A RESTORATION PLAN FOR MESIC DEEP SOIL SAVANNAS
Mary C. Hruska
This work was done by the senior author as partial fulfillment of the requirements for a Master of Science degree at Eastern Illinois University, Charleston, Illinois.
A broad description of a savanna, as used by many natural areas botanists, is an area with scattered or small groves of open-growing trees and a herbaceous, primarily grassy understory. The Natural Areas Inventory of Illinois defined savanna using canopy cover and soil moisture (White 1978). Canopy cover ranged from 10-80% and soil moisture was described as mesic, dry mesic and sand. Anderson (1991 and personal communication) proposed that savannas are not a separate ecosystem but a vegetation continuum separating two ecosystems, the western prairies and the eastern deciduous forests.
During the Natural Areas Inventory of Illinois no grade A, deep soil, mesic savannas were found in the state (White 1978). Since that time only a few small remnants have been located. For this reason it is imperative that reconstruction efforts started to restore existing remnants. A list of ideas to be considered and steps to be taken have been compiled to aid such efforts.
Due to prevailing circumstances, it may not be possible to choose a location for the restoration/reconstruction project. For instance a savanna could be added to an existing prairie or forest or land may have been donated. If a site has not been identified, choose an area with a savanna history. This can be done by consulting vegetation maps such as those developed by Nuzzo (1986) that depict the areas thought to have savanna vegetation. Another possibility is consulting the General Land Office survey records. These are the original records of the surveyors that mapped the country. At every mile and half mile, the distance to and species of the closest tree were recorded. In prairie areas it is common to read "post in mound". Corner posts with long distances to trees probable represented areas that contained savanna vegetation. The important point is to locate the project in an area where there is high probability that it historically hosted savanna vegetation. If possible choose a site with established oak trees (species vary with location). This will speed the restoration project and the trees can be used as a seed source.
Once a site has been located, begin to collect specimens of all species of herbaceous and woody plants found in the area. Give each specimen a number and record characteristics that might be lost after collection (i.e., height of plant, flower color, shape of stem, etc.). The collection should be made over an entire growing season, with new plants being added as they are found. Press and dry the specimens soon after collection. They can be identified and mounted at a later date. This collection has many uses. Everyone involved can use the material for study. Collection of exotic/weedy species will alert those in charge of the current and potential management problems. Collection of forest and prairie species will indicate the beginning potential or starting point of the area.
The best way to monitor changes in the vegetation on the site is to record frequency and density data. By establishing quadrants, either along transects or randomly spaced throughout the area, data can be collected and compared from year to year, or at some regular interval, for example every three to five years. Frequency data, presence or absence of a species in a plot, will show how prevalent a particular species is throughout the project area. Density data, number of stems of a species in a plot, can be used to determine what species are dominant and if the density of a species is changing over time. For example are weedy/exotic species being eliminated and are the native species increasing? If unfamiliar with these techniques, contact a local environmental group such as The Nature Conservancy, and they will know someone who can teach these techniques. The data can also be used to determine if the management techniques being used are effective or if changes need to be made in the management plan.
A list of possible weed problems should be compiled and decisions made about their management. Methods for the elimination of such species are cutting, burning, girdling and herbicide application (if acceptable). Management should be started as soon as possible since it may take several growing seasons to eliminate some species. Weedy annuals will typically be out competed by the native species, so usually are not a problem. Weedy perennials, such as blue grass, teasel and day-lily, are fierce competitors. Some weedy species simple have to be dug out. If digging is not possible at the time of blooming the seed heads can be removed to prevent further spreading. Some weedy species will be eliminated by prescribed burns. If acceptable, herbicides can be applied to weeds while they are growing. Roundup has a short life span, only four weeks, so it can be used to prepare seed beds in the spring. Areas that are covered by rhizome producing grasses, like awnless brome, may need a combination of techniques. The area can be sprayed with herbicide and then disked, or disked for an entire growing season. The rhizomes will be too numerous to dig. Shrubs and trees can be cut, burned, herbicided or girdled. Girdling is very labor intensive. Some species such as black cherry and sassafras are excellent resprouters so long term plans for continued removal must be made. Resprouts can be cut or the site can be burned each spring for several years. Burning will usually cause a decline in stem vigor which will help eliminate the sprouts.
When managing weedy species with fire, the site should be burned for four or five consecutive years. Contact the local fire department and local residents to inform them of the burn. If the site is near a residential area they may want to be present. In some areas permits are needed, check with your local Department of Conservation Office, they will be familiar with the permitting process. Certain equipment is necessary to conduct a safe burn, have the equipment lined up before the burn date. Your equipment list should include a drip torch or lots of matches, water back packs and/or a truck with a water tank and spray hose, rubber flappers or metal snow shovels and rakes. The procedures outlined in McClain (1986, 1991) should be helpful when planning a burn. If small oaks are already present or have been planted, spray with water immediately before the burn and rake litter away from the base to reduce the intensity of the fire as it passes. Savannas are a fire dependent community so continue to burn every 3-5 years. Without fire the savanna will turn into a closed forest.
