Comparing Basal Area Growth Rates in Repeated Inventories: Simpson's Paradox in Forestry
Authors: Thomas, Charles E.; Parresol, Bernard R.
Source: Forest Science, Volume 35, Number 4, 1 December 1989 , pp. 1029-1039(11)
Publisher: Society of American Foresters
Abstract:Recent analyses of radial growth rates in southern commercial forests have shown that current rates are lower than past rates when compared diameter class by diameter class. These results have been interpreted as an indication that the growth rate of the forest is declining. In this paper, growth rates of forest populations in Alabama are studied. Basal area growth (a function of both radius and radial growth squared) by diameter classes is examined for plantation and natural stands. Basal area growth and population distributions for the 1962-1972 and 1972-1982 measurement periods are presented. Also, significance of Simpson's paradox in these analyses is discussed. Basal area growth proves to be consistent with changes that have occurred in tree frequency in diameter classes, i.e., stand structure. In Alabama's natural stands, basal area growth is shown to be relatively constant over the most recent inventories, while it has increased in plantations. Simple comparison of radial growth would be misleading. For. Sci. 35(4): 1029-1039.
Document Type: Journal Article
Affiliations: Mathematical Statistician, USDA Forest Service, Southern Forest Experiment Station, Institute for Quantitative Studies, New Orleans, LA 70113
Publication date: December 1, 1989
- Forest Science is a peer-reviewed journal publishing fundamental and applied research that explores all aspects of natural and social sciences as they apply to the function and management of the forested ecosystems of the world. Topics include silviculture, forest management, biometrics, economics, entomology & pathology, fire & fuels management, forest ecology, genetics & tree improvement, geospatial technologies, harvesting & utilization, landscape ecology, operations research, forest policy, physiology, recreation, social sciences, soils & hydrology, and wildlife management.
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