State 1
Grassland State

The Grassland State defines the ecological potential and natural range of variability resulting from the natural disturbance regime of the Sandy Floodplain ecological site. This state is supported by empirical data, historical data, local expertise, and photographs. It is defined by a suite of native plant communities that are a result of periodic fire, drought, and grazing. These events are part of the natural disturbance regime and climatic process. The Reference Plant Community consists of warm-season tall- and midgrasses, cool-season and sod-forming grasses, forbs, and shrubs. The Midgrass/Tallgrass Plant Community is made up primarily of warm-season midgrasses, with an interspersed cool-season component and decreasing amounts of forbs and tallgrasses. The Midgrass/Shortgrass Plant Community is dominated by midgrasses, shortgrasses, and cool-season midgrasses.

Characteristics and indicators. Tallgrasses and midgrasses are dominant in the Grassland State.

Resilience management. Management strategies that will sustain this state include monitoring key forage species and providing a forage and animal balance.

Community 1.1
Reference Plant Community

Figure 11. MLRA 74 Reference Plant Community.

The interpretive plant community for this site is the Reference Plant Community, and represents the original plant community that existed prior to European settlement. The site is characterized as a grassland essentially free of trees and large shrubs. It is dominated by tall warm-season grasses including sand bluestem, switchgrass, Indiangrass, eastern gamagrass, and common reed. The major midgrass is little bluestem. Combined these grasses will account for 60 percent of vegetation produced annually. Other prevalent midgrasses are Canada wildrye, sand lovegrass, composite dropseed, sand dropseed, and purple lovegrass. Scattered throughout are minor amounts of shortgrasses consisting of blue grama, hairy grama, Scribner’s rosette grass, thin paspalum, and Carolina crabgrass. The site supports a wide variety of legume species, which are interspersed throughout the grass sward. The most abundant are roundhead lespedeza, slender lespedeza, sessileleaf ticktrefoil, Maryland senna, and prairie bundleflower. Other important forbs include Maximilian sunflower, scaly blazing star, Canada goldenrod, Cuman ragweed, and pitcher sage. Leadplant and Jersey tea are low-growing shrubs that occur over the site. Unlike most shrubs, these plants are both quite tolerant to fire. A few large clumps of Chickasaw plum and skunkbush may also be found.

Resilience management. This can be maintained as a stable plant community when adequately managed. A prescribed grazing program that incorporates periods of rest and recovery during the growing season benefits the tallgrasses and even the more palatable forb species. Soils representative of this site are susceptible to wind erosion. Excessive grazing and trailing by livestock can have an impact on the soil and site stability. A lack of plant cover can lead to scour erosion during floods.

Community 1.2
Tallgrass/Midgrass Plant Community

Figure 14. MLRA 74 Midgrass/Tallgrass Plant Community.

The composition of the Tallgrass/Midgrass Plant Community resembles that of the Reference Plant Community. Comparatively, there has been a slight decrease of the more palatable tallgrasses and forbs and a subsequent increase in midgrasses. The dominant grasses are sand bluestem and little bluestem with lesser amounts of switchgrass and Indiangrass. A number of midgrasses have increased in abundance as the taller grasses have been reduced by overgrazing. These include sand dropseed, sand lovegrass, thin paspalum, and composite dropseed. Other secondary grasses are Carolina crabgrass, red lovegrass, tumble windmillgrass, mat sandbur, buffalograss, blue grama, and Scribner’s rosette grass. Sometimes Johnsongrass will invade this site. Combined, these secondary grasses comprise 20 to 30 percent of the total herbage produced annually. Forbs such as Maximilian sunflower, roundhead lespedeza, prairie bundleflower, and Maryland senna have been partially replaced by white sagebrush, Missouri goldenrod, Cuman ragweed, Fendler’s aster, redroot buckwheat, and tenpetal blazingstar. Forbs produce 10 to 12 percent of the total herbage. This site supports a few shrubs. Leadplant and Jersey tea may be scattered throughout the site. Chickasaw plum and skunkbush sumac are common and usually found in small clumps or mottes. Shrubs usually will not comprise over ten percent of the total production.

Resilience management. Periods of rest and recovery are essential in maintaining this as a stable plant community. Sand bluestem is preferred and readily selected and grazed by cattle. When the site is grazed continuously throughout the growing season, sand bluestem is usually overgrazed and thus maintained in a state of low vigor. This results in a gradual reduction of its abundance over time. Where this occurs, sand dropseed, thin paspalum, and mat sandbur replace the taller grasses. In some areas this has led to scour erosion following floods. Prescribed grazing that incorporates periods of rest and recovery during the growing season will improve the vigor and gradual recovery of the more palatable tallgrasses and forbs.

