Questions from the Field ...

“How much do I change the BAF to change the average tree count by one?”

A really good question, actually. I never quite thought of it that way. This cruiser had taken a couple of trial plots with a 50 BAF prism, and had a count of 6, but wanted an average of 5 trees per plot. What should the new BAF be? You know it has to be a bit larger, since that would drop the tree count, but exactly how much?

I won't make you wait for the answer, it is :

(6 trees / 5 trees * 50BAF) = 60 BAF.

The count you have, divided by the count you want is multiplied by the BAF you currently have.

The calculation is not going to come out right on an even BAF all the time, so you will need to round it. On the other hand, it is probably not exactly a preliminary count of exactly 6 either.

We have said before in this newsletter that you can calculate the correct BAF by simply dividing the basal area in the stand by the count you want. In this case, he could have multiplied his count of 6 by the BAF of 50. This gives an estimate of 300 square feet, and divided by 5 trees will give a BAF of 60. The math is the same, but it seems a bit more simple to use this new equation of :

= BAF to use

As we have said before, asking the right question is often the key, and I had never quite thought of it this way.

Thanks for the question, Ken

Kim Iles

Originally published July 2003

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