Papers by Janelle Stevenson
Teaching that requires students to peer down a microscope to resolve tiny particles with 3D form ... more Teaching that requires students to peer down a microscope to resolve tiny particles with 3D form can be pretty challenging. But what if students could pick up and handle these microscopic forms. In recent years 3D printing has transformed the education sphere, with printed 3D models giving the user a better mental image, a tactile experience and a practical way to control orientation vagaries as well as to investigate fine scale structures and function of the sample in question. In the biological sciences most of the focus has been in medicine, primarily through CT scanning and the subsequent 3D production of complex anatomical models. There are, however, numerous lifeforms that are microscopic and beyond the resolution limit of CT scanning. These lifeforms present students with the cognitive challenge of comprehending their 3D form from traditional 2D presentations in texts or when viewed down the light microscope. Research has shown that hand-held 3D models can help overcome many ...
Bookmarks Related papers MentionsView impact
This paper reports the results of an archaeological survey in Ilocos Norte in February 2008. It i... more This paper reports the results of an archaeological survey in Ilocos Norte in February 2008. It is suggested that problems associated with postglacial valley incision and subsequent Holocene infilling will result in a very fugitive record for the Neolithic, unless very deep prospecting is carried out, beyond the ability of field teams with hand augers. A presence of large shell middens can alleviate this problem, as in the Cagayan Valley, but none are reported from Ilocos Norte, owing perhaps to an absence of suitable estuarine conditions for dense shellfish populations. Ilocos Norte undoubtedly has a rich Neolithic archaeological record, but finding it might not be easy. Background In February 2001, en route from Manila via Laoag to the Batanes Islands, Bellwood and Dizon flew over Paoay Lake on approach into Laoag airport. The lake was not visited on this occasion, but the brief aerial view suggested that the sand dune and lake complex would be
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Flotation was tried on several Batanes sites, but was rarely successful owing to a general lack o... more Flotation was tried on several Batanes sites, but was rarely successful owing to a general lack of charcoal in the seasonally wet and dry soil conditions. For instance, it was carried out at Sunget and Mavuyok a Ahchip during the first season of fieldwork on Batan in 2002. Abundant charred plant material was recovered from the latter site, a protected cave with deposits of very recent date, but Sunget by comparison had only a small amount. Unfortunately, expertise to identify the recovered botanical samples was not available and this line of research eventually lapsed.
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Rennix Gap Bog is a sub-alpine topogenic peatland that contains up to 2 m of organic-rich sedimen... more Rennix Gap Bog is a sub-alpine topogenic peatland that contains up to 2 m of organic-rich sediments that have built up over the last approximately 12,000 years. This paper summarises the research and teaching activities that have been undertaken at the site, which has included consideration of the sediment stratigraphy, radiometric dating, palynology, charcoal analyses, dendrochronology and recently, the testate amoebae community composition has been documented. Much of this work is unpublished but has relevance for any future research and provides a long-term context for many contemporary environmental issues, including for issues of relevance to the management of fire in this landscape and vegetation more broadly. In the contemporary environment, the surface of the bog is vegetated with a complex mosaic of Carex fen, sub-alpine Sphagnum shrub bog and Poa costiniana tussock grassland. Pollen analysis suggests that this vegetation has been relatively stable for 10,000 years and prio...
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Dating, pollen, and charcoal particle findings are presented from two mangrove swamp cores recove... more Dating, pollen, and charcoal particle findings are presented from two mangrove swamp cores recovered from Pohnpei, Eastern Caroline Islands, Micronesia. The cores, from opposite sides of the island, provide continuous sediment se- quences dating from the early Holocene. Pollen analysis demonstrates that the giant swamp taro ( Cyrtosperma chamissonis ), an important cultigen on many islands in the Western Pacific, was growing on Pohnpei during prehuman times, indicating that its natural prehuman distribution was far wider than previously suspected. The archaeological implications for the prehuman presence of C. chamissonis are discussed. The cores are inconclusive with regard to the timing of initial human settlement and landscape change on Pohnpei, possibly due to their location deep within large coastal mangrove forests where terrestrial pollen types and charcoal from local fires are poorly dispersed.
Bookmarks Related papers MentionsView impact
Indigenous land use and climate have shaped fire regimes in southeast Australia during the Holoce... more Indigenous land use and climate have shaped fire regimes in southeast Australia during the Holocene, although their relative influence remains unclear. The archaeologically attested mid-Holocene decline in land-use intensity on the Furneaux Group islands (FGI) relative to mainland Tasmanian and SE Australia presents a natural experiment to identify the roles of climate and anthropogenic land use. We reconstruct two key facets of regional fire regimes, biomass (vegetation) burned (BB) and recurrence rate of fire episodes (RRFE), by using total charcoal influx and charcoal peaks in palaeoecological records, respectively. Our results suggest climate-driven biomass accumulation and dryness-controlled BB across southeast Australia during the Holocene. Insights from the FGI suggest people elevated the recurrence rate of fire episodes through frequent cultural burning during the early Holocene and reduction in recurrent Indigenous cultural burning during the mid–late Holocene led to increa...
