Speaknig of Nature

Bigtooth aspen’s leaves, dispersal of seeds fascinating

Sunday, November 3, 2013
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The only way to find leaves like this in the autumn is to take long, quiet walks in the woods and pay attention to the ground.
The only way to find leaves like this in the autumn is to take long, quiet walks in the woods and pay attention to the ground.

It was during the wonderful days of late autumn some 20 years ago that I encountered the bigtooth aspen for the first time. I have one particularly vivid memory of spotting the leaves of this species, but not being able to find the tree from which they came. It was a lovely mystery that will always be tied to the lovely and unusual leaves of this species.

As the name suggests, bigtooth aspen leaves are decorated with a margin of pronounced teeth that make them look as though they had been cut with pinking shears. Sometimes the teeth are quite pointy, like those on a circular saw blade, while other times they are rounded. They are simply so different from the leaves of other trees that they make an impression on the mind.

The bigtooth aspen (Populus grandidentata) is a close relative of the much more widespread quaking aspen (P. tremuloides). Both species are referred to as “pioneer” species, because of their ability to quickly move into areas that have been disturbed. They are also particularly well-suited for living in the well-drained, sandy soils that would be unacceptable for many other species.

The reason they can populate new areas so readily is a result of their reproductive strategy. The seeds of the bigtooth aspen are small and attached to long, threadlike hairs that catch the wind and carry great distances. Imagine a dandelion and you have the basic idea.

A single mature tree can produce more than a million of these small seeds, and can cover vast areas with potential offspring.

The survival rate of these seeds is very low, however. The wind does not always blow in the right direction and the seeds do not always land in the most favorable of places. The seeds, which are only viable for two to three weeks, must get lucky to land in just the proper soils at a time when there is enough moisture to support the new seedlings.

Sooner or later, the law of averages places a few of the seeds in the right places at the right times and their overall mission is accomplished.

At no point have I ever encountered large stands of bigtooth aspen, however. In my wanderings through forests and fields, I have always found bigtooth aspen to be uncommon and thinly dispersed across the landscape. I suppose this is why the sight of these leaves on the forest floor is always a little exciting, like finding lost treasure.

Aspen trees are a favorite of the American beaver for food and building material. The leaves and bark are highly nutritious and are quite desirable in any potential beaver habitat.

Food for grouse

As important as they are to beavers, however, aspen trees are integral to the survival of the ruffed grouse. If you were to lay out a map of the United States and then draw lines that delineate the ranges of the various aspen trees and the range of the ruffed grouse, you would see that they are virtually identical.

This is because ruffed grouse rely heavily on the buds of aspen trees to get them through the winter months. Grouse are small birds, and deep snows would completely exclude them from foraging for food on the ground.

High in the trees, safe from everything but ice storms, are the leaf and flower buds of aspens. Imagine a forest filled with millions upon millions of tiny little Brussels sprouts and you will have the right idea. Without this food source, grouse wouldn’t stand a chance.

Bill Danielson is a professional nature photographer and author living in Altamont. Contact him at www.speakingofnature.com.

 

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