Mechanism analysis of optimized model of conversion from farmland to forestland in the hill-gully sub-region of Loess Plateau
黄土高原沟壑区退耕还林典型优化模式机理分析

Conversion from Farmland to Forestland Program (CFF) is one of the six great ecological forest programs in China.This study covered the CFF model area of the hilly-gully sub-region of loess plateau,and introduced system dynamics and other latest theories and methodologies.Based on the analysis of five modules including that of the site observation of field stations and extensive investigations,and over 10 000 original data obtained in the fields of natural science,social science and economics,the operational mechanism of the optimized model was studied.The optimized operational models integrated maximized ecological,economic and social benefits,while sustainability concepts were proposed for typical CFF sites:The Pinus tabulaeformis Platycladus orientalis Zanthoxylum spp. Robinia pseudoacacia model at the eroded flat ridges of the middle reaches of the Yellow River.The result showed that the ecological,economic and social benefits of the optimized model reflected by main indexes were the best or better,and in the other models,either individual one was the best or others were not.From the viewpoint of comprehensive comparison of three great benefits,the optimized model was most excellent,and had eminent difference comparing to other ones through F test.The relationship between ecological and social benefit was eminent positive correlative.Social benefit was the same with economical one at some degrees.The relationship between ecological and economical benefit was more complicated.On the whole,they were positive correlative,but the economical benefit was not the greatest when the ecological one was the greatest.In general,from the viewpoint of largest comprehensive benefit,the three great benefits were not all the best,indicating that the combination of the modules must be reasonable.In order to achieve the ultimate goal of CFF,we must choose the optimized combination of ecological,economical and social benefits,and can't only pursue any one maximum of three great benefits.