This week we got into the trees of Thatcher Woods. We talked about forest surveys, and how we can analyze trees and forests from a few different perspectives.
While we waited for everyone to arrive, we philosophized: if I have one tree in my yard, is that a forest? What about two trees? At what point does it become a forest? After some rigorous discussion we came to the conclusion that the correct answer was “a bunch”.
For our first exercise we talked about trunk circumference, and how older trees have larger trunks. I told them that different species of trees grow at different rates, called their growth factor. We picked a tree and (using measuring tape) they measured its circumference in inches. Using a random growth factor, we calculated an age estimate and talked about how that’s just an educated guess.
Next we found a few clean-cut stumps, and I equipped them all with sandpaper so they could sand away some dirt and get a good clear look at the rings. Boy, did they like sanding! We talked about how trees expand in the spring and summer (and a bit into fall), and how the big light rings are springwood and the narrow dark bands are summerwood. I asked why some rings are smaller, and they guessed it had to do with water. We counted rings and got an estimate of that particular tree’s age, in a manner that’s more precise than measuring circumference but also a tad more invasive.
For the last exercise, we talked about how many trees there are in Thatcher Woods. Someone brought up that we can’t count them all, which dovetailed nicely into sampling. We got into a line, measured how many feet long our line was, and walked (haphazardly) into the forest, counting every tree we touched. After fifty feet or so, we talked about how we now had an estimate of roughly how many trees there are per square foot. And since we know Thatcher Woods is 245 acres, we can now estimate how many trees there are in total.
Finally, to balance out that last part, I told them about a silly way I found of estimating tree height… We tried it out, and it was, predictably, very silly.