State 1
Reference State

Community 1.1
Tallgrass Bottomland Community

The Tallgrass Bottomland Community (1.1) is the reference community and is characterized as a hardwood savannah with up to 20 percent tree and shrub canopy cover. Both percent species composition by weight and percent canopy cover are used in this ESD. Most observers find it easier to visualize or estimate percent canopy for woody species (trees and shrubs). Canopy cover drives the transitions between plant communities and states because of the influence of shade and interception of rainfall. Species composition by weight remains an important descriptor of the herbaceous community and of the community as a whole. Woody species are included in species composition for the site. Calculating Similarity Index requires use of species composition. The herbaceous community in the drier, open areas is dominated by switchgrass, Indiangrass, big bluestem, little bluestem, eastern gamagrass, vine-mesquite (Panicum obtusum), sideoats grama (Bouteloua curtipendula), and silver bluestem (Bothriochloa laguroides). Sedges, Virginia wildrye, and Canada wildrye dominate the herbaceous plant community in shaded and wet areas. The balance of warm- and cool-season tallgrasses will be driven by the amount of canopy cover from large trees, particularly the amount and size of stands with closed canopy. When the site is open and tree cover is less than 10%, warm-season tallgrasses will approach 40% species composition by weight, while the cool-season grasses will approach 10%. As tree cover approaches the upper limit of the reference community (30%), cool-season grasses and grasslikes will approach 30% species composition by weight and warm-season tallgrasses will approach 20%. Live oak, post oak, elm, hackberry, cottonwood, ash, willow (Salix spp.), pecan, and other large trees create 20% canopy cover. The overstory canopy is densest adjacent to watercourses. Woody understory species include hawthorn (Crataegus spp.), greenbriar (Smilax spp.), and grape (Vitis spp.). Continuous yearlong grazing that exceeds the carrying capacity for a succession of years will tend to move the reference herbaceous plant community towards a herbaceous community of buffalograss (Bouteloua dactyloides) and other shortgrasses. The reference Tallgrass Bottomland Community (1.1) will shift to the Midgrass Bottomland Community (1.2) under the stresses of improper grazing. The first species to decrease in dominance will be the most palatable and/or least grazing tolerant grasses and forbs (namely, eastern gamagrass, Indiangrass, big bluestem). This will initially result in an increase in composition of little bluestem and sideoats grama. If improper grazing continues, little bluestem will decrease and midgrasses such as silver bluestem and vine mesquite will increase in composition. Less palatable forbs will also increase at this stage. Without fire and/or brush control, woody species on the site will increase and the site will transition to the Woodland State. This can occur with or without the understory transitioning to the midgrass community through shift of dominance by tallgrasses to dominance by midgrasses. Continuous abusive grazing with no fire or brush management, or abandoning the site for several years, will allow shrub saplings to establish. Once woody shrubs and saplings invade the site, brush management in some form must be used to maintain the Tallgrass Bottomland Community (1.1). The soils of this site are deep, dark gray to black, calcareous clays. The site receives additional water from outside the site as overflow or as runoff from adjacent sites. The soils have high shrink-swell characteristics. They crack profusely when dry and the cracks take in water rapidly. Once wet, the cracks close and permeability becomes very slow. Surface runoff and permeability are very slow. Soils are highly fertile and hold large amounts of soil moisture. However, the soils have a high wilting point, which reduces plant production in very dry years. In very wet years the site is subject to flooding, which reduces plant production and desirability of the site for grazing. This is a very productive site with high yields of palatable, high quality forage. There is essentially no bare soil in this community. Plant basal cover and litter comprise all of the ground cover. Multiple layer canopy cover approaches 100%.

