St. Anne Woods & Wetlands

B Forest Canopy and Wild Life


While the wetland behind this sign lacks understory shrubs, it does support large trees that form a canopy. These species include the cottonwood (Populus deltoides), with its deeply furrowed bark, and the American sycamore (Platanus occidentalis), with whitish, peeling bark. These species are both native to this region and are known for their hydrophilic (water-loving) tendencies. In contrast, the native tulip poplar (Liriodendron tulipifera), a species not found in floodplains, is absent from the wetland but is common in the area at a slightly higher elevation on the opposite side of the trail.

The tree canopy not only serves as a habitat and foraging environment for many species, but it also creates conditions which contribute to the great diversity of wildlife in the wetland. The architecture of these trees consists of woody branches supporting a canopy of leaf foliage stretching across openings to fill any gaps and trap as much light as possible. The tops of the trees can range in height from about 15 feet to 50 feet off the ground. This variation in height alone creates a diversity of habitats for a range of bird and mammal species. For example, Cardinals and Mockingbirds are found in the lower canopy trees, while Woodpeckers and Nuthatches are more common in the midcanopy, and Warblers are in the highest part of the canopy. In addition to birds, the canopy also provides habitat for Squirrels, Raccoons, Opossum, and a variety of other animals. The canopy captures sunlight and intercepts wind and precipitation, thereby buffering climatic extremes in the understory and forest floor microhabitats.

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Genus Populus

Cottonwood trees are large deciduous trees 20-45 meters tall, distinguished by thick, deeply fissured bark and triangular-based to diamond-shaped leaves that are green on both sides (without the whitish wax on the undersides of balsam poplar leaves) and without any obvious balsam scent in spring. An important feature of the leaves is the petiole, which is flattened sideways so that the leaves have a particular type of movement in the wind.

Male and female flowers are in separate catkins, appearing before the leaves in spring. The seeds are borne on cottony structures that allow them to be blown long distances in the air before settling to ground.

The cottonwoods are exceptionally tolerant of flooding, erosion and flood deposits filling around the trunk.

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Genus Platanus

Sycamores are large deciduous trees ranging from 30-50 meters tall. They are typically found in wetland habitats, though they are able to weather long droughts if necessary.

An American sycamore tree is easily recognized by its mottled exfoliating bark. The bark of all trees has to yield to a growing trunk; in the case of trees such as  silver maple and shagbark hickory, the process is not hidden, but sycamore shows the process of exfoliation more openly than any other tree. The bark of the trunk and larger limbs flakes off in great irregular masses, leaving the surface mottled and greenish-white, gray and brown. Sometimes the smaller limbs look as if whitewashed. The explanation is found in the rigid texture of the bark tissue, which lacks the elasticity common to the bark of other trees, so it is incapable of stretching to accommodate the growth of the wood underneath, and the tree sloughs it off.

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