Ecological dynamics
Information contained in this section was developed using historical data, professional experience, field reviews, and scientific studies. The information presented is representative of very complex vegetation communities. Key indicator plants, animals and ecological processes are described to help inform land management decisions. Plant communities will differ across the MLRA because of the naturally occurring variability in weather, soils, and aspect. The Reference Plant Community is not necessarily the management goal. The species lists are representative and are not botanical descriptions of all species occurring, or potentially occurring, on this site. They are not intended to cover every situation or the full range of conditions, species, and responses for the site.
The reference plant community is well developed woodland dominated by an overstory of black oak and white oak. It is very similar to Chert Upland Woodlands, except that it may be slightly less dense with more afternoon sunlight cutting to the woodland floor. The canopy is moderately tall (60 to 75 feet) but more open (65 to 85 percent cover) than protected slopes and the understory is poorly developed with less structural diversity. Increased light from the open canopy causes a diversity of ground flora species to flourish. In addition, proximity to shallow soil glades and open woodlands provides additional opportunity for increased light and species diversity. Woodlands are distinguished from forest, by their relatively open understory, and the presence of sun-loving ground flora species. Characteristic plants in the ground flora can be used to gauge the restoration potential of a stand along with remnant open-grown old-age trees, and tree height growth.
Fire played an important role in the maintenance of these systems. While the upland prairies and savannas had an estimated fire frequency of 1 to 3 years, Chert Exposed Backslope Woodlands burned less frequently (estimated 5 to 20 years) and with lower intensity. These periodic fires kept woodlands open, removed the litter, and stimulated the growth and flowering of the grasses and forbs. During fire free intervals, woody understory species increased and the herbaceous understory diminished. The return of fire would open the woodlands up again and stimulate the abundant ground flora.
Chert Exposed Backslope Woodlands were also subjected to occasional disturbances from wind and ice, as well as grazing by native large herbivores, such as bison, elk, and white-tailed deer. Wind and ice would have periodically opened the canopy up by knocking over trees or breaking substantial branches off canopy trees. Grazing by native herbivores would have effectively kept understory conditions more open, creating conditions more favorable to oak reproduction and sun-loving ground flora species.
Today, these ecological sites have been cleared and converted to pasture or have undergone repeated timber harvest and domestic grazing. Most existing forested ecological sites have a younger (50 to 80 years) canopy layer whose species composition and quality has been altered by timber harvesting practices. In the long term absence of fire, woody species, especially hickory, encroach into these woodlands. Once established, these woody plants can quickly fill the existing understory increasing shade levels with a greatly diminished ground flora. Removal of the younger understory and the application of prescribed fire have proven to be effective restoration means.
Uncontrolled domestic grazing has also impacted these communities, further diminishing the diversity of native plants and introducing species that are tolerant of grazing, such as buckbrush, gooseberry, and Virginia creeper. Grazed sites also have a more open understory. In addition, soil compaction and soil erosion from grazing can be a problem and lower site productivity.
These ecological sites are only moderately productive, especially when compared to adjacent protected slopes and deeper loess covered units. Oak regeneration is typically problematic. Sugar maple, red elm, and hickories are often dominant competitors in the understory. Maintenance of the oak component will require disturbances that will encourage more sun adapted species and reduce shading effects.
Single tree selection timber harvests are common in this region and often results in removal of the most productive trees (high grading) in the stand leading to poorer quality timber and a shift in species composition away from more valuable oak species. Better planned single tree selection or the creation of group openings can help regenerate and maintain more desirable oak species and increase vigor on the residual trees.
Clearcutting also occurs and results in dense, even-aged stands dominated by oak. This may be most beneficial for existing stands whose composition has been highly altered by past management practices. However, without some thinning of the dense stands, and periodic fires, the ground flora diversity can be shaded out and diversity of the stand may suffer.
A state-and-transition model diagram follows. Detailed descriptions of each state, transition, plant community, and pathway follow the model. This model is based on available experimental research, field observations, professional consensus, and interpretations. It is likely to change as knowledge increases.
State 1
Reference
The reference state for this ecological site was old growth oak woodland dominated by black oak, post oak, and white oak. Periodic disturbances from fire, wind or ice maintained the woodland structure and diverse ground flora species. Long disturbance-free periods allowed an increase in both the density of trees and the abundance of shade tolerant species. Two community phases are recognized in the reference state, with shifts between phases based on disturbance frequency.
This reference state is uncommon today. Some sites have been converted to grassland (State 4). Others have been subject to repeated, high-graded timber harvest coupled with domestic livestock grazing (State 5). Fire suppression has resulted in increased canopy density, which has affected the abundance and diversity of ground flora. Many reference sites have been managed for timber harvest, resulting in either even-age (State 2) or uneven-age (State 3) woodlands.
Community 1.1
Black Oak – White Oak/Fragrant Sumac/Sedge - Little Bluestem
The southern and western exposure limits tree density and provides enough light for abundant woodland ground flora species to persist. The tree canopy is dominated by a mixture of black oak, post oak and white oak, and the understory is relatively open with scattered oak and sassafras saplings. This woodland community has a two-tiered structure, with a canopy that is 60 to 80 feet tall with 60 to 80 percent closure. Historically, these exposed slopes likely burned every 5 to 20 years, so ground flora cover was greater than 75 percent. During long, fire-free intervals the density of trees and saplings increased, as did fire-intolerant tree species such as hickory. Over time, these gradual species changes and increased density result in a community phase transition. Unlike the forest communities on protected slopes, the persistence of oak as a dominant canopy species is not threatened on the exposed slopes.
Forest overstory. The Overstory Species list is based on field reconnaissance as well as commonly occurring species listed in Nelson 2010; names and symbols are from USDA PLANTS database.
