Data from: Surface-water dynamics and land use influence landscape connectivity across a major dryland region

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 km2 semi-arid Murray Darling Basin across a 25-year period (1987 to 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（landscape connectivity）对于栖息于旱地淡水生态系统的物种长期存续至关重要，而时空地表水动态（例如洪水泛滥）通过营造临时生境并提供扩散的短暂契机，维持了景观连通性。加深对景观连通性如何随地表水动态与土地利用变化的理解，是维持动态旱地环境生物多样性的关键一环。本研究借助全新发布且经过验证的陆地卫星专题制图仪（Landsat TM）与增强型专题制图仪（ETM+）地表水时间序列数据集，针对澳大利亚面积达100万平方千米的半干旱墨累-达令盆地内的动态地表水生境，构建了1987至2011年这25年间的景观连通性模型。研究识别出了作为连通性良好的"核心枢纽"或"踏脚石"的关键生境，这些生境可支持物种通过地表水生境网络进行长距离移动。本研究对比了不同干湿季（旱季、平水期、湿季）以及不同土地利用类型下，面向短距离和长距离扩散物种的此类生境分布情况。踏脚石生境与核心枢纽的分布兼具空间与时间异质性，其时间变化由干旱与洪水动态过程驱动。在整个研究时段内，保护区与自然环境中踏脚石生境和核心枢纽的占比均高于预期；但在湿季，受人类活动高度改造的农业景观的重要性有所提升。灌溉型景观中，面向长距离扩散物种的高连通性核心枢纽占比尤其高，但对于活动能力较弱的生物而言，此类景观的连通性仍相对较低。本研究识别出的生境可作为针对性土地利用管理的理想高优先级目标，这类管理旨在维持或提升地表水生境间的物种扩散能力，或可在生境斑块尺度之外为生物多样性带来额外益处。本研究结果同时强调，在高度动态多变的旱地环境中开展景观连通性研究时，需充分考虑时空地表水动态的影响。