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 somewhat shallow soils and dry south to west aspects of Loamy Limestone/Dolomite Exposed Backslope Woodlands limits the growth of trees and supports an abundance of native grasses and forbs in the understory. They may contain small glade complexes and are across from protected backslope forests. While more productive than adjacent glades these sites have only a moderately tall (50 to 70 feet) chinkapin oak and black oak dominated a semi-open overstory, with occasional white oaks and northern red oaks. Shrubs were scattered within a dense matrix of native grasses and forbs. 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. It is likely that these ecological sites, along with adjacent glades and woodlands burned at least once every 5 years. These periodic fires kept woodlands open, removed the litter, and stimulated the growth and flowering of the grasses and forbs. They would have also further limited the growth and dominance of trees, especially eastern redcedar. During fire free intervals, woody species would have increased and the herbaceous understory diminished. But the return of fire would have re-opened the woodlands and stimulated the ground flora.
In the long term absence of fire, woody species, hickories and eastern red cedar have encroached into these ecological sites. Most of these ecological sites today are dense, and shady with a greatly diminished ground flora. Removal of the younger understory and the application of prescribed fire have proven to be effective restoration methods.
Loamy Limestone/Dolomite 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 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.
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 hickory, buckbrush, gooseberry, and Virginia creeper. It also promotes the invasion of Eastern red cedar. Grazed sites 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 loess covered units. Oak regeneration is typically problematic. 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 for this ecological site 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 beneficial for existing stands whose composition has been highly altered by past management practices. However, without some thinning of the dense stands and application of prescribed fire, the ground flora diversity can be shaded out and diversity of the stand may suffer.
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 reference state was dominated by chinkapin oak and black oak. Maximum tree age was likely 150 to 200 years. 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. Reference states are rare today. Many 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 resulted in increased canopy density, which has affected the abundance and diversity of ground flora. Some former reference states have been managed as woodlands with fire (State 2) or without fire (State 3).
Community 1.1
Chinkapin Oak – Black Oak/Red Bud/Virginia Wildrye – Little Bluestem
This phase is an old growth woodland with an overstory of chinkapin oak and black oak. This woodland phase has a two-tiered structure with an open understory with scattered shrubs and a dense, diverse native herbaceous ground flora.
Periodic disturbances including fire, ice and wind created canopy gaps, allowing oak species to successfully reproduce and remain in the canopy. It is likely that this phase burned at least once every 5 years.
Forest overstory. Forest Overstory Composition based on Nelson (2010) and field surveys.
Forest understory. Forest Understory Composition based on Nelson (2010) and field surveys.
Community 1.2
Chinkapin Oak – Black Oak/Hickory - Red Bud/Virginia Wildrye – Little Bluestem
This phase is similar to community phase 1.1 but oak and hickory understory densities are increasing due to longer periods of fire suppression. Displacement of some grasses and forbs may be occurring due to shading and competition from the increased densities of oak and hickory saplings in the understory.
State 2
Fire Excluded Managed Woodland
These stands will slowly increase with more shade tolerant species and white oak will become less dominant. These woodlands tend to be rather dense, with a sparse understory and ground flora. 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. Without periodic disturbance, stem density and fire intolerant species, like eastern redcedar and hickory, increase in abundance. Prescribed fire along with a more open canopy can transition this state to a Fire Managed Woodland state (State 3).
Community 2.1
Black Oak – White Oak – Chinkapin Oak/Hickory – Hazelnut/ Wildrye
This is the only phase associated with this state at this time. See the corresponding state narrative for details.
State 3
Fire Managed Woodland
The Fire Managed Woodland state results from managing woodland communities (States 2) with prescribed fire and canopy thinning,. This state can resemble the Reference State, but with younger maximum tree ages, more open canopies and lower ground flora diversity. Cessation of prescribed fire will allow transition to various managed woodland states.
If controlled grazing is introduced to this state, a silvopasture system can be created. Opening of the canopy may need to occur to allow sufficient light levels to exist for suitable grazing needs.
Community 3.1
Oak –Hickory/Redbud/ Woodland Brome
This is the only phase associated with this state at this time. See the corresponding state narrative for details.
State 4
Grassland
Conversion of woodlands to planted, non-native cool season grassland species such as tall fescue is common for this region. Steep slopes, surface fragments, low organic matter contents and soil acidity make grasslands harder to maintain in a healthy, productive state on this ecological site.
Two community phases are recognized in the grassland state, with shifts between phases based on types of management. Poor management will result in a shift to Community 4.2 that shows an increase in oak sprouting and increases in broomsedge densities. If grazing and active pasture management is discontinued, the site will eventually transition to State 2 from this phase.
Community 4.1
Tall Fescue - 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 and to woodland communities (where liming is not practiced).
Community 4.2
Tall fescue - Broomsedge/Oak Sprouts
This phase is the result of over use, poor grassland and grazing management and lack of adequate nutrient application. Oak sprouts, oak saplings, and invasive species are increasing as a result of poor management.
State 5
High-Graded, Grazed Woodland
States that were subjected to repeated, high-grading timber harvests and uncontrolled domestic grazing transitioned to a High-Graded, Grazed Woodland 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 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 5, grassland or removing livestock, limited harvesting, and allowing long term succession to occur to some other woodland state.
Community 5.1
Black Oak – Chinkapin Oak – Hickory / Serviceberry – Buckbrush / Sedge
This is the only phase associated with this state at this time. See the corresponding state narrative for details.
