Assessment Of Agricultural Ecosystem Service For Soil And Water Conservation Engineering Measures In Yunnan Province

Soil and water conservation measures are important means to prevent soil erosion,preserve soil moisture,improve soil nutrient and increase grain yield,and thus to play an important role in improving the service function of cultivated land ecosystem in mountainous areas.However,each measure has its limitations.Improperly configured measures will not only cause the waste of resources,but also aggravate ecological degradation to a certain extent,resulting in the formation of new ecosystem service trade-offs.Yunnan Province is a typical plateau mountainous province,in which steep slope cultivation is extremely common and soil erosion is severe.Therefore,it is extremely necessary to implement soil and water conservation measures to prevent soil erosion in Yunnan Province,especially the rational allocation of engineering measures can significantly play the role of water and soil conservation.At present,the formation process and mechanism of the ecosystem service trade-off relationship between soil and water conservation engineering measures are not clear,and it is difficult for us to systematically evaluate the ecosystem service functions of various engineering measures.Meanwhile,due to the sloping land causing serious soil erosion problems,soil and water conservation engineering measures are still widespread and accepted,how to build terraces and avoid waste of resources and ecological destruction is a further problem to be solved in Yunnan Province.In this article,we take Yunnan Province as an object.On the basis of building an environmental information database containing soil and water conservation measures,we use the index method to estimate the ecosystem service value of current soil and water conservation engineering measures,such as food supplying,carbon fixation and oxygen releasing services,nutrient cycle,soil sequestering carbon services,soil conservation and habitat support.After that,we use the GIS technology platform and geostatistical methods to clarify the spatial coupling characteristics of different ecosystem service values and to identify the trade-off relationship between ecosystem services.The paper draws the following main conclusions:(1)The current soil and water conservation engineering measures in Yunnan Province were mainly divided into four categories,namely Sloping terrace,Level bench terrace,Intermittent terrace,and Inward-sloping bench terrace.Among them,Sloping terrace had the largest area,accounting for 28.5%of the total measures,followed by Level bench terrace,Intermittent terrace,Inward-sloping bench terrace.Overall,the area of farmland with measures accounted for 53%of the total cultivated land area.Meanwhile,with the increase of slope,the difficulty of the construction of engineering measures and subsequent maintenance had increased,and the area of farmland with measures had been implemented has shown a gradual decrease.(2)The value of ecosystem services provided by the farmland with measures was significantly higher than that provided by the farmland without measures.The average value of grain supplying about the farmland with measures is 1.81 times that of farmland without measures,and the average annual soil retention is 68.65 t/km~2.Moreover,as the slope increased,the value of ecosystem services about the farmland with measures obtained gradually decreases,higher within the slope range of 0-15°.(3)The trade-offs and synergies between the different ecosystem services of farmland with measures were consistent with the performance of farmland without measures,in which there was a synergistic relationship between food supplying and carbon fixation and oxygen releasing services,and a trade-off relationship between carbon fixation and carbon fixation and oxygen releasing services.However,the synergistic relationship among different ecosystem services of the farmland with measures was significantly stronger than the farmland without measures,and the trade-off relationship was weaker than the farmland without measures.The conclusion indicated that the water and soil conservation engineering measures were conducive to promoting the coordinated development among various services of the farmland ecosystems.(4)There were obvious differences in the distribution range of trade-offs and synergies between ecosystem services on the slopes.Among them,the trade-offs between soil sequestering carbon and food supplying mainly occurred on the farmland with measures within the slope range of 0-9°,and on the farmland without measures within the slope range of 0-15°;the synergy between food supplying and habitat support was distributed on the farmland with measures within the slope range of 0-34°,and on the farmland without measures within the slope range of 0-29°.Comparing the four groups of trade-offs and the five groups of synergies between ecosystem services on the slopes,it was found that the distribution about the slope range of the trade-off relationship between different ecosystem services on the farmland with measures was lower than that of the farmland without measures,and the slope range of the synergistic relationship is higher than that of the farmland without measures.Therefore,it was recommended to focus on the trade-off relationship between the three types of services on the farmland with measures with the slope range of 9-25°,including food supply and soil conservation,nutrient cycling and soil conservation,carbon fixation and oxygen release and soil conservation;the trade-off relationship between the three types of services on the farmland without measures with the slope range of 11-22°,including food supply and soil sequestering carbon,nutrient cycling and soil sequestering carbon,carbon fixation and oxygen release and soil sequestering carbon.The results of this study showed that the construction of water and soil conservation engineering measures conducive to maintaining ecosystem stability,alleviating the trade-off relationship between ecological services.The present study will help to provide a scientific basis for the rational layout of the farmland with measures under different areas and slopes and provide case support for the assessment of plateau and mountain ecosystem services.