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HAIDEE CADD MICHAEL‐SHAWN FLETCHER MICHELA MARIANI HENDRIK HEIJNIS PATRICIA S. GADD 《第四纪科学杂志》2019,34(7):491-498
Tasmania's montane temperate rainforests contain some of Australia's most ancient and endemic flora. Recent landscape‐scale fires have impacted a significant portion of these rainforest ecosystems. The complex and rugged topography of Tasmania results in a highly variable influence of fire across the landscape, rendering predictions of ecosystem response to fire difficult. We assess the role of topographic variation in buffering the influence of fire in these endemic rainforest communities. We developed a new 14 000‐year (14‐ka) palaeoecological dataset from Lake Perry, southern Tasmania, and compared it to neighbouring Lake Osborne (<250 m distant) to examine how topographic variations influence fire and vegetation dynamics through time. Repeated fire events during the Holocene cause a decline in montane rainforest taxa at both sites; however, in the absence of fire, rainforest taxa are able to recover. Montane temperate rainforest taxa persisted at Lake Perry until European settlement, whilst these taxa were driven locally extinct and replaced by Eucalyptus species at Lake Osborne after 2.5 ka. Contiguous topographic fire refugia within the Lake Perry catchment probably provided areas of favourable microclimates that discouraged fire spread and supported the recovery of these montane temperate rainforests. Copyright © 2019 John Wiley & Sons, Ltd. 相似文献
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Middle Pleistocene to Holocene sediment variations observed in a 26 metre long core taken during a cruise of the RV Marion Dufresne are presented. Core MD992202 was retrieved from the northern slope of Little Bahama Bank and provides an excellent example for sedimentation processes in a mid‐slope depositional environment. The sediment composition indicates sea‐level related deposition processes for the past 375 000 years (marine isotope stages 1 to 11). The sediments consist of: (i) periplatform ooze (fine‐grained particles of shallow‐water and pelagic origin) with moderate variations in carbonate content, carbonate mineralogy and grain‐size; and (ii) coarser intervals with cemented debris consisting of massive, poorly sorted, mud‐supported or clast‐supported deposits with an increased high‐magnesium calcite content. During interglacial stages (marine isotope stages 1, 5, 7, 9 and 11) periplatform oozes (i) are characterized by higher aragonite contents, finer grain‐size and higher organic contents, whereas during glacial stages (marine isotope stages 2 to 4, 6, 8 and 10), increased low‐magnesium and high‐magnesium calcite values, coarser grain‐size and lower organic contents are recorded. These glacial to interglacial differences in mineralogy, grain‐size distribution and organic content clearly show the impact of climatically controlled sea‐level fluctuations on the sedimentation patterns of the northern slope of Little Bahama Bank. The coarser deposits (ii) occur mainly at the transitions from glacial to interglacial and interglacial to glacial stages, and are interpreted as redeposition events, indicating a direct link between sediment properties (changes in mineralogy, grain‐size distribution, variations in organic contents) and sea‐level fluctuations. Changes in hydrostatic pressure and the wave base position during sea‐level changes are proposed to have triggered these large‐scale sediment redepositions. 相似文献
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