State 1
Grassland State

The Grassland State defines the ecological potential and natural range of variability resulting from the natural disturbance regime of the Loamy 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 the result of periodic fire, drought, and grazing. These events are part of the natural disturbance regime and climatic process.

Characteristics and indicators. The Grassland State is defined by 3 plant communities. The Reference Plant Community consists of warm-season tall- and midgrasses, cool-season and sod-forming grasses, forbs, and shrubs. The Tallgrass/Midgrass 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.

Resilience management. Management strategies that will maintain this state include prescribed grazing and prescribed burning.

Community 1.1
Reference Plant Community

Figure 11. Reference Plant Community

The interpretive plant community for this site is the Reference Plant Community. This represents the original plant community that existed prior to European settlement. The Loamy Floodplain site is characterized as a grassland, essentially free of trees and large shrubs. It is dominated by tall, warm-season grasses including big bluestem, Indiangrass, switchgrass, eastern gamagrass, and prairie cordgrass. All of these grasses, and most of the dominant forbs, have extensive rhizomes. These underground stems often form a dense, intertwined mass throughout the upper four or five inches of the soil surface. Combined these tallgrasses will account for 75 to 85 percent of the total vegetation produced annually. Other prevalent grasses and grasslike plants are Canada wildrye, Virginia wildrye, western wheatgrass, little bluestem, marsh bristlegrass, composite dropseed, and several species of sedges and rushes. A number of forbs are found interspersed throughout the grass sward and include Maximilian sunflower, pitcher sage, blacksamson echinacea, wholeleaf rosinweed, and prairie bundleflower. Other important forbs are Canada goldenrod, white heath aster, tall blazingstar, white sagebrush, American licorice, roundhead lespedeza, and white prairie clover. Desert false indigo and common buttonbush are shrubs that commonly occur on this site, especially along upland drainageways. Eastern cottonwood and black willow are the major trees in the broad bottomlands and are generally located along streambanks. Although the major portion of the site is dominated by herbaceous plants, isolated areas support groves of trees. Protected by streams and rivers, some areas historically escaped the intensity of wildfires. These areas often developed a savannah plant community with an overstory of hardwood trees that may have included eastern cottonwood, black willow, American elm, green ash, bur oak, and black walnut. Eastern cottonwood was usually the dominant tree and often formed large, single-species groves. The understory in these situations usually supported shade-tolerant cool-season plants such as Canada wildrye, Virginia wildrye, Texas bluegrass, and sedges.

Resilience management. This is a stable, resilient, and very productive plant community when adequately managed. A prescribed grazing program that incorporates periods of deferment during the growing season perpetuates the more palatable tallgrasses and forb species. In a number of locations this plant community is managed exclusively for hay production. Mowing tends to reduce the amount of switchgrass and prairie cordgrass plants and favor big bluestem, Indiangrass, and eastern gamagrass. Growth of warm-season grasses on this site typically begins during the period of April 25 to May 10 and continues until late September. As a general rule, 75 percent of total production is completed by mid-July. This varies only slightly from year to year depending upon temperature and precipitation patterns. There are exceptions as big bluestem, eastern gamagrass, and prairie cordgrass will occasionally initiate spring growth as early as April 1 following mild winter temperatures. Also, it is not unusual for other warm-season grasses such as Indiangrass and little bluestem to have some new leaf growth arising from basal buds in late October following moderate fall temperatures. Cool-season grasses, sedges, and rushes generally have two primary growth periods, one in the fall (September and October) and again in the spring (April, May, and June). Some growth may occur in winter months during periods of unseasonably warm temperatures (Indian summers).

