On July 14 (Bastille Day for the Francophiles out there), I joined more than a dozen other intrepid naturalists on a two-hour woods walk led by Tom Wessels. Wessels may be best known for his book, Reading the Forested Landscape, but the other titles he had with him all looked compelling. According to Wikipedia:
Tom Wessels is an American terrestrial ecologist working as a professor at Antioch University New England in the Department of Environmental Studies, where he founded a master’s program in conservation biology. He is the author of five books and is an active environmentalist.
We all met at Shore Acres Preserve, a nearly-40 acre preserve with 1.7 miles of hiking trails, located just off the Greenlaw District Road in Deer Isle. According to the Island Heritage Trust, which manages the preserve, the landed had been forested by the Barter Lumber Company in the 1940s and then sold to a farming family. There are a number of distinct microhabitats on offer — vernal pools, a traditional Maine salt water meadow, rocky coastlines, clam flats, marsh grasses and mossy-floored forests. It’s a great place for folks interested in mosses and lichens.
It was a forlorn and overcast morning, dreary and damp, but not so wet that we had no-shows. Just after 9 a.m. we stepped out of the parking lot and into the woods. The first stop was in front of a very short tree trunk, from which a nearby tree had been separated. Did this happen when the tree was alive or dead, Wessels asked us. After 10 seconds of silence, Wessels told us that a stump this short indicated that the tree had died, and then fallen over (by what we couldn’t say for sure — probably wind). What happens is that dead trees develop a rot collar close to the ground, where its most damp. When the rot has reached a certain stage, the dead tree’s weight is unsustainable and it snaps at the collar. In contrast, a tree that was living when it fell is either going to show us a root ball, or snap higher up the trunk.
(Tom Wessels, center, pointing out the impact of a pine weevil)
Next he pointed out an Eastern white pine, which provided two topics of interest: masting strategies and the impact of a white pine weevil, which kills the terminal leader of eastern white pine trees (among other species) and results in multi-topped and crooked trees. While the weevil changes the tree’s form (and can impact the commercial value of the tree), Wessels said that in general the lifespan of the tree and its overall health are not seriously impeded. About masting — that’s a big topic, but Wessels explained how large-seeded trees, like oaks and pines, collectively “agree” to forego seed production for a period of 3-5 years in order to inundate the forest with seeds in the subsequent mast year. It’s not exactly clear how the trees communicate with each other, but this coordination can take place across regions as large as New England and eastern New York. While some of us asked about trees communicating through mycorrhizal networks — underground fungal networks of mycelium that connect plant roots and facilitate the exchange of water, nutrients, and other resources. — Wessels said recent studies suggest the coordination is occurring through the air.
Picking up a white pine cone, he observed how the scales occurred at the intersection of spiral lines running both left and right around the cone. If you trace these lines, or diagonals, you will count three running in one direction and five in the other. It’s one of many examples of the Fibonacci sequence occurring in nature. He pointed to a nearby spruce with lenticels and pointed out that they, too, were arranged in diagnols which, when counted, would also equal numbers in the Fibonacci sequence.
I think at this point, we’d been on the walk for about 5-6 minutes. So I can’t cover all the rich details of the walk, but here are some interesting points I heard this morning:
- When you look at a New England forest, pay attention to the floor. If it is irregular and lumpy, displaying a pit-and-mound topography (Wessels also called it a pillow and cradle pattern), then it is likely that the woods in view were kept forested and never cleared for farming. In contrast, if the floor seems regular, smooth and level, it was probably a hay or crop field.
- Wessels pointed to an area that was snarled with deadfall and wind blowovers. The temptation is to clear them, he said, for aesthetic purposes, but doing so will undermine the forest’s biodiversity. “Any increase in the complexity of physical structures in an area will accelerate biodiversity,” he said. Oftentimes our modern forestry practices, whose lifespans can be measured in decades, can do more harm than good. “Forests have been around for 320 million years,” Wessels said. “So they have figured it all out already. Most of the time the best practice is to let the forest do its thing.”
- In what represented the first of many examples of mutualism throughout the walk, we observed some skunk cabbage growing in a damp, muddy area beside the trail. When it flowers in early April — despite near-freezing temperatures — the plant’s wine red and green striping can appear like rotting flesh to the carrion beetle. While the cabbage does not offer nutrition for the beetle (nor the beetle for the cabbage), the interior of the skunk cabbage can be 20 degrees warmer than the exterior, thanks to thermogenesis. That’s great for cold-blooded beetles, which might otherwise freeze, and great for the plants, because the beetles inadvertently transfer pollen between the plants, facilitating cross-pollination and the skunk cabbage’s reproduction.
- He pointed to a maple tree about 20 yards off the trail and what looked from that distance like some ivy about a third of the way up to the crown. It was lungwort, a large, bright green, leaf-like lichen that grows only on ash and maples. And it can only grow in wet habitats. It turns out that our location, on the coast, provided a great buffet for lungwort in the form of fog. Wessels said that because of its microscopic structure, fog carries 1000 times the nutrients of rain drops. The frequent fog — very frequent, I should say — is also one reason for the moss-floored forests that abound on our island. One friend remarked a few years ago that our hiking trails were like those he imagined in the Lord of the Rings because of the mossy grounds and lichen-draped trees.
- Maybe the most fascinating point I took away was the concept of “biocognizance” in trees. Wessels showed us two very different looking leaves beneath and oak. “Oaks demonstrate leaf dimorphism,” he said, distinguishing between sun leaves (smaller, angular, sharp notched) and shade leaves (bigger, more deeply lobed). If one of the top limbs with sun leaves falls (wind storm, or ice for example), the shade leaf bearing limbs will be crucial for photosynthesis. After a year, the oak tree somehow “knows” to start producing sun leaves on that limb. It may not resemble human thinking, but tree biocognizance is powerful and adaptive, Wessels said.
- Finally, we all got a good whiff of wintergreen from a yellow birch branch. The wintergreen arises from an “antibrowse” chemical, methyl salicylate, to keep white-tailed deer from decimating it in the winter. Eating yellow birch would give a deer a whooping stomach ache, Wessels said. While we might know it best as a flavoring agent for gum and curiously strong mints, it is also used for pain relief, as a topical agent or as balm (think about the smell of something like IcyHot). But it is also toxic in modest amounts — according to MedlinePlus, consuming as little as a teaspoon of wintergreen oil can be fatal.
We wrapped up the walk almost exactly two hours after we started, eager to get back and learn more about the things we’d just heard about. We all wished we could go only weekly Wessels walks, we agreed.
(Wessels stops by a multi-trunk cedar tree on our walk.)