Planning an Oak Savanna Restoration

There are lots of degraded oak savannas, especially in the hill country of the Midwest where farming was not easy to carry out. Most of these savannas were grazed but were never plowed or logged. Often many of the original open-grown bur oak trees are still present, usually on the ridge tops, but sometimes in the draws or on the south-facing slopes. If the savanna was fairly far from the barn, it may not even have been heavily grazed.

If there are no open-grown oaks left, restoration is impossible. But if open-grown oaks are present, the savanna can be restored! In fact, it may only take a dozen years or so to bring back the savanna understory.

Define the Goals

The most important first step is to define the goals of the restoration. Although these goals may have to be modified later, a goal (or goals) should be set first. These initial goals will depend upon several factors:

  • The character of the site, especially the presence of open-grown (savanna) oaks
  • The ownership of the site and the possibility of long-term protection
  • The financial resources available
  • The location, area, and ease of access of the property
  • The history of the site

A decision to restore a savanna should not be made lightly, as it is a major undertaking. Oak savanna restoration is a long-term activity, and one should not start unless one has a reasonable possibility of making a substantial result.

Examples of different goals for the restoration:

  • Restore the savanna to its presettlement state
  • Enhance the wildlife of the area, especially birds and other charismatic megafauna
  • Improve hunting
  • Establish habitat for endangered species such as Karner Blue butterflies or purple milkweeds
  • Recover a high diversity understory
  • Eradicate invasive shrubs or herbaceous plants
  • Create an attractive recreation area
  • Create an area suitable for education of school groups or the public
  • Or a combination of some of the above

The landowner or land manager can assume the responsibility for developing the management plan, or (depending on financial resources available) an ecological consultant can be hired to carry out this mission.

On the Ground Survey
Although aerial photography provides great insights, recognizing a restorable savanna will require on-the-ground reconnaissance. First impressions will focus on the oaks themselves. The presence of open-grown oaks is critical, since this will indicate that the oaks developed in a savanna environment. (If there are widely spaced oaks but they are not open-grown, the site may not be a savanna but an oak woods that was logged at some time in the past.)

The ideal site for restoration is one with many large open-grown oaks, as well as oaks of medium and young age groups and some native herbaceous speces.

Note the structure of the oaks and their species. Good restorations can be carried out with any of the savanna oaks: bur, white, black, Hill's, etc. Are the oaks being crowded by weed trees such as box elder, red maple, cherry, or elm? If so, it is urgent to remove these weed trees first.



Survey the Plant Understory
In addition to assessing the status of the oaks, the on-the-ground survey should evaluate the understory vegetation, both grasses and forbs. A heavily grazed site may be completely taken over by nonnative pasture grasses, in which case there will be no understory vegetation to record.

The understory vegetation survey should record all species, but place special emphasis on the presence of “savanna indicator” species. These are species that are found in “good” savannas, and indicate that the site is not heavily degraded. (See Brian Pruka’s list) There are numerous savanna indicator species, some common, others less common or rare. Obviously, presence of rare savanna indicators will raise the interest in the site.

If the savanna is highly degraded, with heavy shade probably due to invasive brush or shade-tolerant tree species, there may not be much in the way of a savanna understory. Look around the edges of the site, where more sunlight is available. Small patches of savanna grasses, or even prairie grasses, may be present. The species in the Pruka list might be found in a less degraded (“good”) site, but many other sites with open-grown oaks are suitable for restoration.

The table below presents a list of adaptable groundlayer species that are more likely to survive in degraded oak savannas. Although these species do not imply a high-quality site, the existence of some of these helps to build confidence that the site can be restored.

Make a check list of understory species. Even if the species record is sparse, it will be a valuable historic record and will provide a baseline as the restoration project progresses. Collecting and saving voucher specimens for a herbarium can also be done.

 
Adaptable groundlayer species that might be present in a degraded savanna
Latin name Common name
Agrimonia gryposepala Tall agrimony
Anemone virginiana Tall anemone
Asclepias exaltata Poke milkweed
Carex pensylvanica Pennsylvania sedge
Corylus Americana American hazelnut (shrub)
Desmodium glutinosum Pointed tick trefoil
Dodecatheon meadii Shooting star
Elymus hystrix Bottlebrush grass
Elymus villosus Silky rye
Eupatorium purpurem Purple Joe Pye weed
Eupatorium rugosum White snake root
Fragaria virginiana Wild strawberry
Geranium maculatum Wild geranium
Liatris aspera Rough blazing star
Monarda fistulosa Wild bergamot
Osmorhiza longistylis Sweet cicely
Polygonatum biflora Smooth Solomon's seal
Polymonium reptans Jacob's ladder
Smilacina racemosa False Solomon's seal
Solidago ulmifolia Elm-leaf goldenrod
Triosteum perfoliatum Tinker's weed
Viola soraria Door-yard violet
Zizia aureus Golden Alexanders
 

Obtain a Recent Air Photo and Prepare a Map of the Site

A map of the property is essential for any restoration project. Although elaborate computer software is available for preparing maps, a simple map can be constructed using a recent air photo. Such an air photo can be downloaded from a commercial web site or obtained from a County Agricultural Agent. Various on-line sources for air photos are available, and the quality may vary depending on the source as well as on the location in the Midwest.

