Submitted to: International Society Arboriculture Annual Conference
Publication Type: Abstract Only
Publication Acceptance Date: 8/10/1996
Publication Date: N/A
Technical Abstract: Since 1970 arborists have been using the species rating developed by the Shade Tree Conference, Inc. For the different regions of the country. Some states (such as Illinois and Florida) have developed their own species rating, but such ratings or values have been subjectively derived and are given as a range of values for each species rather than a single specific value. With individual species rating ranging from 20 to 50% difference, problems are bound to arise relative to appraisal consistency that can lead to 50% under appraisal or over appraisal. To resolve this problem, we developed an objective species rating using quantifiable and inherent species characteristics such as: pollution tolerance (ozone, landfill gases, and sulfur dioxide), flood tolerance, longevity, pest prevalence, specific gravity, and soil compaction tolerance. These variables were used to derive the species values for tree species in Louisiana. Each species was evaluated on each of the variables based on published data. One can use as many variables as one wants, but the availability of published information is the principal constraint. Thus, the choice of variables to use must be based on critical factors relative to the area or region. A key issue to remember is not to use directly opposing variables because they diminish or cancel each other's effect. For instance, if flood tolerance used as one of the critical factors, drought tolerance should be excluded. By using this technique, a single and objective species value is derived. We propose that species rating for a given area or region be developed based on quantifiable variables. A single value reflects consistency, after all a loblolly pine is a loblolly pine regardless of its condition and location.