1985-2020年天水市黄土区滑坡灾损土地利用时空变化特征

为探索甘肃省天水市滑坡土地利用特征及时空变化规律,选取秦州区和麦积区作为典型黄土滑坡区的代表,基于12.5 m分辨率的ALOS DEM数据和1985—2020年全球30 m的精细地表覆盖动态监测产品,利用GIS空间分析、土地利用净变化量指数、土地利用转移矩阵和土地利用贡献率,分析滑坡体的特征参数、土地利用/覆被类型、土地利用转移特征及驱动因素。结果表明:(1)研究区共识别出469个滑坡样本,平均高程集中于1 200~1 400 m,平均坡度10°~15°,平均坡向为西向坡,前后缘相对高差100~150 m,滑坡面积1×10⁴~10×10⁴ m²,滑坡长度200~400 m。(2)1985—2020年滑坡区旱地最多,草原次之;期间土地利用类型呈现动态变化特征,分为1985—2000年持续变化阶段和2000—2020年微弱调整阶段;其中1995—2000年变化最剧烈,主要表现为旱地向草原和林地转化。(3)35年间旱地面积转化最多,累计8.74 km²,贡献给草原6.58 km²、封闭落叶阔叶林1.94 km²、不透水表面0.20 km²,其余的土地利用类型占比小,转化微弱;旱地、草原、封闭落叶阔叶林和不透水表面的土地利用净变化量最大。(4)单个滑坡体的利用方式逐年多样化,草原和封闭落叶阔叶林的增加提升区域的植被覆盖度,降低再次发生滑坡的可能性。天水市区滑坡土地利用类型和时空变化规律为区域灾损土地的开发再利用及生态修复提供科学依据。

Spatial and Temporal Variation Characteristics of Landslide Disaster Damage Land Use in Loess Area of Tianshui City from 1985 to 2020

To explore the land use characteristics and spatial and temporal changes of landslides in Tianshui City, Gansu Province, Qinzhou District and Maiji District were selected as the representatives of typical loess landslide areas, based on 12.5 m resolution ALOS DEM data and the global 30 m fine ground cover dynamic monitoring products from 1985 to 2020, using GIS spatial analysis, land use net change volume index, land use transfer matrix and land use contribution ratio to analyze the characteristic parameters, land use/cover types, land use transfer characteristics and driving factors of landslides. The results showed that: (1) A total of 469 landslide samples were identified in the study area, with the average elevation concentrated in 1 200~1 400 m and the average slope concentrated in 10°~15°, the average aspect was westward slope, the relative height difference between the front and back edges concentrated in 100~150 m, the landslide area concentrated in 1×10⁴~10×10⁴ m², and the sliding length concentrated in 200~400 m. (2) From 1985 to 2020, the landslides were the most frequent in rainfed croplands, followed by grasslands; the land use types during the period showed dynamic change characteristics, divided into a continuous phase change phase from 1985 to 2000 and a weak adjustment phase from 2000 to 2020; among them, the most drastic changes were observed from 1995 to 2000, mainly in the transformation of rainfed croplands to grasslands and forest lands. (3) The transformation of rainfed cropland area was the most in the past 35 years, with a cumulative total of 8.74 km², contributing 6.58 km² to grassland, 1.94 km² to closed deciduous broadleaved forest and 0.20 km² to impervious surfaces, while the remaining land use types account for a small proportion and weak transformation; the net land use changes of rainfed cropland, grassland, closed deciduous broadleaved forest and impervious surfaces were the largest. (4) The utilization of individual landslides was diversified year by year, and the increase of grasslands and closed deciduous broadleaves forests enhanced the vegetation cover of the area and reduced the possibility of recurrence of landslides. Land use types and spatial and temporal change patterns of landslides in Tianshui City provided scientific basis for the development, reuse and ecological restoration of disaster-damaged land in the region.