Open Woodland Restoration and Management
Open woodlands are a type of forest community with a canopy coverage between 30% to 80% closure. It has a poorly developed understory, and a diverse herbaceous layer of forbs, grasses, and sedges with 50 to 100% ground cover. Open woodland canopy is composed of fire tolerant trees such as oak and hickory, often with wide spreading crowns. Short-leaf pine is in its native range is also a common tree of an open woodland.. A variety of other fire tolerant trees also occur in woodlands. Unlike modern forests, high quality woodlands contain a diverse forest floor of herbaceous plants, shrubs and vines. Common shrubs and vines include lowbush blueberry, aromatic sumac, New Jersey tea, grape, and Virginia creeper. Characteristic herbaceous plants include little bluestem, big bluestem, wild rye, bottle brush grass, poverty grass, tick trefoils, wild bean, goat's rue, woodland sunflower, goldenrods, asters, and a variety of sedges.
Prior to European settlement, woodlands were maintained by fire which was set by Native Americans or lightning strikes. Historically, woodlands may have been as small as a few acres to tens of thousands of acres. Today woodlands are fragmented and degraded. Most woodland communities have been degraded due to extensive logging, fire suppression, improper grazing, and other disturbances. In the absence of fire, woodlands may succeed to an overstocked, closed canopy community with little herbaceous ground cover. Eastern red cedar is a good example of a tree that invades woodlands where natural fire regimes have been suppressed. Modern open woodlands often appear similar to other forest communities because without a proper disturbance regime the woodland becomes a closed canopy forest that lacks a herbaceous ground cover.
Other threats include conversion for agriculture, feral hogs, unmanaged logging, and invasive plants such as sericea lespedeza, honeysuckle and privet. Fortunately many altered woodlands can be restored. Plant and animal diversity can be increased by reducing grazing of the woodlands, opening of the canopy, and reintroducing fire to the system.
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Woodlands vary in plant composition and canopy coverage based on soil, geology, topography, and fire frequency. A variety of different types of woodlands occur throughout the southeastern United States in both upland and bottomland landscapes. In areas having thinner drier soils, woodland trees develop a more open and wide spreading canopy. In degraded woodlands these trees often have thick buttressed trunks with limbs or knot holes on the trunk close to the ground. Often you will hear these trees called wolf trees because they are not as straight and limbless like ones that have developed in a closed canopy forest. On shallow upland soils and west and south-facing slopes post, white, chinqaupin, chestnut, black, and blackjack oak, as well as mockernut hickory and short-leaf pine (within native range) are the dominant overstory trees. Usually, white oak becomes more abundant in woodlands as soil moisture and productivity increases (mesic woodlands). Herbaceous ground flora varies considerably in upland woodlands depending on soil moisture and the amount of sunlight reaching the woodland floor. Native lespedezas, asters, warm-season grasses, cool-season grasses and sedges are common upland woodland plants. In bottomland woodlands bur, white, swamp chestnut, swamp white oak, and mockernut and shellbark hickory are common canopy species. Native cool-season grasses and sedges are the dominant herbaceous plants in many bottomland woodlands. Bottomland woodlands were once common along larger streams and rivers..
A unique type of woodland called flatwoods occurs on broad level plains and in sinkhole basins. Flatwoods contain a dense claypan or fragipan layer that restricts tree growth. Plants found in flatwoods must be adapted to extremely wet and dry conditions due to the impermeable subsoil layer. Post oak and willow oak are the dominant canopy tree in most flatwoods, but blackjack oak, willow oak, and hickory are also common.
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Typically restoration of woodlands require some level of overstory canopy thinning. Canopy reduction can be accomplished by cutting or girdling of canopy trees. Due to the sensitive nature of many open woodland site soils, the use of a bulldozer or tree clipper to remove woody vegetation should be avoided. However, it may be possible to use a forestry mulcher with low ground pressure to mulch up saplings during winter months when the ground is frozen. Care will need to be taken to make sure that soil compaction is limited and that mulch layers are kept thin unless a prescribed burn is planned for future maintenance.
