Browsing by Author "Smernik, RJ"

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    Environmental change in the coastal wetlands near Adelaide, Australia.
    (Elsevier, 2007-07) Nicholson, ED; Krull, ES; Smernik, RJ; Zawadzki, A; Gell, PA; Gillanders, BM
    The coastal wetlands located near metropolitan Adelaide are comprised almost exclusively of the Grey Mangrove (Avicennia marina). This native vegetation is a natural resource that has numerous suggested functions, including coastal buffering, mitigation of terrestrially derived nutrient runoff, fish nursery habitat and also ecotourism. The coastal wetlands that are the focus of this study exist primarily within two aquatic reserves. As such, it is important to understand how this coastal environment once existed so as to provide a reference for assessing its current condition. In the relatively calm marine environment provided by the Grey Mangrove, sediments are trapped amongst the roots and pneumatophores. Within these sediments, a number of proxies exist, by which past environmental conditions may be reconstructed. These proxies include microfossils, such as diatoms and forams, macrofossils, such as pollen and seeds, but also relatively indistinguishable fractions of the soil matrix generally referred to as OM (organic matter). The ultimate question being asked within the larger context of this palaeoecological study is, “What impact has European settlement had on the coastal environment near Adelaide?” The research presented here will focus on the palaeoecological utility of OM, found in mangrove sediments, toward answering this question. Sediment samples were collected and analysed from among twenty-three modern sites and three sediment cores. In addition, plant samples representing the types of organic matter typically found in the study region (e.g. samphire OM, mangrove OM, seagrass OM, macroalgal OM), were collected from the same modern sites. An analysis of 13C and 15N isotopes was performed, as organic matter sources may be differentiated based upon recognisable isotopic signatures (e.g. marine vs. terrestrial plant origins). 13C-NMR spectroscopy was then used to supplement the stable isotope analysis, providing an additional means of differentiating carbon types and their sources. In order to make inferences about post-European impacts upon the study region, a modern chronology was obtained. 210Pb profiling of the sediment cores was performed in combination with an analysis of exotic Pinus pollen occurrences. This study describes the environmental changes that have occurred in Adelaide’s coastal wetlands since European settlement and the level of impact that may be attributable to anthropogenic influence.
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    Loss and gain of carbon during char degradation
    (Elsevier, 2017-03-01) Bird, MI; McBeath, AV; Ascough, PL; Levchenko, VA; Wurster, CM; Munksgaard, NC; Smernik, RJ; Williams, AA
    We report results of a study examining controls on the degradation of chars produced at 300, 400 and 500 °C from radiocarbon-free wood, deployed for three years in a humid tropical rainforest soil in north Queensland, Australia. The chars were subjected to four treatments (i) no litter (ii) covered by leaf litter, (iii) covered by limestone chips to alter local pH, and (iv) covered by limestone chips mixed with leaf litter. Radiocarbon, stable isotope and proximate analyses indicate significant ingress of exogenous (environmental) carbon and mineral material, strongly correlated with loss of indigenous (char) carbon from the samples. While indigenous carbon losses over three years were generally <8% for the char produced at 500 °C char under any treatment, chars formed at lower temperatures lost 5–22% of indigenous carbon accompanied by ingress of up to 7.5% modern exogenous carbon. The data provide clear evidence of a direct link between the ingress of exogenous carbon, likely at least partly due to microbial colonization, and the extent of char decomposition. Failure to account for the ingress of exogenous carbon will lead to a significant under-estimate of the rate of char degradation. © 2016, Elsevier Ltd.