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 of years.

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.

Savanna/Barrens Community

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 landscape.

Working Together

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.

Conclusion

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.