Late Glacial and Holocene Palaeoecology of the Lake St Clair Region, Tasmania

This thesis presents a history of regional and local changes in vegetation in the Lake St Clair region, supported by modern vegetation and pollen analyses. The records span into oxygen isotope stage 3, with a focus on the last Glacial Holocene transition and fill a gap in the poorly studied region of Central Tasmania. The vegetation during the last glaciation prior to the Last Glacial Maximum was characterised by widespread Pherosphaera hookeriana dominated alpine coniferous heath growing together with a mosaic of alpine grasslands, herbfields, heathland and sedgeland. The lakes at Clarence Lagoon and Excalibur Bog are inferred to have dried up under the cold and dry climate during the Last Glacial Maximum. The legacy of Pherosphaera hookeriana dominated vegetation extends to the early deglacial sediments in Lake St Clair, declining to only trace representation through the remainder of the late Glacial and Holocene in the wider Lake St Clair region. Deglaciation of Lake St Clair was complete by c. 18.3 cal kyr BP and subsequent replacement of an early mosaic of alpine vegetation types, by subalpine Athrotaxis cupressoides and Diselma archeri dominated rainforest and/or woodland in response to rapidly rising temperatures and precipitation, is in sync with postglacial Antarctic warming and rising sea surface temperatures. A 900-year period of renewed grassland expansion is inferred to represent slightly cooler/drier conditions leading into the Antarctic Cold Reversal, abruptly ended by strong increases in rainforest mid-way through the Antarctic Cold Reversal suggesting a shift to a wetter and warmer climate leading to the establishment of Phyllocladus aspleniifolius-Nothofagus cunninghamii rainforest. The abrupt decline in Phyllocladus aspleniifolius at c. 12.4 cal kyr BP marks the expansion of Nothofagus cunninghamii-Atherosperma moschatum callidendrous rainforest growing under optimal conditions during the Early Holocene, which becomes more complex between c. 10-8 cal kyr when Phyllocladus aspleniifolius returns to high values, together with a secondary peak of Athrotaxis/Diselma under an inferred wetter and warm climate. At c. 8 cal kyr BP, the rainforest taxon Anodopetalum/Eucryphia becomes important and the remainder of the Holocene sees an overall decline in rainforest taxa and increase in sclerophyll and herbaceous taxa and fire activity, which intensifies during the late Holocene. The observed changes in the record are consistent with the onset of ENSO and a more variable climate from c. 8 cal kyr BP and an intensification and cooling temperatures from c. 5 cal kyr BP

Neolithic dispersal implications of murids from late Holocene archaeological and modern natural deposits in the Talaud Islands, northern Sulawesi

The Sangihe-Talaud Archipelago represents a group of 77 remote islands located between the Philippines and North Sulawesi, in the northern sector of Wallacea. The Talaud Islands have a rich and significant archaeological record going back to the Pleistocene and are instrumental in understanding Pleistocene colonisation of small islands and later models of Austronesian language dispersal. Here we report on vertebrate material excavated from Leang Mande'et, a late Holocene rockshelter on Karakelang, the main island in the Talaud group. The site represents a periodically occupied shelter used for gardening. Fauna recovered predominately comprises murid elements, with at least four taxa (Rattus rattus, Rattus exulans and two Melomys species) found. The rodents show clear signs of being deposited by raptors rather than humans, unlike the small number of fish remains also recovered. DNA sequences from several Rattus rattus specimens are referrable to Rattus rattus complex lineage IV, a lineage with a southern Indochinese origins and broad modern representation through Indonesia and the Philippines. The lack of any Rattus rattus complex lineage II from Leang Mande’et suggests that the first agricultural inhabitants of this island did not come from Taiwan or northern Indochina, but rather that they either originated from the south or that, once established in the Talauds, opened up significant trade networks to the south and in the process acquired a significant pest

