Browsing by Author "Sniderman, K"

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    Late Pleistocene fossil flora of Henty Bridge, Tasmania, and their implications for glacial climate reconstructions
    (Australian Nuclear Science and Technology Organisation, 2021-11-17) Matley, KA; Hua, Q; Sniderman, K; Drinnan, A
    The climatic extremes of the last glacial period (approx.100,000 years ago to 12,000 years ago) and in particular the last glacial maximum (LGM, approximately 20,000 years ago) are thought to have exerted a significant influence over the current distribution of mesic forest taxa in southeast Australia. However, limited taxonomic resolution afforded by fossil pollen has meant that the nature of glacial biotic communities remains poorly understood. In southeast Australia, pollen-based palaeoclimate reconstructions of the LGM suggest a mostly treeless, ‘glacial steppe’ environment characterised by cold, dry, windy conditions. But hylogeographic evidence suggests that forest taxa persisted widely in southeast Australia, in multiple, disjunct, local refugia. Resolving this apparent conflict is the focus of our study. Pollen is ubiquitous and virtually indestructible, which makes it remarkably useful for palaeoenvironmental reconstruction, particularly in lacustrine or cave environments where sediments accumulate over timescales of millennia. But despite its widespread use in palaeoecology, pollen-based reconstructions are limited by coarse taxonomic resolution. Pollen of narrow-range species that might be used as ecological indicators, for example, can be difficult or impossible to distinguish from the pollen of geographically widespread, and therefore less informative, taxa. Plant macrofossils, by contrast, are routinely identified to species level, and a majority of the species that were present at the LGM still exist today. These improvements to the taxonomic precision of palaeobotanical records allow for the use of bioclimatic niche models to quantitatively reconstruct palaeoclimate. Using our understanding of fossil species’ modern-day climatic niche, we hope to gain a more nuanced reconstruction of the climate at the time of their deposition. We sampled for plant macrofossils at a known LGM palynological site in Henty Bridge, Tasmania (Colhoun, 1985). Using the AMS radiocarbon dating facility at ANSTO, we produced a series of dates which indicate that these fossils were deposited at least 10,000 years prior to the LGM, a significant change to what was previously known of the site. Bioclimatic niche modelling of these fossil species suggests that, in the period preceding the LGM, the climate of western Tasmania was cooler than present by at least 2°C. Moreover, our data show clear evidence of species migration in response to changes in climate; some of the species in the Henty Bridge assemblage are today confined to higher elevations. These results contribute to the globally significant debate around the influence of the Pleistocene climate over the generation and maintenance of terrestrial biodiversity, and also to the increasingly urgent discussion of the degree of sensitivity of Australian plant taxa to changing climate in general. © The Authors
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    Southeast Australian palaeofloras of the late Pleistocene and their implications for glacial palaeoclimate reconstructions
    (International Union for Quaternary Research (INQUA), 2019-07-29) Matley, KA; Sniderman, K; Drinnan, A; Porch, N; Hua, Q
    The climatic extremes of the last glacial period (approximately 100,000 to 12,000 years ago) and particularly the last glacial maximum (approximately 20,000 years ago) are thought to have exerted a significant influence over the current distribution of mesic forest taxa in southeast Australia. However, limited taxonomic resolution afforded by fossil pollen has meant that the nature of glacial biotic communities remains poorly understood. Pollen-based palaeoclimate reconstructions of southeast Australia have invoked a mostly treeless, ‘glacial steppe’ environment characterised by cold, dry, windy conditions. But, in contrast with the Northern Hemisphere evidence of continental-scale migration to and from southern refugia during successive Pleistocene glaciations, contemporary patterns of species diversity and endemism suggest that forest taxa persisted widely in southeast Australia, in multiple, localised refugia. Resolving this conflict is the focus of this study. Based on species-level identifications of plant macrofossils, we will provide precise new insights into the southeast Australian glacial climate and biotic communities. Improvements to the taxonomic resolution of palaeobotanical records will allow for the use of bioclimatic niche models to quantitatively reconstruct palaeoclimate. Porch (2010) demonstrated this concept elegantly, but at Spring Creek, too few beetle taxa available for analysis resulted in an inconclusive finding. By applying this method to the plant macrofossil assemblage from this site, we hope to reconstruct the environmental parameters likely to have predominated at the time. Preliminary results suggest that the climatic tolerances of the late-Pleistocene flora of Spring Creek did not differ substantially from those of the modern-day assemblage. The results of this study will contribute to a globally significant debate about the role of the Pleistocene glacial-interglacial cycles in the generation and maintenance of terrestrial biodiversity, and also to the increasingly urgent discussion of the degree of sensitivity of iconic Australian plant taxa to changing climate in general. © The Authors.