I was doing some deer scouting with a friend on yet another New York City Department of Environmental Protection (NYC DEP) Public Access Area/Water Supply Land . We came upon a squat, but giant, red oak tree. “Mother oak,” said my friend as we walked by. I had never heard that term before, but I was pretty sure I understood what it meant. I was thinking, “Sure, it’s a big old oak and the young trees are growing around it.”
The mother oak tree.
Then I got to thinking that there must be something more to it. An internet search informed me that this tree was evidence of past agricultural land use. Farmers would clear the land for pasture, leaving behind the big trees that could provide shade for livestock and were otherwise useless for lumber. Fast forward to the present and you have an abandoned pasture with younger trees growing up around the mother oaks.
I know of several mother oaks on that particular NYC DEP property. Foresters sometimes refer to these giants as "wolf trees" because they have little economic value and take up space and resources (i.e., water, light, and nutrients) where profitable timber might grow. Of course, they do have historical value and provide food and habitat for wildlife.
I am certain that this land was recently used for pasture based on clues like a plastic insulator for an electric fence and a cow skull resting on the forest floor. But what if the clues had been much more subtle?
A plastic insulator for an electric fence, still visible on this sapling.
A cow skull laying on the forest floor. Notice that the ground is smooth.
While making the case to the MyWoodlot team that this was an old pasture, they recommended that I check out a book by Tom Wessels, entitled Forest Forensics, A Field Guide to Reading the Forested Landscape. This guide demonstrates how to use your observations - for example, a rock wall made of large rocks versus one with both large and fist-sized rocks; or smooth ground versus ground with pits and mounds – to infer a woodlot’s land use history.
The guide is structured as a dichotomous key, or a series of choices that lead the user to a hypothesis about the land use history (e.g., a plowed field, hay field, or forest). It also teaches you how to look for evidence of old growth forest or disturbance events such as windthrow, ice storms, or logging. Based on my experience, it only takes an hour or so to learn how to use the dichotomous key and to know the meaning behind a few of the observations mentioned earlier. Undoubtedly, I still have a lot to learn, but a quick read through this book was enough to get me started. Now I can’t wait to test my skills on a new woodlot.