Hello, all. I just sent a message to the ASCA
executive director for her to pass along to the
CTLC committee. Here it is for you folks too:

To: Beth Palys, ASCA

From: Debbie Ellis, ASCA #305

Date: 1/26/98

Re: CTLA - Trunk Formula Method Revision Suggestion

Dear Beth:

I am aware that the ASCA office handles CTLA matters in some way. I have a suggestion that they may want to consider for the next revision of the Guide. I wonder if you can pass this on to the appropriate person.

Regarding the Trunk Formula method: I have measured the DBH (at 4.5 feet above grade) of thousands of trees in a research project I work in. I also do monetary appraisals from time to time, primarily using the trunk formula method. As we all know, the 4.5-foot measurement point for trunk diameter is often not possible to measure or yields unreasonable figures, due to varying trunk configurations. I suggest that the standard height of measurement remain at 4.5 feet. If this is not possible or does not reasonably reflect the size of the tree however, the height should be moved up or down as little as possible to give a more reasonable measurement, for example just below the lowest permanent branches.

The way that this change could be accounted for would be to adjust the trunk diameter value on a proportional basis relative to the standard 4.5-foot height. For example, suppose 3 large scaffolds originate at 4.5 feet. If I could measure the trunk diameter at 4.5 feet, I would get a diameter of about 22 inches. This includes the scaffold branch flare, and is much greater than the trunk diameter just below these branches at 4.0 feet, which is 12 inches. I will therefore use 12 inches as the trunk diameter and adjust this figure as follows:

12 inches / 4.5 feet = x inches / 4.0 feet. X = 10.67 inches

Since the trunk diameter was moved down to 4.0 feet, the adjusted trunk diameter is reduced because a trunk would normally have a smaller trunk diameter at 4.5 feet than at 4.0 feet. I would use the value 10.67 inches for the trunk diameter, making notation of how and why this was done.


In another example, suppose it seemed more appropriate to measure the trunk diameter above 4.5 feet, say at 5.0 feet. The trunk diameter at 5.0 feet is 12 inches. The adjustment then would be as follows:

12 inches / 4.5 feet = x inches / 5.0 feet. X = 13.3 inches.

Since the diameter was moved upward from the standard height of measurement, the typical trunk diameter at 4.5 feet would be larger than the 12 inches measured at 5.0 feet. The adjustment is upward (trunk diameter increased) to 13.3 inches.

I'd like to know what you think about this.

Reply to post by Deborah Ellis, on January 28, 1998 at 10:34:11:

Debbie, this is not the first time this point has been brought up. It is perfectly fine to measure diameter at 2 inches from grade if you feel that this portion of the trunk is a fair representation of the trees size. You can also measure the diameter of all stems involved if a tree branches very low to the ground and total all stems if they equally contribute to the canopy outline. The 4.5 foot designation is a starting point and the apraisers own experience and knowledge will guide you as to the most appropriate method. I have personally used a number of different locations on the trunks of different trees and argued, sucessfully, as to the justification of not taking a 4.5 foot measurement. I do not know if the Guide specifically addresses these options. But I do know it has been covered in previous ASCA Appraisal Workshops. A measurement anywhere, within reason, is valid if you can substaintiate your method with valid arguement. Russ

Reply to post by Deborah Ellis, on January 28, 1998 at 10:34:11:

Hi Debbie, how's everything going? Your suggestion is good, and partially covered in the GUIDE. If you want to present a new approach or formula, write to Dick Harris and we can cover it at our April CTLA meeting.
Best wishes,
Lew

Reply to post by Deborah Ellis, on January 28, 1998 at 10:34:11:

Hi Deborah:
If you check in the 8th edition of The Guide for Plant Appraisal under the Size chapter
you should find some of the different problems for measuring the trunks of trees. Many
of these are addressed here. If you have any additional comments I will gladly take them
up with the CTLA board as will Lew, I am sure.

Hope this answers some of your questions.