Community 1.2
Midgrass Bottomland Community

The Midgrass Bottomland Community (1.2) typically results from improper cattle grazing management over a long period of time combined with a lack of brush management and fire. It can also be the result of abandoned cropland. Indigenous or invading woody species increase on the site. Growing season stress, usually from overgrazing, causes reduction in vigor and survival of tallgrasses, which allows midgrasses and less palatable forbs to increase in the herbaceous community. Prescribed burning becomes less effective to maintain this community or return it to the Tallgrass Bottomland Community (1.1) due to the moisture content and lack of quantity of the herbaceous fine fuel. Mechanical or chemical brush control as well as prescribed grazing must be applied to move this vegetative state back towards the Tallgrass Bottomland Community. Remnants of Virginia wildrye and big bluestem may still occur but the herbaceous component of the community becomes dominated by lesser producing grasses and forbs. Shade tolerant species such as Texas wintergrass (Nassella leucotricha) and shade tolerant forbs such as grape and greenbriar become more abundant species as canopy cover increases. Trees and shrubs begin to replace the grassland component of the community. The naturally occurring live oak, post oak, elm, hackberry, ash, pecan, and cottonwood will increase. Invasive woody species such as honey locust (Robinia rusbyi) and also increase in density until canopy cover reaches 50 percent. Species whose seeds are windblown (elm, cottonwood, and ash) or animal dispersed (pecan) readily colonize and dominate the site. Numerous shrub and tree species will encroach because overgrazing by livestock has reduced grass cover, exposed more soil, and reduced grass fuel for fire. Typically, trees such as oaks (Quercus spp.) and ash will increase in size, while other tree and shrub species such as bumelia (Sideroxylon spp.), sumacs (Rhus spp.), honey locust, winged elm (Ulmus alata), and Osage orange (Maclura pomifera) will increase in density. Brown and Archer (1999) concluded that even with a healthy and dense stand of grasses, woody species will populate the site and eventually dominate the community until removal by fire or brush control. Heavy continuous grazing will reduce plant cover, litter, and mulch. Bare ground will increase and expose the soil to erosion. Litter and mulch will move off-site as plant cover declines. The Midgrass Bottomland Community (1.2) can be managed back toward the Tallgrass Bottomland Community (1.1) through the use of management practices including prescribed grazing and strategic brush control. It may take several years to achieve this state, depending upon the climate and the aggressiveness of the treatment. Once invasive woody species begin to establish, returning fully to the native community is difficult, but it is possible to return to a similar plant community. Potential exists for soils to erode to the point that irreversible damage may occur. If soil-holding herbaceous cover decreases to the point that soils are no longer stable, the shrub overstory will not prevent erosion of the A and B soil horizons. This is a critical shift in the ecology of the site. Once the A horizon has eroded, the hydrology, soil chemistry, soil microorganisms, and soil physics are altered to the point where intensive restoration is required to restore the site to another state or community. Simply changing management (improving grazing management or controlling brush) cannot create sufficient change to restore the site within a reasonable time frame.

Community 1.3
Hardwood Bottomland Community

The Hardwood Bottomland Community (1.3) has over 50% woody plant canopy, dominated by hardwoods such as oaks and elms. The community loses its savannah appearance with native shrubs filling the open grassland portion of the savannah. This community occurs along the stream channel of the drainageway. While total net primary production is similar to the Tallgrass Bottomland Community (1.1), annual herbage production decreases due to a decline in soil structure and organic matter and has shifted toward the woody component. All unpalatable woody species have increased in size and density. This plant community is a closed (or nearly closed) overstory (50 to 80%) woodland dominated by oaks, elm, hackberry, ash, pecan, and cottonwood. Understory shrubs include hawthorn and willows. Woody vines also occur and include grape and greenbrier. An herbaceous understory is almost nonexistent but shade tolerant species including Uniola spp., sedges, ironweed (Vernonia baldwinii), switchcane (Arundinaria gigantea), eastern gamagrass, and goldenrod (Solidago spp.) may occur in small amounts. Plant vigor and productivity of grass species is reduced due to shade. Shade is a driving factor for the understory plant community. Without brush control, tree canopy will continue to increase until canopy cover approaches 100%. Large-scale prescribed fire is generally not a viable treatment option for conversion of this site back to a semblance of the Tallgrass Bottomland Community. Chemical brush control on a large scale may not a treatment option; however, individual plant treatment with herbicides on small acreages may be a viable option. Mechanical treatment of this site, along with seeding, is the most viable treatment option although it may not be economical.

Pathway 1.1A
Community 1.1 to 1.2

The Tallgrass Bottomland Community requires fire and/or brush control to maintain woody species cover below 20%. This community will shift to the Midgrass Bottomland Community when there is continued growing season stress on tallgrasses. These stresses include improper grazing management that creates insufficient critical growing season deferment, excess intensity of defoliation, repeated, long-term growing season defoliation, and long-term drought. Increaser species (midgrasses and woody species) are generally endemic species released by disturbance. Woody species canopy exceeding 20% and/or dominance of tallgrasses falling below 50% of species composition indicate a transition to the Midgrass Bottomland Community. The Tallgrass Bottomland Community can be maintained through the implementation of fire, brush management, combined with properly managed grazing that provides adequate growing season deferment to allow establishment of tallgrass propagules and/or the recovery of vigor of stressed plants. Regardless of grazing management, without some form of brush control and/or fire, the Tallgrass Bottomland Community will transition to the Woodland State even if the understory component does not shift to dominance by midgrasses. The driver for community shift 1.1A for the herbaceous component is improper grazing management, while the driver for the woody component is lack of fire and/or brush control.

