Once an oak savanna has been restored, long-term management becomes the focus of the project. Management requires a major commitment of resources and personnel and should be built into the original restoration plan.
A written management plan is strongly recommended, even if it must be modified frequently.
Any site larger than 20 acres should probably be divided into smaller units for management. Originally, fairly large management units can be used, which can be subdivided when needed as restoration progresses. Restoration activities can be categorized in two separate ways. The first is by type of activity (such as weeding, controlled burns, brush control, etc) with indications of which units should be dealt with. The second is by individual unit, with a summary for each unit of what kinds of activities need to be carried out in that unit. See this Table for an example.
Restoration activities for long-term maintenance
Controlled burns (prescribed fire)
Control of invasive brush and trees
Control of herbaceous weeds
Seed collecting and introducing further understory species
Wildlife monitoring and management
Planting new areas or overplanting existing areas
Maintenance of access roads or other infrastructure
Maintenance of walking and ATV trails
Research has shown that the health of an oak savanna is best maintained if the site is burned every year. If resources do not permit annual burns, then the site should be burned as often as possible, but under no conditions should the burn frequency be less than three years. In fact, if frequent burns cannot be guaranteed, it might be preferable not to initiate restoration until they can be assured.
See this link for details on carrying out savanna burns.
What do annual burns do? Most importantly, they top kill brush and small saplings and keep them from becoming a problem. If an area is not burned, within three years brush will start to become a problem and within five years brush will be so dense that fire will no longer carry well. Tree saplings become established at slower rates, but can also become a problem. Without burns, within ten years, the site will have returned to its pre-restoration character, and most or all of the restoration work will have been wasted.
Are there any disadvantages of annual burning? The principal concern that some ecologists raise is that fire-sensitive animals, mainly insects, will be eliminated. This concern is due to a misunderstanding of the nature of savanna burns. Even with annual burns, no savanna is burned completely. There are always unburned areas such as fire shadows that will provide refuges for insects and other small animals. Large animals, of course, are mobile enough so that they can escape fires. Reptiles will not be killed if the burn is scheduled for early enough so that they have not come out of hibernation. The timing here will vary with the location of the site.
One of the most difficult problems in long-term maintenance of an oak savanna is control of brush. Brush in this context means shrubs, both native and nonnative, as well as brambles (members of the genus Rubus). Even with annual burns (see above), brush problems will persist. This is partly because no savanna burn has 100% coverage, but mainly because burns only top kill brush, so that viable rootstock remains and quickly becomes reestablished. Although small, this brush persists, and as soon as an area escapes fire, larger-sized plants can appear.
Note that even if all the undesirable brush was removed during the restoration process, there will still be a large “seed bank” in the soil, which will be responsible for resurgence of problem brush. This seed bank is the major concern in the early years after restoration. Under no conditions should invasive brush be allowed to reach the flowering stage, where new seeds are produced.
Details of brush control are given in this link.
Some suppression of brush can be done by competition from native plants, especially tall grasses. In more open savannas, where tall grass can become well established, small brush may eventually disappear with annual burning, although shade-tolerant brush may persist in a minor way indefinitely among the tall grass.
In most cases, competition by native plants will be spotty, and direct brush control will be necessary. Again, it should be emphasized that fire does not eradicate brush. All it does is top-kill it, and dormant buds will soon begin to grow. In most savannas, after several years of fire, each individual plant will have several to many dead stems that were top-killed by fire, among which there will be many new green shoots.
Monitoring the site
Monitoring the site for problems is essential. The best time to spot problems is in the late fall, when native plants are senescing and exotic weeds and brush still retain their green leaves. The first several years after the initial restoration work will be most critical, since many new plants will arise from the seed bank. These should be sprayed then, while they are still small and easy to kill. Monitor to make certain they have been killed, and continue monitoring at least once or twice more during the year, and through the following several years. It may take a year or two for these to be large enough to spot.
The more control of invasive plants that can be done in the early stages of the restoration project, the better!
When controlling the exotic shrubs, a systematic approach is needed. The savanna should be divided into relatively small units, between 2 and 5 acres. Survey the unit using a backpack sprayer loaded with the appropriate herbicide. A systematic survey is best carried out by using marking tape to establish swaths about 10 feet wide, using a compass to run the swaths along a North/South line.
The person (or group of people) with the sprayers moves back and forth through each swath, spraying all target plants. A North-running swath is followed by a South-running swath, and this procedure is continued back and forth until the whole unit has been sprayed.
Although time consuming and perhaps expensive, this systematic approach in the long run will be the cheapest, since after a few years, the main invaders will have been eliminated and only a much less expensive maintenance-level monitoring will be needed.
|Systematic spraying of small buckthorn plants that had arisen from the seed bank in a bur oak savanna. Swaths were marked with flagging and the spraying crew moves systematically along the swath path.
Small invasive trees can be handled just like shrubs.
Black walnut in particular is difficult to get rid of and there will be an extensive seed bank. Small walnut trees are easier to find when they are a few years old. At this time they are still small enough to cut easily with a brush cutter, and the cut stems (there will probably be many) should be treated with Garlon 4 as a basal bark.
Any savanna will be subject to wind onslaught and it is inevitable that some trees will come down. Depending on the circumstances, downed timber can be left to lie, or it can be cut up for firewood or lumber. If a tree has been felled across a fire break, then it must be cut up and removed.
The increased light brought about by opening up the savanna will inevitably lead to growth of invasive weeds such as thistle, wild parsnip, sweet clover, Japanese hedge parsley, and others. Their control was discussed in and the techniques used there will apply to continued management.
It is essential to control the new growth of these invasive weeds as soon as they are detectable. The ideal time to control weeds is early, before they have had time to become a major problem.
|Graph showing the importance of early detection of a weed infestation.
Systematic surveys for weed control
As pointed out earlier, it is essential to seek and destroy invasive weeds early, before they have obtained a foothold. Systematic surveys of the savanna are strongly recommended, preferable three or four times during the growing season. Careful notes and GPS coordinates or marking with flagging tape is essential.
Any systematic survey should involve walking the savanna in widely spaced swaths. It is not sufficient to walk an adjacent road or fire break. One must walk through the middle of the savanna.
After the first year or two, the areas that are likely to be infested will be known, and these areas can be specifically visited in subsequent years. See below for details on mapping.
Mapping the savanna
Restoration and long-term management are greatly facilitated by preparation of a detailed map of the area being worked on. Such a map does not need to be prepared by a surveyor, although an enlargement from a U.S.G.S. topographic map is very useful.
A recent air photo can easily be used to create a map of the property. Air photos are available from both government and private sources. A search string with the following should bring up both government and private sources: [STATE_NAME] orthorectified air photos
White, A. S. 1983. The effects of thirteen years of annual prescribed burning on a Quercus ellipsoidalis community in Minnesota. Ecology 64(5):1081-1085.
David W. Peterson, Peter B. Reich (2001) Prescribed fire in oak savanna: fire frequency effects on stand structure and dynamics. Ecological Applications: Vol. 11, No. 3, pp. 914-927.