The air photo can either be obtained as a print, or it can be downloaded. A download is preferable to a print, since it can be used in a variety of ways in reports and on web sites. The highest resolution and the most recent date available is preferable. If only a print is available, it should be scanned or copied photographically first in order to retain the original in an untouched form.

Note: Satellite imagery is not suitable here. Obtain an air photo that has been taken by an airplane at a relatively low altitude.

Sources of air photos include GlobXplorer, TerraServer, and Google Earth.

To prepare a map, walk the property using a copy of the downloaded air photo, and mark on a transparent overlay various features such as roads, trails, fence rows, open fields, buildings, ravines, rock outcrops, important trees, quarries, etc. Divide the property into management units of manageable size, and mark these on the overlay also. Each management unit should have a number or name.

To make the map, hand draw on the copied photo the various features, including the management units. Use colors to code the units, such as woodlands, savanna, prairie, etc.

The final map is best made on the computer, using a drawing program such as Adobe Illustrator or Corel Draw. Import into the drawing program the downloaded or scanned version of the air photo and then use the various drawing tools to insert the various features. Label each feature.

Determine the area of each management unit using a handheld Global Positioning System (GPS) device. To do this, clear the Track log, start a new track, and walk the periphery of each unit. After returning to the point of beginning, stop the track log and calculate the area.

The area of each management unit will be important when preparing the management plan, for calculating costs, and for determining the amount of seed to be used for planting.

An example of a management map for a fairly large restoration is shown below.

ArcGIS

An even better approach to making a management map is to use ArcGIS, the high-end computer software from ESRI. County, State, and Federal agencies should have access to this very useful software, as will civil engineers, planners, and academics.

However, a perfectly good map can be made using the simple approach presented above.

 




Suppose There Is No Understory?
Even in the absence of significant understory vegetation, restoration is still possible, as long as the open-grown oaks are present.

Why is this possible? Take prairie restoration, for example. Many outstanding tallgrass prairies have been created from barren fields that had been under agriculture or pasturage for many years. The existing, usually nonnative, vegetation was eliminated by use of herbicide, and the field planted with native prairie grasses and forbs. Mowing, burning, and hand weeding over the first few years after planting, until the planted species get established, were necessary to bring the planted prairie into full fruition. Most of these planted prairies are now self-sustaining; all that is needed is a regular burn schedule and periodic monitoring to ensure that invasive species are not becoming a problem.

These same techniques can be used to create a savanna, even on a degraded site, provided the open-grown oaks are present.

Preparing a degraded site

Depending on topgraphy and other conditions, herbicide treatment might be possible with a tractor-operated boom sprayer. If this is not possible, use a sprayer hose or hand-held boom sprayer connected to an herbicide tank in a truck. An electric or gasoline-powered pump at the tank provides pressure.

Spray rig mounted in the back of a pickup truck. A 200 to 300 foot hose can permit reaching most parts of a 5 acre site. Although this rig can be operated by a single person, a two-person team is more efficient, with one person handling the spray nozzle and the other the reel and hose.
High capacity electrically pump can provide sufficient pressure to operate two separate hoses, using a manifold with shut-off valves.
Manifold permitting operation of two separate hoses.
Spraying a 4 acre savanna site.
The adjustable spray nozzle permits selection of various spray patterns. With the appropriate adjustment, spray will carry about 25 feet.
 

 

Avoid driving over the roots of the large trees. Make sure the whole understory is sprayed. After spraying, either burn the dead plant material and thatch (if there is enough fuel) or rake the area to expose the bare ground before seeding. (For Seed Mixes, see this link)

An example of how this approach can be applied to savanna restoration.

Select a five acre site with nice open-grown oaks. Spray the whole site with glyphosate in late spring/early summer. Wait a few weeks and burn off the dead thatch. Wait a few more weeks for regrowth of the undesirable vegetation and spray again. Spray a third time in the early to mid fall. Plant the site with a mix of savanna species in late November/early December. Control undesirable weeds the following summer by hand weeding or spraying. Continue to control weeds for the next several years. Monitor several times a year for presence of desirable species.


This approach to understory restoration assumes that the site had no “good” savanna species. Such a site would most likely be one that had been under pasture and there was no native species left. Many such sites exist in the Midwest.

An example of a successful restoration following this procedure is shown in the photo below. Originally this site was choked with buckthorn and honeysuckle and nonnative herbaceous species.

 


Outline of a Restoration Plan

  1. Baseline ecological description of the site, including plant lists, geology and soils, maps, and air photos
  2. Plans and schedules for all site preparation activities, including plans for contingencies
  3. Written description of the criteria by which the project will be evaluated objectively
  4. Monitoring protocols to be used to assess the success of the project
  5. Long-term management procedures