Community 1.3
Midgrass Plant Community

Figure 15. MLRA 74 Midgrass Plant Community.

The Midgrass Plant Community developed as a result of many years of continuous overgrazing. Midgrasses dominate the site and comprise 50 to 60 percent of the annual production. Most abundant midgrasses include little bluestem, composite dropseed, sand lovegrass, and Florida paspalum. Shortgrasses such as Carolina crabgrass, red lovegrass, Scribner’s rosette grass, tumble windmillgrass, purple threeawn, sand dropseed, buffalograss, and blue grama produce 10 to 15 percent of the vegetation. Remnant plants of sand bluestem, Indiangrass, and switchgrass, although sparse, are often found scattered throughout the site. These plants are usually grazed repeatedly and remain in a low state of vigor. Of these remnants, sand bluestem and switchgrass are generally the most abundant. When in this state, new growth consisting of three to five leaves will emerge in a prostrate position rather than upright. This allows the plants to partially escape grazing. These remnants respond favorably to periods of rest from grazing and may regain vigor in two to three years. Forb production is quite variable and may range from 10 to 30 percent of the total vegetation. This variability is dependent upon the amount and timing of rainfall and flooding events. Perennial forbs include Carruth’s sagewort, white sagebrush, redroot buckwheat, tenpetal blazingstar, bush morning-glory, and Cuman ragweed. Annual forbs common on the site include prairie sunflower, fourpoint evening primrose, camphorweed, annual ragweed, and annual buckwheat. In some locations shrubs such as skunkbush sumac and Chickasaw plum comprise 5 to 15 percent of the vegetation.

Resilience management. Prescribed grazing with adequate rest and recovery periods during the growing season will shift this plant community to include more productive midgrasses. With continued management the taller grasses will gradually increase in abundance.

Pathway 1.1 to 1.2
Community 1.1 to 1.2

Reference Plant Community

Tallgrass/Midgrass Plant Community

These mechanisms include management controlled by repetitive heavy use, no rest or recovery of the key forage species and no forage and animal balance for many extended grazing seasons. This type of management lasting for periods greater than 10 years will shift functional and structural plant group dominance toward a midgrass plant community.

Context dependence. Plant community composition shifts from tallgrass- to midgrass-dominant.

Pathway 1.2 to 1.1
Community 1.2 to 1.1

Tallgrass/Midgrass Plant Community

Reference Plant Community

Causes of plant community shift include management (10-15 years) with adequate rest and recovery of the key forage species (big bluestem, switchgrass, Indiangrass, and little bluestem) within the Reference Plant Community. If woody species are present, prescription fires every 6-8 years will be necessary for their removal and maintenance.

Pathway 1.2 to 1.3
Community 1.2 to 1.3

Tallgrass/Midgrass Plant Community

Midgrass Plant Community

These mechanisms include management controlled by repetitive heavy use, no rest or recovery of the key forage species, and no forage and animal balance for many extended grazing seasons. This type of management lasting for periods greater than 20 years will shift functional and structural plant group dominance toward a Midgrass/Shortgrass Plant Community.

Pathway 1.3 to 1.2
Community 1.3 to 1.2

Midgrass Plant Community

Tallgrass/Midgrass Plant Community

Causes of plant community shift include management (10-15 years) with adequate rest and recovery of the key forage species (little bluestem, sideoats grama, big bluestem, switchgrass, and Indiangrass) within the Midgrass/Tallgrass Plant Community. If woody species are present, prescription fires every 6-8 years will be necessary for their removal and maintenance.

State 2
Shortgrass State

With heavy, continuous grazing, blue grama and buffalograss will become the dominant species and have a sod-bound appearance. Unable to withstand the grazing pressure, only a remnant population of western wheatgrass remains.

Characteristics and indicators. The Shortgrass State is characterized with specific dynamic soil property changes. Changes between the Grassland State and the Shortgrass State have been documented. As plant community cover decreases from bunchgrasses to more of the sodgrasses there is a decrease in infiltration and interception and an increase in surface runoff (Thurow T., 2003).

Resilience management. This is a resistant and resilient state. Grazing management practice should include a forage and animal balance.

Community 2.1
Shortgrass Plant Community

Figure 16. MLRA 74 Shortgrass Plant Community.

