School of Biological, Earth & Environmental Sciences, University of New South Wales, Sydney, New South Wales, 2052, Australia.
Ecol Appl. 2017 Jun;27(4):1124-1137. doi: 10.1002/eap.1507. Epub 2017 Apr 6.
Landscape connectivity is important for the long-term persistence of species inhabiting dryland freshwater ecosystems, with spatiotemporal surface-water dynamics (e.g., flooding) maintaining connectivity by both creating temporary habitats and providing transient opportunities for dispersal. Improving our understanding of how landscape connectivity varies with respect to surface-water dynamics and land use is an important step to maintaining biodiversity in dynamic dryland environments. Using a newly available validated Landsat TM and ETM+ surface-water time series, we modelled landscape connectivity between dynamic surface-water habitats within Australia's 1 million km semiarid Murray Darling Basin across a 25-yr period (1987-2011). We identified key habitats that serve as well-connected "hubs," or "stepping-stones" that allow long-distance movements through surface-water habitat networks. We compared distributions of these habitats for short- and long-distance dispersal species during dry, average, and wet seasons, and across land-use types. The distribution of stepping-stones and hubs varied both spatially and temporally, with temporal changes driven by drought and flooding dynamics. Conservation areas and natural environments contained higher than expected proportions of both stepping-stones and hubs throughout the time series; however, highly modified agricultural landscapes increased in importance during wet seasons. Irrigated landscapes contained particularly high proportions of well-connected hubs for long-distance dispersers, but remained relatively disconnected for less vagile organisms. The habitats identified by our study may serve as ideal high-priority targets for land-use specific management aimed at maintaining or improving dispersal between surface-water habitats, potentially providing benefits to biodiversity beyond the immediate site scale. Our results also highlight the importance of accounting for the influence of spatial and temporal surface-water dynamics when studying landscape connectivity within highly variable dryland environments.
景观连通性对于栖息在旱地淡水生态系统中的物种的长期生存至关重要，时空地表水动态（例如洪水泛滥）通过创造临时栖息地和提供短暂的扩散机会来维持连通性。提高我们对景观连通性如何随地表水动态和土地利用而变化的理解，是维持动态旱地环境中生物多样性的重要步骤。我们使用新获得的经过验证的 Landsat TM 和 ETM+地表水时间序列，对澳大利亚 100 万平方千米半干旱墨累-达令盆地内动态地表水栖息地之间的景观连通性进行了建模，时间跨度为 25 年（1987-2011 年）。我们确定了关键栖息地，这些栖息地作为连通良好的“枢纽”或“踏脚石”，允许通过地表水栖息地网络进行长距离移动。我们比较了这些栖息地在旱季、平均季和湿季以及在不同土地利用类型下短距离和长距离扩散物种的分布情况。踏脚石和枢纽的分布在空间和时间上都有所变化，时间上的变化是由干旱和洪水动态驱动的。保护区和自然环境在整个时间序列中都包含了高于预期的踏脚石和枢纽比例；然而，高度改造的农业景观在湿季变得更加重要。灌溉景观对于长距离扩散者来说包含了特别高比例的连通良好的枢纽，但对于行动迟缓的生物来说，仍然相对不连通。我们的研究确定的栖息地可能是针对特定土地利用的管理的理想高优先级目标，旨在维持或改善地表水栖息地之间的扩散，从而为生物多样性提供超出直接站点范围的益处。我们的研究结果还强调了在高度可变的旱地环境中研究景观连通性时，考虑空间和时间地表水动态影响的重要性。
