Response Of Agricultural Eco-economic System To Land Use Changes On County Scale In Loess Plateau Gully Area

Considering the contradictions among resources, population and grain are becoming more and more serious, the issues of response of agriculture eco-economic system to land use changes was investigated on county scale in Loess Plateau Gully Area, by taking data such as land use data, social economic statistics data and peasant household survey data. These were land use changes and characteristics of land use structure, potential grain productivity and security under the background of―Grain for Green‖policy, land use and agro-ecolomic system coupling in household scale and agro-ecolomic system coupling degree in1949-2008 on county scale were analysed, and the results are as follows:Based on the understanding of connotation of land use structure, this study investigated land use structure characteristics Changwu county in 2009, by selecting quantitative indices combined with GIS technology. The main feature of land use structure in the county could be generalized as: arable land and forest land patches constitute landscape matrix, regional land combination type comprises forest land, arable land, garden plot and unused land. The plateau-gully-slope morphological pattern of Loess Plateau provided a natural foundation of land use structure in the country. There was mighty significant correlation between population density and land use degrees. Land use structure was embodied by location advantage of residents, industrial and mining land to some extent. Land use structure in Loess Plateau didn't reflect economic levels, land use status should be adjusted and optimized in this region.In this study, the data of agricultural meteorology in Changwu County in 1993 and 2009 were used to evaluate the grain productivity potentiality. The farmland area and its geographical distribution in 1993 and 2009 were used to check the farmland change and the grain security in the county. The potential productivity for each meterological factor limitation level for main grain plants and the degree of potentiality exploited was calculated using mechanism methodology. Compared with 1993, the achievable potential productivity in 2009 reduced by 7.8%, while the actual grain productivity increased by 4.0%, so the fulfilling rate of the potential natural productivity increased from 61.58% in 1993 to 68.59% in 2009. During the past 17 years, the planting area of main grain plants decreased by 27.8%, grain yield per hectare improved by 44.1%, population increased by 12.5%, the grain planting area per capital decreased 35.9%, the grain yield per capital declined by 7.5% from 320.1 kg to 296.0 kg. The potential productivity was promoted due to the raise of effective coefficient of temperature and land, while the actual grain yield was restricted by the quantity of farmland. Farmland shrinking and population accretion are two core problems in the grain security in the area. So improvement of per capital grain yield is the guarantee for grain security.Based on the peasant housld investigation, the coupling relationships of agro-economic system were analyzed by using structural equation. It was shown that industrial situation and economic benefit had covariant relation, they had negative correlation (-0.14, -0.37) on land utilization. The improvement of industrial situation and economic benefit restrained the development of crop and plant cultivation. The agricultural resources had direct effects on the land utilization, with coefficient being 0.51. The land use analysis showed that coupling situation had definite effects on industrial situation and economic benefit, with the influence coefficient being 0.57, 0.61, with economic benefit to industrial situation 0.81, agricultural resources to coupling situation 0.14. The coupling analysis of agro-ecolomic system reflected the mechanism relationship between agricultural ecosystem and agricultural economic system were restricts mutually, promote each other, developing upward spiral.Coupling processes of agricultural eco-economic system in the gully area of the Loess Plateau were investigated through the analysis of the coercing and dynamic evolution relationship between agricultural economic system and agricultural ecosystem based on coupling degree model. The weight of each indicator was determined using improved entropy method. Results showed that from 1949 to 2008, the agricultural eco-economic system in the county experienced the three stages of―early traditional agricultural development‖,―agricultural mechanization‖, and―agricultural pre-modernization‖. Corresponding to the implements of national macro policies, the coupling degree reached two peaks standing for utmost increasing phase and three valleys standing for coordinate development phase. The coupling degree of the agricultural eco-economic system was in the utmost increasing phase in the periods of 1955-961 and 1984-1992, which indicates a damaged ecosystem. The two periods of 1962-1965 and 1981-1983 were the rapid transition periods responding to the national-wide policies controlling. Before the two periods, it was the two low-level coordinated development phases of 1949-1954 and 1966-1980. Since 1993, the system has been in the harmonious phase by a spiral development. However, the agricultural eco-economic system has a potential risk changed from the harmonious phase to the utmost development phase at present.In conclusion, Land use structure and status should be adjusted and optimized. Analysis on scale of county and peasant household didn't reflect economic efficiency. The way to solve grain security needs improvement of per capital grain yield. To improve economic efficiency, management should be aimed at scale and industrialization. Appropriate agricultural policies and a better external environment can promote the stable development of the agricultural eco-economic system in a harmonious level, otherwise, a retrogressive system may be expected.