Bookmarks Related papers MentionsView impact
We analyze sedimentary charcoal records to show that the changes in fire regime over the past 21,... more We analyze sedimentary charcoal records to show that the changes in fire regime over the past 21,000 yrs are predictable from changes in regional climates. Analyses of paleo- fire data show that fire increases monotonically with changes in temperature and peaks at intermediate moisture levels, and that temperature is quantitatively the most important driver of changes in biomass burning over the past 21,000 yrs. Given that a similar relationship between climate drivers and fire emerges from analyses of the interannual variability in biomass burning shown by remote-sensing observations of month-by-month burnt area between 1996 and 2008, our results signal a serious cause for concern in the face of continuing global warming.
Bookmarks Related papers MentionsView impact
Wetlands
Understanding long-term ecological development of wetlands is critical to effective management. T... more Understanding long-term ecological development of wetlands is critical to effective management. The islands of Bass Strait, southeast Australia, have several biologically diverse natural wetlands, including Ramsar sites, yet little is known about their ecology. Here, through a multi-proxy palaeoecological approach, we seek to understand how wetland floristic composition and hydrology has changed on truwana/Cape Barren Island (CBI), and how changes in fire regimes have affected wetland integrity and ecological dynamics. We use wetland fossil pollen, non-pollen palynomorphs and sediment geochemistry to reconstruct wetland development and compare it to existing records of terrestrial vegetation and fire regimes from the island. Our results suggest periods of moderately saline–brackish conditions and moderate fire activity supported high floristic richness in wetlands, while floristic richness reduced during periods of extremely high or low salinity or high fire activity. Past changes in precipitation regimes primarily drove water-level changes in wetlands; however, changes in wetland and surrounding terrestrial vegetation cover also contributed to wetland water level dynamics. We recommend long-term monitoring of wetland salinity and water-level changes to track potential changes in wetland floristic richness on truwana/CBI. Controlled fires could also be used to manage wetland biodiversity after careful consideration and experimentation to determine appropriate fire levels that maximize wetland floristic richness and biocultural values.
Bookmarks Related papers MentionsView impact
Journal of Biogeography
Bookmarks Related papers MentionsView impact
Nature Ecology & Evolution
It has been suggested that Iberian arrival in the Americas in 1492 and subsequent dramatic depopu... more It has been suggested that Iberian arrival in the Americas in 1492 and subsequent dramatic depopulation led to forest regrowth that had global impacts on atmospheric CO2 concentrations and surface temperatures. Despite tropical forests representing the most important terrestrial carbon stock globally, systematic examination of historical afforestation in these habitats in the Neotropics is lacking. Additionally, there has been no assessment of similar depopulation–afforestation dynamics in other parts of the global tropics that were incorporated into the Spanish Empire. Here, we compile and semi-quantitatively analyse pollen records from the regions claimed by the Spanish in the Atlantic and Pacific to provide pan-tropical insights into European colonial impacts on forest dynamics. Our results suggest that periods of afforestation over the past millennium varied across space and time and depended on social, economic and biogeographic contexts. We argue that this reveals the unequal ...
Bookmarks Related papers MentionsView impact
Journal of Biogeography
Understanding long‐term heathland development is key in mitigating their current attrition global... more Understanding long‐term heathland development is key in mitigating their current attrition globally. However, such knowledge is limited in Australia and the wider Southern Hemisphere. We aim to identify potential climatic and environmental drivers of Holocene heathland development in temperate‐oceanic Australia (Bass Strait), and also assess the applicability of Iversen's conceptual model of interglacial vegetation development to the area. We used multiple sedimentary pollen and charcoal records from truwana/Cape Barren Island (CBI) in Bass Strait to reconstruct vegetation and fire history. We also used rarefaction analysis on pollen records to estimate floristic richness for all sites, and magnetic susceptibility and organic content were derived for two of the four sites as proxies for local sedimentary changes. Reconstructed vegetation and fire histories were then compared to independent records of climate and sea‐level change in temperate Australia, using a Detrended Correspondence Analysis ordination, to identify major drivers of heathland development. Major heathland expansion occurred on truwana/CBI between the early and mid‐Holocene in response to sea‐level rise, high effective precipitation, reduced seasonality and increased Indigenous burning. Increasing seasonality, low effective precipitation, El Niño‐Southern Oscillation intensification, stable sea level, and decreased fire activity drove the expansion of scrub and woodland at the expense of heathland in the late Holocene. The overall vegetation development on truwana/CBI fits poorly with the classic Iversen conceptual model of interglacial vegetation development in the Northern Hemisphere, due to the significant role of interglacial sea‐level rise on truwana/CBI. Therefore, a modified model, which takes into account the role of sea‐level change, is proposed for Southern Hemisphere‐temperate‐oceanic settings. Heathland developments in both hemispheres reflect some level of homogeneity, considering the roles of increased Indigenous burning and reduced seasonality in both hemispheres. Frequent, controlled burning strategies are recommended to maintain heathland on truwana/CBI.