Community 1.2
Tallgrass/Midgrass Community

The composition of this plant community is dominated by a mixture of tall- and midgrasses. Compared with the Reference Plant Community, the more palatable tallgrasses and forbs have decreased and the midgrasses subsequently increased. Although reduced by overgrazing, tallgrasses such as big bluestem, Indiangrass, and switchgrass remain dominant. The proportion of midgrasses, sedges, and rushes in the overall production of the site has increased. These include composite dropseed, little bluestem, western wheatgrass, marsh bristlegrass, and sideoats grama. Other secondary grasses that have increased are Texas bluegrass, Kentucky bluegrass, vine mesquite, and sedges. Combined these secondary plants now comprise 30 to 40 percent of the total herbage produced annually. Forbs such as Maximilian sunflower, wholeleaf rosinweed, and prairie bundleflower have decreased and largely been replaced by white heath aster, white sagebrush, Cuman ragweed, interior ironweed, and Canada goldenrod. Forbs produce 8 to 10 percent of the total herbage. In some locations the site supports an increasing amount of shrubs and trees. The most abundant shrubs are desert false indigo, common buttonbush, roughleaf dogwood, Great Plains false willow, and coralberry. Eastern cottonwood, black willow, and American elm are the major trees found on the site. Shrubs and trees usually may comprise 5 to 10 percent of the total production.

Resilience management. Periods of deferment from grazing are essential to maintaining the production of some of the major grasses found in this plant community. Eastern gamagrass and big bluestem are especially preferred and selectively grazed by cattle. When the site is grazed continuously throughout the growing season, these grasses are usually overgrazed and thus maintained in a lower state of plant vigor. When continued for many years, overgrazing results in a gradual reduction in the abundance of these grasses. However, prescribed grazing that incorporates periods of deferment during the growing season will improve the vigor and gradual recovery of the more palatable tallgrasses and forbs.

Community 1.3
Midgrass/Shortgrass Community

Figure 13. Midgrass/Shortgrass Plant Community

This plant community results from many years of overgrazing. The amount of tallgrasses has decreased significantly and the site is dominated by mid- and shortgrasses. Major midgrasses are composite dropseed, sand dropseed, silver beardgrass, purpletop tridens, sideoats grama, western wheatgrass, and marsh bristlegrass. Shortgrasses include Kentucky bluegrass, Texas bluegrass, Texas dropseed, buffalograss, and blue grama. Major forbs on the site are Cuman ragweed, Canada goldenrod, Missouri goldenrod, white sagebrush, Carruth’s sagewort, white heath aster, annual marshelder, and annual ragweed. In some locations the site supports an increasing amount of shrubs and trees. The most common shrubs along upland drainways are desert false indigo, common buttonbush, roughleaf dogwood, and coralberry. Eastern cottonwood, black willow, peachleaf willow, American elm, eastern redcedar, (Juniperus virginiana) and osage orange (Maclura pomifera) are the major trees found on the site. Shrubs and trees usually will not comprise over ten percent of the total production.

Resilience management. Remnant plants of big bluestem, Indiangrass, switchgrass, prairie cordgrass, eastern gamagrass, and Maximilian sunflower are often found scattered throughout the site. These plants are usually grazed repeatedly and maintained in a low state of vigor. These remnants respond favorably to periods of rest from grazing during the growing season and often regain vigor in a few years.

Pathway 1.1 to 1.2
Community 1.1 to 1.2

The following describes the mechanisms of change from Plant Community 1.1 to Plant Community 1.2. 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 ten years will shift functional and structural plant group dominance towards Plant Community 1.2.

Pathway 1.2 to 1.1
Community 1.2 to 1.1

The following describes the mechanisms of change from Plant Community 1.2 to Plant Community 1.1: management (10-15 years) that includes adequate rest and recovery of the key forage species (sand bluestem, switchgrass, and Indiangrass) within the Reference Plant Community. If woody species are present, prescription fires every 6-8 years will be necessary for their removal and/or maintenance.

Context dependence. The time that is takes for a community shift is estimated to take 10-15 years. This will vary depending upon many variables.

Pathway 1.2 to 1.3
Community 1.2 to 1.3

The following describes the mechanisms of change from Plant Community 1.2 to Plant Community 1.3: long-term (>10 years) management that includes continuous, heavy use of the native vegetation; management that is void of a forage and animal balance; and inadequate rest and recovery of native grasses during the growing season.