When working on savanna reconstructions, it may be necessary to seed large areas. These areas can be prepared by plowing, disking and herbicide application. Plowing can turn up weedy seeds that are buried in the soil, but may be necessary if the soil is extremely hard or the area is covered with non-native rhizome forming grasses that are hard to kill. For example, awnless brome, meadow fescue and blue grass can out compete many native species. Alternatively, disking will turn up less soil and less weed seed. Both can be combined with prior herbicide application for a better kill of non-native species. If time permits, areas can be tilled once a month for an entire growing season to eliminate weedy species with out herbicide usage. Another method is plowing and/or disking strips instead of entire areas. Keep the strips approximately 10 meters apart and with time the native plants will spread into the unplanted areas, reducing the initial seed/plant cost. All these methods will reduce the amount of competition experienced by the native plants. After prescribed burns, bare spots can be tilled and seeded by hand.
Photostations can be used to record long term changes in the project. Metal posts will last the longest, place one on each corner and one in the center of the project. With large or meandering sites more can be used. Always take photographs in the same direction so comparisons can be make, take photos in the spring and fall.
Before acquiring any plants or seeds, research what species were native in the area of the project and make a species list. This can be done several ways. Visit local prairies and forests and talk to the stewards to learn which species are native. Talk to local botanists at universities or organizations like the Department of Conservation or The Nature Conservancy to get their perspective on what is native. Some of these organizations have publications on native plants. Some communities have organizations that specialize in natural areas restoration. Old plant lists can be used, like Dr. Mead's list, that was published in the Prairie Farmer in 1846. Also read the current literature. Presently there are discussions about what species were found in savanna areas. If possible use local genotypes, they will be best suited for the conditions in the area. If local genotypes are not available try to obtain seeds and plants from as close to the project area as possible.
There are several possible sources for seeds and plants. Many nurseries are now specializing in native species. Seed may be collected from unattended road ditches. With permission, seed may be collected from local preserves or established natural areas, but you must GET PERMISSION FIRST and FOLLOW THEIR RULES! The steward for the area may already have plans for that years seed, but it may be available in future years. Get to know these people, they may be a source of information and assistance. If the trees on the project site are small or have to be planted, (i.e., no shade), start with herbaceous species that can tolerate full sun. Add the more shade-tolerant species later.
Shrubs were a major component of many savanna areas. Some examples include: dogwood (Cornus spp.), hazelnut (Corylus americana), plum (Prunus americana), blackberry (Rubus allegheniensis), raspberry (Rubus occidentalis) and dewberry (Rubus flagellaris). Some of these will be brought in by birds, others can be purchased or acquired by the same means suggested for the herbaceous plants.
For mesic deep soil savannas, oaks (Quercus spp.) are the tree of choice with the species depending on the project location. If the site has established oaks, collect these acorns for planting in open or new areas. If the oaks are old they will probably be local genotypes. If there is an area that has a high concentration of small trees, use a tree digger to move these to less populated areas. Acorns can be collected from local woods but find out if you need permission first. In Illinois, small trees can be purchased from the Department of Conservation.
It is not advisable to attempt the introduction of these species during the early stages of restoration projects. These species typically have special habitat requirements which are available only in natural systems or well-developed restorations. Also these species are controlled by state and federal regulations. For this reason their introduction should be attempted only in the later stages of restoration and then only in compliance with the previously mentioned regulations. Herkert (1991) gives the status of all threatened and endangered plant species for Illinois, and similar publications are available for most other states.
Give everything time to grow as restoration projects take time. If at the end of the first growing season the prepared seed beds are full of foxtail and other annuals, do not worry. Although the native plants appear to grow slowly at first (they are growing roots), they will be able to out compete the non-native annuals in a few years.
Anderson, R. C. 1991. Savanna concepts revisited. BioScience 41:371.
Herkert, J. R. 1991. Endangered and threatened species of Illinois: status and distribution- Volume 1 - Plants. Illinois Endangered Species Protection Board. 158 pp.
McClain, W. E. 1986. Illinois prairie: past and future-a restoration guide. Division of Natural Heritage, Illinois Department of Conservation. Springfield, IL. 27 pp.
Mead, S. B. 1846. Catalogue of plants growing spontaneously in the state of Illinois, the principal part near Augusta, Hancock County. Prairie Farmer 6:35-36, 60, 93, 119-122.
Nuzzo, V. A. 1986. Extent and status of midwest oak savanna: Presettlement and 1985. Natural Areas Journal 6:6-36.
White, J. 1978. Illinois natural areas inventory technical report, Vol. I: Survey methods and results. Illinois Natural Areas Inventory, Urbana, Ill. xix+426 pp.