Foppen Ruud P B, Chardon J Paul, Liefveld Wendy
Department of Landscape Ecology, Research Institute Alterra, Wageningen University and Research Centre, P.O. Box 47, 6700 AA, Wageningen, The Netherlands.
Conserv Biol. 2000 Dec 18;14(6):1881-1892. doi: 10.1111/j.1523-1739.2000.99022.x.
Populations in agricultural landscapes often occur in source-sink situations: small patches of marginal habitat (sinks) are supported by an immigration flux from larger patches of high-quality habitat (sources). We sought to demonstrate that this situation occurs for Reed Warblers (Acrocephalus scirpaceus) in a riverine, mainly agricultural landscape in the Netherlands. We collected data on occurrence and habitat features in a large number of mostly small marshlands. We used a stochastic model to simulate the population dynamics in a metapopulation with sinks and sources. A statistical analysis of the field data, using regression techniques with occupation probability and abundance index as dependent variables, showed that habitat quality was less favourable in small habitat patches (e.g., ditches with reeds) than in larger patches ( large, heterogeneous marshlands). The spatial cohesion of the landscape also played an important role: abundance of breeding Reed Warblers in regions with low spatial cohesion was low. Local extinctions and recolonizations occurred, and their rates depended on the spatial parameters of the patch. This supports the hypothesis that metapopulation theory is applicable here. The results of the modeling study demonstrated that, besides the trivial dependence of sinks on sources, a larger amount of sink area and increased exchange of individuals increased the stability of source patches. This was shown not only by the larger size of the source population but also by increased resilience after a catastrophe. The area of the sink seemed less important than its distance to the source. The simulation indicated an optimal area of a few hectares (compared to a 10-ha area of the source) and a maximum distance of 2-5 km from the source. In creating sustainable landscapes, for example, by setting up an ecological network consisting of a limited number of high-quality patches, these small and seemingly insignificant habitat patches could play an important role and should be taken into consideration.
农业景观中的种群常常处于源 - 汇格局：小片边缘栖息地（汇）依靠来自大片优质栖息地（源）的迁入流来维持。我们试图证明，在荷兰一个主要为农业的河滨景观中，芦苇莺（Acrocephalus scirpaceus）就处于这种格局。我们收集了大量大多为小型沼泽地的出现情况和栖息地特征的数据。我们使用一个随机模型来模拟一个包含汇和源的集合种群的种群动态。以占据概率和丰度指数为因变量，运用回归技术对实地数据进行统计分析，结果表明，小型栖息地斑块（如长满芦苇的沟渠）的栖息地质量不如大型斑块（大型、异质的沼泽地）。景观的空间连通性也起着重要作用：空间连通性低的区域，繁殖芦苇莺的数量也少。局部灭绝和重新定殖时有发生，其速率取决于斑块的空间参数。这支持了集合种群理论在此适用的假设。建模研究结果表明，除了汇对源的明显依赖外，更大面积的汇区域以及个体交流的增加会提高源斑块的稳定性。这不仅体现在源种群规模更大，还体现在灾难后的恢复力增强。汇的面积似乎不如其与源的距离重要。模拟结果表明，最佳面积为几公顷（与源的10公顷面积相比），距源的最大距离为2 - 5公里。例如，在创建可持续景观时，通过建立由数量有限的高质量斑块组成的生态网络，这些小型且看似微不足道的栖息地斑块可能会发挥重要作用，应予以考虑。
