Oak Savanna Restoration
Fort McCoy Military Installation encompasses approximately 60,000
acres of diverse and relatively rare ecosystems in west central Wisconsin.
The installation is situated within the unglaciated area, also known
as the Driftless Area, of Wisconsin. The Driftless Area is considered an
ancient landscape, eroding into an intricate system of ridges and coulees for millions
Fort McCoy lies at the intersection of two major ecotones, giving it a unique
place on the landscape. On the east to west continuum, the transitions from eastern
forest to western prairie influence the vegetation types of Fort McCoy. This
mix of forest and prairie results in the savanna ecosystem that dominates the installation.
On the north to south continuum Fort McCoy lies just south of the
band termed the tension zone by John Curtis, author of The Vegetation of Wisconsin.
This is a relatively narrow band that separates the northern coniferous
forests from the central deciduous forests. Within the tension zone there is gradation
between these two plant provinces. Many plants reach their northern or
southern limits within this zone. Fort McCoy lies within this zone and the mix of
vegetation on post is indicative of both the northern and southern forests.
Drier soils and greater frequency of fires (historically) resulted in a system dominated
by oak forest, savanna/barrens and brushlands. Frequent fires maintained
the oak forest, preventing the natural succession to white pine, considered the climax
forest in the region. In areas where fire has been suppressed, considerable
amount of red maple, black cherry, and white pine are found in the understory.
Savanna/barrens plant communities are dependent on fire and disturbance to
maintain the typical open structure. With fire suppression, the vegetation in the
savanna communities quickly succeeded to a more closed forest condition. Oak
grubs existed for decades in the presence of fire, slowly growing deep, established
root systems, while the vegetation would be repeatedly burned. These oak grubs
took advantage of the fire suppression and grew profusely for several seasons. In
pre-settlement times a few oaks would attain a thick corky bark during periods
without fire and then be able to survive later fires. This process established the
open structure of the savanna communities. With twenty years of fire suppression
the canopy of the former oak barrens closed and caused a change in the
ground layer. The typical mix of prairie and woodland plants slowly degraded to
a low diversity woodland ground layer. The seed bank will exist for many decades
in a degraded ecosystem. Prescribed fire and thinning the oaks can release this
remnant seed bank.
The oak savanna/barrens community is considered one of the rarest plant communities
in Wisconsin. In pre-settlement times it is estimated there was between
7 and 10 million acres of Wisconsin savanna; presently, only 2,000 acres of high
quality savanna remain, with about 300 acres at Fort McCoy. The Karner blue
butterfly, a federally endangered species, along with a whole host of federal and
state concern species, are dependent on a diverse savanna community. With up
to 20,000 acres of low quality oak forest on Fort McCoy, there is great potential
for oak savanna restoration activities. Prescribed fires, timber cuts, shredding and
selective herbicide use have been instrumental in the management and restoration
of these areas.
Invasive plants such as leafy spurge and spotted knapweed have been found within many of the savanna remnants and along the peripheries of low quality
oak forests. Exotic invasive plant species have a very strong impact on native
plant communities and may replace the majority of native species if left
unchecked. One consideration with restoring low quality oak forest to savanna
is the potential to increase such invasive plant species populations. Many of the
invasive species associated with savanna cannot survive in more closed canopy
forests, but if the forest canopies are thinned out or removed, suitable environment
for these species will result.
The Military Mission
Savannas provide excellent areas for military training and maneuvers. And likewise,
disturbance from military training has helped to maintain the diversity of
the savanna ecosystem. Fires resulting from military training and the lack of intensive
agricultural practices have kept areas of Fort McCoy in a quality savanna/
barrens complex.Moderate soil disturbance has reduced the rate of canopy
closure and helped propagate the spread of some beneficial plant species, in particular
wild lupine, the host plant of the endangered Karner blue butterfly.
However, disturbance can also degrade training lands and ecosystems. Overuse
of areas can result in the loss of native vegetation, causing soil erosion and spread
of invasive plants. Close coordination with military trainers and Integrated Training
Area Management (itam) can minimize the impacts due to over use of the
So how are the military and ecosystem needs met? The concept is simple—communication
and cooperation. The work, however, is not always so simple. To be
truly successful, there needs to be a bridge of communication and support. The
itam Program is this bridge. Its job is to maintain the quality of training lands
that allow the successful completion of the military mission. Coordination between
itam and natural resources managers allows military training without disruption
while managing healthy and productive native ecosystems.
Specific Strategies for Oak/Savanna Restoration
The Integrated Wildland Fire Management Plan (iwfmp), identifies forested areas
that should be harvested and managed as savanna/prairie systems as a way to
keep wildfires limited to the ground and easier to contain. Timber sales have
thinned approximately 850 acres near ranges and the installation boundary to remove
most of the pine and thin oaks to reduce the chances of severe wildfires.
This has increased the amount of savanna/prairie habitat.
The Land Rehabilitation and Maintenance Program (lram), a component of
itam, reduces the amount of slash after a timber sale with a severe duty shredder.
This reduces the intensity of the first prescribed burn and may even take the
place of prescribed burns in areas near the boundary where private homes may
be adversely affected by smoke.
lram also uses native grasses and forbs for the restoration (reseeding) of disturbed
locations. The species selection is based on those found in the area. Seed
collection is done on the installation whenever possible. Planners will also incorporate
annual cover crops, such as rye, to reduce erosion while the natives get a
foothold. Soil enrichment is also being incorporated when needed using nitrogen
fixers (legumes). The key is to avoid planting of non-native and/or invasive species.
Other savanna management strategies include 5-10 year prescribed burns
(based on The Nature Conservancy and other savanna management recommendation
developed through examination of historical/natural frequency).
Rotation burns are also done within larger blocks of grasslands and savanna—
primarily those greater than 100 acres and dependent on overall management
goals (i.e., grassland bird nesting requirements, Karner blue butterfly habitat, and
other rare species in the area, etc). This reduces the impacts to the biological community
by leaving residual vegetation for nesting, and reduces impacts in insect
populations required for brood rearing and wildflower pollination.
Working closely with military trainers, and using the tools available from the itam
program, the Ft. McCoy Biological and Cultural Resources Team has developed
effective strategies for restoring and maintaining one of the rarest and most biologically
diverse ecosystems in Wisconsin. And, this has been accomplished in a
way that enhances the military mission by providing additional oak savanna/ barrens
lands for military training.