Photo by Eric Epstein
- WDNR
Aspen and birch-dominated forests make up a significant part of the forested landscape in northern Wisconsin. Although this type only occupied approximately 4% of northern Wisconsin circa 1800 (Schulte et al. 2002), it is now the second most common forest cover type in that region after maple. Aspen-birch is not a tracked natural community by the Natural Heritage Inventory (NHI), as it is a short-term early successional stage that under natural conditions would give way to other, more mature, forest types. However, Aspen-birch forests receive a high degree of management emphasis on both public and private lands due to their significance to the forest products industry and importance to several wildlife species, and are described here to present a more complete picture of forest types in Wisconsin, as well as to illustrate how managers can increase habitat suitability for a greater variety of species within Aspen-birch forests if desired.
Aspen and birch-dominated forests can occur on a wide variety of landforms and soil conditions from outwash sand to lacustrine clay and from dry to wet moisture regimes. Stands with 50% or more of their basal area in trembling aspen (Populus tremuloides), big-toothed aspen (Populus grandidentata), or paper birch (Betula papyrifera) are included here; for stands with a smaller component of aspen and birch, see the relevant NHI community type. Aspen is a "pioneer" tree species generally growing in even-aged stands regenerated following a major disturbance such as catastrophic fire, blow down, clearcut, or coppice harvest. Aspen often outgrows other associated species and can form nearly pure stands. In undisturbed or unmanaged stands, more tolerant associates replace aspen over time through natural succession.
Other tree species associated with aspen and birch are variable and depend greatly on the soil type and moisture regime, but may include red maple (Acer rubrum), balsam fir (Abies balsamea), red oak (Quercus rubra), eastern white pine (Pinus strobus), and on mesic sites, sugar maple (Acer saccharum). Most other major tree species occurring in Wisconsin can also be found as occasional associates in aspen stands. Shrubs are also variable depending on the age of the stand and moisture regime but are typically absent to sparse when stands are young, dog-hair thickets, gradually increasing in density over time. Exceptions to this trend are clonal species that persist under moderate shade and resprout aggressively when cut, such as hazelnut. The groundlayer is also extremely variable, depending greatly on soil type, moisture regime, and past disturbance.
Several bird SGCN (e.g. Golden-winged Warbler) utilize young stands of aspen at various life history stages. Other SGCN utilize conifers embedded within aspen stands, such as Swainson's Thrush, which requires a dense understory of spruce and fir. Maintaining or increasing the conifer component is necessary for most SGCN to utilize these forests. In addition, landscape context is critical for most SGCN that utilize aspen and birch forests for part of their life cycle.
The following Species of Greatest Conservation Need are listed according to their level of association with the Aspen-Birch natural community type, based on the findings in Wisconsin's 2015 Wildlife Action Plan.
Scores: 3 = high association, 2 = moderate association, and 1 = low association. See the key to association scores for complete definitions.
| Amphibians | Score | |
|---|---|---|
| Four-toed Salamander | Hemidactylium scutatum | 3 |
| Mink Frog | Lithobates septentrionalis | 1 |
| Pickerel Frog | Lithobates palustris | 1 |
| Ants, wasps, and bees | Score | |
|---|---|---|
| Sanderson's Bumble Bee | Bombus sandersoni | 1 |
| Birds | Score | |
|---|---|---|
| American Woodcock | Scolopax minor | 3 |
| Golden-winged Warbler | Vermivora chrysoptera | 2 |
| Least Flycatcher | Empidonax minimus | 2 |
| Swainson's Thrush | Catharus ustulatus | 2 |
| Black-backed Woodpecker | Picoides arcticus | 1 |
| Eastern Whip-poor-will | Antrostomus vociferus | 1 |
| Long-eared Owl | Asio otus | 1 |
| Northern Goshawk | Accipiter gentilis | 1 |
| Grasshoppers and allies | Score | |
|---|---|---|
| Crackling Forest Grasshopper | Trimerotropis verruculata | 1 |
| Huckleberry Spur-throat Grasshopper | Melanoplus fasciatus | 1 |
| Speckled Rangeland Grasshopper | Arphia conspersa | 1 |
| Mammals | Score | |
|---|---|---|
| American Marten | Martes americana | 1 |
| Big Brown Bat | Eptesicus fuscus | 1 |
| Northern Flying Squirrel | Glaucomys sabrinus | 1 |
| Northern Long-eared Bat | Myotis septentrionalis | 1 |
| Woodland Jumping Mouse | Napaeozapus insignis | 1 |
| Reptiles | Score | |
|---|---|---|
| Wood Turtle | Glyptemys insculpta | 3 |
Please see Section 2. Approach and Methods of the Wildlife Action Plan to learn how this information was developed.
The Natural Heritage Inventory has developed scores indicating the degree to which each of Wisconsin's rare plant species is associated with a particular natural community or ecological landscape. This information is similar to that found in the Wildlife Action Plan for animals. As this is a work in progress, we welcome your suggestions and feedback.
| Scientific Name | Common Name | Score |
|---|---|---|
| Adlumia fungosa | Climbing Fumitory | 1 |
| Boechera missouriensis | Missouri Rock-cress | 1 |
The following Ecological Landscapes have the best opportunities to manage for Aspen-Birch, based on the Ecological Landscapes of Wisconsin Handbook.
| Ecological Landscape | Opportunity |
|---|---|
| North Central Forest | Major |
| Northeast Sands | Major |
| Northern Highland | Major |
| Northwest Lowlands | Major |
| Northwest Sands | Major |
| Superior Coastal Plain | Major |
| Central Sand Plains | Important |
| Forest Transition | Important |
| Central Lake Michigan Coastal | Present |
| Central Sand Hills | Present |
| Northern Lake Michigan Coastal | Present |
| Southeast Glacial Plains | Present |
| Southwest Savanna | Present |
| Western Coulee and Ridges | Present |
| Western Prairie | Present |
Major (3 on map)
A major opportunity for sustaining the natural community in the Ecological Landscape exists, either because many significant occurrences of the natural community have been recorded in the landscape or major restoration activities are likely to be successful maintaining the community's composition, structure, and ecological function over a longer period of time.
Important (2 on map)
Although the natural community does not occur extensively or commonly in the Ecological Landscape, one to several occurrences do occur and are important in sustaining the community in the state. In some cases, important opportunities may exist because the natural community may be restricted to just one or a few Ecological Landscapes within the state and there may be a lack of opportunities elsewhere.
Present (1 on map)
The natural community occurs in the Ecological Landscape, but better management opportunities appear to exist in other parts of the state.
Conservation actions respond to issues or threats, which adversely affect species of greatest conservation need (SGCN) or their habitats. Besides actions such as restoring wetlands or planting resilient tree species in northern communities, research, surveys and monitoring are also among conservation actions described in the WWAP because lack of information can threaten our ability to successfully preserve and care for natural resources.
Threats/issues and conservations actions for natural communities
Click to view a larger version. Please considering donating your photos to the Natural Heritage Conservation Program for educational uses. Photo use
This dense thicket of aspen saplings was the result of management activities intended to regenerate oak. Black River State Forest.
Photo by Eric Epstein.
Note: photos are provided to illustrate various examples of natural community types. A single photograph cannot represent the range of variability inherent in a given community type. Some of these photos explicitly illustrate unusual and distinctive community variants. The community photo galleries are a work in progress that we will expand and improve in the future.