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

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.