State 1
Native tallgrass

This state comprises the communities within the range of natural variability under historic conditions and disturbance regimes. Patterns created by wildlife use and fire would have created a mosaic of communities across the landscape; however, warm-season tallgrasses are dominant, with a subdominant to minor contribution from native cool-season grasses, forbs, and shrubs.

Fire and bison herbivory were the dominant disturbance regimes that historically maintained the tallgrass dominance with a diverse forb component. Furthermore, bison grazing was closely linked to fire patterns as the animals preferred grazing burned areas offering lush regrowth devoid of decadence and of higher nutritive quality. Thus, historic plant communities were subjected to occasional burning and grazing, with substantial rest/recovery periods as the fuel load rebuilt to eventually start this process again. Fire return intervals of 3-4 years served to suppress woody species, particularly the various deciduous tree and shrub species prevalent in adjacent riparian corridors.
The degree to which observed conditions represent this state largely depends on how closely the management has mimicked these past disturbance effects.

Community 1.1
Big bluestem-Little bluestem (Andropogon gerardii-Schizachyrium scoparium)

Figure 8. Subirrigated 1.1

This is the interpretive plant community and can be found on areas that are properly managed with prescribed grazing that allows for adequate recovery periods following each grazing event.

The plant community consists of 80-95% grasses and grass-likes, 5-10% forbs and 0-5% shrubs. Dominant grasses include big bluestem, indiangrass, and switchgrass. Other grasses and grass-likes are little bluestem, sideoats grama, western wheatgrass, and sedges. Forb species are diverse and often include western ragweed and Missouri goldenrod.

This plant community is diverse, stable, and productive. Plant community dynamics, nutrient cycles, water cycles, and energy flow are functioning properly. Plant litter is properly distributed with negligible movement off-site and natural plant mortality is very low. This community is resistant to many disturbances except continuous, season-long heavy grazing, tillage, or non-use. Broadcast herbicide application will dramatically reduce forb diversity and abundance.

Total annual production, during an average year, ranges from 4300 to 5600 pounds per acre air-dry weight and will average 5100 pounds.

Community 1.2
Prairie cordgrass-Big bluestem (Spartina pectinata-Andropogon gerardii)

Figure 11. Subirrigated 1.2

Prairie cordgrass has replaced big bluestem as the dominant species. Other species, such as reed canarygrass, little bluestem, and western wheatgrass have also increased. While still within the range of natural variability, energy capture, nutrient cycling, and hydrology are not functioning at their full potential relative to the reference condition.

Pathway 1.1A
Community 1.1 to 1.2

Big bluestem-Little bluestem (Andropogon gerardii-Schizachyrium scoparium)

Prairie cordgrass-Big bluestem (Spartina pectinata-Andropogon gerardii)

Grazing management which does not provide adequate recovery periods will cause a shift from big bluestem and Indiangrass towards less palatable species, particularly prairie cordgrass.

Pathway 1.2A
Community 1.2 to 1.1

Prairie cordgrass-Big bluestem (Spartina pectinata-Andropogon gerardii)

Big bluestem-Little bluestem (Andropogon gerardii-Schizachyrium scoparium)

Management that provides adequate recovery periods and does not annually prevent tallgrass seedset or otherwise impair vigor will facilitate a return to community phase 1.1. In the case of dought, the return to more typical precipitation patterns will promote shift towards tallgrass species.

State 2
Native/invaded mix

This state can manifest three ways: 1) the appearance of introduced cool-season grasses, 2) the expansion of deciduous shrubs and/or trees, or 3) some combination of these. Kentucky bluegrass and smooth brome are the primary cool-season grass invaders in this region, commonly found in roadsides, disturbed areas, and pastures intentionally seeded for cool-season forage. Management practices and/or environmental conditions that are not favorable to native grass vigor may allow introduced grasses to invade the site thereby decreasing native diversity and abundance, particularly of forbs. While reed canarygrass is a native, it may act in much the same way as the introduced species.

In the absence of the historic fire regime, woody deciduous species may also expand to become an influential component of the community. The invasive component tends to have very high reslience, is extremely difficult to eradicate, and what might be considered a new "contemporary" range of natural variability is seen as competition between the native grasses and introduced/woody species for space and resources.

