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Publications - Occasional Papers

Procedures for the Study of Snow Avalanche Chronology Using Growth Layers of Woody Plants

INSTAAR Occasional Paper 23

1976, 54 pp. Reprinted. (cost: $5)

[From the Introduction] This handbook is a brief description of the background to and procedures for the use of annual growth layers (annual rings) of woody plants for dating snow avalanche events. Trees are most often used as subjects for study but there are some possibilities for using shrubs to date events over short intervals. The methodology of ring-dating is based on the growth behavior of woody plants in cold and temperate climates with marked differences between summer and winter temperature regimes. The winter conditions cause the plants to slow or stop their growth so that there is a discernible difference between the cell size and structure at the end of a growing season compared with that at the beginning of a new growing season. The numbers of rings in cross-sections of selected stems can provide a means of dating and reconstructing events of the past such as glacier fluctuations (Lawrence 1950, Sigafoos and Hendricks 1961), timberline changes (La Marche and Mooney 1972), lake level fluctuations (Cameron 1957, Lawrence 1972), landslides (Heath 1959, 1960), floods (Grant 1965, 1966), fires (Spurr 1954), and other natural and man-made changes. For the purposes of this handbook, the methodology will be referred to as tree-ring analysis, rather than dendrochronology. The latter term has come to be applied, more narrowly, to the somewhat more specialized methodology of use, for dating, cross-dating (to extend chronologies) and climatic analysis of sequences of wide and narrow growth layers in sensitive species in arid or cold climates (Glock 1937, Fritts 1966, 1969, Ferguson 1970, Suess 1970, La Marche and Fritts 1971, Fritts and Blasing 1974). Nevertheless, both methodologies make much the same use of knowledge of the characteristics of tree growth and wood structures. In certain rare circumstances, mentioned later, dendrochronological techniques might be applied to the dating of snow avalanches. Techniques most useful in tree ring analysis are described by Lawrence (1950), Potter (1969), and Stokes and Smiley (1968).

This handbook is couched in simple terms which can be understood by non-biologists; references are given to fuller accounts of aspects of the subject and a glossary of terms is included at the end. The book is specifically relevant to the forests and mountains of Colorado, but it could be adapted for use in other areas.

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