Long-term environmental change in eastern Tasmania: Vegetation, climate and fire at Stoney Lagoon

Abstract

Tasmania's dry, inland east is ideally positioned to inform models of late Quaternary environmental change in southern Australasia. Despite this, it remains poorly represented in the palaeoecological record. Here, we seek to address this with a >13,000-year vegetation and fire history from Stoney Lagoon, a site at the eastern margin of Tasmania's inland Midlands plains. Pollen and charcoal analysis indicates that here, a relatively moist early deglacial was followed by a dry later deglacial (ca. 14,000-12,000 cal. BP), when sclerophyll forests became well established and burning increased. This suggests that the Midlands' vegetation responded to the climatic signals characterising Australia's southeastern coast rather than those governing developments in western Tasmania. Dry sclerophyll forest persisted throughout the Holocene; with a pronounced transition from more to less grassy understoreys between ca. 9000 and 7000 cal. BP. From the mid-Holocene, the sclerophyll community remains relatively stable. However, increased fire activity and trends in moisture-sensitive taxa suggest generally drier conditions coupled with greater hydroclimatic variability under the strengthening influence of the El Niño-Southern Oscillation (ENSO). Overall, these results highlight the role of macro-scale climatic shifts in shaping vegetation development in Tasmania's inland east, while hinting at the concurrent importance of local ecological drivers. This highlights the need for spatially diverse studies to understand interactions between drivers of long-term environmental change in sub-humid southern Australia. This research also supports conservation by strengthening understandings of pre-colonial baselines in this highly modified landscape.

Long‐term drivers of vegetation turnover in Southern Hemisphere temperate ecosystems

“…High richness is associated with low moisture availability, which might relate to weakened SWW and/or ENSO intensification in this region (Table 2). Increasing drought under a warmer climate, likely promoted species‐rich drought‐tolerant sclerophyllous woodland, especially on the mainland from the mid‐Holocene (Hopf et al., 2000; Jones et al., 2017; Kershaw et al., 1991; Pickett et al., 2004; Yuan et al., 2017). Aboriginal managed burning is thought to have also promoted vegetation richness in Australia in the past (Bird, Bird, & Codding, 2016; Bowman, 1998) and the overlap between richness trends and human occupation patterns across regions suggests Aboriginal land use may have also promoted/maintained richness, especially on the mainland and Tasmania in the past (Figure 5).…”

Pleistocene divergence of two disjunct conifers in the eastern Australian temperate zone

“…Given the poor dispersal of Callitris pollen (Luly, 2001), as demonstrated by the fact that Callitris pollen is nearly completely absent from pollen cores sampled from eastern Tasmania but outside the range of either Callitris species (e.g. Jones, Thomas, & Fletcher, 2017;Thomas & Kirkpatrick, 1996), this level of pollen is likely to represent a regional presence and/or the local survival of scattered trees. Species distribution modelling suggests that both species have remained remarkably close to LGM refugia that occurred on the modern and LGM coast suggesting very limited dispersal of these species in the post-glacial as is also likely to explain some modern distribution gaps in the species range (Kirkpatrick and Fowler 1998).…”

Evaluation of PMIP2 and PMIP3 simulations of mid-Holocene climate in the Indo-Pacific, Australasian and Southern Ocean regions

“…There is a vast amount of palaeoclimate AOGCM output that is freely available from PMIP (Joussaume and Taylor, 2000;Braconnot et al, 2007Braconnot et al, , 2012. The PMIP initiative includes data from transient simulations of the last millennium along with time slice simulations of the pre-industrial era ca.…”

“…Regional reconstructions of temperature over the southern Maritime Continent, Australasia and the Southern Ocean (immediately due south of Australia) have previously been compared with Paleoclimate Modelling Intercomparison Project (PMIP; Joussaume and Taylor, 2000) AOGCM simulations for the past millennium (PAGES 2k-PMIP3 group, 2015). The PAGES 2k-PMIP3 group (2015) study provides an estimate of mean temperatures for the whole region (specifically 0-50 • S and 110-180 • E) instead of subdividing into smaller climatic zones (e.g.…”