A history of Australia's riverine habitats and vegetation

Abstract

Our understanding of vegetation in Australia's riverine landscapes is greatly enhanced by an understanding of its history and dynamics over long timescales. Individuals and cohorts of structurally dominant riverine plant species, such as 'Eucalyptus camaldulensis' (river red gum), 'E. largiflorens' (black box) and 'E. cooiabah' (coolibah), can live for several hundred years and possess numerous adaptations that allow them to persist through long periods of suboptimal conditions. Similarly, it can take many years for plant taxa to disperse into newly created or transformed habitats within temporally dynamic riverine landscapes. Consequently, it is not possible to fully understand current species distributions and associations without knowledge of past states of riverine vegetation communities as well as their rates and trajectories of change. In contrast, many plants within riverine wetlands respond extremely rapidly to changing water regimes. Drying can desiccate water plants in a matter of days and dry lake beds can be colonised by native and exotic weedy taxa within a few months. Seeds buried in riverine sediments can also respond rapidly to rewetting, providing the period of drying is not prolonged, enabling wetland plant communities to recover. Shifts in the prevalence of rewetting, however, can lead to loss of seed banks over decadal scales and affect the capacity of wetland plant communities to respond to flooding. Changes in water quality can also dramatically affect aquatic ecosystems with increased nutrients, salts and turbidity all capable of inducing vegetation responses.