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 white oak, black oak and post oak. The canopy is 60 to 70 feet tall but less dense (55 to 75 percent canopy) than protected slopes and the understory is open 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 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.
Fire played an important role in the maintenance of these systems. It is likely that these ecological sites burned at least once every 5 to 10 years. 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.
Dry Footslope 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 fragrant sumac, coralberry, 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.
Dry Footslope Woodlands are moderately productive. Oak regeneration is typically problematic. Sugar maple, red maple, and hickory 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.
A State and Transition 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 was dominated by white oak and black oak. Periodic disturbances from fire, wind or ice maintained the dominance of oaks by opening the canopy and allowing more light for oak reproduction. Long disturbance-free periods allowed an increase in more shade tolerant species such as hickory. The reference state is rare today and may be extinct. Two community phases are recognized in this state, with shifts between phases based on disturbance frequency.
The reference state is rare today. Some sites have been converted to grassland (State 4). Others have been subject to repeated, high-graded timber harvest coupled with uncontrolled domestic livestock grazing (State 5). Fire suppression has also 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) forests.
Community 1.1
White Oak – Black Oak/ Fragrant Sumac/ Sedge – Little Bluestem
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
White Oak – Black Oak/ Fragrant Sumac – Hickory Saplings/ Sedge – Little Bluestem
Pathway P1.1A
Community 1.1 to 1.2
No disturbances (10+ years)
Pathway P1.2A
Community 1.2 to 1.1
Disturbances (fire, wind, ice) every 3-5 years
State 2
Even-Age Managed Forest
These former woodland are now 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) forests.
Dominant resource concerns
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Plant productivity and health
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Plant structure and composition
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Terrestrial habitat for wildlife and invertebrates
Community 2.1
White Oak – Black Oak/Flowering Dogwood / Wildrye
State 3
Uneven-Age Managed Forest
Composition and age are altered from the reference state depending on tree selection during harvest. In addition, without a regular 15 to 20 year harvest re-entry into these stands and use of prescribed fire, they will slowly increase in more shade tolerant species such as hickory, and white oak will become less dominant.
Dominant resource concerns
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Plant productivity and health
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Plant structure and composition
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Terrestrial habitat for wildlife and invertebrates
Community 3.1
Black Oak – White Oak /Hickory/ Indian Woodoats
State 4
Grassland
Conversion of forests to planted, non-native pasture species such as tall fescue has been common in this MLRA. If grazing and active pasture management is discontinued, the site will eventually transition, over time, to State 2 (Even-Age).
Community 4.1
Tall Fescue - Red Clover
Dominant resource concerns
Community 4.2
Tall fescue - Broomsedge/Oak Sprouts
Dominant resource concerns
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Sheet and rill erosion
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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
Pathway P4.1A
Community 4.1 to 4.2
Over grazing; no fertilization
Pathway P4.2A
Community 4.2 to 4.1
Brush management; grassland seeding; grassland management
State 5
High-Graded/Grazed Woodland
Woodland 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 buckbrush, 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).
Community 5.1
Tall Fescue - Red Clover
Transition T1A
State 1 to 2
Harvesting; even-aged management; fire exclusion
Transition T1B
State 1 to 3
Harvesting; uneven-age management; fire exclusion
Transition T1C
State 1 to 4
Clearing; grassland planting; grassland management
Transition T1D
State 1 to 5
High-grade harvesting; uncontrolled grazing
Restoration pathway R1B
State 2 to 1
Extended rotations; prescribed fire; forest stand improvement
Transition T2A
State 2 to 3
Uneven-age management; thinning
Restoration pathway R1B
State 3 to 1
Extended rotations; prescribed fire; forest stand improvement
Transition T3A
State 3 to 2
Even-age management; thinning
Transition T4A
State 4 to 2
Tree planting; long-term succession; no grazing
Transition T5B
State 4 to 3
Uneven-age management; tree planting; no grazing
Transition T5B
State 5 to 3
Uneven-age management; tree planting; no grazing
Restoration pathway T5A
State 5 to 4
Clearing; grassland planting; grassland management
