You walk along a raised walkway, it is warm out but cool up here in the canopy. Birds are calling, hidden in the dense foliage, ants move up and down the tree trunks carrying cargo back and forth, the sunlight-dappled forest floor is far below. You could be up in the canopy of a rainforest in Costa Rica or the Amazon, but in fact you are exploring the new canopy walkway at the Vermont Institute of Natural Science (VINS) in Quechee, Vermont. Squirrels instead of monkeys leap from branch to branch and youíll find scarlet tanagers and wood peewees nesting up there instead of parrots. I was able to get a preview of the canopy walk while it was under construction this summer and canít wait to get back after it officially opens this fall and walk out and up into the full splendor of the forest canopy in full fall foliage.
We live in a place defined by one of the most beautiful forests in the world-the temperate deciduous forest. Pre-development (and even now) huge forests dominated the landscape. Because of our unique combination of temperature and precipitation these trees are broad-leaved deciduous trees, lots of big flat leaves that come in a variety of shapes and sizes and are programed to fall off in the autumn as the tree prepares for the long cold winter ahead.
Just like a rainforest, temperate deciduous forests can have many layers. The canopy is the top layer ó the largest trees concentrate their leaves up here to gather as much sunlight as possible. While the canopy can be dense, it generally allows enough light in to reach the forest floor-enabling other layers to develop. Saplings and shade-tolerant trees occupy the next layer down. Often the saplings are lying in wait, waiting for a canopy tree to topple and let in enough light for more growth. Sugar maples are a great example of this ó a sugar maple can grow, slowly, under the canopy ó often for decades until a hole in the canopy opens up and they can finally grow into magnificent mature syrup producers.
When there is enough light a third layer will form, an understory layer of shrubs, like witch hazel, spicebush or viburnum, and below this a fourth layer of smaller non-woody forest plants, ferns for instance. Or spring wildflowers that have most of their growth in the spring, before the leaves in the canopy grow in and create too much shade: plants like jack in the pulpit, ladyís slipper, Canada mayflower, bunchberry or the tiny partridgeberry.
Another layer that really isnít a layer is comprised of the mosses and lichens that grow up the trunks of the trees-mosses nestled anywhere with enough water to support growth and lichens almost everywhere.
While the canopy is considered one layer of the vertical zonation of a forest, the different raptors that nest there further subdivide the layer. For example Goshawks (fairly rare around here) nest at the base of the canopy while sharp-shinned and Cooperís hawks usually build their nests higher up. Bald eagles prefer nesting towards the top of tall conifers that protrude above the forest canopy (the emergent layer). They build their nests below the crown, whereas ospreys prefer the top of a protruding dead or dead-topped tree. These same kinds of patterns for nesting and foraging can be found in a variety of other birds-warblers, for example, can often be identified by where they are found in a tree as much as by song or plumage.
The VINS canopy walk takes advantage of its location on a bank overlooking a river. Almost all of the boardwalk is accessible because you can walk straight out from the top of the hill and the land gradually falls away beneath you. As you walk out you in effect climb higher until you are up in the canopy of the forest, up amongst the oak and maple leaves that are up high and out of reach. Youíll find lichen growing on tree trunks almost 100 feet above the forest floor. You can crawl out onto a human-sized spider web and experience what it is like for one of these high-altitude spinners. You can climb up above the canopy and get a 360 degree view of the surroundings-just like an eagle perched and scanning its domain or listen to caterpillars munching on leaves. What a great way to experience the forest!.
Susan Pike, a researcher and an environmental sciences and biology teacher at St. Thomas Aquinas High School, welcomes your ideas for future column topics. She may be reached at email@example.com. Read more of her Nature News columns online.