Community 2.1
Subdominant Smooth brome-Reed canarygrass (Bromus inermis-Phalaris arundinaceae)

While native warm-season grasses still dominate the site, introduced cool-season species have established a foothold in the system and can be found interspersed throughout the stand. The stand may still have a native tallgrass appearance overall, but brome and/or reed canarygrass can be easily found.

Deciduous shrub/tree species may also have begun to expand into areas where they did not persist historically, but the overall appearance can vary depending on the propagation method of a particular species.

Community 2.2
Codominant Smooth brome-Reed canarygrass (Bromus inermis-Phalaris arundinaceae)

Figure 14. Subirrigated 2.2

This community is comprised of a relatively even mix of native grasses and invasive species overall. This may manifest as a well-distributed interspersion of natives and invaders, as distinct patches wherein competitors dominate locally, or some combination. Forb diversity and abundance is further diminished.

Pathway 2.1A
Community 2.1 to 2.2

Management and/or environmental conditions have afforded a persisting competitive advantage to introduced cool-season grasses, and they begin to dominate the ecological dynamics of the site. The robust invasive component is able to quickly and effectively exploit opportunities to outcompete and displace natives. Repeated summer use of an area will place the bulk of stressor impacts on native plants, reducing native vigor and allowing invaders to thrive. Likewise, a climate pattern limiting natural moisture to the spring and fall months coincides with peak cool-season growth and may support a similar process.

Pathway 2.2A
Community 2.2 to 2.1

The native component remains in an abundance that can facilitate a return towards more historic conditions if management is modified to shift stressor impacts to the invasive species, and promote warm-season grass vigor. Environmental conditions and/or disturbance regimes that strongly favor warm-season grasses can also trend the site towards the reference.

State 3
Invasive dominant

Introduced cool-season invasion has progressed to the point that native species comprise a negligible portion of the community and the aggressively rhizomatous invasives preclude native germination and seedling survival. The native component may be completely absent, and the site resembles a seeded pasture.

Alternatively, the dominant invasives may be deciduous woody species. Woody competitiveness for sunlight, water, space, and other resources continues to increase as desirable herbaceous species are shaded out, crowded out, or otherwise suppressed.

Community 3.1
Smooth brome-Reed Canarygrass (Bromus inermis-Phalaris arundinaceae)

Figure 16. Subirrigated 3.1

This community is typically composed of smooth brome with bluegrass interspersed among the brome tillers. Warm-season natives, if present, are sparse yet often conspicuous due to pronounced differences in growth habits and metabolic pathways.

Community structure and function have been dramatically simplified relative to the reference condition, and very few biotic functional groups are represented in amounts that would influence ecological function. The invasive grass root skein provides good site stability; however, replacement of the deeper roots and complex bunchgrass canopy with the shallower roots and erect tiller canopy of the invaders results in reduced interception and infiltration rates.

State 4
Annual/pioneer

Nutrient cycling, hydrologic function, and/or soil stability have been severely altered, and possibly compromised. This is a highly variable state in which the specific plants observed will depend largely on the original community and the nature of the disturbance. This condition encompasses (but is not necessarily limited to) events such as severe fire impacts, heavy continuous grazing, heavy nutrient inputs, and abandoned cropland.

Community 4.1
Variable native and introduced

Figure 18. Subirrigated 4.1

This community is heavily dominated by annual plants that thrive in disturbed areas and often includes annual ragweed, hoary verbena, or amaranths. It is also particularly vulnerable to noxious weed invasion with the most common species being musk and Canada thistles. Leafy spurge becomes more common northward in the MLRA.

State 5
Woody dominant

Under historic disturbance regimes, frequent and uncontrolled fire and wildlife browsing served to keep woody species in check. However, in the absence of fire (either wild or prescribed), it's not uncommon for the woody trees and shrubs normally limited to riparian areas to expand into the floodplains, regardless of herbaceous community composition. Wildlife may introduce a seed source to areas not associated with a waterway, such as interdunal depressions.

Community 5.1
Native deciduous overstory

Figure 19. Subirrigated 5.1a

Figure 20. Subirrigated 5.1b early encroachment

Deciduous woody species have encroached and established, typically with species such as maples, cottonwood, boxelder, green ash, and swamp oak. Eastern redcedar may also establish, but is not usually as dominant as seen on drier sites.

