Objectives Observations from wetlands across the globe suggest a consistent pattern of woody encroachment into wetland grasslands, altering habitat structure and ecological function. The extent to which hydrological changes have contributed to woody invasion of wetland grasslands is unclear. Our objective was to compare rates of woody encroachment in Australian floodplain wetlands between wet and dry hydrological phases. We test the hypothesis that contraction of non-woody wetland vegetation (grasses and rushes) would be concentrated in dry phases, co-incident with recruitment of the River Red Gum Eucalyptus camaldulensis lower in the floodplain. Methods We conduct the first detailed mapping of habitat change in two of the largest forested wetlands in inland Australia, comparing wet and dry hydrological phases. Detailed photogrammetry, supported by extensive ground survey, allowed the interpretation of high resolution aerial photography to vegetation community level. Results We found a consistent pattern of decline in non-woody vegetation, particularly amongst grasses utilising the C 4 photosynthetic pathway. The C 4 grasses Pseudoraphis spinescens and Paspalum distichum showed steep declines in the Barmah Millewa and Macquarie Marshes respectively, being replaced by River Red Gum E . camaldulensis. C 3 sedges proved more resilient in both systems. Conclusions Our results suggest that a pattern of tree expansion into non-woody wetland vegetation, characteristic of wetlands across the globe, is a major habitat structural change in the Australian floodplain wetlands studied. Projected hydrological impacts of climate change are likely to further restrict wetland grass foraging habitat in these semi-arid floodplain wetlands.

中文翻译：

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澳大利亚温带湿地树木的恢复力和草原对气候变化的脆弱性

目标 对全球湿地的观察表明，木本植物侵占湿地草原的模式一致，改变了栖息地结构和生态功能。水文变化在多大程度上导致湿地草原的木本入侵尚不清楚。我们的目标是比较澳大利亚漫滩湿地在湿水文和干水文阶段之间的木本侵占率。我们检验了非木本湿地植被（草和灯心草）的收缩将集中在干燥阶段的假设，这与洪泛区较低的红桉 Eucalyptus 河的补充同时发生。方法 我们对澳大利亚内陆两个最大的森林湿地的栖息地变化进行了首次详细测绘，比较了干湿水文阶段。详细的摄影测量，在广泛的地面调查的支持下，可以将高分辨率航空摄影解释到植被群落层面。结果我们发现非木本植被的下降趋势一致，特别是在利用 C 4 光合途径的草中。C 4 草 Pseudoraphis spinescens 和 Paspalum distichum 在 Barmah Millewa 和 Macquarie Marshes 分别表现出急剧下降，被 River Red Gum E 取代。金雀花。事实证明，C 3 莎草在两个系统中都更具弹性。结论 我们的研究结果表明，作为全球湿地特征的树木向非木本湿地植被扩张的模式是所研究的澳大利亚漫滩湿地的主要栖息地结构变化。