State 1
Grassland State

The Grassland State defines the ecological potential and natural range of variability resulting from the natural disturbance regime of the Clay Hills 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 10. MLRA 74 Loamy Floodplain 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 big bluestem, Indiangrass, switchgrass, eastern gamagrass, and prairie cordgrass. All of these grasses and most of the dominant forbs are strongly rhizomatous. These underground stems often form a dense, intertwined mass throughout the upper four or five inches of the soil profile. Combined these tall grasses will account for 75 to 85 percent of the total vegetation produced annually. Little bluestem is the major midgrass. Other prevalent midgrasses and grasslike plants are Canada wildrye, Virginia wildrye, western wheatgrass, 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, compassplant, wholeleaf rosinweed, and prairie bundleflower. Other important forbs are Canada goldenrod, white heath aster, tall blazing star, white sagebrush, American licorice, roundhead lespedeza, and white prairie clover.

Desert false indigo and common buttonbush are shrubs that commonly occur, especially along upland drainageways. Eastern cottonwood and black willow are the major trees in the broad floodplains and are generally located along streambanks. Although the major portion of the site was dominated by herbaceous plants, isolated areas supported groves of trees. The protection by streams and rivers allowed some of these tree areas to escape the intensity of wildfires. These areas often developed a savannah plant community with an overstory of hardwood trees that may include eastern cottonwood, black willow, bur oak, American elm, green ash, and black walnut. Eastern cottonwood is the dominant tree and often forms 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.

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 to favor big bluestem, Indiangrass, and eastern gamagrass.

Growth of warm-season grasses on this site typically begins during the period of May 1 to May 15 and continues until mid 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 and eastern gamagrass will occasionally initiate spring growth in early April 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 spring (March through early June) and again in the fall (September and October). Some growth may occur in winter months during periods of unseasonably mild temperatures.

Resilience management. This is a stable plant community when grazing and fire are adequately managed. A prescribed grazing program that incorporates periods of deferment during the growing season benefits the tallgrasses and even the more palatable forb species. Concentrated livestock use, such as winter feeding areas, can cause compaction of the wet, clay soils and stress the dominant tallgrasses.

Community 1.2
Tallgrass-Midgrass Plant Community

Figure 13. MLRA 74 Tallgrass-Midgrass Plant Community.

This plant community developed as a result of many years of repeated, heavy grazing. The composition of this plant community is dominated by a mixture of tallgrasses and midgrasses. Compared with the Reference Plant Community, there has been a decrease in the more palatable tallgrasses and forbs and a subsequent increase in midgrasses.

Although reduced by overgrazing tall grasses, 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 bristle grass, and sideoats grama. Other secondary grasses that have increased are Texas bluegrass, Kentucky bluegrass, vine mesquite, smooth bromegrass 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, compassplant, and prairie bundleflower have decreased and largely been replaced by white heath aster, white sagebrush, Cuman ragweed, Baldwin's 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 false indigo bush, common buttonbush, rough leaf dogwood, smooth sumac, Great Plains false willow (Baccaris salicina), 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 in 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 health and 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 Plant Community

Figure 14. MLRA 74 Midgrass-Shortgrass Plant Community.

This plant community developed as a result of long-term, heavy, continuous overgrazing. The amount of tallgrasses has decreased significantly and the site is dominated by midgrasses and shortgrasses. Major midgrasses are composite dropseed, sand dropseed, silver beardgrass, purpletop tridens, sideoats grama, western wheatgrass, and marsh bristlegrass. Two introduced cool-season grasses, smooth bromegrass (Bromus inermis) and tall fescue (Lolium arundenaceum), commonly invade this plant community. 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 drainageways are desert false indigo, common buttonbush, rough leaf 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, prairie cordgrass, eastern gamagrass, and switchgrass are only found in protected locations. These plants are usually grazed repeatedly and remain in a low state of health and vigor. Of these remnants, big bluestem is generally the most abundant. It has rhizomes that can persist for many years in a weakened condition. When in this state of vigor, 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 remnant plants respond favorably to periods of rest from grazing and may regain vigor in two to three years. However, their numbers or percentage of composition is greatly reduced that it may take many years to regain a large role in the plant community. Prescribed grazing with adequate rest and recovery periods during the growing season will shift this plant community to include more productive tallgrasses. With continued management the taller grasses will gradually increase in vigor and abundance to dominate the landscape.

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 ten years will shift functional and structural plant group dominance towards 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 or maintenance.

Pathway 1.2 to 1.3
Community 1.2 to 1.3

Tallgrass-Midgrass Plant Community

Midgrass-Shortgrass 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 towards a Midgrass-Shortgrass Plant Community.

Pathway 1.3 to 1.2
Community 1.3 to 1.2

Midgrass-Shortgrass 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 or 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 has 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-Midgrass Plant Community

This plant community presents a distinctive shortgrass aspect on the landscape. It is dominated by a mixture of shortgrasses and midgrasses. It occurs following many years of heavy, 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 arvensis), 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, and white sagebrush. A number of thistles, both native and introduced, are common in this plant community and may include wavyleaf thistle, yellowspine thistle, tall thistle, Canada thistle (Cirsium arvense), bull thistle (Cirsium vulgare), and nodding pumeless thistle (Carduus nutans). The most common shrub 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, common sunflower (Helianthus annuus), and poison hemlock (Conium maculatum).

Although productivity is significantly reduced, when compared to the Reference Plant Community, this plant community can be managed as a stable community. Currently, restoration to the Grassland State has not been observed.

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

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 in a period as short as 20 to 30 years. Cottonwood and willow produce an abundance of seed that is distributed by the wind for long distances. Russian olive, common hackberry and eastern redcedar are spread by birds. Periodic burning tends to hinder the establishment of most of these woody species and favor forb and grass species.

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, smooth bromegrass, 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.

Herbage production is significantly reduced because of the tree and shrub competition for light and moisture. Grass yields vary from 30 to 40 percent of the total vegetative production. Forbs generally produce 5 to 10 percent of the total.

Usually a prescribed burning program, accompanied with a plan of prescribed grazing, 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 having the intensity to control the 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.

Resilience management. The shrub and tree plant community is sustained by the absence of fire and brush control.

State 4
Tillage State

Extensive areas of the historic Loamy 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/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/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. The tillage state 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 the 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 earlier 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, smooth bromegrass, 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 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 on 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 earlier 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, 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).