基于RS和GIS的陕西省洛川县土地利用类型和植被覆盖变化特征

明确土地利用类型转变和植被覆盖度变化的范围、幅度和归因是评估生态工程环境效应的前提。然而，在黄土高原塬区县域尺度类似的研究鲜有报道。基于长时间序列NDVI数据和Landsat系列卫星数据，探究了黄土高原洛川县土地利用和植被覆盖度的变化状况。结果表明：退耕还林（草）工程实施以来，洛川县植被覆盖度从0.6（2000年）增至0.9（2020年），耕地面积减少了481.8 km²，其中212.8 km²为坡度＜15°的适耕区转为苹果园，耕地改种苹果后植被覆盖度从0.5增至0.8。由于坡耕地还林草的面积在洛川县土地变化总面积中仅占1.5%，远小于其他地类改种苹果的面积（占20.0%），因此，洛川县植被覆盖度的提升主要是政府大力推广苹果树种植的结果。本研究可为黄土高原经济林建设提供基础数据和科学参考。

Characteristics of land-use types and vegetation cover changes in Luochuan County of Shaanxi Province based on RS and GIS

Background, aim, and scope Vegetation change reflects regional environmental conditions to a large extent, and land use change is the specific manifestation of human activities on natural ecosystems. To assess ecological environmental effects, we need to clarify the scope, magnitude and attribution of changes in land-use types and vegetation cover. However, similar studies at the county level on the Loess Plateau have been rarely reported. Remote sensing can be used to quickly evaluate the effectiveness of economic policies and ecological environmental governance. For the sustainable development of ecosystems, it helps to study spatiotemporal changes in vegetation and land use types and their responses to human activities. Materials and methods To understand the ecological effects of planting economic forests under the Grain for Green Project, we analyzed the regional land use and vegetation changes in Luochuan County, Shaanxi Province, using long-term data series of the normalized difference vegetation index (NDVI) and land use. Results The results showed that the vegetation coverage increased from 0.6 (2000) to 0.9 (2020) in the study area. By 2020, the area of croplands had decreased by 481.8 km², which included 212.8 km² croplands with slopes of less than 15° that were converted to apple orchards in response to local government promotion. After these croplands were converted into apple orchards from 2000 to 2020, the vegetation coverage increased from 0.5 to 0.8. The area of forest converted from sloping croplands (accounts for 1.5% of the total area) was much smaller than the increasing area of apple orchards (accounted for 20.0% of the total area). Discussion In this study, the vegetation cover increased the most in the early stage of ecological project, and the land transfer status showed that the forest area in the study area did not change much, and the increase in the apple orchard area was mainly due to the transformation of grasslands. Thanks to the popularization of apple planting in a large area of Luochuan County, the vegetation coverage has been improved in a large area, which not only accelerates economic development but also strengthens environmental protection and improvement. As the local government has vigorously supported and promoted the transformation of agricultural land into apple orchards, the local economy has greatly developed. The economic benefits and the increase in vegetation coverage induced by land use change in Luochuan County are the results of both the regional vegetation restoration and characteristic economic demand. The results of this study can provide basic data and a scientific reference for planting economic forests on the Loess Plateau. The development model of this area will help to clarify the relationship between socioeconomic development and ecological environmental protection. Conclusions During the ecological project, the vegetation coverage of Luochuan County significantly increased. The areas of vegetation improvement were concentrated in western and northern of Luochuan County, and the main vegetation cover change in these areas was the conversion of cultivated land into apple orchards and forests. From 2000 to 2020, the land use changes in Luochuan County were mainly manifested as the development of apple orchards in suitable arable areas, the conversion of sloping grasslands into apple orchards, and the restoration of sloping farmlands into forests and grass. The main vegetation cover structure was greater in the forests than in apple orchards or grasslands. By 2020, the vegetation coverage of Luochuan County had been comprehensively improved. Our results indicated that the increase in vegetation coverage in Luochuan County was mainly caused by the vigorous promotion of apple tree planting. Recommendations and perspectives In future vegetation restoration on the Loess Plateau, the ecological benefits of different vegetation types at the typical county scale should be further studied, and quantitative analysis should include climate and other factors to formulate corresponding ecological restoration plans and strategies and realize the coordinated development of the economy and environment.