Tree allometry

Tree Allometry

Defined as the growth or size of some part of a tree in relation to the growth or size of different parts of a tree.

The study of allometry is extremely important in dealing with measurements and data analysis in the practice of forestry. Allometry in general is defined as the growth of a part of an organism in relation to the growth of the whole organism or some part of it [www.dictionary.com] . Tree allometry narrows the definition to applications involving measurements of the growth or size of trees. Allometric relationships are often estimating difficult tree measurement, such as volume, from an easily-measured attribute such as diameter at breast height (DBH).

The use of allometry is widespread in forestry and forest ecology. In order to develop an allometric relationship there must be a strong relationship and an ability to quantify this relationship between the parts of the subject measured and the other quantities of interest [Smith, W.B., and G.J. Brand. 1983 Allometric biomass equations for 98 species of herbs, shrubs, and small trees. Research note NC-299. USDA Forest Service, North Central Forest Experiment Station, St. Paul, MN 8p.] . Also when developing this equation one must play in factors which affect tree growth such as age, species, site location, etc. [Avery and Burkhart. Forest Measurements. Copyright 2002 by McGraw-Hill Companies Inc. New York.] . Once all these guidelines are met, one may attempt to develop an allometric equation.

First thing to do is select a group of some subject (for forestry: trees). Then measure several easily measured attributes such as DBH, height, species, etc. Graph the results and perform a regression analysis and transform some of the variables until a correct regression is found.

There are different tree species compositions in each region in the world and most of those regions have at least one equation that estimates tree volume from DBH. Research and the application of forest allometry have meshed over time to develop these quick equations to accurately estimate how much volume a particular forest stand holds.

The general allometric equation for mathematics and science is written below, where: b=allometric coefficient; a=slope; Y=measure/process; X=size [ [http://weber.ucsd.edu/~jmoore/courses/allometry/allometry.html Allometry ] ]

Y=aX^b

However in forestry the equation tkae on many forms in order to represent relationships between the many various attributes of tree size and growth. Below is an example...

Y=b₀+b₁X

References