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

© 2020 John Wiley & Sons Ltd Aim: Knowledge of the drivers of ecosystem changes in the past is key to understanding present ecosystem responses to changes in climate, fire regimes and anthropogenic impacts. Northern Hemisphere-focussed studies suggest that climate and human activities drove turnover during the Holocene in temperate ecosystems. Various drivers have been invoked to explain changes in Southern Hemisphere temperate vegetation, but the region lacks a quantitative assessment of these drivers. To better understand the regional drivers of past diversity, we present a quantitative meta-analysis study of turnover and richness during the lateglacial and Holocene in Australian temperate ecosystems. Location: South-east Australia (Tasmania, Bass Strait, SE mainland). Methods: We conducted a meta-analysis study of 24 fossil pollen records across south-east Australian temperate ecosystems, applying an empirical turnover threshold to fossil records to identify periods of major turnover for the first time in Australia. We tested pollen richness as a proxy for vegetation richness to estimate past richness and applied this to fossil pollen data. The resulting reconstructions were compared to independent records of climate, sea-level change and fire through generalized linear modelling. Results and conclusion: Our results show changes in available moisture and sea level drove turnover and richness in most parts of SE Australia in the past, explaining up to c.97% deviance. However, fire mainly drove turnover in Bass Strait. Our richness reconstructions also support the intermediate disturbance hypothesis, suggesting that high biodiversity was partially maintained by anthropogenic-managed fire regimes. While temperature change is considered key to Northern Hemisphere palaeodiversity, past turnover and richness in Southern Hemisphere temperate ecosystems responded mainly to moisture availability and sea-level change (considering its role in modulating regional oceanic climate)

Smallest Late Pleistocene inhabited island in Australasia reveals the impact of post-glacial sea-level rise on human behaviour from 17,000 years ago

Late Pleistocene records of island settlement can shed light on how modern humans (Homo sapiens)adapted their behaviour to live on ecologically marginal landscapes. When people reached Sahul(Pleistocene New Guinea-Australia), between 65 and 50 ka, the only islands they would have encoun-tered were in the tropical north. This unique geographic situation therefore offers the only possibility ofmodelling human adaptive behaviour to islands in Australasia during the Late Pleistocene. Cave exca-vation on the uplifted limestone island of Panaeati in the Massim region of Southeastern New Guinearevealed a cultural sequence commencing from 17,300e16,800 cal. BP, suggesting habitation of highercoastlines occurred as low-lying shorelines destabilised during the initial stages of deglacial sea-levelrise. No cave use was evident between 12,400 and 4780 cal. BP when the continental shelf was fullyinundated, and Panaeati reduced in size by 90%. It is likely that diminished coastlines and the reducedresources of low-lying islands could no longer support pre-agricultural populations during this time.Cultural groups that were better adapted to living on small islands returned to Panaeati by 4780e4490 cal. BP when sea levels had stabilised, lagoons formed, and coastal ecosystems had diversified.Investigations demonstrate the role of larger islands as refugia during deglacial sea-level rise and theeffects on human dispersals and cultural diversity.The project was funded by an Australian Research Council Discovery Early Career Award (DECRA, DE170100291) awarded to Shaw for the period 2017e2019, and by the University of New South Wales Faculty of Science. Radiocarbon dating was partly funded by an Australian Nuclear Science and Technology Organisation grant AP11908. We acknowledge the financial support from the Australian Government for the Centre for Accelerator Science at ANSTO through the National Collaborative Research Infrastructure Strategy (NCRIS)

The influence of climatic change, fire and species invasion on a Tasmanian temperate rainforest system over the past 18,000 years

We aim to understand how did cool temperate rainforest respond to changes in climate and fire activity over the past 18 kcal yrs, interrogating the role that flammable plant species (such as Eucalyptus) have in the long-term dynamics of rainforest vegetation. We used high-resolution pollen and charcoal analysis, radiometric dating (lead and carbon), modern pollen-vegetation relationships, detrended correspondence analysis, rarefaction (palynological richness), rate of change and granger causality to understand the patterns and drivers of change in cool temperate rainforest from the sediments of Lake Vera, southwest Tasmania through time. We record clear changes in key rainforest taxa in response to climatic change throughout the record. The spread of rainforest through the lake catchment in the early and mid- Holocene effectively negated disturbance from fire despite a region-wide peak in fire activity. An anomalously dry period in the late-Holocene resulted in a local fire that facilitated the establishment of Eucalyptus within the local catchment. Granger causality tests reveal a significant lead of Eucalyptus over fire activity in the Holocene, indicating that fires were enhanced by this pyrogenic taxon following establishment