Pathway 1.2A
Community 1.2 to 1.1

The Midgrass Bottomland Community will return to the Tallgrass Bottomland Community with brush control and proper grazing management that provides sufficient critical growing season deferment in combination with proper grazing intensity. Favorable moisture conditions will facilitate or accelerate this transition. The understory component may return to dominance by tallgrasses in the absence of fire (at least until shrub canopy cover reaches 50%). Reduction of the woody component will require inputs of fire and/or brush control. The understory and overstory components can act independently when canopy cover is less than 50%, i.e., an increase in shrub canopy cover can occur while proper grazing management creates an increase in desirable herbaceous species. The driver for community shift 1.2A for the herbaceous component is proper grazing management, while the driver for the woody component is fire and/or brush control.

State 2
Invaded Woodland State

Community 2.1
Invaded Woodland Community

The Invaded Woodland State (2) has over 50% woody plant canopy cover, dominated by invaded woody species such as honey mesquite and Ashe juniper. The appearance is similar to that of the Hardwood Bottomland Community (1.3) but native shrubs being replaced by invaded species. The herbaceous understory is almost non-existent. Cool-season grasses dominate this sparse understory. Plant vigor and productivity of grass species is reduced due to shade. Shade is a driving factor for the understory plant community. Without brush control tree canopy will be close to 100%. Prescribed fire is not a viable treatment option for conversion of this site back to a semblance of the Tallgrass Bottomland Community. Chemical brush control on a large scale may not be a treatment option; however, individual plant treatment with herbicides on small acreages may be a viable option. Mechanical removal of invasive woody species, along with seeding and ongoing management of invasives, is the most viable treatment option although it may not be economical. Without maintenance, invasive species are likely to return (probably rapidly) due to presence of propagules in the soil.

State 3
Converted Land State

Community 3.1
Converted Land Community

The Converted Land Community (3.1) occurs when the site, either the Bottomland State (1) or Invaded Woodland State (2), is cleared and plowed for planting to cropland, hayland, native grasses, tame pasture, and used as non-agricultural land and restored native Prairie or Woodland. The Converted State includes cropland, tame pasture, hayland, rangeland, and go-back land. Agronomic practices are used with non-native forages in the Converted State and to make changes between the communities in the Converted State. The native component of the prairie is usually lost when seeding non-natives. Even when reseeding with natives, the ecological processes defining the past states of the site can be permanently changed. The Clayey Bottomland site is frequently converted to cropland or tame pasture sites because of its deep fertile soils, favorable soil/water/plant relationship, and level terrain. Hundreds of thousands of acres have been plowed up and converted to cropland, pastureland, or hayland. Small grains are the principal crop, and Bermudagrass is the primary introduced pasture species on loamy soils in this area. The Clayey Bottomland site can be an extremely productive forage producing site with the application of optimum amounts of fertilizer. Refer to Forage Suitability Group Descriptions for specific management recommendations, estimated production potentials, and species adaptation. Cropland, pastureland, and hayland are intensively managed with annual cultivation and/or frequent use of herbicides, pesticides, and commercial fertilizers to increase production. Both crop and pasturelands require weed and shrub control because seeds remain present on the site, either by remaining in the soil or being transported to the site. Converted sites require continual fertilization for crops or tame pasture (particularly Bermudagrass) to perform well. NRCS Forage Suitability Group Descriptions describe adapted species, management, and production potentials on pasturelands and haylands. Common introduced species include coastal Bermudagrass, kleingrass, and Old World bluestems (Bothriochloa spp.) which are used in hayland and tame pastures. Wheat, oats, forage sorghum, grain sorghum, cotton, and corn are the major crop species. Cropland and tame pasture require repeated and continual inputs of fertilizer and weed control to maintain the Converted State. Without agronomic inputs, the site will eventually return to either the Bottomland or Invaded Woodland State. The site is considered go-back land during the period between active management for pasture or cropland and the return to a native state.

Community 3.2
Abandoned Land Community

The Abandoned Land Community (3.2) occurs when the Converted Land Community (3.1) abandoned or mismanaged. Mismanagement can include poor crop or haying management. Pastureland can transition to the Abandoned Land Community when subjected to improper grazing management (typically long-term overgrazing). Heavily disturbed soils allowed to “Go Back” return to the Invaded Shrubland State. These sites may become woodland thicket over time. Long-term cropping can create changes in soil chemistry and structure that make restoration to the Bottomland state (1) very difficult and/or expensive. Return to native Bottomland State is more likely to be successful if soil chemistry, microorganisms, and structure are not heavily disturbed. Preservation of favorable soil microbes increases the likelihood of a return to reference conditions. Restoration to native Bottomland will require seedbed preparation and seeding of native species. Protocols and plant materials for restoring prairie communities is a developing portion of restoration science. Sites can be restored to the Bottomland State in the short-term by seeding mixtures of commercially-available native grasses. With proper management (prescribed grazing, weed control, brush control) these sites can come close to the diversity and complexity of Tallgrass Bottomland Community (1.1) it is unlikely that abandoned farmland will return to the Bottomland State without active brush management because the rate of shrub increase will exceed the rate of recovery by desirable grass species. Without active restoration the site is not likely to return to reference conditions due to the introduction of introduced forbs and grasses. The native component of the Bottomland is usually lost when seeding non-natives. Even when reseeding with natives, the ecological processes defining the past states of the site can be permanently changed.