Bookmarks Related papers MentionsView impact
Global Ecology and Biogeography
Aim Knowledge of the drivers of ecosystem changes in the past is key to understanding present eco... more 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).
Bookmarks Related papers MentionsView impact
Elem Sci Anth
Mercury (Hg) contamination is an environmental concern as a by-product of legacy mining in Austra... more Mercury (Hg) contamination is an environmental concern as a by-product of legacy mining in Australia. Here we investigate the spatial and temporal distribution of Hg in the Molonglo River system in New South Wales, Australia, and assess the physical and chemical factors influencing that distribution. Mercury concentrations in sediment cores were measured in conjunction with 210Pb and 137Cs dating to establish historical contamination. This was done at the source mine site of Captains Flat, New South Wales, and the system’s sink in Lake Burley Griffin, Australian Capital Territory. Additionally, surficial sediment Hg concentrations along the Molonglo River were analyzed to determine the spatial distribution of Hg. Analytical results showed the primary physical and chemical factors influencing Hg dispersion to be distance, total organic matter, and the presence of iron oxides and oxyhydroxides. The highest Hg concentrations were near the mine site at Captains Flat and decreased signif...
Bookmarks Related papers MentionsView impact
Palaeogeography, Palaeoclimatology, Palaeoecology
Abstract There is a paucity of long and continuous continental records from South East Asia suita... more Abstract There is a paucity of long and continuous continental records from South East Asia suitable to inform on past changes and underlying causes of the region's climate and associated diverse ecosystem evolution during the late Quaternary. In 2015, the Towuti Drilling Project (TDP) collected a series of sedimentary drill cores from the tectonic, ferruginous, and highly biodiverse Lake Towuti, Sulawesi, one of Indonesia's oldest lakes. The drill cores contain ~1 Myr of uninterrupted lacustrine sedimentation to document long-term environmental and climatic change in the tropical western Pacific, the impacts of geological and environmental changes on the biological evolution of aquatic taxa, and the geomicrobiology and biogeochemistry of metal-rich, ultramafic-hosted lake sediment. Here we use lithostratigraphic, mineralogical, geochemical, and geochronological datasets to elucidate Lake Towuti's tectonic emergence and its biogeochemical responses to climatic and volcanic forcings since lake formation. Our data document that Lake Towuti emerged during a phase of accelerated tectonic subsidence from a landscape characterized by active river channels, shallow lakes and swamps into a permanent lake at ~1 Ma. The lacustrine sediments feature quasi-rhythmic alternations of green organic rich and red sideritic clay beds reflecting changes in lake mixing and biogeochemistry as a response to temperature and hydrological changes driven by orbital-scale changes in insolation and continental ice volume through the mid- to late Pleistocene. Clay deposition is interrupted by two beds of diatomaceous oozes composed primarily of planktonic diatoms that reflect phases of substantially increased primary productivity. The occurrence of these diatomaceous oozes in close association with multiple tephra beds suggests a trophic state change driven by the addition of volcanically sourced P, possibly in combination with a lake mixing state that supports recycling of P. Data on lake age and ontogeny are also in agreement with molecular-clock estimates of ~0.7 Ma (0.18–1.37 Ma) for the divergence of Lake Towuti's Telmatherinid fishes from a riverine ancestor. Our data therefore are compatible with an evolutionary model in which Lake Towuti's endemic fauna is a result of geographic speciation in the Malili Lakes, a set of large lakes in Southeast Sulawesi, driven by physical or chemical dispersal limits imposed by the regional rivers and lakes. More detailed chronological constraints and refined climate and environmental proxy datasets are currently in preparation and will help to paint a more detailed history of the region's climate and environmental history in future studies.
Bookmarks Related papers MentionsView impact
Peopled Landscapes: Archaeological and Biogeographic Approaches to Landscapes, 2012
Bookmarks Related papers MentionsView impact
The Archaeology of Sulawesi: Current Research on the Pleistocene to the Historic Period, Nov 13, 2018
Bookmarks Related papers MentionsView impact
The Early Prehistory of Fiji, Dec 1, 2009
Bookmarks Related papers MentionsView impact
Uploads
Papers by Janelle Stevenson