Ian Thomas

A 5600-yr history of changing vegetation, sea levels and human impacts from the Black Sea coast of Georgia

Mid-late Holocene pollen evidence from the Ispani-II Sphagnum bog in lowland Western Georgia shows that 4500 years ago Castanea (chestnut)-dominated woods rapidly declined to be replaced by alder swamps and, later, during the first millennium bc, by open, marshy landscapes in which fire played a prominent part. Around 1900 years ago, Sphagnum blanket bog encroached on the marshes and dense Fagus-Carpinus (beech-hornbeam) forest enveloped the surrounding land. This vegetation remained until the mid-twentieth century, when forests were clear-felled and marshes were drained for large-scale, mechanized agriculture. Previous studies have emphasized climate’s governing role in setting the course of Holocene vegetation development in lowland Western Georgia, but our results provide little support for this hypothesis. To a much greater degree, episodes of coastal subsidence, sea-level rise and human impact have shaped the vegetation history of coastal Western Caucasus.

A Holocene record of sea level, vegetation, people and fire from western Tasmania, Australia

The analysis of a 10 000 calendar year (cal. ka) pollen record on the west coast of Tasmania has revealed a suite of changes that can be related to sea level, fire and people. Fire-promoted moorland has occupied the site for the entire period and challenges the long-held assumption that rainforest dominated the landscape of western Tasmania through the early to mid Holocene. Changes in wetland taxa and the occurrence of benthic marine diatoms indicate a Holocene sea-level high-stand between 6.3 and 5.8 cal. ka. A significant and sustained rise in charcoal concentration occurs after 6 cal. ka, reflecting the combined effects of anthropogenic burning and hydrological changes that were probably modulated by regional climatic forcing. Finally, European colonisation resulted in a significant decrease in charcoal, rapid peat accumulation and a suite of vegetation changes.

Sediments as Archives of Industrialisation: Evidence of Atmospheric Pollution in Coastal Wetlands of Southern Sydney, Australia

The history of heavy metal pollution in southern Sydney was reconstructed from wetland sediments using chemical analysis. Seven wetlands along the Pacific coast were examined for present day concentrations of acid-extractable Cd, Cu, Fe, Pb and Zn. Additionally, four of these sites were cored in order to assess past levels of these metal contaminants, changes in organic content and magnetic susceptibility variations. The low nutrient status and closed catchments of the study sites suggested that the pollutants were predominantly derived from atmospheric sources. Surficial sediments were enriched with Cd, Cu, Fe, Pb and Zn levels 5.0, 16.4, 22.7, 8.2 and 22.5 times baseline levels, respectively. In some cases, the concentrations of trace metals were in excess of environmentally acceptable levels. The results show a strong spatial association between sources and levels of pollutants, and the increase in metals levels in sedimentary records corresponds well to documentary historical evidence.This study demonstrates the utility of coastal wetlands in the reconstruction of atmospheric pollution histories, and their particular vulnerability to contamination from airborne pollutants in urban areas.

The Holocene history of mediterraneantype plant communities, Little Desert National Park, Victoria, Australia

This paper begins to identify the relative roles of climiiate change, people and fire as factors in the late-Pleistocene and Holocene evolution of one of the most diverse terrestrial ecosystems in southern Australia. Our research illustrates that pollen from mediterranean-type heathlands can be recognized from sediments taken from small basins in semi-arid ecosystems. The use of pollen and carbonized particle analyses from sedimenitcores, in conjunction with ecological research on planit-fire relationships, establishes a role for palaeoecological techniques in the interpretationi of long-term processes in semi-arid heathlands in Australia. Radiocarbon dates indicate that the treeless structure at our study site in the Little Desert of western Victoria has existed since at least the early Holocene. Pollen evidence indicates an increase in plant diversity, especially in Proteaceae and fire ephemerals, and a decrease in fire-sensitive taxa (e.g.. Callitris spp., Allocasuarina muelleriana type) our the last 4000 years. This decline octirs in conjunction with increases in the frequency of carbonized particles.