This plant community developed as a result of many years of continuous overgrazing. Shortgrasses dominate the site and comprise 30 to 60 percent of annual production. The most abundant shortgrasses include blue grama, sand dropseed, hairy grama, red lovegrass, and mat sandbur. Remnant plants of sand bluestem, Indiangrass and switchgrass are very sparse and scattered. They persist in a low state of vigor, often being semi-dormant or dormant. Forb production is variable and may range from 25 to 50 percent. Perennial forbs include Carruth’s sagewort, white sagebrush, and Cuman ragweed. Annual forbs include prairie sunflower, camphorweed, sleepingplant, and annual ragweed. Trees and shrubs can add another 500 or more pounds. Where remnant tallgrasses persist, total rest from grazing or a prescribed grazing period will result in a dramatic increase in sand bluestem, with lesser increases in switchgrass and Indiangrass. Trees and shrubs can comprise up to 15 percent of this community. This annual yield is in current growth of tree leaves and twigs, which is not available to most grazers and browsers.

Resilience management. Recovery of the tallgrasses, midgrasses, and associated forb characteristics of the Reference Plant Community will require many years of careful management that includes prescribed grazing and extended periods of rest during the growing season. If remnant stands of the desired species are not present or located nearby as seed sources for reestablishment, interseeding measures may be necessary to create pioneer colonies for seed dispersal throughout the community. Prescribed burning can be a useful tool if used strategically to benefit the desired species, especially in the later stages of the recovery process.

State 3
Woody State

The Woody State is dominated by a shrub and/or tree plant community. The increase and spread of shrubs and trees results from an absence of fire. Woody plants can increase up to 34 percent from a lack of fire according to a study from 1937 to 1969, in contrast to a 1 percent increase on burned areas (Bragg and Hulbert, 1976). Periodic burning will hinder the establishment of most woody species and favor forbs and grasses. However, it should be pointed out that not all unburned areas have a woody plant invasion. Birds, small mammals, and livestock are instrumental in the distribution of seed and accelerating the spread of most trees and shrubs common to this site. The speed of encroachment varies considerably and can occur on both grazed and non-grazed pastures. Many species of wildlife, especially bobwhite quail, turkey, and white-tailed deer, benefit from the growth of trees and shrubs for both food and cover. When management for specific wildlife populations is desirable, these options should be considered in any brush management plan.

Characteristics and indicators. Hydrologic function is affected by the amount of vegetative cover. Canopy interception loss can vary from 25.4 percent to 36.7 percent (Thurow and Hester, 1997). A small rainfall event is usually retained in the foliage and does not reach the litter layer at the base of the tree. Only when canopy storage is reached and exceeded does precipitation fall to the soil surface. Interception losses associated with the accumulation of leaves, twigs, and branches at the bases of trees are considerably higher than losses associated with the canopy. The decomposed material retains approximately 40 percent of the water that is not retained in the canopy (Thurow and Hester, 1997). Soil properties affected include biological activity, infiltration rates, and soil fertility.

Resilience management. Special planning will be necessary to assure that sufficient amounts of fine fuel are available to carry fires with enough intensity to control woody species. In some locations the use of chemicals as a brush management tool may be desirable to initiate and accelerate this transition.

Community 3.1
Shrub and/or Tree Community

This plant community is dominated by shrubs consisting primarily of Chickasaw plum, skunkbush sumac, and smooth sumac. Roughleaf dogwood, common buttonbush, and golden currant occur in some locations. Trees, primarily eastern redcedar (Juniperus virginiana), eastern cottonwood, and sandbar willow, have invaded and become established in isolated areas. Shrubs and trees combined may comprise 40 to 60 percent of the total vegetation. The spread of shrubs and trees results from the longtime absence of fire. Periodic burning tends to hinder the establishment of most of these woody species and favor forb and grass species. Birds and small mammals are instrumental in the distribution of seed and accelerating the spread of shrub and tree species over the site. Encroachment may be on areas subjected to longtime continuous overgrazing. In these situations the associated grasses will usually consist of sand dropseed, sand lovegrass, purple lovegrass, and Scribner’s rosette grass. Shrubs also will invade and spread on areas where both grazing and fire have been excluded for many years. Heavy accumulations of plant mulch and litter retard herbage growth and provide a favorable habitat for seed germination and eventual establishment of many shrub species. The associated grasses in this situation are usually sand bluestem, little bluestem, Indiangrass, switchgrass, sedges, and Canada wildrye. Grass production is significantly reduced because of the shrub competition. Grass yields vary from 20 to 40 percent of the total vegetative production. Forbs generally produce 20 to 40 percent of the total. Major forbs include white sagebrush, Carruth’s sagewort, redroot buckwheat, Cuman ragweed, camphorweed, and tenpetal blazingstar. Most of this annual yield is in current growth of tree leaves and twigs, which is not available to most grazers and browsers. Many species of wildlife, especially bobwhite quail and whitetail deer, benefit from the growth of shrubs for both food and as cover. When higher wildlife populations are desired, this should be considered in any brush management plan.

