Sediment records suggest post British-invasion declines in diversity of wetland plant communities in the Koondrook-Perricoota Forest, Murray River, NSW
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Date
2022-12-06
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Australasian Quaternary Association
Abstract
Floodplain wetlands support enormous biodiversity and range of other vital ecosystem services. However, these wetlands are threatened by a range of processes. In the Murray-Darling system of southeast Australia, these processes include altered wetting regimes, cropping, grazing, invasive species and even forestry. Detecting and monitoring changes to these systems is limited by poor benchmark data, which would otherwise provide the basis for establishing the degree and nature of changes as well as possible drivers. This study sought to establish benchmark conditions and temporal patterns of change in wetland plant communities by examining stratigraphic changes in preserved plant and animal remains. Sediments from 12 wetlands in the Koondrook-Perricoota Forest were sampled at 2 cm intervals to depths of 30 cm to 40 cm. Lead-210 dating of the sediment profiles suggest the upper 10 to 16 cm of these sediment sequences were deposited in the last 100 years. Identified remains included Azolla megaspores, charophyte oospores, bryozoan statoblasts, chironomid head capsules, cladoceran ephippia and orobatid mites. The preserved remains assemblages of the pre and post-invasion period were generally distinct, though the degree of change varied among wetlands. In general, the post-invasion period is characterised by declining richness and diversity and to a lesser extent abundance in charophyte oospores in several of the wetlands. While there is no compelling evidence as to a specific cause of these changes, they are likely a response to declining frequency of flooding of the wetlands as a result of flow regulation and water abstraction. In the case of the apparent declines in charophytes, the impact of introduced grazers such as cattle could well have been a factor given that trampling and increased turbidity arising from their presence in and around the wetlands is likely to have been detrimental to the persistence of these submerged plants.
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Keywords
Wetlands, Species diversity, Ecosystems, Australia, Cultivation techniques, Grazing, Plants, Forestry
Citation
Reid, M., McIntosh, L., & Woodward, C. (2022). Sediment records suggest post British-invasion declines in diversity of wetland plant communities in the Koondrook-Perricoota Forest, Murray River, NSW. Paper presented to the AQUA 2022 Conference, 6-8th December, Adelaide, (pp. 90-91). Retrieved from: https://aqua.org.au/conference/aqua-2022/aqua-2022-conference-program-and-abstracts/