Ellis

Reply to post by Lew Bloch, on January 28, 1998 at 10:34:11:

Debbie: You raise an interesting point because the Trunk Formula is based on the measurement at 4.5' and using a different point of measurement (even though correct by the guides) is not staying with the assumption that the measurement was correct at 4.5'. We even project, calculate, or guesstimate what the measurement would be at 4.5' from a stump or a stump hole. So why should we use a diameter value different than what the formula calls for? For example, when the crown starts before 4.5', I always use the smallest diameter below 4.5" and record that height of measurement and reason why. But that does not equate with the assumption of the tapered trunk above the root flare that the Trunk Formula assumes. It does, doesn,t it? Debbie, your method is sound but will add time to an appraisal. However, when programmed, the TFMethod is so much faster than the Replacement Method when you have to research replacement costs and determine installation costs for that location.
As for the Trunk Formula, it is my first choice. But inexperienced tree appraisers arrive at unrealistically high values, especially in woods or multiple tree locations. My last two opponents were still using the 6th Edition of the Guide!
The revised Ohio Guide, 5th Ed. is to go on sale this weekend at the Ohio Tree Care Conference. The major change is the reduction of the basic price of $35.00 /sq.in. for an 8" tree (retail planted) graduated down to $14/in for a 12.5" tree (wholesale, in ground) because it is increasingly less likely to be replaced with each half inch diameter increase between 8" and 12.5". The result will be more reasonable values as far as realestate values are concerned.
Fred

Reply to post by Fred J Robinson, on January 29, 1998 at 18:16:34:

Hi, Fred. Good to see you found us.

The 4.5' measurement is a suggested standard, and was originally based more on convenience than anything else. It only gives us a point to start from when determining where to measure. Obviously, it is not practical to go too high up a stem. Your method of taking the smallest diameter at or below 4.5' (for trees with low limbs) is what the Guide recommends. The point is not to compare every tree to an absolute standard, but to arrive at a recognized and repeatable point to measure. The factors of form and trunk taper as they relate to species comes into play.

I think it is less important to worry about comparing to a 4.5' measurement than it is to get a reproducable measurement.

Russ

Reply to post by Russ Carlson, on January 30, 1998 at 10:25:49:

Let me throw this cookie out there for you all to gnaw on..... Is it possible to develop a species specific parameter (trunk diameter or whatever) that would reflect the age of the tree rather than just size? This goes back to the problems of how you compare the value of ancient Japanese maple trees versus young redwood trees based on size alone. Just a thought. Let the crumbs fall where they may.
Dorothy!

Reply to post by Dorothy Abeyta, on January 30, 1998 at 11:57:43:

>>..... Is it possible to develop a species specific parameter (trunk diameter or whatever) that would reflect the age of the tree rather than just size?


The problem I see with that, Dorothy, is that size is not dependent on age as much as on local conditions. A tree in a good natural site will often grow much faster than a tree on a poor site that has been modified. For example, I've encountered white oaks that are less than 100 years old, and are over 30 inches standard height. I've also encounter one site (actually a natural site most of the tree's life) where 12 inch diameter white oaks were over 150 years old. If age is to play into the concept of value, it must be verifiable, through cores sampling or cross-sectioning- one technique more destructive than the other. Even then, does the age itself really matter, if the condition of the tree is poor due to extremely slow growth? Or that the size is small, despite the great age?

The value of a tree is tied to the benefits it provides. Since most of the benefits increase as the size increases 9shade, cooling effects, oxygen production, etc), isn't size a better indicator of the value of those benefits?

Russ

Reply to post by Russ Carlson, on February 05, 1998 at 08:07:43:

I am also of the opinion that afe MAY not be important. I capitalize "may" because you may want to adjust the appraised value because of this. I think that is covered under Location in the contribution coverage as other considerations; to wit, Historic, rare or unusual specimen. As appraisers, we are given the latitude to do our own thing, so to speak, as long as we can justify it. Keep the cookie crumbs crumbling.
Very treely,
Lew

Reply to post by Lew Bloch, on February 05, 1998 at 09:03:13:

Another aspect in the size aspect is rarity. Is a small uncommon tree more or less valuable than a large uncommon tree of the same species? Some years ago I undertook a large inventory of one of British Columbia's earliest arboretum sites. Many of the trees were exotic, and we were asked to provide a rating for heritage value. The problem was, that for many of the species found, we had (still have) no long-term track record, because many of these trees have not yet gone through one whole rotation; they were planted in the early part of this century. Eventually we used comparison of known specimens in the region, in combination with health and condition ratings. Had this been an appraisal exercise it would have been much harder to place a value on species with such slight track records. But, I agree that size alone is a poor indicator of health, or appraisal value. I used 80 year old Douglas-fir for the newel posts in my house - diameter about 5- 6 inches. The stringers were 40 year old fir from the same site, about 2 feet in diameter.

Julian Dunster