Thursday, October 13, 2011

Aspens (and Grouse) -- © Dave Spier

If there's one plant that's key to the winter survival of grouse, it's the aspen tree. Closely related to cottonwood, another poplar, aspens come in two species, the quaking (or trembling) and the bigtooth. Both are fast-growing, short-lived trees that colonize old fields, woodland edges, burned forests and sunny breaks in a woods where a large tree has blown down. They need plenty of light to grow and will not reproduce in the shade of their parents or other large trees. On the other hand, the shade they produce makes a good habitat for long-lived trees like oaks, maples and beech. The aspens stabilize the soil and reduce erosion and their shade suppresses competition from shrubs. Although grouse need the shrubs for escape cover and autumn berries, it's the large aspens with their abundant crop of flower buds that will get the birds through the winter. The grouse is so dependent on the aspen that the range of both these species corresponds very closely across North America.
Young aspens, when comingled with bushes, provide grouse with protective cover to raise their broods. As the trees reach 12 to 15 years of age, the grouse lose interest and move on. The woods have become too open for the grouse to hide. As the aspens reach 30 years of age, the situation reverses and grouse return to the trees during cold weather beginning as early as October. Grouse particularly relish the large male flower buds, the ones that will resemble pussy willows in the spring -- if they're not eaten before they can open. The fruits of female poplars hang in long, clustered catkins that release cottony seeds. These are eaten by numerous birds and mammals in addition to the Ruffed Grouse. Aspens also reproduce by cloning themselves from long, underground stems. In this way, they often form circular, monocultural groves with tall trees in the center and short, young ones on the edges.
Poplars, aspens and cottonwoods are all members of the same genus (Populus) in the willow family. The leaves are toothed and triangular shaped or rounded-triangular. In one species, the Quaking Aspen (Populus tremuloides), the long leafstalks are flattened, allowing the leaves to flutter in a light breeze. The Quaking Aspen might otherwise be called the small-toothed poplar. Its close relative, the Bigtooth Aspen (Populus grandidentata) has very coarse saw-like teeth around the leaf edges.
When they're young, aspen trees have smooth, greenish or light-gray bark that changes to dark and furrowed as they mature. When the bark is particularly light, aspens can be mistaken for birch. The bark of aspen saplings is an important food in the diet of beavers.
Aspens seldom grow more than 40 or 50 feet high and a foot in diameter before disease, insects or storms kill them. The soft and brittle wood has been used to make paper pulp and woodenware. Dead aspens quickly rot, but this is an advantage to the chickadee which can use its short bill to excavate a nesting cavity in the soft pulp.
It might be said of the aspen, "Live fast; die young."

Big-toothed Aspen leaf on trail to Harper Falls (Grass River)  © Dave Spier
(This is the third article in a loose series around the theme of Ruffed Grouse.)
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