Resilience management. The shrub and tree plant community is sustained by the absence of fire and brush control. Usually a prescribed burning program accompanied with prescribed grazing will gradually return the plant community to one dominated by grasses and forbs. Special planning will be necessary to assure that sufficient amounts of fine fuel are available to carry fires with enough intensity to control woody species. Careful planning and execution of prescribed burning can result in brush control, reverse the grazing patterns, enhance animal performance, and increase browse availability for deer. In some locations use of chemicals as a brush management tool will be necessary to initiate and accelerate this transition.

State 4
Tillage State

Extensive areas of the historic Sandy Floodplain plant communities were plowed and converted to production of cultivated crops by the early European settlers and subsequent generations. In addition to destroying the original plant community, repeated tillage commonly resulted in major changes in soil conditions. Reductions in organic matter, mineral levels, soil structure, oxygen levels, and water-holding capacity, along with increased runoff and erosion and shifts in the populations of soil-dwelling organisms, were common on these sites. The extent of these changes depended upon duration of cropping as well as crops grown and other management practices. The Tillage State consists of abandoned cropland that has been naturally revegetated (go-back) or planted or seeded to grassland. Many reseeded plant communities were planted with a local seeding mix under the Conservation Reserve Program (CRP) or were planted to a monoculture of sideoats grama. Go-back communities are difficult to define due to the variability of plant communities that can exist. Many of these communities are represented by the genus Aristida (threeawns).

Characteristics and indicators. This is an alternative state since the energy, hydrologic, and nutrient cycles are altered to that of the Reference State in its natural disturbance regime. Bulk density, aggregate stability, soil structure, and plant functional and structural groups are not fully restored to that of the Reference State. Mechanical tillage can destroy soil aggregation. Soil aggregates are an example of dynamic soil property change. Aggregate stability is critical for infiltration, root growth, and resistance to water and wind erosion (Brady and Weil, 2008).

Resilience management. The Tillage State is a result of a land use management decision.

Community 4.1
Reseed Plant Community

This plant community occurs on areas that were formerly farmed and reseeded with a mixture of native species common in the Reference Plant Community. Most seeding mixtures consisted of a blend of grasses that include sand bluestem, Indiangrass, switchgrass, little bluestem, sideoats grama, blue grama, and western wheatgrass. In some locations, seed of legumes and forbs such as prairie bundleflower and Maximilian sunflower were included in the mixture. Once these areas become fully established, production is comparable to that of the Reference Plant Community. Total annual production varies according to the species planted, established plants, and years of establishment. When reseeded areas and areas supporting native rangeland exist in the same pasture, they seldom are utilized at the same intensity because domestic livestock usually prefer plants growing on the native rangeland areas. When feasible, reseeded plant communities should be managed as separate pastures or units. Some seeded areas are invaded by trees and shrubs during the establishment period of the desired plants. These invader species commonly include elm, common hackberry, eastern redcedar, and eastern cottonwood. Occasional burning is effective in controlling establishment of these woody plants.

Resilience management. Following termination of cultivation, total annual production is quite variable and full recovery of the original plant community, including forbs and legumes, may take many decades. Additions of organic matter and minerals, deferred grazing, prescribed burning, and related management practices described for this ecological site can be beneficial to the rehabilitation.

