Ecological dynamics
The Claypan Savannah ecological site evolved and was maintained by the grazing and herding effects of native wild large ungulates, periodic fires, and climatic fluctuations. Conversion of this site to cropland and the subsequent abandonment of cropping removed the natural native vegetation, organic matter, fertility, and allowed woody species to invade the site. Continuous grazing by domestic livestock and the suppression of fire on non-cropland sites removes little bluestem (Schizachyrium scoparium), Indiangrass (Sorghastrum nutans), switchgrass (Panicum virgatum), Engelmann's daisy (Engelmannia peristenia), yellow neptunia (Neptunia lutea), and gayfeather (Liatris elegans). Less productive perennial and annual grasses, forbs, vines, and shrubs will replace these plants. With continued continuous grazing, no brush management, and the absence of periodic fires, a community dominated by winged elm (Ulmus alata), eastern persimmon (Diospyros virginiana), mesquite (Prosopis glandulosa), yaupon (Ilex vomitoria), post oak (Quercus stellata), blackjack oak (Quercus marilandica), and eastern red cedar (Juniperus virginiana) will replace the savannah.
State 1
Savannah
One community exists in the Savannah State, the 1.1 Tallgrass/Oak Savannah Community. The State is dominated by warm season perennial grasses and the overstory canopy cover is less than 20 percent.
Community 1.1
Tallgrass/Oak Savannah
The interpretive plant community of this site is the reference plant community. This site is a fire-climax savannah of post oak and blackjack oak trees that shade 15 to 20 percent of the ground. The herbaceous component is tall and midgrasses dominated by little bluestem, Indiangrass, and brownseed paspalum (Paspalum plicatulum), which usually make up 50 to 75 percent of the total annual yield. Purpletop tridens (Tridens flavus), Florida paspalum (Paspalum floridanum), switchgrass, tall dropseed (Sporobolus compositus), and thin paspalum (Paspalum setaceum) also occur. Cool-season forage plants occurring on this site include Canada wildrye (Elymus canadensis), Engelmann's daisy, and sedges (Carex spp.). A variety of shrubs, vines, and forbs occur in this community. Grazing prescriptions that permit acceptable grazing periods and allow adequate rest periods with prescribed fire every three to five years are important in the maintenance of the herbaceous plant community and the savannah landscape structure. Continuous overgrazing or over rest and the absence of fire tend to allow a vegetative shift towards woody species such as eastern persimmon, eastern red cedar, and winged elm. Without corrective measures, this shift will continue to the Shrubland State.
State 2
Shrubland
One community exists in the Shrubland State, the 2.1 Oak Scrub/Shrubland Community. The herbaceous production is not as great compared to the Savannah State, and overstory canopy has increased between 20 and 50 percent.
Community 2.1
Oak Scrub/Shrubland
This plant community is a transitional community between the Savannah and Woodland State. It develops in the absence of fire or mechanical or chemical treatments. It is usually the result of abandonment following cropping or yearly continuous grazing. Trees and shrubs begin to replace the grassland component of the savannah community. In addition to the naturally occurring post oak and blackjack oak, winged elm, water oak (Quercus nigra), mesquite, eastern persimmon, bumelia (Sideroxylon lanuginosum), eastern red cedar, yaupon, and greenbriar (Smilax spp.) increase in density and canopy coverage (20 to 50 percent). Species whose seeds are windblown (elm) or animal dispersed (persimmon, mesquite, eastern red cedar, bumelia) are the first to colonize and dominate the site.
Remnants of little bluestem and Indiangrass may still occur but the herbaceous component of the community becomes dominated by lesser producing grasses and forbs. Silver bluestem (Bothriochloa laguroides), tall dropseed, arrowfeather threeawn (Aristida purpurascens), Scribner’s dichanthelium (Dichanthelium oligosanthes), thin paspalum, Hall’s panicum (Panicum hallii), western ragweed (Ambrosia psilostachya), croton (Croton spp.), and narrowleaf sumpweed (Iva angustifolia) commonly occur. If the woody shrub canopy has not exceeded 50 percent, prescribed burning on a three to five year interval in conjunction with prescribed grazing is a viable option for returning this community to a Savannah State that may resemble the reference plant community. If the woody canopy exceeds 50 percent, chemical or mechanical brush control must also be applied to move this transitional community back towards the reference plant community.
State 3
Woodland
One community exists in the Woodland State, the Post Oak/Elm Woodland Community. The site is characterized by little herbaceous production. The overstory canopy is over 50 percent and shrubs also limit light to the surface.
