• Stable-Carbon Isotope Time Series From Tropical Tree Rings Indicate A Precipitation Signal

      Fichtler, Esther; Helle, Gerhard; Worbes, Martin; Georg August Universität Göttingen, Department of Crop Sciences, Agronomy in the Tropics; Institute of Chemistry and Dynamics of the Geosphere, Research Centre Jülich (Tree-Ring Society, 2010-01)
      Although studies on stable-carbon isotopes in trees from temperate zones provide abundant paleoclimatic data, tropical trees are still understudied in this context. Therefore this study examined the variability of intra- and inter-annual stable-carbon isotopic pattern in several tree species from various tropical climates. The 𝛿¹³C values of samples of 12 broadleaved trees (seven species) from various paleotropical and neotropical sites along a climatic moisture gradient were investigated. The inter-annual variability between species and sites was studied. Further the relationship between 𝛿¹³C and precipitation time series was analyzed. Results show that tropical tree species show a similar variability in carbon isotopic composition as temperate tree species. Significant correlations between annual precipitation and tree-ring 𝛿¹³C time series were negative. Successful crossdating of a tree-ring 𝛿¹³C time series highlights the potential of carbon isotope measurements for tropical tree-ring analytical studies. Tropical broadleaved trees are able to capture a carbon isotopic signal in their annual rings even under everwet conditions and show good potential for paleoclimatic research.
    • Technique To Improve Visualization Of Elusive Tree-Ring Boundaries In Aspen (Populus tremuloides)

      DeRose, R. Justin; Gardner, Richard S.; Department of Wildland Resources and Ecology Center, Utah State University; Department of Wildland Resources, Utah State University (Tree-Ring Society, 2010-01)
      A simple, quick, and inexpensive technique to improve visualization of aspen (Populus tremuloides) tree rings under the microscope, the ‘shadow technique’, is described. The technique assumes appropriate preparation of increment cores or cross-sections and works well on the lighter portions of the sample with fungus- and bacteria-free wood. The shadow technique was used successfully to elucidate tree-ring boundaries in small diameter (<5 cm DBH) aspen from northern Utah that commonly had >100 annual rings. Crossdating verified whether the elusive rings were missing or false rings. Aspen tree-ring measurement will be greatly enhanced with the shadow technique and preliminary investigation suggests it could be used on other species such as curlleaf mountain mahogany (Cercocarpus ledifolius).