• Climate Response Of Oak Species Across An Environmental Gradient In The Southern Appalachian Mountains, USA

      White, Philip B.; Van De Gevel, Saskia L.; Grissino-Mayer, Henri D.; LaForest, Lisa B.; Deweese, Georgina G.; Department of Geography and Planning, Appalachian State University; Laboratory of Tree-Ring Science, Department of Geography, University of Tennessee; Department of Geosciences, University of West Georgia (Tree-Ring Society, 2011-01)
      We investigated the climatic sensitivity of oak species across a wide elevation range in the southern Appalachian Mountains, an area where greater knowledge of oak sensitivity is desired. We developed three tree-ring chronologies for climatic analyses from oak cores taken from the Jefferson National Forest, Virginia, and Great Smoky Mountains National Park, Tennessee. We statistically compared the three chronologies with monthly climatic data from 1930 to 2005. The results of our analyses suggest that oak species in the southern Appalachian Mountains require a cool, moist summer for above average-growth to occur. The climate signal increased in duration from high to low elevational and latitudinal gradients, indicating a strong moisture-preconditioning signal during the previous fall at our lowest elevation site. A notable finding of this research was the degree of responsiveness in oaks that are growing in forest interior locations where strong climate sensitivity would not be expected because of the effects of internal stand dynamics. Furthermore, the relationships between evapotranspiration rates and the geographic factors of elevation, latitude, and aspect influence the climate signals at the three sites. Our research suggests that oaks located in a warm and xeric climate experience more physiological stress and put forth a more varied climatic response.
    • Do Females Differ From Males Of European Yew (Taxus Baccata L.) In Dedrochronological Analysis?

      Cedro, Anna; Iszkulo, Grzegorz; Climatology and Marine Meteorology Department, Szczecin University; Institute of Dendrology, Polish Academy of Sciences, ul. Parkowa 5, 62-035 Kórnik, Poland; University of Zielona Góra, Department of Biology, Prof. Z. Szafrana 1 (Tree-Ring Society, 2011-01)
      Female and male plants often differ in reproductive effort and habitat requirements. The aim of this study was to analyze these differences between the sexes and the effect of climate on tree-ring width in European yew (Taxus baccata). The study was conducted in five yew populations in western Poland. Wood samples were taken from 196 trees (98 females and 98 males) and subjected to the standard procedure of dendrochronological dating. Mean tree-ring width was significantly higher in males since about the beginning of sexual maturity. No such relationship was observed in the youngest population, which is the most distant from the current geographic limit for this species. In most of the analyzed populations, width of tree rings in female individuals, in contrast to males, was negatively correlated with high temperatures in August and September in the year prior to the formation of the tree ring, and correlated positively with precipitation in June and July in the current year. The differentiation of tree-ring width between males and females likely began when the yew trees reached sexual maturity, probably because of the assumed greater reproductive effort of females in comparison with males. The lack of difference in the youngest population may result from a short time since the beginning of sexual maturity or from a milder climate in that region. Different reactions of the two sexes to climate indicate that this may affect the range and viability of populations at the limits of the range.
    • Incorporating Climatological Techniques To Improve Tree-Ring Site Selection In Complex Terrain

      Wise, Erika K.; Department of Geography, University of North Carolina at Chapel Hill (Tree-Ring Society, 2011-01)
      Dendroclimatologists often approach field work with the intent of reconstructing a particular climate variable (e.g. temperature, streamflow, precipitation). Although guidelines exist for species and site selection, isolating the signal of interest is difficult in areas with complex terrain or a lack of ideal sites. In this case study, I suggest climatological techniques for a more efficient sampling scheme and apply these techniques to identify criteria for selecting sites sensitive to winter precipitation in the north-central Rocky Mountains. These techniques include examining factors influencing the regional response of tree growth to climate by utilizing the International Tree-Ring Databank (ITRDB), using eigenvector analyses to identify modes of variability between sites, and delineating climate regions based on the variable of interest through climate regionalization. Results suggest that low- or mid-elevation Pseudotsuga menziesii sites should be targeted for maximizing the winter precipitation signal in the case study area. The season of precipitation impacting growth was found to be a major component of the overall variability between sites.