基于土地利用变化的喀斯特断陷盆地景观格局演变与生态安全评价

喀斯特地区生态重要性与脆弱性并存,研究喀斯特断陷盆地景观生态安全格局演变对当地土地利用高效管理和生态修复具有重要意义。以云南、四川、贵州三省交界处的喀斯特断陷盆地为研究对象,基于2000-2020年土地利用数据,通过构建土地利用转移矩阵、计算景观格局指数和景观生态安全指数,系统分析土地利用、景观格局与景观生态安全水平的时空演变特征。结果如下：（1）林地、草地、耕地是研究区主要土地利用类型,面积占比超过96%。土地利用变化主要发生在2005-2010年和2015-2020年,空间上表现出整体稳定而局部变化剧烈的特点,以退耕还林还草和林地向草地转换为主,耕地面积在过去20年共减少了386.62 km²。（2）景观多样性与均匀度上升,景观蔓延度下降。林地的最大斑块面积比例下降而草地上升,多数用地的斑块密度上升而集聚度下降,土地利用结构整体优化,但破碎化趋势明显,尤其是林地、耕地和草地。此外,建设用地呈连片化扩张。（3）景观生态安全水平明显提升,一般安全及以上安全区面积占比由2000年的62.35%上升到2020年的98.11%。在石漠化治理和生态保护的推动下,南部的生态安全水平大幅提高,推动空间格局从"北高南低"逐步转向"南北相对均衡"。景观生态安全水平的空间集聚性明显,高-高值集聚区主要在北部而低-低值集聚区主要在南部,需进一步推动北部生态保护以保障其生态屏障功能的发挥,并加强南部生态修复来提升其生态安全水平。此外,需持续推进石漠化治理并合理调控当地经济发展与生态保护间的关系,来维持生态安全水平的长期稳定。

The spatial and temporal evolution of landscape pattern and landscape ecological security assessment in Karst Fault Basin based on land use change

Karst region is characterized by its ecological significance and vulnerability. Exploring its spatial and temporal evolution of landscape ecological security pattern will shed light on local land use management and ecological restoration. Here, we examined in depth the features of spatial and temporal evolution of land use change, landscape pattern, and landscape ecological security pattern in Karst Fault Basin at junction of Yunnan, Sichuan, and Guizhou provinces, based on five phases of land use data in 2000, 2005, 2010, 2015, and 2020 and used methods of land use transition matrix analysis, landscape pattern index, and landscape ecological security index calculation. The results were as follows. (1) In terms of land use change, forest, grass land and cultivated land were the dominant land use types in the past two decades, aggregately accounting for over 96% of the study area. Land use transformation took place mainly in 2005-2010 and 2015-2020. It were manifested by two major forms, including the conversion of cultivated land into forest and grass land and the conversion of forest into grass land. As a result, the area of cultivated land declined by 386.62 km² in the past two decades. In general, the land use spatial structure kept relatively stable while that of some parts of the study region demonstrated drastic change during the study periods. (2) As for landscape pattern, the landscape diversity and evenness index increased while the contagion index dropped. Specifically, the largest patch index of forest decreased while that of grass land rose. For most land use types, the patch density grew while the aggregation index fell, indicating an increasing fragmentation trend against the background of land use structure generally optimizing, especially for forest, cultivated land, and grass land. In the meantime, continuous expansion of construction land was observed. (3) In terms of landscape security pattern, the past two decades witnessed a remarkable improvement of the landscape ecological security level in the study area. The proportion of area with a security level higher than "relatively low security" surged from 62.35% in 2000 to 98.11% in 2020. As for the spatial features of landscape security pattern, the level of landscape ecological security was high in the north and low in the south initially. Thanks to relentless efforts put into rocky desertification control and ecological improvement, the security level of the south increased considerably. This consequently contributed to a relative balance of security level between the north and south of the study area. In addition, the landscape ecological security index was featured by significantly spatial agglomeration, with high-high value clustered in the north and low-low value clustered in the south. These findings underscore the need for further advanced ecological conservation to ensure the ecological barrier function in the north and further intensified ecological restoration to improve the landscape ecological security level in the south of the study area. In addition to vigorously enhancing rocky desertification control, it is also crucial to strike a balance between economic development and ecological conservation to ensure the long-term stability of local landscape ecological security.