• Tree-Ring Analysis of Taxus Baccata from the Western Himalaya, India, and its Dendroclimatic Potential

      Yadav, Ram R.; Singh, Jayendra; Birbal Sanhi Institute of Palaeobotany, Lucknow, India (Tree-Ring Society, 2002)
      A 345-year (AD 1656-2000) ring-width chronology of common yew (Taxus baccata L.) from the western Himalaya has been prepared. This provides the first record of a well crossdated ring-width chronology of yew from the Himalayan region, India. The mean temperature of the premonsoon (March-June) season has an indirect relationship with tree growth. The yew chronology is also significantly correlated with an Abies pindrow chronology prepared from the same stand as well as A. spectabilis from the treeline zone of an adjacent site. Such a significant relationship indicates the good potential of yew for dendroclimatic studies in the Himalayan region.
    • Tree-Ring Research in Semi-Arid West Africa: Need and Potential

      Tarhule, Andover; Hughes, Malcolm K.; Department of Geography, University of Oklahoma, Norman, OK; Laboratory of Tree-Ring Research, University of Arizona, Tucson, AZ (Tree-Ring Society, 2002)
      High-resolution paleoclimatic data for West Africa are needed to provide context for contemporary climatic and ecological dynamics. Six hundred trees (22 botanical families, 43 genera and over 70 species) from semi-arid West Africa were evaluated for their suitability for dendrochronological research; specifically ring development. The samples were classified as 'potentially useful', 'problematic', or 'poor' based on the presence and distinctiveness of annual rings, ability to achieve crossdating between radii using skeleton plots on at least some samples, circuit uniformity, ring wedging, and variability of ring widths. Samples were classified as potentially useful if (a) they exhibited distinctive annual rings that could be identified and counted with little uncertainty and be independently verified by a second person with little or no error, (b) crossdating between radii could be successfully achieved, at least on some samples, (c) the rings were generally consistent throughout the stem cross section, (d) ring wedging was minimal (in the relative sense) or absent, and (e) the ring widths were variable, indicating the possibility of climatic sensitivity. Seven species, including five from the Caesalpiniaceae family (Cassia sieberiana, Cordyla pinnata, Daniella oliveri, Isoberlinia doka, Tamarindus indica), and one each from Mimosaceae (Acacia seyal) and Verbenaceae (Gmelina arborea) families, that most closely satisfied these criteria were classified as 'potentially useful'. The 'problematic' category includes those samples that satisfied some of the criteria but for which greater diligence is required to detect rings. Eight species from three families were classified in this category. Finally those samples on which ring detection appears futile given current methods and techniques were classified as 'poor'. Most of the samples classified as 'potentially useful' belong to three botanical families, Caesalpiniaceae, Mimosacae, and Verbenaceae. These results are consistent with the findings of other studies, and therefore support further investigation of the potential of West African trees for tree-ring analysis focusing on these families. Furthermore, inability to crossdate between trees and to explain several ring anatomical features underscores the pressing need for comprehensive field studies of cambial activity during the growing season, and for the identification of dormant seasons. This requirement, and other difficulties discussed suggest a need for increasing the local dendrochronological expertise in West Africa.
    • Tree-Ring Society

      Tree-Ring Society, 2002
    • Trends in Quercus Macrocarpa Vessel Areas and their Implications for Tree-Ring Paleoflood Studies

      St. George, Scott; Nielsen, Erik; Conciatori, France; Tardif, Jacques; Geological Survey of Canada, Winnipeg, Manitoba, Canada; Manitoba Geological Survey, Winnipeg, Manitoba, Canada; Centre for Forest Interdisciplinary Research, University of Winnipeg, Winnipeg, Manitoba, Canada (Tree-Ring Society, 2002)
      Changes in mean earlywood vessel areas in mature Quercus macrocarpa were analyzed to determine possible sources of bias in paleoflood records derived from anatomical tree-ring signatures. Tree-ring cores were collected at intervals along the vertical axis of four Q. macrocarpa in a flood-prone stand near the Red River in Manitoba. The WinCELL PRO image analysis system was used to measure mean vessel areas in each annual ring. Most cores displayed a pronounced juvenile increase in mean vessel area before stabilizing between 40 and 60 years. The lowest samples from several trees contain rings with anomalously small mean vessel areas that are coincident with high-magnitude Red River floods in 1950 and 1997. The anatomical response of Q. macrocarpa appears to be conditional on the relative timing of earlywood development and flooding. Flood signatures are most strongly developed near the tree base and become less evident up the trunk. Most signatures disappear between one and three meters in height. Differences in flood response between trees are likely caused by internal differences rather than hydrological or topographic factors. Paleoflood studies based on samples obtained exclusively at breast height may miss some anatomical flood signatures and underestimate flood frequency relative to earlier intervals.