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| Undisturbed stand density: a benchmark for damage assessment |
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Boris Zeide
Professor of Forestry, School of Forest Resources, University of Arkansas at Monticello, Monticello, AR 71656-3468, USA
Email: zeide@uamont.edu,
Phone: 870-460-1648, Fax: 870-460-1092
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The study of the tradeoff between growth and defense in plants requires an assessment of damage caused by primary consumers. To assess this damage we need to describe the undisturbed conditions, preferably by a single number applicable to all stands of a given species, regardless of their age and size. For many years, foresters have been searching for such a number to express normal density, that is, stand density of fully stocked stands. Yet, none of existing measures is entirely satisfactory. A majority of these (stand density index, basal area, leaf area, canopy closure) present the change in number of trees per unit area as a function of one factor: the increase of average tree size. This paper introduces the second factor driving self-thinning: a decreasing tolerance of trees resulting in the accumulation of gaps between tree crowns. A model accounting for both factors allows us to quantify stand density and find a single number characterizing undisturbed stands of any age and tree size. The number changes with species, being higher for more shade tolerant ones.
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