【摘要】 “三北”防护林工程建设使三北地区生态环境得到明显改善，并产生了显著的社会和经济效益。然而，市场经济的建立又使工程建设面临多重困难和考验。如何使“三北”防护林工程建设能够持续、稳定地发展，实现两个根本性转变，采取增加投入、分类经营、加大科技含量、引进并建立新的经营机制以及各种资源的合理优化配置等措施，就成为今后工程建设的关键更多还原

【Abstract】 The Three North" protective forest engineering started in 1978. It is a world known, huge ecology improving project in China . As an important part of the engineering, the Gansu Three North" Protective Forest System covers 384 000 square kilometers,which involves 12 districts and 69 counties, about 84% of th e total area of Gansu Province and 3 43% of the total land area of the  Three North" region of China. Since the Three North" project being put into practice, Gansu Province has taken the developing strategies of positive planting, comprehensive control , rational exploiting and using. The construction of Gansu Three North" engineering has been going smoothly and gained great success. It has not only improved the ecological environment by renovating land, controlling desertification and preventing soil erosion, but also gained remarkable social and economic effects such as releasing farmer’s economic burden, increasing local people’s economic income and strengthening communitys economy. Along with the establishment of market economic system, the construction of Three North" protective forest system is facing some new challenges and difficulties. The Three North" project is a ecological and public welfare project. It is carried out under administration of the government. All levels of governments are the manager, builder and investor of the project. In Gansu Province, almost 57% of the main part of the project was completed by community and individuals. At present, driven by economic benefit, people are enthusing over planting economic trees. Because of the lack of money and lower economic results, large number of barren hills have lost their original attraction. Moreover, the market econo my provides the builders of the project more other choices. They are easy to engage in more profitable social services. For keeping a sustainable, stable and efficient development of the Three North" protective forest engineering and realizing the two essential transforms of forestry, various measures which include adding invest, sorting management, using new technology, establish ing share co operative system of planting tree, optimizing resources disposition etc. must be carried out to guide various kinds of funds to flow into forestry, to heighten the economic contribution of the engineering , and to follow the way of forestry supperted by the profits of itself". Thes e will be the optimum choice of the Three North" protective forest system cons truction.更多还原