Aspen Bibliography

Comparison of the structures of even-aged aspen stands in three geographic regions

Document Type

Article

Journal/Book Title/Conference

Canadian Journal of Botany

Volume

64

Issue

1

First Page

122

Last Page

129

Publication Date

1986

Abstract

Even-aged aspen (Populus tremuloides Michx.) stands in regions with contrasting climates differ from one another in the growth rates of individual stems and in the rates at which they self-thin. The dependence on stand age of four statistics describing stand structure (the mean, standard deviation, and skewness of the distribution of tree girths and the number of trees in a 400-m2 plot) were studied in three geographical regions: northern Alberta, Yukon, and the Foothills of the Rocky Mountains in southern Alberta. Each region has unique stand statistics. The annual radial increment is least in the Yukon, presumably because of the short growing season. Foothills plots are unique in having girth distributions that are approximately symmetrical at all ages; this contrasts with the other two regions, where girth distributions exhibited positive skewness in young stands and skewness decreased with age. Also in Foothills plots, the standard deviations of the girths increased more slowly with age than in the other two regions. A model was devised to simulate the progressive changes in these statistics in a stand as it ages. To run the model, one begins with data from an actual, observed stand for which the distribution of the trees in different size classes is known. It is then assumed that the trees grow; the growth rate of a tree is greater the larger the tree was initially. Simultaneously, trees die; the probability that a tree will die is greater the smaller the tree was initially. Thus, the values that the descriptive statistics of a given young stand are expected (according to the model) to have when the stand is old can be predicted; the predictions can be compared with current statistics of observed stands that are already old.

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