Pathway 1.3 to 1.2
Community 1.3 to 1.2

The following describes the mechanisms of change from Plant Community 1.3 to Plant Community 1.2. Management (approximately 10 years) that includes adequate rest and recovery of the key forage species in the Midgrass Community 1.2 (big bluestem, Indiangrass, switchgrass, little bluestem, composite dropseed, western wheatgrass, and sedges). Implement prescription fires at a frequency of 6-8 years. Depending upon the level of woody vegetation encroachment, the fire return interval might require an adjustment to two consecutive years of prescribed fires.

Context dependence. Timing of this pathway is estimated to take 10 years. This temporal scale is an approximate due to many variables.

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. Species diversity has been reduced further. Water infiltration is reduced and runoff is increased due to the sod nature of the blue grama and buffalograss. Specific dynamic soil property changes between the Grassland State and the Sod-bound State have been documented. As plant community cover decreases from bunchgrasses to more of the sodgrasses, infiltration and interception decrease and surface runoff increases (Thurow T., 2003).

Resilience management. This is a stable state and recovery to the Grassland State has not been recorded.

Community 2.1
Shortgrass Community

This plant community is dominated by a mixture of shortgrasses and midgrasses. It occurs following many years of continuous overgrazing. Usually pastures are small and associated with farming enterprises. In the past they were often used as holding areas in anticipation of seasonal wheat pasture or other cropland forages. Dominant grasses are blue grama, buffalograss, Carolina crabgrass, thin paspalum, sideoats grama, composite dropseed, silver beardgrass, western wheatgrass, and vine mesquite. Annual grasses including sixweeks fescue, Japanese brome (Bromus japonicus), cheatgrass (Bromus tectorum), little barley (Hordeum pusillum), tumblegrass, prairie threeawn, purple threeawn, and fall panicgrass are common during seasons of normal or above-normal precipitation. Major forbs are Cuman ragweed, Missouri goldenrod, crested prickly poppy, hoary verbena, annual marshelder, prairie broomweed, interior ironweed, white sagebrush, and wavyleaf thistle. The most common shrub in the Shortgrass Community is coralberry. Areas where sediment has been deposited during recent flood events will generally support a large number of annual forbs. These may include snow on the mountain (Euphorbia marginata), cocklebur (Xanthium strumarium), annual ragweed, giant ragweed, common sunflower (Helianthus annuus), marijuana (Cannabis sativa), and poison hemlock (Conium maculatum).

Resilience management. Although productivity is significantly reduced when compared to the Reference Plant Community, this plant community can be managed as a stable community. Restoration to a Midgrass/Shortgrass Plant Community within the Grassland State is not documented nor typical and known to occur in Major Land Resource Area (MLRA) 79.

State 3
Woody State

This 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 in 1937 to 1969, in contrast to a 1 percent increase on burned areas (Bragg and Hulbert, 1976). Periodic burning tends to hinder the establishment of most woody species and favors forbs and grasses. However, it should be pointed out that not all unburned areas have a woody plant invasion.

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. 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. 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.

Resilience management. Without fire, or some other means of woody removal, this state will remain very stable.

Community 3.1
Shrub/Tree Community

Trees and shrubs dominate this plant community and may produce 40 to 50 percent of the total vegetation. Major trees include eastern cottonwood, black willow, peachleaf willow, American elm, Siberian elm (Ulmus pumila), common hackberry, osage orange, eastern redcedar, and Russian olive (Elaeagnus angustifolia). More abundant shrubs are roughleaf dogwood, coralberry, smooth sumac, desert false indigo, and common buttonbush. The spread of these woody plants results in the absence of fire and may occur on the site regardless of grazing management. However, not all unburned areas have a woody plant problem. Encroachment may occur on areas that have been overgrazed for years as well as on areas where both grazing and fire have been excluded. The speed and method of encroachment varies considerably but, under favorable conditions, can happen within a 20 to 30 year period. Cottonwood and willow produce an abundance of seed that is distributed by wind over long distances. Russian olive, common hackberry, and eastern redcedar are generally spread by birds. Periodic burning tends to hinder the establishment of most of these woody species and favor forbs and grasses. Where woody plants have invaded overgrazed areas, understory vegetation is generally dominated by plants such as Texas bluegrass, Kentucky bluegrass, composite dropseed, purpletop tridens, marsh bristlegrass, sedges, white sagebrush, interior ironweed, and white heath aster. Where woody plants have encroached onto areas essentially ungrazed for many years, the understory consists largely of big bluestem, Indiangrass, little bluestem, Virginia wildrye, Canada wildrye, sedges, prairie bundleflower, Canada goldenrod, and Maximilian sunflower.

