近40年野骆驼历史分布区土地利用变化及生境破碎化驱动因素

Abstract

野骆驼是中亚地区重要的迁徙物种，历史上完整、连续的野骆驼栖息地目前已成为孤岛状。为了解野骆驼历史分布区受人类活动的影响，明确造成其历史分布区破碎化的驱动因素，研究选取土地利用和道路两个因素，通过对近40年来的野骆驼历史分布区土地利用变化和动态度分析，以及道路密度和影响域计算，定量评估野骆驼历史分布区景观格局，以期为野骆驼栖息地整体连通性的改善，避免或缓解线性基础设施建设对野骆驼栖息地的影响提供科学的建议。结果表明：（1）近40年，野骆驼历史分布区内以未利用土地和草地为主体的格局保持不变，尤其是沙地、戈壁为主的未利用土地始终占比很大（>80%）；（2）野骆驼历史分布区范围内道路密度为0.0410 km/km²，但道路的阻隔作用明显，野骆驼当前分布区呈3个孤岛的格局与道路隔离形成的景观格局是一致的；（3）野骆驼历史分布区斑块数为914个，西部历史分布区斑块数为78个，远低于中部的373个和东部的463个，斑块数和平均斑块面积两个景观指数表明西部的栖息地破碎化程度比中部和东部栖息地要低；（4）从最大斑块指数来看，残存的大面积、无路区斑块是当前野骆驼种群得以存续的庇护所。根据当前的景观格局和破碎化状况，西部分布区和中部分布区间通过实施科学的栖息地连通和廊道建设规划，将极有可能实现两个孤立种群的交流连通，中部分布区和东部分布区间种群已基本无连通的可能。建议将更多的保护资源和努力投入到西部和中部分布区种群的维持和连通。在未来的道路规划建设和布局中，要考虑道路规划和建设对野骆驼最小生境面积的影响，并且要将影响评估尺度放大到整个野骆驼历史分布区的尺度上考虑道路的阻隔作用。;The wild camel (Camelus ferus) is an important migratory species in Central Asia. Unfortunately, its historically intact and continuous distribution has become three isolated regions of habitat (western, middle, and eastern region) as a result of human activity. In an effort to better clarify the driving factors of fragmentation, this study calculated the dynamic index of land use change from 1980 to 2018. Specifically, we evaluated the effects of land use via calculation of road density and road-effect zone to evaluate the impact of roadways. The results showed that:(1) in the past 40 years, unused land and grassland in the species' historical distribution range has remained unchanged, especially unused land dominated by sand which accounted for over 80% of the wild camel's historical distribution range. (2) Road density in the historical distribution range was 0.0410 km/km², but road barrier effects were large and consistent with the three isolated habitat regions in the current distribution area. (3) The total number of habitat patches in the historical distribution range of the wild camel was 914. These were comprised of 78 patches in the western region, which was much lower than the 373 and 463 patches in the middle and eastern regions, respectively. The number of patches and mean patch size indicated that the degree of habitat fragmentation in the western region was lower than that of the middle and eastern regions. (4) The largest patch index showed that the remaining large and roadless patches were critical for the survival of the current wild camel population. Present-day landscape fragmentation patterns suggest that the western and middle regions could be connected with corridor construction. However, the results indicate that it would be impossible to connect the middle and eastern regions. We recommend that conservation resources and efforts should focus on population maintenance and connectivity of the western and middle regions. Future road building plans must consider the impact of their construction and barrier effect on wild camel habitat, and decision makers should expand assessment to include the entirely historical distribution range of the wild camel, not just the three current isolated habitat regions.