State 1
Savannah

This is the reference state for this ecological site. It represents the historical variability of plant communities for the site.

Characteristics and indicators. Tallgrasses dominate the plant communities within this state. Other vegetative components include numerous forbs, midgrasses, and bottomland hardwood tree species. Woody canoy averages 30-50 percent.This canopy may vary substantially as areas adjacent to creeks and streams are more protected from fire. This often leads to a feathered effect of low canopy further from the the water course and higher canopy adjacent to it.

Resilience management. The plant communities within this state evolved under disturbance from periodic fire and grazing. Woody species vigor and reproduction is restricted by periodic fires. As grazing pressure increases, more palatable tallgrass species and forbs will decline in vigor and may be replaced by less desirable midgrass species.

Community 1.1
Tallgrass Savannah (R)

Figure 10. Tribbey Soils. Reference community. Lincoln County, OK

This plant community is the reference plant community for the site. It contains a mixture of tallgrasses, perennial forbs, shrubs, and trees. The representative grasses are Switchgrass (Panicum virgatum), Eastern Gamagrass (Tripsacum dactyloides), and Prairie Cordgrass (Spartina pectinata). Forbs include Bonesets (Eupatorium spp.), Verbenas (Verbena spp.), Western Ironweed (Vernonia baldwinii), Goldenrods (Solidago spp.), and many others. Shrub species present may include Buttonbush (Cephalanthus occidentalis), Indigo bush (Amorpha fruticosa), Grape (Vitis spp.), and Poison Ivy (Toxicodendron radicans). The trees occurring in this community are primarily, Black Willow (Salix nigra), Pecan (Carya illinoinensis), Eastern Cottonwood (Populus deltoids), and occasionally Common Persimmon (Diospyros virginiana).

This plant community provides good habitat for many species of wildlife and domestic grazing animals. There is abundant herbaceous litter between plants and very little bare ground. Water from rainfall events may percolate rapidly, depending upon the depth of the water table. There is very little soil loss within this plant community and soil biota should be able to flourish.

The following species cover, structure, and production tables have been developed using collected data and professional knowledge. As with anything in nature, there is a large amount of variability from year to year even within a relatively stable plant community. This is true for both vegetative production as well as foliar cover produced by a plant species. The following figures are to be viewed only as a representation of the estimated potential for a given species. As more data is collected and measurement methods are refined some values may be updated through future revisions.

Community 1.2
Midgrass/Tallgrass Savannah

Figure 13. Tribbey soils. Community 1.2 under heavy grazing pressure. Remnant switchgrass.

This plant community has developed as the result of long term abusive grazing and the exclusion of fire and/or other brush management. This abusive grazing has involved stocking rates that exceed the carrying capacity for the reference community without adequate rest provided for recovery of the palatable grasses. Therefore, the dominant tallgrasses from the reference community (1.1) have declined and have been replaced by less palatable species. These less palatable species including Bulrush (Schoenoplectus spp.), Broomsedge Bluestem (Andropogon virginicus), and Paspalums (Paspalums spp.), have received less pressure from grazing animals and have been able to thrive. The more palatable legumes and forbs have also decreased and allowing for the increase of Ragweeds (Ambrosia spp.) and Sumpweed (Iva annua). Woody species such as Pecan and Common Persimmon have increased in the absence of fire. This plant community will most often still contain the fine fuel loads required to implement prescribed burning, however, proper planning and evaluation will be necessary to implement this practice. On some sites large, rank Switchgrass plants have been avoided by grazers and will persist in this plant community.

Pathway 1.1A
Community 1.1 to 1.2

Tallgrass Savannah (R)

Midgrass/Tallgrass Savannah

If the reference plant community (1.1) is subjected to abusive grazing for long periods of time, it may begin to shift to a Midgrass/Tallgrass Savannah plant community (1.2). With heavy grazing pressure on preferred tallgrass species, they will decrease in vigor and eventually be replaced by less palatable midgrasses. This shift can be avoided by following proper stocking rates and allowing periodic rests between grazing events. This shift may also be the result of a long term drought resulting in a lowered water table, as the tallgrass species tend to be less drought tolerant than some midgrasses. While the soils of this site are not considered excessively droughty and typically will maintain an elevated water table, long dry periods can begin to have an impact on the plant community. These impacts are compounded with improper grazing management (inadequate rest). Without the impacts of fire, this plant community will also be subjected to an increase in tree and shrub cover. The readily available subsurface water coupled with the fertile bottomland soils creates a suitable environment for woody species encroachment.

Pathway 1.2A
Community 1.2 to 1.1

Midgrass/Tallgrass Savannah

Tallgrass Savannah (R)

With the implementation of a prescribed grazing system that involves light stocking rates and periodic growing season rest (deferment), this plant community may shift back to the reference plant community (1.1). Additionally, prescribed fire or another form of brush management will be required to control the increasing woody canopy of Pecan and Persimmon saplings.

State 2
Woodland

This ecological state is the result of long term exclusion of fire from the ecosystem.

Characteristics and indicators. Woody species that were historically controlled by periodic fire have been allowed to reproduce and have encroached in the savannah ecosystem of the reference state (1).

Resilience management. The ecological function of the site has been altered and is now dominated by woody species. While sites in this state may be grazed by cattle, the production of palatable herbaceous species is diminished. Thus, the production value of grazing is greatly reduced. Some species of wildlife will find use of the site in this state; however, other species will not persist as the site becomes dominated by woody plants.

