On points calculations and large cottonwoods.

General discussions of measurement techniques and the results of testing of techniques and equipment.

Moderators: edfrank, dbhguru

Post Reply
Posts: 100
Joined: Sun Dec 25, 2011 2:18 pm

On points calculations and large cottonwoods.

Post by fooman » Thu Aug 29, 2013 5:30 pm

As previously mentioned, there are some large specimens of Populus deltoides in New Zealand, planted as introduced specimen trees over a hundred years ago.

A recent addition to the New Zealand Tree Register of notable trees is a large cottonwood called the Waiohika Poplar (http://register.notabletrees.org.nz/tree/view/1123). The raw dimensions are larger than the (now declining) NZ champion, the Frimley Poplar (http://register.notabletrees.org.nz/tree/view/210)

Frimley Tree: 138 ft high, 112 ft spread, 33' 6" cbh
Waiohika Tree: 141 ft high, 157 ft spread, 33' 8" cbh

The Waiohika tree would have a points score of 585 vs 568 for the Frimley tree, but for a small secondary stem (pictures are availble at the above links) disqualifiying it as a single stem tree.

Anyway, this got me thinking, and I wonder if anyone has suggested the following modifcation to the points calculation for multi-stem trees where the largest stem girth is not known:

points = height (ft) + spread/4 (ft) + [cbh/n] (in), where n is the number of stems at breast height.

This would not discount trees with execptional heights, or spreads, but modify the bias in the formula towards girth, such that it accounts for large girths influenced by multiple stems. I do see it as an approximation when, for example, the largest stem girth is not measured and subsituted into the formula. But then, do you use the height and spread for that single stem in the points calculation?

Such a modification seems obvious, so I am curious if anyone has suggested it before? In the example above, the Waiohika tree has 383 points, rather than 585. Still a big tree, just not a champion. A measurement using the largest stem would increase this score, which does point out such a modification is still an approximation of an actual score (but more accurate than a score of 0!)


Post Reply

Return to “Measurement and Dendromorphometry”