• The Use and Limitations of Dendrochronology in Studying Effects of Air Pollution on Forests

      Cook, Edward R.; Tree-Ring Laboratory, Lamont-Doherty Geological Observatory of Columbia University (Laboratory of Tree-Ring Research, University of Arizona (Tucson, AZ), 1985-05)
      The annual ringwidths of trees can be used to search for hypothesized air pollution effects on forests. This search is extremely complicated by the inherent statistical properties of ringwidth data and the high level of uncertainty regarding the sources of variance observed in the ringwidths. A linear aggregate model for ringwidths is described which highlights the general classes of variance which may be found in a tree-ring series. Dendrochronological principles and techniques are described which can be used to create a tree-ring chronology that is suitable for rigorous statistical analysis and hypothesis testing. The need to model climatic influences on tree growth prior to the search for pollution effects is necessary and a method for achieving this is described. Only after the variance due to age trends, stand dynamics effects and climatic influences has been accounted for can any confidence be placed on inferred pollution effects. An analysis of a red spruce tree -ring chronology indicates that a decline in ringwidths since 1968 cannot be explained by a linear temperature response model using monthly climatic variables. However, threshold responses to climate that could be responsible for the decline need to be considered before the anomalous decline can be attributed to non-climatic influences such as pollution.
    • Using Dendrochronology To Measure Radial Growth of Defoliated Trees

      Swetnam, Thomas W.; Thompson, Marna Ares; Sutherland, Elaine Kennedy; Laboratory of Tree-Ring Research, University of Arizona; Laboratory of Tree-Ring Research, University of Arizona; Laboratory of Tree-Ring Research, University of Arizona (U.S. Department of Agriculture, Forest Service, Cooperative State Research Service, 1985-06)
    • Western Spruce Budworm Outbreak History in the Sacramento Mountains, New Mexico, U.S.A.

      Archambault, Sylvain; Swetnam, Thomas W.; Lynch, Ann M.; Centre d'etudes nordiques, Universite Laval, Ste-Foy (Quebec) Canada; Laboratory of Tree-Ring Research, University of Arizona; USDA Forest Service, Rocky Mountain Forest and Range Experiment Station (Laboratory of Tree-Ring Research, University of Arizona (Tucson, AZ), 2013-10-04)
      Western spruce budworm (Choristoneura occidentalis Freeman) outbreak history was reconstructed for the Sacramento Mountains of south-central New Mexico, at the southern limit of the species distribution range. Six host tree-ring width chronologies (Douglas -fir and white fir) and three non -host control chronologies (ponderosa pine) were used for this reconstruction spanning from 1800 to 1990. Both the host and non-host species had similar climatic response so the non-host chronologies were confidently used as climatic controls. Up to eight defoliation events were documented within individual stands and at least seven major regional outbreaks were identified among the stands back to 1800. At least five major outbreaks occurred in the twentieth century: 1890s- 1900s, 1910s- 1920s, 1940s, 1960s, and 1980s. The 1960s and 1980s outbreaks were verified by Forest Service aerial and ground survey records. These recent outbreaks seemed to have been more synchronous among the different stands than outbreaks that occurred in the 19th century. There were similarities between this outbreak history and an outbreak history reconstructed for northern New Mexico, a distance of about 340 km to the north. The regional-scale pattern identified in these histories lends support to a hypothesis that past logging and fire suppression has changed western spruce budworm dynamics.
    • Western U.S. Tree-Ring Index Chronology Data for Detection of Arboreal Response to Increasing Carbon Dioxide

      Graybill, Donald A.; Laboratory of Tree-Ring Research, University of Arizona (Laboratory of Tree-Ring Research, University of Arizona (Tucson, AZ), 1985-04-26)
      Ongoing research designed to expand a grid of tree-ring chronologies in the western U.S. that can be used to examine tree growth response to increasing atmospheric CO2 is summarized in this interim report. Current and projected sampling is designed to cover most of the Great Basin and the Southwestern U.S., focusing on long -lived species growing under stressful climatic conditions. Older trees growing in these circumstances provide the best potential for analytical discrimination of climatic and CO2 signals. A descriptive statistical summary of all current data sets is provided and potential directions of the project are discussed.