• Paleoclimatic Analyses of Tree-Ring Reconstructed Summer Drought in the United States, 1700-1978

      Fye, Falko K.; Cleaveland, Malcolm K.; Department of Geosciences, University of Arkansas at Fayetteville, Fayetteville, AR (Tree-Ring Society, 2001)
      A 155-point US grid of tree-ring reconstructed summer (JJA; Cook et al. 1996) averaged Palmer Drought Severity Index (PDSI) was used to document the history and investigate the external forcing of growingseason climate anomalies for the period 1700 to 1978. Statistical analysis software was used to composite years temporally by computing averages for the years of known dates of major potential climate-forcing events. A geographic information system (GIS) was used to display the composites as well as individual years. The forcing factors investigated were the 22-year Hale solar magnetic cycle, major El Niño (warm) and La Niña (cold) events based on the Southern Oscillation Index (SOI), and large magnitude low latitude volcanic eruptions. Positive and negative moisture anomalies appear around Iowa in the alternate 11-year sunspot cycles that make up the Hale solar magnetic cycle. Experimentation with the grouping of years in the Hale cycle composites led to unexplained spatial shifts of the moisture anomalies in the same region. The El Niño episodes usually show positive (wet) PDSI anomalies in the Southwest from California to Texas, while La Niña events usually have drought in the same area, with some inconsistent signals in the north central Plains and the Northwest. The eastern and northern US were unaffected by the Southern Oscillation, although the summer season reconstructed PDSI may have missed the SOI variation, which is primarily a winter signal. The three largest tropical volcanic eruptions since 1800 failed to follow a consistent pattern, but the 1815 eruption of Tambora in Indonesia was followed by a very strong positive growth anomaly in the Southwest in 1816 and 1817. Important regional studies with the winter-spring season could be done with this network of tree-ring chronologies and observed monthly PDSI data.
    • Relationships Between Ring-Width Variation and Soil Nutrient Availability at the Tree Scale

      Sheppard, Paul A.; Cassals, Pere; Gutiérrez, Emilia; Department d'Ecologia, Universitat de Barcelona, Barcelona, España; Department de Biologia Vegetal, Universitat de Barcelona, Barcelona, España (Tree-Ring Society, 2001)
      Within the framework of the linear aggregate model of dendrochronology, the potential role of soil nutrient availability in explaining multi-decadal variation in radial growth at the tree level was studied in the central Spanish Pyrenees. Increment cores were collected from 20 mature Pinus uncinata Ram. and analyzed dendrochronologically. One ion-exchange resin capsule was buried within the root zone of each sampled tree for just over eight months. The resins were chemically extracted and measured for NH₄, NO PO₄, Ca, and K. Statistical relationships between indexed tree growth and soil nutrient availability were determined with regression analysis and bivariate plots. The single most important soil nutrient with respect to decadal-scale dendrochronological tree-growth variables in this study was N in the form NO which explained 22% of variation of trend in growth since 1950. The 20 values of NO₃ availability fell into two subgroups, one of trees with relatively higher NO₃ availability and the other with lower NO₃ availability. When the tree-growth data were grouped based on NO₃ availability, the two resultant index chronologies had different low-frequency features since 1950. Trees with low NO₃ availability have been growing as expected based on past growth, but trees with high NO availability have been growing better than expected. Measuring and analyzing soil nutrient availability at the tree level might enhance environmental applications of dendrochronological research. With soils information at this spatial scale, it is possible to distinguish between subgroups of trees within a tree-ring site and thereby construct subchronologies that differ significantly, especially for variation at the decadal scale. Subsite-chronologies may then lead to different and presumably more informative environmental interpretations relative to those based on a full-site chronology.
    • Response to Winter Precipitation in Ring-Width Chronologies of Pinus Sylvestris L. from the Northwestern Siberian Plain, Russia

      Thomsen, Gerner (Tree-Ring Society, 2001)
      Six mean ring-width tree-ring chronologies were constructed for living Scots pine (Pious sylvestris L.), growing near the species' upper and northern limits in the area between the Ob River and the subpolar Ural Mountains in Russia. All ring-width series were standardized by fitting cubic smoothing splines and chronologies were constructed as biweight robust means. The six chronologies ranged from 181 to 276 years in length. Response function analysis showed all chronologies to have negative responses to winter precipitation. Most chronologies also showed positive, but relatively low responses to temperatures of the current and previous summer. Total October-May precipitation was reconstructed back to A.D. 1843 using the lagged and unlagged chronologies as candidate predictors. In addition to reflecting an unstable and time-varying growth-climate link, moderate verification results may partly be due to problems with short verification periods. The reconstruction contains almost equal amounts of high-frequency (<8 years) and low-frequency ( >8 years) variations, among them a significant 30-year variation. The precipitation signal may add an important aspect to reconstructing paleoclimatic fluctuations in the northern hemisphere. Continuing work with the Scots pine from this area depends on improving the quality of a precipitation reconstruction and finding older living and subfossil wood.
    • Tree-Ring Dating and the Ethnohistory of the Naval Stores Industry in Southern Georgia

