扎龙湿地丹顶鹤繁殖栖息地的选择及扩散

景观演变对野生动物栖息地质量和连接度造成的影响,一直是威胁全球生物多样性保护的关键问题,开展扎龙湿地丹顶鹤（Grus japonensis）繁殖栖息地选择及繁殖期生境间的扩散研究,对野生丹顶鹤的保护具有重要的意义。首先利用需要“出现点”的生态位MAXENT模型,进行适宜栖息地选择研究。从水源、食物、干扰、隐蔽物四个方面选择明水面距离、土壤湿度、NDVI、道路距离和居民地距离五个环境变量作为丹顶鹤繁殖栖息地选择的影响因子,预测扎龙保护区可供丹顶鹤进行营巢繁殖的栖息地分布,并分析各影响因子的反应曲线。结果显示：丹顶鹤易于选择远离道路和居民地干扰且靠近明水面的区域作为营巢栖息地,栖息地土壤湿度较高并且植被覆盖较多。从MAXENT模型中提取了38个适宜栖息地斑块,基于电路理论模拟丹顶鹤繁殖期失去飞行能力时的多路径扩散,最大电流密度图突出了可能的“夹点”,模拟出具有一定宽度范围的连接区域,可供丹顶鹤在繁殖期间进行扩散。累积电流密度图突出了在维持网络连通性方面起到积极作用的斑块,并进行面积加权来评估适宜栖息地斑块的综合重要性。结果表明,在MAXENT模型预测出的适宜栖息地斑块基础上,考虑丹顶鹤繁殖期的迁移扩散行为,利用累积电流密度面积加权来评估适宜栖息地斑块的综合重要性,得到的适宜性等级更符合丹顶鹤真实巢址的分布。研究成果可为保护区丹顶鹤栖息繁殖生境的恢复和保护提供科学依据。

Habitat selection and dispersal of red-crowned cranes during breeding period in Zhalong Wetland National Nature Reserve

The impact of landscape changes on the quality and connectivity of habitats for multiple wildlife species is a global conservation concern. Zhalong Wetland is not only the priority areas of biodiversity conservation in China, but also the largest haibitat in the world with a large number of red-crowned cranes (Grus japonensis) breeding. The red-crowned crane was listed as a globally endangered species by the IUCN Red List of threatened species (IUCN, 2012), which is the umbrella species and the most sensitive biological indicator species of ecological changes in Zhalong Wetland. The selection of breeding habitat and the dispersal between suitable habitats in the study area are of great significance to the protection of wild red-crowned cranes. Firstly five variables (distance to water, soil wetness, NDVI, distance to roads and distance to buildings) were derived, which was hypothesized to influence the quality of habitat for red-crowned cranes according to the actual investigation within an area encompassing the entire Zhalong Nature Reserve. The MAXENT model was used to predict the suitable habitat distribution of red-crowned crane and analyze the response curve of each factor. The results showed that the red-crowned cranes were more likely to inhabit far away from roads and residents, and the breeding habitat might be close to water with more vegetation in a higher soil moisture condition. Finally, 38 suitable habitat patches were extracted from MAXENT model to simulate the multipath dispersal of red-crowned cranes when they lost flight ability based on circuit theory in landscape connectivity. Our map of maximum current flow between patches highlighted the possible pinch points, which can be used for red-crowned cranes moving directly between patch pairs. Current flow summed across all pairs of patches highlighted areas important for keeping the entire network connected. The results show that based on the suitable habitat patches predicted by MaxEnt model, considering the migration and diffusion behavior of the red-crowned crane in the breeding period, the comprehensive importance of the suitable habitat patches is evaluated by using the area weighting of the cumulative current density, and the suitability level is more consistent with the real nest distribution of the red-crowned cranes. Map results can be used to support the planning efforts concerned with the maintenance of red-crowned cranes metapopulation structure, as well as to protect the landscape features that facilitate the dispersal process.