Community 4.2
Go-back Plant Community

This plant community also occurs on areas that were formerly farmed. When tillage operations ceased, the areas were allowed to revegetate or “go back” naturally in contrast to artificial reseeding to a selected species or group of species. The go-back process is a slow, gradual transformation that requires many years and many successional changes or stages in the plant community. The speed and extent of revegetation depends on the size of the area, level of grazing management, and the proximity of the area to existing seed sources. In the initial stages of revegetation the site is usually dominated by annual forbs such as annual ragweed, slender snakecotton, Canadian horseweed, prairie sunflower, common sunflower, Mexican fireweed, camphorweed, and annual buckwheat. Gradually these are replaced by annual grasses including prairie threeawn, mat sandbur, tumblegrass, little barley, cheatgrass, and witchgrass. As plant succession progresses the plant community gradually becomes dominated by perennials. The major grasses include sand dropseed, composite dropseed, thin paspalum, purple lovegrass, red lovegrass, Scribner’s rosette grass, Carolina crabgrass, silver beardgrass, and tumble windmillgrass. Common forbs are Cuman ragweed, white sagebrush, Carruth’s sagewort, white heath aster, Missouri goldenrod, and sand milkweed. Combinations of these plants can form a stable community. In time with prescribed grazing management, other perennial grasses and forbs common in the Reference Plant Community will return to the site. Blue grama is a shortgrass that is very common to the native plant communities on this site. However, it seldom occurs in go-back communities, even after 40 to 50 years of plant succession. Some go-back areas are invaded by trees and shrubs. The more common include elm, common hackberry, eastern redcedar, eastern cottonwood, and roughleaf dogwood. Occasional burning is effective in controlling these woody plants. Total annual production varies by site. This depends upon seasonal precipitation and the stage of plant succession in the plant community.

Resilience management. Following termination of cultivation, total annual production is quite variable and full recovery of the original plant community, including forbs and legumes, may take many decades. Additions of organic matter and minerals, deferred grazing, prescribed burning, and related management practices described for this ecological site can be beneficial to the rehabilitation.

Transition 1 to 2
State 1 to 2

Long-term management (approximately 30 years) without a forage and animal balance and heavy, continuous grazing without adequate recovery periods between grazing events will convert the Grassland State to a Shortgrass State made up of blue grama and buffalograss sod. Drought in combination with this type of management will quicken the rate at which this transition occurs.

Constraints to recovery. The ecological processes affected are the hydrologic and nutrient cycles. There is an increase in evaporation rate, runoff, and in bulk density. There is a decrease in infiltration, a change in plant composition, and the functional and structural groups have changed dominance. These are all examples of the soil and vegetation properties that have compromised the resilience of the Grassland State and therefore transitioned to a Shortgrass State.

Transition 1 to 3
State 1 to 3

Changes from a Grassland State to a Woody State lead to changes in hydrologic function, forage production, dominant functional and structural groups, and wildlife habitat. Understory plants may be negatively affected by trees and shrubs by reductions in light, soil moisture, and soil nutrients. Increases in tree and shrub density and size have the effects of reducing understory plant cover and productivity, and desirable forage grasses often are most severely reduced (Eddleman, 1983). As vegetation cover changes from grasses to trees, a greater proportion of precipitation is lost throughout interception and evaporation; therefore, less precipitation is available for producing herbaceous forage or for deep drainage or runoff (Thurow and Hester, 1997).

Constraints to recovery. Recovery is possible through management.

Transition 1 to 4
State 1 to 4

This transition is triggered by a management action as opposed to a natural event. Tillage, or breaking the ground with machinery for crop production, will move the Grassland State to a Tillage State.

Constraints to recovery. The resilience of the Reference State has been compromised by the fracturing and blending of the native virgin sod. The energy, hydrologic, and nutrient cycles are altered and vary from that of the Grassland State.

Restoration pathway 3 to 1
State 3 to 1

Restoration efforts will be costly and labor-intensive, and can take many years, if not decades, to return to a Grassland State. Once canopy levels reach greater than 20 percent, estimated cost to remove trees is very expensive and includes high energy inputs. The technologies needed in order to go from an invaded Woody State to a Grassland State include but are not limited to: prescribed burning—the use of fire as a tool to achieve a management objective on a predetermined area under conditions where the intensity and extent of the fire are controlled; brush management—manipulating woody plant cover to obtain desired quantities and types of woody cover and/or to reduce competition with herbaceous understory vegetation, in accordance with overall resource management objectives; and prescribed grazing—the controlled harvest of vegetation with grazing or browsing animals managed with the intent to achieve a specified objective. In addition, to grazing at an intensity that will maintain enough cover to protect the soil and maintain or improve the quantity and quality of desirable vegetation. When a juniper tree is cut and removed, the soil structure and the associated high infiltration rate may be maintained for over a decade (Hester, 1996). This explains why the area near the dripline usually has substantially greater forage production for many years after the tree has been cut. It also explains why runoff will not necessarily dramatically increase once juniper is removed. Rather, the water continues to infiltrate at high rates into soils previously ameliorated by junipers, thereby increasing deep drainage potential. In rangeland, deep drainage amounts can be 16 percent of the total rainfall amount per year (Thurow and Hester, 1997).