      Grissino-Mayer, Henri D.; Blount, Harry C.; Miller, Alison C.; Department of Geography, The University of Tennessee, Knoxville, TN; Department of Geography, The University of South Carolina, Columbia, SC; Department of Physics, Astronomy, and Geosciences, Valdosta State University, Valdosta, GA (Tree-Ring Society, 2001)
      Since the mid-1700s, slash (Pinus elliottii Engelm.) and longleaf (Pinus palustris Mill.) pines growing in the coastal plain region of the southeastern United States were intentionally wounded ("boxed" and/or "chipped ") to induce the production of resin, which was then collected and distilled into turpentine and its derivatives (termed "gum naval stores "). Relicts from this once-dominant industry are seen throughout southern pine forests as boxed and chipped stumps or (rarely) still living trees. In this study, we dated the years of chipping on slash pines growing in two locations in Lowndes County, Georgia, to (1) better understand past forest land use patterns, and (2) raise public awareness of the ethnohistorical importance of these trees to the cultural heritage of southern Georgia. We collected cores from ten living trees with characteristic chipped surfaces ("catfaces ") from Taylor-Cowart Memorial Park (TCMP) in Valdosta, Georgia, and cross sections from ten chipped stumps in the area surrounding Lake Louise, 12 km south of Valdosta. We conclude that chipping at TCMP occurred in 1947-1948, while two chipping events occurred at Lake Louise around 1925 and between 1954-1956. Our dating was facilitated by observing periods of growth suppression, distorted and /or discolored rings, and the absence of some growth rings that may indicate possible chipping events. We recommend that these chipped stumps and living trees be preserved intact for their ethnohistorical significance, educational importance, and potential for future research.
    • Tree-Ring Evidence for Great Plains Drought

      Woodhouse, Connie A.; Brown, Peter M.; NOAA Paleoclimatology Program, NGDC, Boulder, CO | Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO; Rocky Mountain Tree-Ring Research, Fort Collins, CO (Tree-Ring Society, 2001)
      A new collection of tree-ring chronologies developed from trees and remnant material located in the western and central Great Plains makes an important contribution to the spatial coverage of the US tree- ring chronology network. Samples from 24 sites were collected from the west-central Great Plains, and to date, ten chronologies have been produced. When correlated with a set of 47 single-station PDSI records, the chronologies display relationships with regional spring and summer drought. The reconstruction of spring PDSI for eastern Colorado generated in this study suggests that the inclusion of Great Plains trees can improve the quality of Great Plains drought reconstructions. The eastern Colorado drought reconstruction explains 62% of the variance in the instrumental record and extends to 1552. This reconstruction provides information about the regional character of major droughts over the past four and a half centuries. Major eastern Colorado droughts include events in the 1580s, 1630s, 1660s, 1730s, and the 1930s. The late 16th century drought, noted as an especially severe drought in the southwestern US, appears in this reconstruction as only slightly more severe than other major droughts in this region.
    • Xylem Tracheid Development in Pinus Resinosa Seedlings in Controlled Environments

      Danzer, Shelley R.; Leavitt, Steven W.; Panyushkina, Irina P.; Mergner, Andreas; Garcia, Evelyn; Best-Svob, Valeria; Laboratory of Tree-Ring Research, University of Arizona, Tucson, AZ (Tree-Ring Society, 2001)
      Progressive tree-ring xylem cell size changes may reveal the influence of changing environment during the growing season. This study examines xylem tracheid cell growth in red pine (Pious resinosa Ait.) seedlings grown in cabinets under controlled environment, where single parameters (temperature, light, soil moisture and CO2) were varied step-wise in each chamber at ca. 30-day increments for ca. 6 months. Control and temperature treatments were replicated. Cross-sections (20 μm thick) sliced with a sliding microtome from each of four seedling stems from each cabinet were mounted on glass slides. Lumen diameters and cell-wall thickness were measured on 4 orthogonal tracheid radial files on 4 radii of each stem. Mean cell sizes were 11-17 μm among treatments and growth periods, whereas numbers of cells formed averaged 0.2-1.3 cells per day. Cell size increased throughout the experiment in most of the treatments, including one of the control treatments and those with the greatest potential to limit growth (decreasing temperature, light and soil moisture). Soil moisture was the only environmental parameter that tended to cause late declining growth, and CO, up to 500 (μmol mol⁻¹ did not appear to influence cell development. Despite a substantial range of environmental shifts in the chambers (100 μmol mol⁻¹ CO₂; 125 μEinsteins m⁻² s⁻¹ light; 8 °C temperature; 35% relative humidity; watering every day to every 5th day), the continued stem elongation and cell-size increases indicate that conditions never became significantly limiting to growth in most treatments. Although the range of environmental variability is undoubtedly much greater in most natural red pine systems, these results indicate that fairly large variations in environment during development of juvenile wood in seedlings may not leave an imprint retrievable from cell-size measurements made on the earliest rings of mature trees.