Study On The Cultivated Land Use Efficiency Of Guangxi Based On Emergy Theory

Cultivated land as an important means of production, is the foundation of agricultural production. The current situation of cultivated land protection in Guangxi is not optimistic. From the internal perspective, Guangxi cultivated land reserve resources are lacked and land use efficiency is not high. From the external perspective, industrialization and urbanization process, agricultural structure adjustment and agricultural environmental pollution change the cultivated land area inevitably. Thus, although food supply and marketing in Guangxi is in balance state right now, the sense of urgency about food security which as an global and strategic issues must be held all the time. Therefore, we should evaluate the cultivated land use efficiency and find out its obstacle factors. It has an important and practical significance for promoting cultivated land use more effective and ensuring food security.This paper summarizes the research progress on emergy theory and then find out the research thoughts of this paper according to the questions existing in current study.Firstly,it has a detailed analysis on current status and dynamic changes of cultivated land use about the study area, pointing out that situation of cultivated land protection in Guangxi is not optimistic. Secondly, according to the amount of emergy invested and output of cultivated land system, it analyses the time series variation of Guangxi cultivated land system during the period of 2003-2013 a and spatial difference of city cultivated land system in 2013 a.Thirdly, we construct an evaluation index system based on emergy theory from economic- social-ecological aspects and analyze each single index. Then,we calculate the index weight by combination weighting approach, normalize the index data and put the results into the weighted model of multi-factor synthetic evaluation for calculating the scores of cultivated land use efficiency about Guangxi in 2003-2013 a. Nexty,analyse its time series variation. This paper calculates the scores of cultivated land use efficiency of 14 cities in 2013 a as well. We use hierarchical clustering method to grade the scores evaluated in order to analyze its spatial differences.The main conclusions about this paper are as follows:(1)In 2003-2013 a, the total emergy invested into the cultivated land system in Guangxi is in overall upward trend. Among them, the environmental contribution rate shows an overall downward trend, the proportion of industrial emergy invested is relatively large and shows an upward trend. From the spatial perspective, the index values of emergy invested are different.(2) In 2003-2013 a, the total emergy output from the cultivated land system in Guangxi shows an “increase-decrease-increase” trend. From the internal structure perspective, the change of emergy output about Guangxi is mainly due to the changes in economic crop yield. From the spatial perspective, different regions have different dominant species. The emergy output of rain crops, economic crops and other crops are relatively variant.(3) In recent 11 years, cultivated land use economic efficiency and social efficiency of Guangxi are in overall upward trend, but the ecological efficiency is in a downward trend. Overall, the comprehensive efficiency of cultivated land use is continuously improving.(4)The study show that the values of economic efficiency, ecological efficiency and comprehensive efficiency of cultivated land use in 14 cities vary remarkably, but the ecological efficiency varies relatively small. We use hierarchical clustering method to grade the values of economic efficiency, social efficiency, ecological efficiency and comprehensive efficiency about the cultivated land use in order to reveal the characteristics of spatial differences.Lastly, this paper put forward the corresponding suggestions according to the problems existing in each cultivated land use efficiency partition.