延安平山造城前后土地利用/覆被变化动态和特征

Dynamics and characteristics of land use and cover change before and after the mountain excavation and city construction project in Yan'an New District

关键词:  延安平山造城  土地利用变化  遥感影像  地理信息技术

Key words:  mountain excavation and city construction (MECC) in Yan'an  land use change  remote sensing image  GIS

摘要:

延安平山造城（MECC）极大地改变了区域地表景观格局，土地利用/覆被（LUCC）变化显著。文章结合遥感（RS）、地理信息系统（GIS）和数学方法，使用多尺度分割和监督分类（最邻近法）解译不同时间段（2009年、2015年和2022年）延安新区的高分辨率（分辨率为0.5 m）卫星影像数据（GeoEye-1、Pleiades、WorldView-2），从土地利用变化速度、转移方向和土地利用程度三方面分析了延安平山造城前后土地利用变化/覆被动态和特征。研究结果表明：（1）2009—2022年，自然地类（草地、林地、农地）总面积净减少11.4 km²，建设用地净增10.8 km²，平山造城工程对区域土地利用格局产生了深刻影响。平山期（2009—2015年）是土地利用变化最为剧烈的时期，以自然地类大量缩减和未利用地急剧扩张为特征；建城期（2015—2022年）变化趋于和缓，自然地类有所恢复，但建设用地仍持续增长。（2）平山期（2009—2015年），82.51%的地类发生转换，草地和林地转出贡献率合计86.18%，主要转为未利用地（转入贡献率61.60%）和建设用地（转入贡献率20.01%），工程初期以植被破坏和裸地大规模形成为主；建城期（2015—2022年），74.21%的地类变化，未利用地转出贡献率66.92%，主要转为建设用地、草地和林地；建设用地转入贡献率50.02%，主要源于未利用地（72.84%）和草地（23.84％），城市化加快且生态恢复同步推进。（3）延安新区综合土地利用动态度从平山期的10.61%减少至建城期的6.62%，说明区域内土地利用变化速率逐渐减缓；根据土地利用程度变化率发现，平山造城工程对土地利用的影响是阶段性的（平山期为−0.13，建城期为0.61），且通过合理的城市规划以及生态保护可以抵消部分城镇化带来的负面影响（平山造城前后变化为0.29，对延安土地资源起到正面保护作用）。

Abstract:

Background, aim, and scope The mountain excavation and city construction (MECC) project in Yan’an has profoundly altered the regional land surface landscape, resulting in significant land use and land cover change (LUCC). This study aimed to quantify the magnitude, direction, and intensity of these changes and to identify their stage-specific characteristics during mountain excavation and subsequent urban construction. Materials and methods This study integrated Remote Sensing (RS), Geographic Information System (GIS), and mathematical methods to interpret high-resolution (0.5 m) satellite imagery (GeoEye-1, Pleiades, and WorldView-2) from 2009, 2015, and 2022, using multiscale segmentation and supervised classification (nearest neighbor algorithm). Three indicators—amplitude, direction, and intensity of land use change—were employed to characterize LUCC dynamics before and after the MECC project. Results (1) From 2009 to 2022, natural land types (grassland, forest land, and agricultural land) decreased by a total of 11.4 km², while construction land increased by 10.8 km². The mountain excavation phase (2009—2015) was the most drastic period, characterized by substantial reduction in natural land types and rapid expansion of unused land and construction land, whereas the urban construction phase (2015—2022) showed more moderate changes with partial recovery of natural land types but continued growth in construction land. (2) During the mountain excavation phase, 82.51% of the study area underwent land-use conversion with grassland and forest land contributing 86.18% of total outflows, primarily converting to unused land (inflow contribution rate of 61.60%) and construction land (20.01%). In the urban construction phase, 74.21% of land use changed, with unused land contributing 66.92% of total outflows, mainly converting to construction land, grassland, and forest land; construction land had the highest inflow contribution rate (50.02%), primarily derived from unused land (72.84%) and grassland (23.84%). (3) The integration indicator of land use change in Yan’an New District decreased from 10.61% during the mountain excavation phase to 6.62% during the urban construction phase. The land use degree change rate was negative (−0.13) during the mountain excavation phase and positive (0.61) during the urban construction phase, with an overall change of 0.29. Discussion Compared to other MECC projects on the Loess Plateau, such as the Lanzhou New Area, the patterns of land use transfer and changes in Yan’an New District show similarities, with the main transfer directions involving the conversion of grassland and forestland to unused land and construction land. Both the MECC projects in Lanzhou and Yan’an City show a trend of ecological quality declining initially and then improving over time. This suggests that, due to policy guidance and the rational planning of urban land use, the restoration of the regional eco-environment in the later stages of the MECC project has partially offset the negative impacts of urbanization, indicating that Yan’an New District is likely to achieve the sustainable utilization of land resources. Conclusions The MECC project had a phased impact on land use in Yan’an New District, characterized by initial destruction followed by reconstruction. The project promoted the comprehensive development and utilization of regional land, and through effective urban planning and ecological protection, some negative effects of urbanization can be mitigated. Ultimately, the project would play a positive role in protecting land resources. Recommendations and perspectives Continuous monitoring and evaluation of land use changes are essential for guiding scientific decision-making and understanding the project’s impact on the landscape. It is recommended that the data obtained from this study could be integrated with advanced remote sensing techniques, GIS methodologies, and mathematical models for more in-depth analyses of regional landscape patterns in the future. Future urban development should better coordinate construction-land expansion with ecological restoration and natural-land protection to mitigate the adverse effects of urbanization.