Helena National Forest

Elkhorns Wildlife Management Unit

Aspen Workshop

Elkhorns: Wildlife: Aspen

A SUMMARY OF THE ASPEN WORKSHOP
GRAND JUNCTION, CO
JUNE 2000

ASPEN ON THE HELENA NATIONAL FOREST: HOW WILL WE MANAGE?

INFORMATION COMPILED BY
JODIE CANFIELD

Aspen are important in terms of biodiversity, productivity, aesthetics, and cultural values.

There has been a 64% decline in aspen in Montana. Most research suggests a combination of fire suppression (conifers invade) and livestock/wildlife browsing.

There are 3 descriptions of aspen stands in the west:

1. Stable – reproducing, multi-age, closed canopy (check for mollic soil)
2. Seral – conifers move into in the absence of disturbance
3. Decadent – 1 age class, open canopy, falling apart, reproduction being eaten

Aspen Ecology in a nutshell:

• Reproduces from root suckers – what affects one affects all; can reproduce from seed but very difficult because of exacting temperatures and moisture requirements for seedlings to grow.
• Suckering is stimulated when a high ratio of cytokinins to auxins exists in the root. Suckering occurs at a low level under normal conditions and at an enhanced level when either the root or the stem is severed completely.
• Aspen need sunlight and are “picky” in regard to soil temperature (not too warm, not too cold) and soil moisture (not too wet and not too dry), but can occupy a wide range of landforms, elevations, aspects, and soils.
• Aspen is readily killed by fire, but aspen stands are difficult to burn due to high soil moisture.
• The number of suckers produced following treatment is influenced by the timing and type of treatment, the condition of the parent root system at time of treatment, and soil types.
• The survival of aspen suckers is primarily a function of browsing both by livestock and wild ungulates.
• Aspen are subject to a variety of fungi and disease and since the bark is “living”, wounds from browse activity provide infection sites for pathogens including sooty bark canker and cytospora. In addition, normal infections can become lethal when sprouts are stressed by excess moisture, insufficient moisture, and defoliation.
• Browsing by both livestock and wildlife is influenced by numbers, season, slope and aspect, patch size and stocking level, as well as the kind and amount of forage in the surrounding landscape and the presence of predators; patches less than 10 acres without protection may be futile to treat without wildlife-proof fencing.
• If enough area is treated, or if the treated area is fenced, the expectation is that sprouting will be prolific, but then aspen sprouts will naturally thin out over time. You need about 5-10,000 sprouts initially to sustain the clone.

Aspen Relationships and Theories

• Most of the mature aspen we see originated around the turn of the century. There are two reasons for this – large catastrophic fire events and low big game numbers due to market hunting.
• Aspen stands are more stable at lower elevations where short fire intervals historically eliminated conifer seed sources. Conifers inhibit aspen by chilling the soils, competing for water, and reducing light
• Reproduction from seed is important in providing genetic variability; expect some after large fire events; survival is low because they do not have the resources of the clonal root system.

How to treat Aspen:

1. Interrupt flow of auxin in leaves to stimulate roots to sucker.
2. Provide for full sunlight
3. Protect from browsing

Tools for hormonal stimulation include:

• Clearcutting (partial cutting is ok – must get enough disturbance to trigger root suckering
• Mechanical Root stimulation
• Removal of competing vegetation
• Rx burning (partial burning is ok – see clearcutting)
• Fencing: leave until sprouts are 3 cm dbh or 8-10 years

The options for managing aspen successfully are:

• Treat large areas outside of big game winter range
• Fence treatment areas with 7’-high fences @ 6,000/mile
• Reduce big game populations in aspen treatment zones (or introduce predators)
• Restore historic fire regimes and/or create alternative foraging areas in conjunction with aspen treatments

Priorities for Treating Aspen:

1. Where conifers occupy over 50% canopy cover in the aspen stand
2. Where aspen is less than 40% canopy and sagebrush is at least 15% canopy
3. Probability for success increases with good soils and good moisture in May/June
4. Be careful treating riparian aspen; tendency is to increase water tables and get poor response.

Slim Sam Aspen - A Case Study

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USDA Forest Service - Helena National Forest
Last Modified: Monday, 25 June 2007 at 12:56:54 EDT