Tree-Ring Analysis And Natural Hazard Chronologies: Minimum Sample Sizes And Index Values*

Authors

  • David R. Butler,

    1. DAVID R. BUTLER (Ph.D., University of Kansas), is Assistant Professor of Geography, University of Georgia, Athens, GA 30602. His research interests include mountain environments, geomorphology, and natural hazards.
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  • George P. Malanson,

    1. GEORGE P. MALANSON (Ph.D., University of California, Los Angeles), is Assistant Professor of Geography, University of Iowa, Iowa City, IA 52242. His research interests include biogeography and disturbance and resilience in ecosystems.
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  • Jack G. Oelfke

    1. . JACK G. OELFKE (M.Sc., Oklahoma State University), is currently employed with the National Park Service, Midwest Regional Office, Omaha, NE 68102. His research interests are resource and wilderness management and natural hazards.
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  • *

    Fieldwork and tree-ring collecting were supported by grants to Butler and Malanson from the Burlington Northern Foundation and the Association of American Geographers and to Oelfke from the Society of Sigma Xi. Sampling permits and access to field sites were approved by personnel of Glacier National Park, MT. Assistance in the field was provided by Lori Oelfke and in both the field and laboratory by Susan Panciera. The assistance of the reviewers, Laura Conkey and Jerome DeGraff, is gratefully acknowledged.

Abstract

Tree-ring dating is employed to reconstruct chronologies of occurrence for a variety of natural hazards. The number of trees sampled varies greatly as does the minimum number of tree-ring responses. The number of trees to be sampled and an acceptable tree-ring response index should be dictated by the nature and geographical extent of the specific hazard under study. Repetitive sampling of different numbers of 30 avalanche-damaged trees showed significant differences in number of tree-ring responses over a 55-year-period. More sampling and use of a higher minimum response index allowed greater confidence in the chronology constructed from tree-rings and compared to historical records. Three geographic scales of analysis that can confound tree-ring responses are identified, and three guidelines for choosing sample size, given variations in processes, are suggested.

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