退耕还林草对黄土丘陵区土地利用的影响

为了检验退耕还林草工程对土地利用的影响，对案例区域——宁夏回族自治区固原市原州区有关政府部门和典型村的农户进行了调查。考察了退耕还林草实施的目标、过程、方式、进度安排，其中存在的问题及各部门的政策建议，收集了面上资料；座谈访问农户的家庭基本情况、退耕还林草工程参与情况、农地地块退耕前后的利用和投入产出状况、家庭各业生产情况等。将调查得到的各种数据输入到Excel软件中，利用统计功能和函数进行分析研究。结果表明，原州区退耕对象的瞄准精度不高，退耕的陡坡地尚不及退耕地总面积的50%；退耕还林提高了林地在土地利用结构中的比重，而草地比重却变化不大；退耕还林草后农户减少了低价值粮食作物的种植面积，增加了收益较好、适合当地生长的作物种植面积；退耕还林草提高了耕地资源的利用效率和效益，提高了平地和缓坡地对陡坡地的替代率；退耕后的耕地集约化程度显著提高，单位面积耕地的有机肥、化肥施用量和劳动用工量增加幅度在30%～75%之间。总体而言，退耕还林草对原州区的土地利用有着显著的正面影响，也存在一些不容忽视的负面影响。

The Impacts of Conversion of Cropland to Forest and Grassland on Land Use in the Loess Hilly Area

In order to examine the affection of the land conversion policy,the Yuanzhou district of Ningxia Hui autonomous region,which lies in the western of the loess plateau and upriver of the Yellow river,was chosen as study area,to conduct field survey.The objective,process,way,schedule of land conversion as well as existent problems relevant advices from related departments of local government were learned.We have also collected the general information,investigated the specific conditions of the participation of farmers' families to the project,the utilization and investment as well as output of the land before and after implementation of land conversion policy.Excel software was used to analyze all the data from field survey.The results show that the collimation precision of the plots is not perfect in Yuanzhou district,the ratio of steep sloping land that has been converted is not even reach 50% of the total area of the converted,although conversion of cropland to forest and grassland enhanced the proportion of woodland in land use,while the proportion of grassland remains almost the same as before.After the land conversion,the farmers reduced the area of low-value crop and added the area of higher-walue economic crops.Land conversion enhanced the efficiency and benefit of the use of farmland resources and also enhanced the proportion of utilizing flat and slow sloping field while reduced that of steep sloping field.After the project,the intensive degree of farmland enhanced prominently.The use of organic fertilizers and chemical fertilizers as well as labor force used in unit area increased between 30% and 75%.Generally the conversion of cropland to forest and grassland has remarkable effects.However,Conversion of cropland to forest and grassland has adverse impact for land use.For example,soil moisture would be excessively consumed if the area of woodland were too large.As the mean of ecological rehabilitation,Conversion of cropland to forest and grassland sometimes deviate the local condition.