Rainforest response to glacial terminations before and after human arrival in Lutruwita (Tasmania)

Limited understanding of how Indigenous people have created and managed the Australian landscape continues to have repercussions on how landscapes are culturally interpreted and managed today. Addressing this is critically important as climate change is increasing the frequency and intensity of wildfires, whilst challenging the objectives, methods and efficacy of contemporary landscape management practices. Here we compare the palaeoecology of vegetation changes across glacial to interglacial states before (Termination II) and after (Termination I) human occupation of the cool temperate rainforests of western Lutruwita (Tasmania). Sediment from Darwin Crater (Termination II) and Lake Selina (Termination I) were analysed using radiometric dating, fossil pollen, charcoal, geochemical, environmental magnetic and sedimentary methods to produce a comprehensive reconstruction of vegetation and landscape dynamics. Results show marked differences in the rainforest response to the transition from glacial to interglacial climates before and after human arrival at c. 43,000 years ago (ka). In the absence of human disturbance, Phyllocladus aspleniifolius-Nothofagus cunninghamii lowland rainforest taxa dominated the last interglacial period (∼77% of the pollen sum) but was reduced in the current interglacial (∼41%) and largely replaced by Gymnoschoenus sphaerocephalus buttongrass moorland (10–23%). This demonstrates the legacy of Indigenous Palawa managed landscapes, primarily using fire to promote landscape openness and prevent the dominance of an ecologically climax rainforest community, until their forced removal via invasion and colonisation ca. 1806

Imaging complex nutrient dynamics in mycelial networks

© Cambridge University Press 2007 and Cambridge University Press, 2009. Basidiomycetes are the major agents of decomposition and nutrient cycling in forest ecosystems, occurring as both saprotrophs and mycorrhizal symbionts (Boddy and Watkinson, 1995; Smith and Read, 1997). The mycelium can scavenge and sequester nutrients from soil, concentrate nutrients from decomposing organic matter, relocate nutrients between different organic resources, and ultimately make nutrients available to plants to maintain primary productivity. Hyphae of both saprotrophic and ectomycorrhizal basidiomycetes that ramify through soil often aggregate to form rapidly extending, persistent, specialized high-conductivity channels termed cords (Rayner italic., 1994, 1999; Boddy, 1999; Watkinson, 1999; Cairney, 2005). These cords form complex networks that can extend for metres or hectares in the natural environment. The distribution of resources is extremely heterogeneous and unpredictable in space and time, and these fungi have developed species-specific strategies to search for new resources and to capitalize on resources landing on their mycelial systems (Chapter 6, this volume). Thus the architecture of the network is not static, but is continuously reconfigured in response to local nutritional or environmental cues, damage or predation, through a combination of growth, branching, fusion or regression (Boddy, 1999; Watkinson, 1999; Chapter 6, this volume). At this stage it is not clear whether specific global mechanisms exist to couple local sensory perception and responses over different length scales specifically to maximize the long-term success of the whole colony, or whether such collective behaviour is an emergent property arising solely from local interactions of individual hyphae

The impacts of intensive mining on terrestrial and aquatic ecosystems: A case of sediment pollution and calcium decline in cool temperate Tasmania, Australia

Mining causes extensive damage to aquatic ecosystems via acidification, heavy metal pollution, sediment loading, and Ca decline. Yet little is known about the effects of mining on freshwater systems in the Southern Hemisphere. A case in point is the region of western Tasmania, Australia, an area extensively mined in the 19th century, resulting in severe environmental contamination. In order to assess the impacts of mining on aquatic ecosystems in this region, we present a multiproxy investigation of the lacustrine sediments from Owen Tarn, Tasmania. This study includes a combination of radiometric dating (14C and 210Pb), sediment geochemistry (XRF and ICP-MS), pollen, charcoal and diatoms. Generalised additive mixed models were used to test if changes in the aquatic ecosystem can be explained by other covariates. Results from this record found four key impact phases: (1) Pre-mining, (2) Early mining, (3) Intense mining, and (4) Post-mining. Before mining, low heavy metal concentrations, slow sedimentation, low fire activity, and high biomass indicate pre-impact conditions. The aquatic environment at this time was oligotrophic and dystrophic with sufficient light availability, typical of western Tasmanian lakes during the Holocene. Prosperous mining resulted in increased burning, a decrease in landscape biomass and an increase in sedimentation resulting in decreased light availability of the aquatic environment. Extensive mining at Mount Lyell in the 1930s resulted in peak heavy metal pollutants (Pb, Cu and Co) and a further increase in inorganic inputs resulted in a disturbed low light lake environment (dominated by Hantzschia amphioxys and Pinnularia divergentissima). Following the closure of the Mount Lyell Co. in 1994 CE, Ca declined to below pre- mining levels resulting in a new diatom assemblage and deformed diatom valves. Therefore, the Owen Tarn record demonstrates severe sediment pollution and continued impacts of mining long after mining has stopped at Mt. Lyell Mining Co