Photo above: The canopy of an unhealthy aspen grove
Testing techniques aimed at boosting the health of our aspen groves
By Lani Fernandez, Pine Meadow Ranch crew member
Did you know that aspen trees are considered a keystone species? This means that an unusually large amount of other species in their ecosystems heavily depend on them. Wildlife rely on aspen groves for thermal cover, nesting habitat, protection from predators and food. Many plants desirable for forage grow in the understory of aspen trees. In fact, if aspen trees were to disappear, local forage for wildlife and livestock could be reduced by up to 70 percent. Aspen groves also provide benefits to people—the cooler, more humid microclimate created by aspen groves can serve as a buffer against fires.
We have several small aspen groves here at Pine Meadow Ranch that are unfortunately in declining health. Mature trees are beginning to die and they are not regenerating young aspen (also known as suckers) at the rate that’s expected for a healthy grove.
There are a few possible factors contributing to this decline. First, browse damage from deer and elk may be causing suckers to die or become stunted. Also, aspen trees often rely on disturbance, such as fire, to stimulate vegetative reproduction or “suckering.”
Due to fire suppression, there has not been significant disturbance to this area. Another side effect of fire suppression is encroachment by conifers such as ponderosa pine and Western juniper. Conifers, in the absence of natural checks and balances such as fire, can outcompete aspen trees for light, water and nutrients.
We will be testing a few techniques aimed at boosting the health of our groves. First, we will be putting up wire fencing around some of the young aspen to see if browse from deer and elk is causing the aspen suckers to not be successful. This technique has been used nearby at Indian Ford Meadow Preserve, and caged trees have been significantly more successful.
If the aspen here at the ranch seem to be doing better in the absence of browse pressure, we can consider this to be a major contributing factor in grove health decline. If this doesn’t seem to have an effect, we will do some light burning in the winter to promote the mature trees to produce suckers. Lastly, we will consider thinning some of the smaller ponderosa pines and juniper will allow more light, space and water for the aspen trees. It may even require a combination of these management techniques to improve the health of our aspen.
For more information on how to assess and manage the health of your own aspen groves, check out this OSU Extension Service’s guide for aspen management in Oregon.
Photos below, left to right:
Example of a healthier aspen grove with a ring of reproduced vegetation, or suckers, growing around some mature trees.
An unhealthy grove—mature trees dying and little to no suckering and conifer encroachment.
Evidence of browse damage on a sucker—the terminal leaves are missing.
The overstory composition (and a little bird)—the bare branches belong to a dying aspen tree. Ponderosa pine trees make up most of the living overstory.
Lani Fernandez, Pine Meadow Ranch crew member