Forest understory. The Understory Species list is based on field reconnaissance as well as commonly occurring species listed in Nelson 2010; names and symbols are from USDA PLANTS database.
Community 1.2
Black Oak – White Oak - Hickory/Fragrant Sumac/Sedge - Little Bluestem
The southern and western exposure limits tree density and provides enough light for woodland ground flora species to persist. The understory is relatively dense, with scattered hickory, oak and sassafras saplings. This woodland community has a multi-tiered structure, and a canopy that is 60 to 80 feet tall with 80 to 100 percent closure.
Pathway 1.1A
Community 1.1 to 1.2
This pathway is a gradual transition that results from extended, disturbance-free periods of roughly 50 years or longer.
Pathway 1.2A
Community 1.2 to 1.1
This pathway results from ecological disturbances such as fire, ice storms, or violent wind storms. Historically, native grazers such as bison provided disturbance events as well.
State 2
Even-Age Managed Woodland
These forests tend to be rather dense, with an under developed understory and ground flora. Thinning can increase overall tree vigor and improve understory diversity. Continual timber management, depending on the practices used, will either maintain this state, or convert the site to uneven-age (State 3) woodlands.
Dominant resource concerns
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Plant productivity and health
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Plant structure and composition
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Wildfire hazard from biomass accumulation
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Terrestrial habitat for wildlife and invertebrates
Community 2.1
Black Oak – White Oak – Post Oak/Hazelnut
This woodland community has a simple, dense, single-tiered structure, with canopy height that varies with age, and 100% canopy closure. The understory and ground flora is depauperate. Thinning can increase overall tree vigor and improve understory diversity. However, in the absence of fire, the diversity and cover of the ground flora is still diminished.
State 3
Uneven-Age Managed Woodland
Uneven-Age Managed Woodlands resemble their reference state. The biggest differences are tree age, most being only 50 to 90 years old and denser understory. Composition is also likely altered from the reference state depending on tree selection during harvest. Scarlet oak is often more abundant than historically. In addition, without a regular 15 to 20 year harvest re-entry into these stands, they will slowly increase in more shade tolerant species and white oak will become less dominant. Without periodic disturbance, stem density and fire intolerant species, like hickory, increase in abundance.
Dominant resource concerns
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Plant productivity and health
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Plant structure and composition
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Wildfire hazard from biomass accumulation
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Terrestrial habitat for wildlife and invertebrates
Community 3.1
Black Oak – Hickory/Common Serviceberry/Hairy Woodland Brome
This woodland community has a multi-tiered structure, and 60 to 90 percent canopy closure.
State 4
Grassland
Type conversion of forests to planted, non-native pasture species such as tall fescue has been common in this MLRA. Steep slopes, abundant surface fragments, low organic matter contents and soil acidity make non-native pastures challenging to maintain in a healthy, productive state on this ecological site. If grazing and active pasture management is discontinued, the site will eventually transition to State 2 (Even-Age).
Community 4.1
Tall Fescue - Red Clover
This is an herbaceous community that is typically dominated by tall fescue. Various other grass and forb species are typically present, in various amounts.
Community 4.2
Tall Fescue - Broomsedge/Oak Sprouts
Shrub and pioneer tree species such as eastern redcedar and oak and hickory sprouts typically invade sites that are not regularly managed.
Dominant resource concerns
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Ephemeral gully erosion
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Nutrients transported to surface water
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Plant productivity and health
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Plant structure and composition
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Plant pest pressure
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Terrestrial habitat for wildlife and invertebrates
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Feed and forage imbalance
State 5
High-Graded/Grazed Woodland
Ecological sites subjected to repeated, high-graded timber harvests and uncontrolled domestic grazing transition to this State. This state exhibits an over-abundance of hickory and other less desirable tree species, and weedy understory species such as coralberry, gooseberry, poison ivy and Virginia creeper. The vegetation offers little nutritional value for cattle, and excessive stocking damages tree boles, degrades understory species composition and results in soil compaction and accelerated erosion and runoff. Exclusion of livestock from sites in this state coupled with uneven-age management techniques will cause a transition to State 3 (Uneven-Age).
Dominant resource concerns
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Ephemeral gully erosion
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Plant productivity and health
-
Plant structure and composition
-
Plant pest pressure
-
Wildfire hazard from biomass accumulation
-
Terrestrial habitat for wildlife and invertebrates
Community 5.1
Black Oak-Hickory/Sassafras/Buckbrush
Transition T1A
State 1 to 2
This transition typically results from even-age forest management practices, such as clear-cut, seed tree or shelterwood harvest and fire suppression.
Transition T1B
State 1 to 3
This transition typically results from uneven-age forest management practices and fire suppression.
Transition T1C
State 1 to 4
Clearing; grassland planting; grassland management
Transition T1D
State 1 to 5
Poorly planned harvests; uncontrolled grazing
Restoration pathway R1B
State 2 to 1
Forest management; prescribed fire; extended rotations
Transition T2A
State 2 to 3
This transition typically results from uneven-age forest management practices, such as single tree or group selection harvest.
Restoration pathway R1A
State 3 to 1
Forest management; prescribed fire; extended rotations
Transition T3A
State 3 to 2
This transition typically results from even-age forest management practices, such as clear-cut, seed tree or shelterwood harvest.
Transition T4A
State 4 to 2
This transition typically results from tree planting; long-term succession; no grazing
Transition T5A
State 5 to 2
This transition results from the cessation of cattle grazing and associated pasture management such as mowing and brush-hogging. Herbicide application, tree planting and timber stand improvement techniques can speed up this otherwise very lengthy transition.
Transition T5B
State 5 to 3
Uneven-age management; no grazing; forest stand improvement
Restoration pathway T5A
State 5 to 4
Clearing; grassland planting; grassland management
