• Radial Growth of Oak and Aspen Near a Coal-Fired Station, Manitoba, Canada

      Boone, Rachel; Tardis, Jacques; Westwood, Richard; Centre for Forest Interdisciplinary Research (C-FIR), University of Winnipeg, Winnipeg, Manitoba, Canada R3B 2E9 (Tree-Ring Society, 2004)
      Eighteen stands of bur oak (Quercus macrocarpa Michx.) and trembling aspen (Populus tremuloides Michx.) were sampled and analyzed using dendrochronological methods to study the potential effects on tree growth of emissions from a 132 MW coal-fired generating station. Sixteen stands were sampled within a 16-km radius of the station, and two control stands were sampled outside of the range of influence, at distances . 40 km. All stands showed similar radial growth patterns from 1960-2001, regardless of distance from or direction relative to the generating station, and a number of stands, including the controls, had below average growth after 1970. Both species were significantly affected by climatic factors, showing decreased radial growth with increasing June temperature. The species differed in their growth responses to spring precipitation and temperature in the previous October. One bur oak site displayed marked radial growth decline beginning in the mid-1970s, strongly pronounced following 1977. This decline does not appear to be related to emissions from the station, but is suspected to be a result of poor site conditions (shallow soil developed over calcareous till), confounded by a change in drainage (a road was built adjacent to the stand in 1977, perpendicular to the direction of drainage). The below average growth seen in 1970-2001 across most stands is likely attributable to stand dynamics and age effects.
    • Tree-Ring Studies on Agathis Australis (Kauri): A Synthesis of Development Work on Late Holocene Chronologies

      Fowler, Anthony; Boswijk, Gretel; Ogden, John; School of Geography and Environmental Science, The University of Aukland, Auckland, New Zealand (Tree-Ring Society, 2004)
      The potential of kauri (Agathis australis) for paleoclimate research is well established. Multiple treering chronologies have been derived from living and sub-fossil material and growth-climate relationships have been identified. Work has progressed to the stage where raw ring-width data and chronologies covering the last half of the second millennium can confidently be placed in the public domain, to facilitate multiproxy paleoclimate studies. This paper outlines progress in deriving kauri tree-ring chronologies, summarises data availability and quality, and explores the scope for developing composite chronologies. Statistical quality control of the available data was undertaken, following application of an "optimum" standardisation technique. Variations in sample depth with time and between sites result in a complex evolving pattern of chronology quality across sites. Analysis of inter-site statistical relationships identified a pervasive regionalscale signal in kauri with some minor secondary patterns. In light of the strong common signal, a kauri master chronology was built by pooling tree-ring series. Analysis of the quality of this chronology indicates that high-quality master chronologies can be derived for A.D. 1597-1996 from as few as 25 trees from seven sites.