• Dendrochronology of Abies Religiosa in Michoacan, Mexico

      Huante, Pilar; Rincón, Emmanuel; Swetnam, Thomas W.; Centro de Ecología, UNAM, Ciudad Universitaria, México; Laboratory of Tree-Ring Research, University of Arizona, Tucson, Arizona (Tree-Ring Society, 1991)
      An exploratory investigation of tree growth and climate relationships in Abies religiosa from Michoacan, Mexico, produced the first crossdated and standardized tree-ring chronology from the North American tropics. Pearson correlation coefficients and principal components response function analysis were employed. Results indicate that ring-width series from this species have moderately high signal-to-noise ratio (S/N = 13.42). A substantial percentage of the ring-width signal can be explained by instrumented monthly climate data, particularly spring precipitation and winter temperature. Although correlation between climate data and the tree-ring measurements indicate that growth of Abies religiosa is highly influenced by year-to-year climate variation, longer climate records and tree-ring chronologies are needed from this tropical region to improve understanding of climate -tree growth relationships, and for dendroclimatic reconstruction.
    • Identifying Low-Frequency Tree-Ring Variation

      Sheppard, Paul R.; Laboratory of Tree-Ring Research, University of Arizona, Tucson, Arizona (Tree-Ring Society, 1991)
      I propose an approach to provide 95% confidence intervals for a chronology of low-frequency tree-ring variation so that a level of significance or importance for trends can be inferred. The approach also visually reveals the portions of a chronology in which sample depth is so poor that low-frequency variation is not robustly estimated. A key characteristic of the approach is that it is essentially a reordering of the individual steps commonly used in constructing standard tree-ring chronologies; consequently, it is computationally simple for researchers who already routinely construct standard tree-ring chronologies. The most important ramification of the approach is that each year of the chronology has a distribution of smoothed index values with which to estimate confidence intervals around the chronology of low-frequency variation. It can be argued that the approach constitutes multiple significance testing of means, which causes the α level for the confidence interval to be unknown. Nonetheless, the approach is still useful in that it provides a way to evaluate the probable importance of low-frequency trends expressed in tree-ring chronologies.
    • Special Sanding Films and Sandpapers for Surfacing Narrow-Ring Increment Cores

      Yamaguchi, David K.; Brunstein, F. Craig; Mountain Research Station and Institute of Arctic and Alpine Research, University of Colorado, Boulder, Colorado; U. S. Geological Survey, Denver, Colorado (Tree-Ring Society, 1991)
      Special sanding films (400 grit to 23 micron) and fine sandpapers (1200-1500 grit) can be used to surface increment cores containing narrow rings (e.g., >50 rings per cm) so that rings are clearly visible for microscopy and photography.