Ecosystem Services Evaluation of Karst New Urban Areas Based on Net Primary Productivity of Guanshanhu District, Guiyang, Guizhou Province, China

Net Primary Productivity (NPP) is the basis of the material and energy transport calculation in ecosystem studies. NPP directly reflects the production capacity of plant communities under natural conditions. Ecosystem services are hot topics in the field of ecology. Many studies calculate ecosystem service value based on NPP. Taking Guanshanhu District of Guiyang City, Guizhou Province as the research object, using TM, ETM+, Gaofen2 and MOD17A3HGF.006 as data sources, this paper analyzed the change of ecosystem service value based on NPP in 2000, 2010 and 2020. The results showed that the area of forest ecosystem increased during 2000-2010 and decreased during 2010-2020. The artificial surface grew rapidly from 1146.82 hm2 to 7544.29 hm2 during 2000-2020. The farmland ecosystem decreased from 13308.29 hm2 to 6342.33 hm2 during 2000-2020. With the dynamic changes in ecosystem spatial distribution and component structure, the total NPP in 2000, 2010 and 2020 was 12.58 × 104 t, 11.90 × 104 t and 11.78 × 104 t, respectively, showing a decreasing trend. The total value of natural and semi-natural ecosystems services based on NPP showed an increasing trend, which was ￥ 6.938 × 108 in 2000, ￥ 8.052 × 108 in 2010 and ￥ 10.306 × 108 in 2020 respectively. The ecosystem contributed the most to the ecological service value in 2000 was farmland, but in 2010 and 2020, it was the forest ecosystem. The ecological service value of grassland and wetland was relatively small, while the ratio of the wetland ecological service value displayed a decreasing trend. In the future, it is necessary to establish a strict pretrial system for land use, so as to effectively protect the natural and semi-natural ecosystems and fulfill the growing ecological demands of residents.

Analysis of Specialized Production of Transaction Services Based on Essential Services Quantity

The specialized production of e-commerce transaction systems is an important research topic, which is of great significance for evaluating the development level and forecasting the development direction of e-commerce. However, there is a certain disparity between the current mainstream research model and reality, which leads to a deviated result. This paper puts forward a definition of ＂transaction efficiency＂ based on essential transaction services and establishes a model of the middleman＇s specialized production decision of transaction services. The research result shows that （1） transaction efficiency plays an important role in improving the middleman＇s specialized production level, （2） only when the transaction efficiency is higher than a certain threshold will the distribution middleman appear, and （3） the degree of economic specialization, price of commodities and transaction services, and other associated factors also affect the evolution of e-commerce transaction systems.