Resilience management. Because of tree and shrub competition for light and moisture, herbage production is significantly reduced. Grass yields vary from 30 to 40 percent of the total vegetative production, and forbs generally produce only 5 to 10 percent of the total. Usually a prescribed burning program, accompanied by a prescribed grazing plan, will 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. Use of additional brush management tools such as chemicals or mechanical methods may be necessary to initiate and accelerate this transition in some locations.

State 4
Tillage State

The Tillage State consists of abandoned cropland that has been naturally revegetated (go-back) or planted/seeded to grassland.

Characteristics and indicators. 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).

Resilience management. 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).

Community 4.1
Reseed Community

This plant community occurs on areas that were formerly farmed. When farming operations ended, the area was seeded and established to a mixture of plants. These were usually native species commonly found in the Reference Plant Community. Most seeding mixtures consisted of a blend of grasses that included big bluestem, Indiangrass, switchgrass, and little bluestem. In some locations seed of additional plants such as eastern gamagrass, prairie bundleflower, and Maximilian sunflower were included in the mixture.

Resilience management. 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 on the native rangeland areas, reseeded plant communities should be managed as separate pastures or units when feasible. Reseeded areas are also generally productive when managed for hay production. Some seeded areas are invaded by trees and shrubs during the establishment period of the desired plants. These invader species commonly include Siberian elm, common hackberry , eastern redcedar, eastern cottonwood, black willow, roughleaf dogwood, and Great Plains false willow. Occasional burning is effective in controlling their establishment.

Community 4.2
Go-back Community

This plant community occurs on formerly farmed areas. When tillage operations were discontinued, the areas were allowed to revegetate or “go-back” naturally in contrast to artificial reseeding with a selected species or group of species. This is a slow, gradual process that entails many years and many successional changes or stages in the plant community.

Resilience management. The speed and extent of revegetation depends upon 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, Canadian horseweed (Conyza canadensis), common sunflower, annual marshelder, and golden tickseed. Gradually these are replaced by annual grasses including prairie threeawn, prairie cupgrass (Eriochloa contracta), little barley, cheatgrass, and bearded sprangletop (Leptochloa fusca ssp. fascecularis). Usually plant succession will progress until the plant community is dominated by perennial grasses and grasslike plants including composite dropseed, foxtail barley, marsh bristlegrass, silver beardgrass, buffalograss, Torrey’s rush, and sand dropseed. These plants can form a stable community. In time and with prescribed grazing management, other perennial grasses and forbs common in the Reference Plant Community return to the site. Some go-back areas are invaded by trees and shrubs such as Siberian elm, common hackberry, eastern redcedar, eastern cottonwood, black willow, roughleaf dogwood, and Great Plains false willow. Occasional burning will effectively control these woody plants.

Transition 1.3 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. Ecological processes affected are the hydrologic and nutrient cycles.

Constraints to recovery. 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.

Context dependence. It is estimated this transition can occur in a 30 year time frame. The variability of the situation will dictate the temporal scale among the many variables involved.

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 through interception and evaporation; therefore, less precipitation is available for producing herbaceous forage, or for deep drainage or runoff (Thurow and Hester, 1997). Tree and shrub establishment increases while fine fuel loads decrease. As trees and shrubs increase at levels of greater than 20 percent canopy cover, the processes and functions that allow the Woody State to become resilient are active and dominant over the processes and systems inherent to the Grassland State. Due to a lack of fine fuel loads, using prescribed fire as a standalone management tool is unsuccessful to eradicate the trees and shrubs.

Constraints to recovery. Canopy percentages above 45 percent need further investigation in recovery efforts to a Grassland State.

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, 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 necessary 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, manage 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 equal 16 percent of the total rainfall amount per year (Thurow and Hester, 1997).

Context dependence. Restoration is dependent upon the canopy percentage.