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Title: Measuring wood specific gravity, correctly

Author: Williamson, G. Bruce; Wiemann, Michael C.;

Date: 2010

Source: American journal of botany. Vol. 97, no. 3 (2010): p. 519-524.

Publication Series: Miscellaneous Publication

Description: The specific gravity (SG) of wood is a measure of the amount of structural material a tree species allocates to support and strength. In recent years, wood specific gravity, traditionally a forester’s variable, has become the domain of ecologists exploring the universality of plant functional traits and conservationists estimating global carbon stocks. While these developments have expanded our knowledge and sample of woods, the methodologies employed to measure wood SG have not received as much scrutiny as SG’s ecological importance. Here, we reiterate some of the basic principles and methods for measuring the SG of wood to clarify past practices of foresters and ecologists and to identify some of the prominent errors in recent studies and their consequences. In particular, we identify errors in (1) extracting wood samples that are not representative of tree wood, (2) differentiating wood specific gravity from wood density, (3) drying wood samples at temperatures below 100 °C and the resulting moisture content complications, and (4) improperly measuring wood volumes. In addition, we introduce a new experimental technique, using applied calculus, for estimating SG when the form of radial variation is known, a method that significantly reduces the effort required to sample a tree’s wood.

Keywords: Specific gravity, moisture, wood moisture, wood density, measurement, error analysis, mathematical statistics, temperature, drying, wood drying, volume, calculus, increment borers, moisture content, increment cores, Wiemann approximation, review article

Publication Notes:

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  • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.



Williamson, G. Bruce; Wiemann, Michael C. 2010. Measuring wood specific gravity... correctly. American journal of botany. Vol. 97, no. 3 (2010): p. 519-524.


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