I am a newly certified aroborist reading the 9th edition of the Guide for Plant Appraisal and completing the workbook for same. The ISA Western Chapter book states: "The Basic Price (cost per unit square inch of trunk area) used to determine the cost of a large tree over that of a replaceable tree is 60% of the wholesale cost per square inch of trunk of the 48" box tree in the appraised tree's group" What in the heck is the logical basis for the discount of 60%? When I sent for all of the materials to take the course, I was sent the Species Classification and Group Assignment from the ISA Western Chapter with a November 17, 1992 publishing date. Also included was a workbook insert with a publishing date of 1992! It states that: "The basic price (think of it as the basic unit price per square inch, to avoid confusion with the wholesale price of the entire tree or the installed cost)for group one has been determined empirically by the Northern California Regional Tree Appraisal Group as sixty-percent of the wholesale cost per square inch of trunk area of the 48 inch boxed tree..." To me,empirically means derived by or guided by experience. How does one explain the logic to a judge, jury, or knowlegeable cross examining attorney and how does one justify using 1992 data for trial that occurs in 2002? As a person that has spent considerable time on the stand as an expert witness, I can tell you that the answer,in the witness box, to the question "Where did you come up with the number 60%?" cannot comfortably be: " I really don't know, it was just published by the ISA as having been derived empirically" and to the question: "why are you using data published in 1992", I don't want to answer: "that's just the latest publication sent by the Western Chapter of the ISA". As a brand new arborist trying to work thru and understand the appraisal course, I would appreciate some guidance. I should note that I am sensitive to the fact that the appraisal course is only one leg of a comprehensible and defendable appraisal and that reasonableness standards and market value approaches also have to be considered.

Reply to post by Philip A Bjorkman, on December 06, 2001 at 18:37:44:

Well since no one has answered your question I'll jump in. I'm here on the East coast so have no direct knowledge of the rationale for 60% wholesale. It has been explained to me but I remain unclear.

I suggest you contact the WC-ISA committee... I think they are working on a 9th Ed. update.

I agree with your question for at least three reasons.

First I suspect the committee has "empirically" related cost to some measure of central tendancy, perhaps as related to property value. Even if updated to 2002 costs, this is blanket or implicit depreciation by 40% (the complement of 60%). (The cost is updated bu getting current ones but the 60% relationship remains old even if valid, but read on). It A) makes the appraisal unobjective for trees or properties above the central range and B) makes it difficult to communicate the appraiser's rational since depreciation is not explicit.

Second, the same effect results from constraining the appraiser to wholesale, depreciating by at as much as 2/3 before even applying the 60%. How is a damaged party made whole by a wholesale tree sitting on the ground in the nursery? To be made whole the tree must be transported, planted and guaranteed. If the appraiser explicitly depreciates down from that cost to reflect value, fine. But there is no mechanism to add value back if the wholesale cost understates value.

Third, the implicit depreciation ignores variation in the contribution of the tree to the landscape. Is it the only tree, one of ten or one of 100?

Well, OK fourth, it constrains every appraisal to some "empiriccal" definition of value... maybe market relationship. But value in a case may ot be market value but some form of value in use. The beneficiary(s) may vary.

What field was your expert witness experience in?

Reply to post by Scott Cullen, on December 06, 2001 at 18:37:44:

Expert witness in logging and timber harvest valuations, trespass, fire casualty loss of timber, timber volume determinations (timber cruises) & forest practices. Phil