Myrtaceae pollen morphology study from Bass Strait islands, Australia, is effective in separating region-specific fossil Myrtaceae pollen types

The identification of Myrtaceae pollen to species level in fossil records has challenged palynologists due to the similarity of pollen grains produced by species in this family. Here, we present a pollen morphological study of the Myrtaceae species found in a specific region of southeastern Australia, the islands of the Furneaux Group in Bass Strait, and apply this to fossil pollen records from the same region to confirm its utility in differentiating Myrtaceae pollen to type level. We examined 23 species of Myrtaceae, belonging to 6 genera, and were able to identify 11 distinct types. The observed Myrtaceae pollen taxa can be confidently separated to genus level, apart from Euryomyrtus, which is indistinguishable from Leptospermum. Specifically, separation to species level is most achievable within the genus Melaleuca, as well as Kunzea and Calytrix, which are each represented by a single species. Conversely, Eucalyptus could only be separated into major types, while Leptospermum species could not be clearly separated, although differences in exine patterns exist. We also demonstrate that our pollen morphological types can be applied to Holocene and Pleistocene fossil records from the Furneaux Group. We recommend that studying the Myrtaceae of a specific area is more helpful in identifying fossil Myrtaceae pollen from that area than using general Myrtaceae pollen morphological descriptions or keys that are not site- or region-specific.The authors acknowledge that this research was made possible through an Australian Research Council Centre of Excellence for Australian Biodiversity and Heritage support grant (CE170100015)

A comparison of classification algorithms within the Classifynder pollen imaging system

We describe an investigation into how Massey University's Pollen Classifynder can accelerate the understanding of pollen and its role in nature. The Classifynder is an imaging microscopy system that can locate, image and classify slide based pollen samples. Given the laboriousness of purely manual image acquisition and identification it is vital to exploit assistive technologies like the Classifynder to enable acquisition and analysis of pollen samples. It is also vital that we understand the strengths and limitations of automated systems so that they can be used (and improved) to compliment the strengths and weaknesses of human analysts to the greatest extent possible. This article reviews some of our experiences with the Classifynder system and our exploration of alternative classifier models to enhance both accuracy and interpretability. Our experiments in the pollen analysis problem domain have been based on samples from the Australian National University's pollen reference collection (2890 grains, 15 species) and images bundled with the Classifynder system (400 grains, 4 species). These samples have been represented using the Classifynder image feature set. In addition to the Classifynder's native neural network classifier, we have evaluated linear discriminant, support vector machine, decision tree and random forest classifiers on these data with encouraging results. Our hope is that our findings will help enhance the performance of future releases of the Classifynder and other systems for accelerating the acquisition and analysis of pollen samples. © 2013 AIP Publishing LLC

Aboriginal impacts on fire and vegetation on a Tasmanian island

Aim To evaluate the influence of climate and Aboriginal landscape management on Holocene vegetation and fire activity. Location Flinders Island, Bass Strait, Tasmania where archaeological data document extended periods of human presence and absence over the past 12,000 years. Methods We evaluated climate–human–fire interactions through high-resolution pollen, charcoal and geochemical analyses of sediment cores from two wetland sites. Proxies for environmental change are qualitatively compared with archaeological data documenting Aboriginal occupation and later abandonment during the mid-Holocene. Results Warm and dry conditions of the early Holocene combined with anthropogenic ignitions promoted frequent fires that sustained highly fire-tolerant Eucalyptus savanna. During the mid-Holocene, when both temperatures and precipitation reached Holocene maxima, archaeological data suggest Aboriginal populations abandoned Flinders Island. At this time, Eucalyptus savanna was replaced by Casuarinaceae and broadleaf forests and fire activity decreased. The late Holocene was marked by a transition to increased incidence of intense fires that was associated with a shift from Casuarinaceae forests to xerophytic scrub dominated by Callitris rhomboidea, a conifer that is sensitive to frequent fires but regenerates well following infrequent fires. Main conclusions Palaeoenvironmental analyses from Flinders Island document significant shifts in fire regimes and vegetation types through the Holocene. In the early Holocene, Aboriginal landscape management played a key role in maintaining open Eucalyptus savanna, a prime habitat for marsupial prey species. Increasing aridity and strengthening of the El Niño Southern Oscillation climate mode during the mid to late Holocene contributed to the cessation of permanent human occupation and concomitant reduction of ignitions. Infrequent fire activity led to the dominance of xerophytes, especially Callitris, a genus adapted to drought and infrequent high-severity fires. This study highlights how climate change affects the persistence of human populations on islands and the capacity of human-set fires to create savanna habitats.This research was supported by National Science Foundation (NSF) PIRE grant OISE 0966472, NSF GSS 1024413 and Australian Research Council (Grant DP110101950). Permission to core wetland sites on Flinders Island was grant by the Department of Primary Industries, Parks, Water & Environment (Tasmanian State Government, permit number E11133