Transition T1A
State 1 to 2

In the presence of introduced cool-season grasses, environmental conditions and/or management that reduces native vigor and stand resilience, and frees up resources (space, sunlight, nutrients, water) will allow for colonization of Kentucky bluegrass, smooth brome and/or reed canarygrass. Likewise, similar processes may also allow for woody species to expand, particularly willows and cottonwoods.

Transition T1B
State 1 to 4

There are many possible triggers for this transition that may occur as acute events (e.g. plowing) or cumulative impacts of chronic events (e.g. long-term undermanaged grazing.) The absence of deep-rooted perennial cover exposes the site to topsoil loss, open nutrient cycle, and free space which collectively allow for opportunistic annual species to dominate.

Transition T1C
State 1 to 5

All herbaceous communities are vulnerable to woody encroachment in the absence of fire and/or browsing nad hoof action impacts. This is particularly prominent in areas adjacent to riparian corridors which supply a constant seed source. As tree establishment progresses, the conditions grow increasingly favorable for woody deciduous germination and growth.

Restoration pathway R2A
State 2 to 1

Eradication of introduced cool-season grasses from this site will require long-term, targeted management efforts to create an adverse environment during the spring and late fall when bluegrass and brome are most actively growing, with favorable conditions during the summer to promote native warm-season species. Targeted practices such as prescribed burning, flash grazing, and herbicide are often employed at strategic times of the year to set back undesirable species. The combination of practices should strive to mimic the historic disturbance regimes to which the desirable native species are best adapted.

Transition T2A
State 2 to 3

If the conditions which initiated and fomented the colonization and expansion of cool-season invasion are not removed or mitigated, stand composition will continue to shift in this direction and begin to resemble a monoculture of brome and/or canarygrass. Due to the dense rhizomatous root mat of brome and bluegrass, native species suffer decreasing opportunities to contribute propagules, and individual plants lost are not replaced by desirable natives.

Transition T2B
State 2 to 4

There are many possible triggers for this transition that may occur as acute events (e.g. plowing) or cumulative impacts of chronic events (e.g. long-term undermanaged grazing.) The absence of deep-rooted perennial cover exposes the site to topsoil loss, open nutrient cycle, and free space which collectively allow for opportunistic annual species to dominate.

Transition T2C
State 2 to 5

All herbaceous communities are vulnerable to deciduous encroachment in the absence of fire and/or browsing impacts. This is particularly prominent in areas adjacent to riparian corridors which supply a constant seed source. As tree establishment progresses, the conditions grow increasingly favorable for woody deciduous germination and growth.

Transition T3A
State 3 to 2

Aggressive intervening actions will be required to simultaneously recolonize native grasses and suppress vigor in undesirable species. Restoration follows the same principles as the R2A pathway, but may also require native range seeding if the latent seedbank is inadequate.

Transition T3B
State 3 to 4

Nutrient cycling, hydrologic function, and/or soil stability have been severely altered, and possibly compromised. This is a highly variable state in which the specific plants observed will depend largely on the original community and the nature of the disturbance.

Context dependence.Site disturbance resulting in annual plant dominance

Transition T3A
State 3 to 5

All herbaceous communities are vulnerable to deciduous encroachment in the absence of fire and/or browsing impacts. This is particularly prominent in areas adjacent to riparian corridors which supply a constant seed source. As tree establishment progresses, the conditions grow increasingly favorable for woody deciduous germination and growth.

Restoration pathway R4A
State 4 to 1

Restoration strategies will depend on the nature of the disturbance and the viability of the seedbank. On pastures, changes to gazing management and favorable moisture conditions may produce a perennial community. However, in abandoned cropland range seeding will likely be necessary to recolonize desirable perennial species.

Restoration pathway R5A
State 5 to 1

The combination of tree size, reduced herbaceous understory, and more mesic conditions makes it increasingly difficult for natural disturbances to restore/maintain the historic tallgrass community, and mature woodlands can no longer be restored with fire. Intensive brush management will be required to mechanically remove the established overstory. Woody control and maintenance will be an ongoing process and may also require chemical methods if sprouting species are present.