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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The dendroclimatology of modern and neolithic scots pine (Pinus sylvestris l.) in the peatlands of northern Scotland

Moir, Andy January 2008 (has links)
For the first time in northern Scotland, Modern tree-ring chronologies for Scots pine growing on peat are compared against those growing on mineral substrates. Mean tree-ring growth of pine on active bogs/mires is found to be limited to 0.5 to 1 mm yr-1, compared to ≥1.5 mm yr-1 on adjacent mineral sites. Almost instant change of radial growth rates in response to changes in water levels highlights the potential use of pine in reconstructions of lake levels and water tables in bog and mire. Dendroclimatological analysis identifies January and February temperatures to often be more important than summer temperature. Positive correlation of ring-width and North Atlantic Oscillation (NAO) indices also occur in January and February. Lower winter temperatures, due to increased altitude and distance from the moderating effects of the ocean, may be important in limiting tree growth near its northern margin. Moving correlation functions identify a widespread reduction in the response of pine growing on both substrates from the 1920s. Nine subfossil pine site chronologies located beyond the species current northern limit are cross-matched to form a chronology called WRATH-9. This chronology is tentatively crossdated against Irish pine chronologies to provide the first picture of Neolithic Scots pines 200 year expansion from c. 3200 BC and subsequent 250 year retreat across northern Scotland at annual resolution. The mean orientation of maximum radial growth at eleven modern pine sites is found to coincide well with the W/SW prevailing wind, suggesting Scots pine may provide a good proxy indicator of wind. Six coeval Neolithic sites indicate a broadly consistent northerly prevailing wind. This provides tentative evidence for a change of prevailing wind that may be related to a southward incursion of the polar front in the eastern N. Atlantic. The potential of this exciting subfield of dendroclimatological analysis is called dendroaeology and is highlighted for further research.
2

Progress In Constructing A Long Oak Chronology From The Central United States

Stambaugh, Michael C., Guyette, Richard P. 07 1900 (has links)
We describe methods and progress in developing the American Long Oak Chronology (ALOC), an effort to construct an oak tree-ring chronology from the Central US that spans the Holocene. Since 2000, we have collected and measured ring widths on over 550 pieces of subfossil oak (Quercus) wood. Over 330 oak samples have been radiocarbon dated, with ages ranging up to 14,000 cal yr B.P. A 1,093- year-long tree-ring record has been constructed from live and subfossil bur oaks (Q. macrocarpa Michx.) and swamp white oaks (Q. bicolor Willd.) growing along and buried in sediments of streams that flow through northern Missouri and southern Iowa, USA. Here we describe the ALOC for the period A.D. 912–2004 to demonstrate its dendrochronological value, display the material quality, and emphasize the importance of chronology construction. We also report on progress in developing older floating chronologies. The development of more long, multi-millennium chronologies will be an important contribution to dendroclimatology. These chronologies will be particularly useful to the Central US, a region with a continental climate and limited temporal depth of annually resolved paleorecords. Perhaps more critical is its location in the middle of one of the most important agricultural regions in the world.

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