Community 2.1
Woody Invasion

Figure 14. Tribbey soils. Woody invasion

Figure 15. Tribbey soils. Eastern Redcedar and Salt Cedar invasion

This plant community is dominated by woody species including Pecan, Persimmon, Black Willow, and Green Ash. Invasives such as Eastern Redcedar and Salt Cedar are common and may take over some sites. The woody canopy may average around 50 – 60%. Some herbaceous species still occupy canopy interspaces. The herbaceous community may include remnants of Switchgrass, Purpletop, Dropseeds, Broomsedge Bluestem, and a variety of Sedge species depending on current and prior grazing management. Shrub species including Poison Ivy, Greenbriar, and Buckbrush are also common.

Community 2.2
Closed Canopy

Figure 16. Tribbey soils, closed canopy beyond road right-of-way

Figure 17. 2.2 to 2.1 community shifting. Fire has thinned understory.

This plant community is the result of long term fire exclusion from the ecosystem. In the absence of fire, woody species have encroached and now completely dominate the site. The fertile, coarse bottomland soils and close proximity to groundwater are favorable for woody plant growth. Major woody invaders include Common Persimmon, Pecan, Green Ash (Fraxinus pennsylvanica), and Eastern Redcedar (Juniperus virginiana). American Elm (Ulmus Americana) and Hackberry (Celtis laevigata) may also invade this site. Some understory woody species include Saw Greenbriar (Smilax bona-nox), Eastern Poison Ivy (Toxicodendron radicans), and Virginia Creeper (Parthenocissus quinquefolia). Some of these woody species occur in small amounts within the reference state (1), however, most have been limited by periodic fires. Once the species are fully mature they are very difficult to control with fire alone (except for wildfires). The closed canopy created by these woody species creates a mesophytic microclimate in the understory that favors woody species and a few shade tolerant herbaceous species. This plant community may provide some benefits to wildlife species that use it for browse and cover, but the value of the site for cattle grazing has severely deteriorated. There is potential for use of this plant community by goats due to the amount of understory woody species.

Pathway 2.1A
Community 2.1 to 2.2

Woody Invasion

Closed Canopy

Without periodic fire, this plant community will be susceptible to further woody encroachment and may shift to a closed canopy woodland plant community.

Pathway 2.2A
Community 2.2 to 2.1

Closed Canopy

Woody Invasion

Through some selective thinning of woody species and re-introduction of fire through prescribed burning, the closed canopy plant community may be shifted to a more open community (2.1).

State 3
Converted

This ecological state is the result of reseeding herbaceous plant species or abandonment following a period of cultivation. The plant communities within this state are highly variable in both species composition and production. The species composition, ecological function, and soil health may never be restored to reference conditions. Therefore, careful consideration should be taken when evaluating a bottomland site that may have been broken out for cultivation in the past.

Community 3.1
Cropland/Tame Pasture

Figure 18. Tribbey Soils planted to Bermudagrass and Fescue

Figure 19. Tribbey Soils "Go Back" with invading Johnsongrass

Some areas of this ecological site were broken out for farming purposes in the past. However, due to flooding and high water tables, most areas are no longer in crop production. These areas were either abandoned and allowed to “go back” to some kind of vegetative cover or planted to an introduced pasture species.

The “go back” plant community is the result of abandonment or range seeding after cultivation. The pioneer species of a “go back” plant community might include Purpletop (Tridens flavus), Broomsedge Bluestem (Andropogon virginicus), Giant Ragweed (Ambrosia trifida), and often times Johnsongrass (Sorghum halepense). There is often a large amount of variability within both species composition and production within this community. Some sites may be seeded to a diverse mixture of native grasses, forbs, and legumes, while other sites were seeded with very few species or simply abandoned. It is important to remember that without periodic fire or other brush management, the site may be invaded by woody species, regardless of the establishment methods of herbaceous plants.

When this site is taken out of crop production, it is often planted to an introduced perennial grass. The most common species are Bermudagrass (Cynodon dactylon) and Tall Fescue (Schedonorus arundinaceus). Many of these sites are used for grazing, cut for hay, or both. The productivity of these perennial grasses is greatly dependent upon nutrient inputs (fertilizer). Nutrient management is key to the establishment and management of these introduced species. Additionally, the addition of nutrients may help to expedite the buildup of soil microorganisms and potentially soil organic matter. For more information about suitable pasture species, planting specifications, and yield data, refer to ag extension publications, web soil survey, and forage suitability group descriptions (if available).

Transition T1A
State 1 to 2

In the absence of fire, many woody species are allowed to encroach across the landscape. Once these woodies are abundant enough, they begin to drive the ecological functions of the site.

Constraints to recovery.Shading negatively affects the herbaceous plants and hydrologic changes may lower the water table, limiting available water for these species. As the woody species begin to dominate the site, it will transition to a woodland ecological state (2).

Transition T1B
State 1 to 3

Many of these sites have been plowed for farming purposes over the last century, although typically for short durations. Once the site is cultivated, it transitions to an alternative state (3).

Constraints to recovery.The soils structure, organic matter, and biota have been altered and will no longer function the same as the soils in the reference state. A majority of the sites that were once cultivated have been abandoned or reseeded to non-native perennial grasses.

Restoration pathway R2A
State 2 to 1

Through an integrated program of Brush Management (selective thinning), Grazing Management (deferment), and Prescribed Fire, the Woodland State may be restored to the Reference Savannah State (1). Selective thinning will be required to remove undesirable woody species while leaving the large bottomland trees that occur in the Reference State. Prescribed grazing will be required in order to allow the tallgrasses, forbs, and legumes recover and re-establish once the canopy is thinned. This will also be required in order to establish proper fuel loads in order to successfully implement a prescribed fire program. Prescribed fire will be necessary in order to clean up remaining understory species and can be used as a management tool to prevent future woody encroachment.