19 research outputs found

    Limited release of previously-frozen C and increased new peat formation after thaw in permafrost peatlands

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    Permafrost stores globally significant amounts of carbon (C) which may start to decompose and be released to the atmosphere in form of carbon dioxide (CO 2 ) and methane (CH 4 ) as global warming promotes extensive thaw. This permafrost carbon feedback to climate is currently considered to be the most important carbon-cycle feedback missing from climate models. Predicting the magnitude of the feedback requires a better understanding of how differences in environmental conditions post-thaw, particularly hydrological conditions, control the rate at which C is released to the atmosphere. In the sporadic and discontinuous permafrost regions of north-west Canada, we measured the rates and sources of C released from relatively undisturbed ecosystems, and compared these with forests experiencing thaw following wildfire (well-drained, oxic conditions) and collapsing peat plateau sites (water-logged, anoxic conditions). Using radiocarbon analyses, we detected substantial contributions of deep soil layers and/or previously-frozen sources in our well-drained sites. In contrast, no loss of previously-frozen C as CO 2 was detected on average from collapsed peat plateaus regardless of time since thaw and despite the much larger stores of available C that were exposed. Furthermore, greater rates of new peat formation resulted in these soils becoming stronger C sinks and this greater rate of uptake appeared to compensate for a large proportion of the increase in CH 4 emissions from the collapse wetlands. We conclude that in the ecosystems we studied, changes in soil moisture and oxygen availability may be even more important than previously predicted in determining the effect of permafrost thaw on ecosystem C balance and, thus, it is essential to monitor, and simulate accurately, regional changes in surface wetness

    THE COUNTRY UNDER THE CITY: THE SYMBOLIC TOPOGRAPHY OF THE RUSTIC PAST IN LATE REPUBLICAN AND EARLY IMPERIAL ROME

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    This dissertation, The Country under the City: The Symbolic Topography of the Rustic Past in Late Republican and Early Imperial Rome, argues that fundamental to the Roman conception of their capital city was the idea of its being superimposed on top of a pre-existing rural topography, quite literally, a “rus sub urbe.” To demonstrate the various strategies by which this “monumentalization” of the city’s rustic past was achieved, the project considers a number of sites that rarely feature in discussions of Roman topography, largely because there is no trace of them in the archaeological record, ranging from plots of un-built public land termed “meadows” (prata) to the electoral voting precinct designated as the “Sheepyard” (Ovilia). Using the accounts of authors writing across a wide array of genres – pastoral and bucolic poetry, history and antiquarian investigation, as well as the agronomic writings of Cato, Varro, and Pliny the Elder – and comparison with existing structures, I reconstruct their physical appearance in order to demonstrate how, for centuries, the city’s evolving architectural forms and preserved open spaces insisted on Rome’s rustic origins, even as its growth into a pan-Mediterranean empire would suggest otherwise. Ultimately, the research shows that – even in the context of the march toward empire, even as the city’s older buildings burned or fell down and were gradually replaced with ever grander ones – Romans used key topographic features both to vivify the story of the city’s rise from humble beginnings, and to foster a genuine sense of continuity with the landscape and religion of their farmer ancestors, beyond mere nostalgia or conceit
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