The final canopy coverage of the woodland should range from 30% to 80% depending on the soil type, slope, and aspect of the woodland being restored. The final basal area of the area should range between 30 ft2/acre to 80ft2/acre. Upland woodlands on drier, shallower soils will typically have a more open canopy while mesic and bottomland woodland canopies may have a greater canopy coverage. As a rule, woodlands should have a more open canopy on south and west facing slopes, adjacent to glades or savannas and on gently rolling landscapes. Generally, woodlands on north and east facing slopes, in protective ravines, deeply dissected hills and in moist areas should have a more closed canopy. These sites may also be a forest stand within a woodland community and should be managed differently than true woodlands.
When selecting trees for removal, you should select less fire tolerant species such as eastern red cedar, elm, locust, beech, and maple for removal. The remaining canopy trees should consist primarily of larger diameter oak and some hickory. In its native range short-leaf pine should also be left as part of the dominant woodland canopy tree or it should be reestablished if absent. Other species should be left in lesser amounts for greater plant diversity. Trees to be cut can be felled, girdled, or frilled. When girdling a tree, cut the tree with a chain saw one to two inches deep all the way around the trunk. Two girdles, 6 to 12 inches apart, are more effective than a single girdle. Small diameter trees (less than 6 inches in diameter) can be treated with the frill or hack and squirt method. This technique simply involves cutting the tree at breast height with a hatchet and then treating the cuts with an approved herbicide. For most species, it takes about one cut for every 3 inches of trunk diameter. Almost all degraded open woodlands will require some thinning to allow sunlight to hit the forest floor and encourage herbaceous growth. Treat stumps, frills, and girdles of undesirable trees such as locust, elm, maple, or non-native trees with an approved herbicide to prevent resprouting. Avoid applying herbicides during periods of heavy sap flow (late winter - spring). There is no need to treat the stumps of eastern red cedar. Consult with your local forester or biologist on the recommended thinning level, trees to be managed, and other recommendations.
Reintroducing prescribed fire is essential to restoring a diverse open woodland community. Fire will suppress small diameter woody vegetation, remove leaf and woody litter and stimulate herbaceous plant growth on the woodland floor. Frequent prescribed burns, on a 1 to 2 year rotation, will be necessary for the first 10 to 20 years to suppress woody sprouts and restore the rich ground flora of forbs, grasses and sedges. Continue to use prescribed fire on a 2 to 6 year rotation to maintain a diverse woodland community once the desired vegetative response has been achieved. Fire intervals greater than 6 years may allow woody sprouts enough time to outgrow fire flame heights and eventually succeed back to a closed canopy woodland. Historically woodlands burned between September and April, with most fires occurring in late summer through late fall. Burning between September and February will favor native forbs, sedges and cool-season grasses. Fall and winter burns are not as effective at controlling woody sprouts and will only top kill small diameter trees. Fall or early winter is also a good time to burn cedar slash since dormant season fires are usually not as hot or violate as spring burns. Care should be taken to avoid have volatile, hot burning fires.
For additional information on planning and conducting a prescribed fire see our Prescribed Fire section.
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Overgrazing of woodlands is one reason for the degradation of open woodlands. Improper grazing results in shifts in plant communities from a herbaceous layer to a more shrub dominated understory. If the grazing pressure is heavy enough can result in high moretality of mature tees through soil compaction and lack of seedling regeneration due to grazing. Although it is often recommended to not graze woodlands, grazing of open woodlands did historically occur. The reason for the push not to graze woodland is the result of past grazing that resulted in degradation of woodland due to overstocking for long periods. Some grazing of woodlands is beneficial in maintaining plant communities along with fire. Cattle if stocked at to0 high a rate and for too long of a period with strip out the herbaceous understory, trample vegetation, compact the soil, and result in increased erosion. If you plan to graze your open woodland you should develop a lower stocking rate then for open grassland. Grazing should not occur during winter and should be limited to short periods of a couple of weeks with six weeks or more rest between rotations during the growing season. Open woodlands with a more open canopy can be grazed heavier than those with a more closed canopy.
Invasive Plant Control
Invasive plants such as autumn olive, sericea lespedeza, Japanese honeysuckle, kudzu, privet, and honeysuckle may be a problem in woodlands near roads or urban areas. Scout woodlands regularly for invasive plants and treat immediately when found. See Invasive Species Control for more information on controlling invasive plants.
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