Station 6:
Tools of Forestry

Before forest landowners can make a decision on what to do with their forest, they must know what resources their forest has.  For this reason, a forest inventory must be conducted to obtain the necessary information.  Forest inventories can be complex, depending on how thorough you want to be and what information you desire.  Inventorying 100 percent of your property may be expensive, and most likely unnecessary, unless you have extremely high valued timber (i.e. black walnut or black cherry) of exceptional quality.  For this reason, foresters use statistically proven inventory techniques, of which several exist.

Before statistical models can be applied, field data must be obtained.  Tree species, height, diameter, and age are some of the data foresters collect.  Foresters use an assortment of tools that assist in collecting data.  


Tree Height

How do you measure a tree's height without climbing it?  Through a trigonometric calibrated tool.  Two common tools can be used to determine the height of a tree: the Merritt hypsometer and the clinometer.  Both of these tools are used at a distance of 66 feet from the tree; therefore, given that distance the height can be determined by observing the angle from the top of the tree to the bottom of the tree.  The top of the

  tree is generally determined by its merchantable timber value.  It is not included if it can not be used for lumber.

Tree Diameter

There are several tools available that allow foresters to determine a tree's diameter.  One tool, the Biltmore stick, is included in the same measuring stick as the Merritt hypsometer.  A more accurate tool that is frequently used by foresters is the D-tape (diameter tape).  This tape is calibrated to measure a tree's diameter based on its circumference.  Almost all tree diameters are measured at breast height, four and a half feet above ground level.  Due to the unevenness of the ground, ground level is considered the highest point at the tree's base.  These standard measuring procedures allow foresters to collect reproducible data. 


Tree Age

Besides cutting down a tree, the easiest way to determine a tree's age is to collect a core sample with an increment borer and count the growth rings.  Each year a tree produces a ring of wood that adds to its diameter.  By taking a closer look at these rings, foresters can determine the rate trees are growing, which is useful for establishing timber stand improvements (TSIs) by removing competing trees to increase tree growth.

Core from a white pine

Tree rings can tell scientist more than just how fast a tree is growing.  As a matter of fact, the study of tree rings is a science in itself, known as dendrochronology.  By closely investigating the growth patterns of old trees, dendrochronologists can better understand significant events in archeology (i.e. when trees were last felled), climatology (i.e. investigating pre-record, before records were kept, precipitation per year), ecology (i.e. investigating the effects of air pollution on tree growth), hydrology (i.e. dating when trees were damaged by floods), and pyrochronology (i.e. dating fire scare to determine their frequency).  Much information that we know today about pre-record global conditions comes from researching tree rings.

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