Stem volume
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General observations
When thinking in terms of timber-production oriented forest management, stem volume is one of the most relevant variables in forest inventory. The volume unit in the metric system is cubic meter (\(m^3\)). Stem volume is one of those variables that can not be measured directly in a forest inventory but that needs to be modeled and predicted from more easily measurable variables. Volume is either determined for the entire stem (total volume) or for defined stem sections (such as commercial volume).
Calculating volume
Direct measurement
The only method of tree volume measurement is by water displacement. However, this is a theoretical approach and not an option in forest inventory…
Volume calculation by section
Tree volume determination is always based on measurements of diameter and length. When we do a section-wise volume calculation, the stem is subdivided into sections of which length \(l\) and basal area \(g\) are measured; basal area is either taken at the middle of the section \(g_m\) or at both the lower end \(g_l\) and the upper end \(g_u<_math>. Then, the following simple formulae are common for section volume calculation: :{| |Huber |<math>v=g_ml\,\) |- |Smalian |\(v=\frac{g_u+g_o}{2}l\,\) |- |Newton |\(v=\frac{g_u+4g_m+g_o}{6}l\,\) |} where the “Huber formula” is simply another name for the volume formula of a cylinder.
The taper curve
References
