Browsing by Author "Bramley-Alves, J"

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    Antarctic mosses reveal high resolution records of local microclimates
    (Australian Nuclear Science and Technology Organisation, 2021-11-17) Waterman, MJ; Bramley-Alves, J; Casanova-Katny, A; Zúñiga, GE; Hua, Q; Robinson, SA
    Introduction Life in Antarctica is living in the extreme. To survive there, life must be resilient to sub-zero temperatures, high levels of damaging ultraviolet and solar radiation, strong winds and waterlimiting environments. In this harsh continent where water is locked up as snow and ice for most of the year, mosses are the dominant plant form. Like many living things, these small plants rely on liquid water to survive. The amount of potential water that is available to drive growth, distribution and survival of Antarctic flora is strongly influenced by the changing climate, especially temperature, precipitation and winds. However, meteorological climate records in most of the biologically diverse regions in Antarctica are sparse and limited to a few decades or less. In these areas, there is an increasing need for local climate proxies. We show that Antarctic moss species can be used as living proxies for local water availability through preserved stable carbon isotopes captured in cellulose. Methods and Results Using accelerator and isotope ratio mass spectrometry techniques, we obtained radiocarbon ages and δ¹³C signatures along 26 cores of long shoots of moss collected from the Windmill Islands, East Antarctica and South Shetland Islands in the Maritime Antarctic. AMS radiocarbon results showed that these once living cores are up to 500 years old. The five moss species studied grew at different rates; the slowest species grew at less than 1 mm/year while the fastest achieved 8 mm/year. These moss cores provide a high-resolution record, at annual to decadal scales, of their microclimate. Our results also reveal that growth patterns of these Antarctic plants are dependent on local moisture environments. Trends in δ¹³C signatures indicate microclimates in these regions are drying. Conclusion This work suggests that mosses have considerable potential as climate proxies by providing a temporal and spatial history of microclimate in Antarctica. Applying these measures will allow us to determine which terrestrial sites are at risk of the negative impacts of climate change in order to inform critical conservation efforts in a rapidly changing environment. © The Authors
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    Radiocarbon bomb spike reveals climate change is stunting growth of century old Antarctic moss shoots
    (Ecological Society of America (ESA), 2012-08-09) Robinson, SA; Clarke, LJ; Waterman, MJ; Bramley-Alves, J; Hua, Q; Wanek, W; Fink, D
    The Antarctic has experienced major changes in temperature, wind speed and stratospheric ozone levels over the last 50 years. However until recently continental Antarctica appeared to be little impacted by climate warming, thus biological changes were predicted to be relatively slow. Detecting the biological effects of Antarctic climate change has been hindered by the paucity of long-term data sets, particularly for organisms that have been exposed to these changes throughout their lives. We have shown that radiocarbon signals preserved along shoots of the dominant Antarctic moss flora can be used to determine accurate growth rates over a period of several decades, allowing us to explore the influence of environmental variables on growth and providing a dramatic demonstration of the effects of climate change. Detailed 60-year growth records have been generated for Ceratodon purpureus and three other East Antarctic moss species (Bryum pseudotriquetrum, Schistidium antarctici and Bryoerythrophyllum recurvirostre) using the 1960s radiocarbon bomb spike. Growth rate and stable carbon isotope (d13C) data show that C. purpureus’ growth rates are correlated with key climatic variables, and furthermore that the observed effects of climate variation on growth are mediated through changes in water availability. Many of the sites investigated showed evidence of drying over recent decades and this was associated with reductions in moss growth rate. The most likely cause of this drying is increased wind speeds around the coast of Antarctica linked to depletion of the ozone layer. The finding that stable isotope signals laid down as the mosses grow can be used to determine changes in microhabitat water availability over recent decades means that in future, Antarctic mosses could be used as proxies for past coastal climate. Changes in water availability during the growing season may determine the fate of these mosses and the associated communities that form oases of Antarctic biodiversity. © 2012 Ecological Society of America