system theory. Generally speaking, the evaluation of soil and water conservation based on the theory of ecological services is more scientific and systemic. The character of comprehensive benefit evaluating in soil and water conservation based on system theory is distinguish function, which can point out the main problems in the soil and water conservation.In this article, the theories and methods of comprehensive benefits evaluation for soil and water conservation based on the theory of ecosystem services were theoretically discussed. The application of ecosystem services assessment was expanding. The methods and models of comprehensive benefits evaluation for soil and water conservation according to the theory of ecosystem services were established. The basic parameters in the models were determined. The empirical study was established. The main problem and solving methods of restricting the improvement of ecosystem services were discussed. The previous purpose of this thesis has basically achieved. On the foundation of former research, the comprehensive benefits evaluation for soil and water conservation according to the theory of ecosystem services was proposed.