Pollen image classification using the classifynder system: Algorithm comparison and a case study on New Zealand honey

We describe an investigation into how Massey University’s Pollen Classifynder can accelerate the understanding of pollen and its role in nature. The Classifynder is an imaging microscopy system that can locate, image and classify slide based pollen samples. Given the laboriousness of purely manual image acquisition and identification it is vital to exploit assistive technologies like the Classifynder to enable acquisition and analysis of pollen samples. It is also vital that we understand the strengths and limitations of automated systems so that they can be used (and improved) to compliment the strengths and weaknesses of human analysts to the greatest extent possible. This article reviews some of our experiences with the Classifynder system and our exploration of alternative classifier models to enhance both accuracy and interpretability. Our experiments in the pollen analysis problem domain have been based on samples from the Australian National University’s pollen reference collection (2,890 grains, 15 species) and images bundled with the Classifynder system (400 grains, 4 species). These samples have been represented using the Classifynder image feature set.We additionally work through a real world case study where we assess the ability of the system to determine the pollen make-up of samples of New Zealand honey. In addition to the Classifynder’s native neural network classifier, we have evaluated linear discriminant, support vector machine, decision tree and random forest classifiers on these data with encouraging results. Our hope is that our findings will help enhance the performance of future releases of the Classifynder and other systems for accelerating the acquisition and analysis of pollen samples

Palaeochannels of Australia's Riverine Plain - reconstructing past vegetation environments across the Late Pleistocene and Holocene

Riverine Plain palaeochannels record periods of fluvial activity for Late Pleistocene southeastern Australia. In an attempt to develop a more detailed palaeoenvironmental record for this semi-arid region, we investigate the fine overbank sediments of the palaeochannel fill that cap and underlie the coarser-grained fluvial channel sands of the Tombullen (41-29 thousand years (ka) ago) and the Yanco (29-18 ka) phases. New single grain Optically Stimulated Luminescence (OSL) age determinations for the overlying palaeochannel fills suggest an overall slowing of sedimentation rates since the phase of fluvial activity in late Marine Isotope Stages 3 and 2. delta C-13(TOC) data for the palaeochannel fill sediments range between -28 parts per thousand and -22 parts per thousand, implying variable C4 contributions (0-40%) to a predominantly C3 vegetation mosaic. Modelled C4 abundance for the last 50 thousand years (kyr) decreased from 40% to 10% at around 40 ka with predicted representation remaining low towards the Last Glacial Maximum (LGM). Post LGM C4 grasses are seen to expand to 30-40% and sustained through the Holocene. Pollen preservation is restricted to the upper two metres of the cores, with the distribution showing shifts in dominance from Poaceae and Asteraceae to Eucalyptus up sequence. Increasing Eucalyptus/Poaceae ratios correspond with increasing C4 abundance suggesting that as woodland expanded in the Holocene the associated decreasing grass component shifted from C3 to C4. However, some evidence for the persistence of Poaceae and/or Asteraceae dominance argues that the likely shift from C3 to C4 grasses during the Holocene was in places independent of expanding woodland. Bulk sediment elemental ratios reveal wetting and drying cycles during the deposition of the overbank deposits. While these traits appear to be a product of local sedimentation changes, rather than regional climate, our model of C4 contraction and subsequent expansion across the last 50 kyr is likely reflecting changing summer monsoon intensity and its effects on regional aridity