Pathway 3.1A
Community 3.1 to 3.2

The shift from the Converted Land Community to the Abandoned Land Community occurs due to land being abandoned or idled from crop and pastureland production.

Pathway 3.2A
Community 3.2 to 3.1

Restoration from the Abandoned Land Community can be accomplished through the use of brush management, prescribed grazing, and crop cultivation.

Transition T1A
State 1 to 2

The introduction of aggressive woody invader species creates risk for transition to the Invaded Woodland State. This transition can occur from any community within the Bottomland State, it is not dependant on degradation of the herbaceous community, but on introduction of aggressive woody species. Risk of invasives increases on poorly managed or Go-back Land. Improper grazing, prolonged drought, and a warming climate will provide a competitive advantage to shrubs adapted to warmer, drier conditions which will accelerate this process. Without control, invasive woody species can dominate the site. Invasive introduced to a healthy Bottomland Community will be mixed with native over and understory. The driver for this transition is the introduction of invasive species.

Transition T1B
State 1 to 3

The transition to the Converted State from the Bottomland State (T1B) occurs when the bottomland is plowed for planting to cropland or hayland. The size and density of brush in the Woodland State will require heavy equipment and energy-intensive practices (i.e. rootplowing, raking, rollerchopping, or heavy disking) to prepare a seedbed. The threshold for this transition is the plowing of the prairie soil and removal of the woody plant community. The Converted State includes cropland, tame pasture, and go-back land. The site is considered “go-back land” during the period between cessation of active cropping, fertilization, and weed control and the return to the “native” states. Agronomic practices are used to convert rangeland to the Converted State and to make changes between the communities in the Converted State. The driver for these transitions is management’s decision to farm the site.

Restoration pathway R2A
State 2 to 1

Restoration of the Invaded Woodland State to the Bottomland State requires substantial energy input. The driver for this restoration pathway is removal of invasive woody species, restoration of native herbaceous and overstory species, and ongoing management of invasives. Without maintenance, invasive species are likely to return (probably rapidly) due to presence of propagules in the soil.

Transition T2A
State 2 to 3

The transition to the Converted State from the Woodland State (T2A) occurs when the bottomland is plowed for planting to cropland or hayland. The size and density of brush in the Woodland State will require heavy equipment and energy-intensive practices (i.e. rootplowing, raking, rollerchopping, or heavy disking) to prepare a seedbed. The threshold for this transition is the plowing of the prairie soil and removal of the woody plant community. The Converted State includes cropland, tame pasture, and go-back land. The site is considered “go-back land” during the period between cessation of active cropping, fertilization, and weed control and the return to the “native” states. Agronomic practices are used to convert rangeland to the Converted State and to make changes between the communities in the Converted State. The driver for these transitions is management’s decision to farm the site.

Transition T2A
State 2 to 3

The transition to the Converted State from the Woodland State (T2A) occurs when the bottomland is plowed for planting to cropland or hayland. The size and density of brush in the Woodland State will require heavy equipment and energy-intensive practices (i.e. rootplowing, raking, rollerchopping, or heavy disking) to prepare a seedbed. The threshold for this transition is the plowing of the prairie soil and removal of the woody plant community. The Converted State includes cropland, tame pasture, and go-back land. The site is considered “go-back land” during the period between cessation of active cropping, fertilization, and weed control and the return to the “native” states. Agronomic practices are used to convert rangeland to the Converted State and to make changes between the communities in the Converted State. The driver for these transitions is management’s decision to farm the site.

Transition T3A
State 3 to 2

Transition from the Converted State can occur in the short term through active restoration or over the long-term due to cessation of agronomic practices. Cropland and tame pasture require repeated and continual inputs of fertilizer and weed control to maintain the Converted State. Heavily disturbed soils are more likely to return to the Invaded Woodland State. Without continued disturbance from agriculture the site can eventually return to the Invaded Woodland state. The level of disturbance while in the converted state determines the direction of the site restoration pathway. Return to the Invaded Woodland State is more likely to be successful if soil chemistry and structure are heavily disturbed. Converted sites can be returned to the Invaded Woodland State through active restoration, including seedbed preparation and seeding of native grass and forb species. Protocols and plant materials for restoring prairie communities is a developing part of restoration science. The driver for both of these restoration pathways is the cessation of agricultural disturbances.