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.
This ecological site is well-developed woodland dominated by an overstory of white oak, along with occasional red oak and black oak. The canopy is moderately tall (60 to 80 feet) with a 50 to 75 percent canopy closure. Increased light from an open canopy causes a diversity of woodland ground flora species to flourish. 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.
Because of their proximity to prairies, fire played a significant role in the maintenance of these ecological sites which likely burned at least once every 3 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.
Loamy Upland Drainageway Woodlands were also subjected to occasional disturbances from wind and ice, as well as grazing by native large herbivores, such as bison, elk, and 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 woodland ground flora species.
Typically, with the narrow floodplain setting and frequent flooding, many upland drainageway sites still remain. They often occur as a rather narrow band of timber traversing the headwater streams, often in a matrix of upland forest. Occasionally, on wider drainageways, this ecological site is typically cleared and converted to cropland or pasture, with a narrow strip of woodland retained along the stream edge. In such cases, severe flooding may cause stream bank erosion and complete loss of this site.
Uncontrolled grazing by domestic livestock in the remaining strips of woodland can also kill trees and remove the ground cover, resulting in de-stabilization and potential loss of this system as well. Some carefully planned timber harvest can be tolerated in this system, but high grading of the timber will degrade the system.
Re-establishment of these riparian drainageway woodlands is important for stream quality and health, as well as for migratory birds. Replanting of these systems has proven to be quite successful, and but species selection needs to pay attention to local soil and moisture conditions.
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 historical reference state for this ecological site was old growth oak woodland. The woodland was dominated by white oak and black oak. Maximum tree age was likely 150 to 300 years. Periodic disturbances from fire, wind or ice as well as grazing by native large herbivores 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. Reference states are very rare today. Fire suppression has resulted in increased canopy density, which has affected the abundance and diversity of ground flora. Most Reference States are currently altered because of timber harvesting, domestic grazing or clearing and conversion to grassland or cropland.
Community 1.1
White Oak – Black Oak/Aromatic Sumac/Virginia Wildrye – Pennsylvania Sedge
This community phase is very rare today. To maintain this phase fire frequency's of 3 to 10 years are needed.
Forest overstory. The Forest Overstory Species list is based on commonly occurring species listed in Nelson (2010).
Forest understory. The Forest Understory list is based on commonly occurring species listed in Nelson (2010).
Community 1.2
White Oak – Black Oak/Hickory - Elm/Virginia Wildrye – Pennsylvania Sedge
This phase is the result of fire suppression that has resulted in increased canopy density, which has affected the abundance and diversity of ground flora. This phase is also very rare.
State 2
Even-Age Managed Woodland
An even-age managed forest can resemble the reference state. The primary difference is tree age, most being only 50 to 90 years old. Composition is also likely altered from the reference state depending on tree selection during harvests and disturbance activities. Without a regular 15 to 20 year harvest re-entry into these stands, they will slowly increase in more shade tolerant species such as sugar maple and white oak will become less dominant.
This state can be restored to a reference state by modifying or eliminating timber harvests, extending rotations, incorporating selective thinning, and re-introducing prescribed fire.
Community 2.1
Black Oak – White Oak /Red Elm/ Tick Trefoil
State 3
Uneven-Age Managed Woodland
Due to selective single tree harvesting canopy densities have increased. Composition is likely altered from the Reference State depending on tree selection during harvest. This state will slowly increase in more shade tolerant species and white oak will become less dominant and is also dense because of fire suppression. Without periodic canopy disturbance, stem density and fire intolerant species, like hickory and maple will increase in abundance.
This state can be restored to a reference state by modifying or eliminating timber harvests, extending rotations, incorporating selective thinning, and re-introducing prescribed fire.
Community 3.1
White Oak – Black Oak – Sugar Maple/Ironwood/ Woodland Brome
State 4
Cropland
This is a State that exists currently with intensive cropping of corn, soybeans, and wheat occurring. Some conversion to cool season grassland, especially when commodity prices are high, occurs for a limited period of time before transitioning back to cropland.
Community 4.1
Corn, Soybeans, Wheat
State 5
Grassland
Conversion of other states to non-native cool season species such as tall fescue, orchard grass, and red clover has been common. Occasionally, these pastures will have scattered oaks. Long term uncontrolled grazing can cause significant soil erosion and compaction. A return to the reference state may be impossible, requiring a very long term series of management options. If oak sprouting is left unchecked and grazing is eliminated or reduced then over time this state will transition to an even-age managed woodland (livestock controlled and woodland management initiated) or to a high-graded/grazed woodland (continued grazing, high graded harvesting, and no woodland management).
Community 5.1
Tall Fescue – Orchard Grass - Red Clover
This phase is well-managed grassland, composed of non-native cool season grasses and legumes. Grazing and haying is occurring. The effects of long-term liming on soil pH, and calcium and magnesium content, is most evident in this phase. Studies show that these soils have higher pH and higher base status in soil horizons as much as two feet below the surface, relative to poorly managed grassland (phase 5.2) and to woodland communities (where liming is not practiced).
Community 5.2
Tall fescue - Broomsedge/Oak Sprouts
This phase is the result of over use, poor grassland and grazing management and lack of adequate nutrient application.
State 6
High Graded/Grazed Woodland
States that were subjected to repeated, high-grading timber harvests and uncontrolled domestic grazing will transition to a High-Graded/Grazed Woodland State. This state exhibits an over-abundance of hickory, elm and other less desirable tree species, and weedy understory species such as buckbrush, gooseberry, poison ivy and Virginia creeper. The existing vegetation offers little nutritional value for cattle, and excessive cattle stocking damages tree boles, degrades understory species composition and results in soil compaction and accelerated erosion and runoff.
Two common transitions from this state are woody clearing and conversion to state 4, Cropland or removing livestock, limited harvesting, and allowing long term succession to occur to some other woodland state (state 2 or 3).
Community 6.1
Hickory - Oak / Buckbrush - Gooseberry/ Aster