Late Holocene vegetation and environments of the Mersey Valley, Tasmania

A record of vegetation and environmental change over the past 3000 years was obtained through pollen and charcoal analysis of sediments from a grassy plain in the Mersey Valley, Tasmania. The results tentatively suggest that Aborigines had an impact on the environment of the Mersey Valley, although the scale of the impact is difficult to quantify owing to complexities associated with the. re history and sedimentary processes. In addition, a strong regional climate signal ( drier late Holocene environments) was observed, suggesting that both anthropogenic and climatic factors are required to explain pre-European environments. The study also showed the dramatic impact European settlers had on the Australian environment, with massive land clearance, introduction of exotic plant types and increased sedimentation rates.

An assessment of the relationship between tree-ring counts and basal girth of high-altitude populations of Eucalyptus pauciflora (Myrtaceae)

We investigated the relationship between the number of growth rings (a surrogate for approximate age of stems) and basal girth for Eucalyptus pauciflora (Maiden & Blakely) L.A.S.Johnson & Blaxell. Using basal-girth measurements and growth-ring counts obtained from trees felled on ski slopes at three Victorian alpine ski resorts, as well as seedlings destructively sampled from near the tree line on four summits, we modelled the relationship between growth rings and basal girth by using simple linear and non-linear regression methods. We compared our data to growth-ring–basal-girth data collected from low- and high-altitude E. pauciflora woodland stands in Kosciuszko National Park. The relationship between the number of tree rings and basal girth at Victorian sites was non-linear (growth ringsu2009=u20093.62u2009×u2009girth0.63, R2u2009=u20090.96). In general, the Victorian and Kosciuszko datasets were in broad agreement, although caution is required when attempting to estimate the age of trees with >115-cm girth. We suggest that the model we have developed can be combined with dendrological techniques to estimate the age of older trees accurately.

In situ agrobiodiversity conservation: Examples from Nepal, Turkey and Switzerland in the first decade of the convention on Biological Diversity

Abstract Applications of in situ agrobiodiversity conservation practices within agricultural production systems have the potential to reduce the risks of agricultural modernisation and enhance sustainable development. The aims and approaches for in situ conservation differ according to the requirements of communities and nations. Approaches to in situ conservation in the decade after the Convention of Biological Diversity are reviewed within the contexts of marginal agricultural systems in Nepal, Turkey and Switzerland. Numerous approaches are currently utilised, including: the informal de facto retention of agrobiodiversity; the provision of state assistance; the marketing of agrobiodiversity products; the use of technological innovations to develop local diversity; the establishment of conservation reserves; community assistance programmes and the raising of awareness of the issue amongst all sectors of societies. Emerging complementary in situ approaches applicable in the rural margins suggest a framework for effectively conserving agrobiodiversity by working with local people.

Excavations at Sos Höyük, 1995: Second Preliminary Report

La campagne de fouilles menee durant lete 1995 a Sos Hoyuk avait pour but de poursuivre le degagement de lhabitat medieval (trois phases de construction) au sommet du tell, ainsi que le grand bâtiment de la periode hellenistique, visiblement detruit par un violent incendie vers 150 av. J.-C. Des fouilles ont egalement ete realisees dans les tranchees plus basses du nord-ouest du tell afin de clarifier la nature des depots des IIIe et IIe millenaires av. J.-C. (sols dhabitat, fosses, ceramiques). Un sondage vertical a ete entrepris independamment de ces fouilles afin dobtenir les premieres donnees concernant loccupation du site a lAge du Fer. Autour du site, la prospection de terrain intensive destinee a trouver les sources dobsidienne sest poursuivie, une etude paleoecologique detaillee de la region a ete ouverte cette annee et une prospection magnetique a ete menee dans les cimetieres entourant le site afin de definir leurs limites. Enfin, un effort a ete fait en faveur de lorganisation dune nouvelle exposition couvrant les campagne de fouilles de Buyuktepe Hoyuk et Sos Hoyuk au Musee dErzurum

Models and prima-donnas in southwest Tasmania

The following is a brief reply to Cosgrove et al. (1994). I have confined myself to addressing the few substantive considerations raised by those authors in regard to my previously published paper (Thomas 1993a). The issues are discussed in order as they appear in Cosgrove et al. (1994). Â

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

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 south-eastern 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.