The assembly of the vegetation near the treeline during the Late Glacial and Holocene in south-central Tasmania

Context In Tasmania, most glacial pollen records suggest treeless conditions during the Last Glacial Maximum (LGM), but molecular evidence points to glacial survival of tree species in unexpected refugia. Plant macrofossils can help clarify whether woody species survived in local microrefugia or tracked their climatic preferences across the landscape. Aims This study investigates vegetation changes near the treeline in south-central Tasmania to understand species survival, dispersal, and community assembly during the Late Glacial–Holocene transition. Methods We used the analysis of plant macrofossils from Lake Dobson (1034 m asl) to reconstruct vegetation changes over the past 15,000 years. Key results Our findings show that alpine conifers were present in the subalpine area of Lake Dobson by c. 15 thousand calibrated years before present (cal kyr BP) and probably assembled from local microrefugia. Although present in the Late Glacial, species such as Nothofagus cunninghamii increased with the onset of warmer climates in the early Holocene. In contrast, subalpine eucalypts appeared later, c. 8 cal kyr BP. Overall, the results imply that the modern configuration of the vegetation, i.e. Eucalyptus open woodlands, was not reached before ~6 cal kyr BP. Conclusions This study has highlighted the variability in plant responses and community assembly during the Late Glacial–Holocene transition, a period of significant environmental change that is not yet well understood in the southern hemisphere. Implications Treeline investigations spanning the transition from late-glacial to interglacial conditions allow us to understand how fast plant species responded to past environmental fluctuations and how species may respond to projected climate change.