Community 3.1
Post Oak/Elm Woodland
This plant community is a closed overstory (50 to 80 percent) woodland dominated by post oak, winged elm, blackjack oak, black hickory (Carya texana), eastern red cedar, and water oak. Understory shrubs and sub-shrubs include yaupon, farkleberry (Vaccinium arboreum), possumhaw (Ilex decidua), and American beautyberry (Callicarpa americana). Woody vines also occur and include Alabama supplejack (Berchemia scandens), poison ivy (Toxicondendron radicans), grape (Vitis spp.), greenbriar, trumpet creeper (Campsis radicans), Virginia creeper (Parthenocissus quinquefolia), and peppervine (Ampelopsis arborea). A herbaceous understory is almost nonexistent but shade tolerant species including longleaf woodoats (Chasmanthium sessiliflorum), broadleaf woodoats (Chasmanthium latifolium), cedar sedge (Carex planostachys), ironweed (Veronia baldwinii), and goldenrod (Solidago spp.) may occur in small amounts.
Prescribed fire may be used to convert this site back to the Tallgrass/Oak Savannah but may take many consecutive years of burning due to light fine fuel loads. Chemical brush control on a large scale is usually not a treatment option on this site due to the herbicide resistance of yaupon. Individual plant treatment with herbicides on small acreage may be a viable option. Mechanical treatment of this site, along with seeding, is the most viable option for reversion back to a Tallgrass/Oak Savannah, but the economic viability of this option is questionable.
State 4
Converted
The Converted Land State contains one community, the 4.1 Converted Land Community. The state is characterized by the land manager farming crops or planted grasses.
Community 4.1
Converted Land
Conversion of this site to cropland occurred from the middle 1800's to the early 1900's. Some remains in cropland today, typically cotton (Gossypium spp.), corn (Zea mays), sorghum (Sorghum spp.), and soybeans (Glycine max). Ditching, land leveling, and levee construction has significantly changed the topography and hydrology on many acres of this site. While restoration of this site to a semblance of the reference plant community is possible with seeding and prescribed grazing, complete restoration of the reference community in a reasonable time is very unlikely.
Following crop production, this site is often planted to native or introduced grasses and legumes for livestock grazing or hay production. Typical species planted include improved Bermudagrass varieties, bahiagrass, switchgrass, dallisgrass, kleingrass (Panicum coloratum), old world bluestems (Bothriochloa spp.) annual ryegrass (Lolium multiflorum), and white clover. Many of the introduced species (bahiagrass, Bermudagrass, and dallisgrass) are invasive-moving by wind, water, and animals. Once established, they are extremely difficult to remove and will hinder the reestablishment of native species. The establishment and maintenance of these species requires cultivation, fertilization, weed control, and prescribed grazing management.
Transition T1A
State 1 to 2
The Savannah State will transition to the Shrubland State when continued heavy grazing pressure, no brush management, and/or field abandonment continues. The transition is evident when woody species canopy cover exceeds 20 percent and grasses shift composition to more shade-tolerant species.
Transition T1B
State 1 to 4
The transition to the Converted State occurs when the site is plowed for planting crops or pasture. The driver for the transition is the land manager's decision to farm the site.
Restoration pathway R2A
State 2 to 1
Restoration back to the Savannah State requires brush management, prescribed grazing and/or prescribed fire. Mechanical or chemical controls can be used to remove the woody overstory species and shrubs. Prescribed grazing may require destocking and/or deferment.
Transition T2A
State 2 to 3
The Shrubland State will transition to the Woodland State when continued heavy grazing pressure, no brush management, and/or field abandonment continues. The transition is evident when woody species canopy cover exceeds 50 percent and grasses shift composition to more shade-tolerant species.
Transition T2B
State 2 to 4
The transition to the Converted State occurs when the site is plowed for planting crops or pasture. The driver for the transition is the land manager's decision to farm the site.
Restoration pathway R3A
State 3 to 1
Restoration back to the Savannah State requires substantial energy inputs. Brush management and prescribed grazing will be needed to shift the community back to the reference state. Mechanical or chemical controls can be used to remove the woody overstory species back below 20 percent. Prescribed grazing may require destocking and/or deferment to manage the understory grasses back to those found in the reference community. Fire may be an option, but only if adequate amounts of fine fuel exist in the understory.
Transition T3A
State 3 to 4
The transition to the Converted State occurs when the site is plowed for planting crops or pasture. The driver for the transition is the land manager's decision to farm the site.
Restoration pathway R4A
State 4 to 1
The restoration to State 1 can occur when the land manager ceases agronomic practices. Range planting of native species found in the reference community will be required to bring back a similar community as the State 1 plant composition. The extent of previous soil disturbances will determine how much seedbed preparation will be needed, as well as the ability to be restored. Proper grazing and brush management will be required to ensure success.
Transition T4A
State 4 to 3
The Converted Land State will transition to the Woodland State when continued heavy grazing pressure, no brush management, and/or field abandonment continues. The transition is evident when woody species canopy cover exceeds 50 percent and grasses shift composition to more shade-tolerant species.
