Sodic Subirrigated
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
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Transition T1A
Introduction of exotic cool-season grasses
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Transition T1B
Introduction of exotic cool-season grasses
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Transition T2A
Heavy grazing or long-term non-use or very light grazing and no fire.
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Restoration pathway R4A
Long-term prescribed grazing and prescribed burning.
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Restoration pathway R5A
Successful range planting
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Restoration pathway R5B
Successful/unsuccessful range planting, secondary succession.
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Restoration pathway R5C
Unsuccessful range planting.
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Restoration pathway T6A
Cessation of annual cropping
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No transition or restoration pathway between the selected states has been described
Target ecosystem state
Select a state
Description
This plant community represents the natural range of variability that dominated the dynamics of this ecological site prior to European influence. Thickness of the A horizon (depth to claypan) creates a mosaic of tall-warm season grasses (State 1.1 Thick-Reference State) with short cool-season grass and bare ground (State 1.2 Thin-Reference State). Dynamics of the state were largely determined by variations in sodicity, climate and weather (e.g., precipitation/freeze thaw cycles), as well as that of fire (e.g., timing, frequency) and grazing by native herbivores (e.g., frequency, intensity, selectivity). Due to those variations, the Mosaic Reference is thought to have supported two Reference States, Thick-Reference State and Thin-Reference State, based on thickness of the A horizon found in a mosaic pattern across the site (see Figure 12).
State 1.1 Thick-Reference State
This state is represented by a thick A horizon (depth to claypan ranging from 3 to 13 inches) dominated by tall warm-season grasses and a diversity of forbs. Salinity ranges from an E.C. of 0 to 8 dS/m. E.C. ratings below 6 have little effect on plant growth or diversity. Higher E.C. levels may begin to effect plant diversity and growth. However, the sodium absorption ratio (SAR) can range from 3 to 20, negatively impacting plant growth once SARs reach 10 or greater.
State 1.2 Thin-Reference State
This state is represented by a thin A horizon with depth to claypan of less than 3 inches. The shallow depth to claypan limits plant diversity favoring plants that can tolerate a restrictive root layer (claypan). The shallow depth to claypan also correlates to a high sodium absorption ratio (SAR of 20 to 40) and a strongly to very strongly alkaline soil reaction class (pH 8.5 to 9.6), severely impacting plant growth. The plant community is dominated by short-statured grasses, such as foxtail barley and inland saltgrass, with a low diversity of forbs.
State 1.1 with the community phases of 1.11 and 1.12 on the custom model are shown on standard diagram as by community phases 1.1 (1.11) and 1.2 (1.12).
State 1.2 with the community phases of 1.21 and 1.22 on the custom model are shown on standard diagram as by community phases 1.3 (1.21) and 1.4 (1.22).
Characteristics and indicators
Because of changes in disturbances and other environmental factors (particularly the widespread occurrence of exotic species), the Reference State is considered to no longer exist.
Resilience management
If intact, the reference state should probably be managed with current disturbance regimes which has permitted the site to remain in reference condition as well as maintaining the quality and integrity of associated ecological sites. Maintenance of the reference condition is contingent upon a monitoring protocol to guide management.
Submodel
State 2
Thick-Native/Invaded State
Description
This state is similar to 1.1 Thick-Reference State but has now been colonized by the exotic cool-season grasses (e.g., Kentucky bluegrass, smooth brome, quackgrass, or perhaps redtop) which are now present in small amounts. Although the state is still dominated by native grasses, an increase in the exotic cool-season grasses can be expected.
The exotic cool-season grasses can be quite invasive on the site and are particularly well adapted to heavy grazing. They also often form monotypic stands. As these exotic cool-season grasses increase, both forage quantity and quality become increasingly restricted to late spring and early summer due to the monotypic nature of the stand, even though annual production may increase. Native forbs generally decrease in production, abundance, diversity, and richness compared to that of State 1.1: Thick-Reference State.
These exotic cool-season grasses have been particularly and consistently invasive under extended periods of no use and no fire. To slow or limit the invasion of these exotic cool-season grasses, it is imperative that managerial techniques (e.g., prescribed grazing, prescribed burning) be carefully constructed, monitored, and evaluated with respect to that objective. If management does not include measures to control or reduce these exotic cool-season grasses, the transition to State 4: Thick-Invaded State should be expected. Annual production of this state can be quite variable, in large part due to the amount of exotic cool-season grasses.
Characteristics and indicators
The presence of trace amounts of exotic cool-season grasses indicates a transition from State 1 to State 2. The presence of exotic biennial or perennial leguminous forbs (i.e., sweet clover, black medic) may not, on their own, indicate a transition from State 1 to State 2 but may facilitate that transition.
Resilience management
To slow or limit the invasion of these exotic grasses, it is imperative that managerial techniques (e.g., prescribed grazing, prescribed burning) be carefully constructed, monitored, and evaluated with respect to that objective.
Grazing management should be applied that enhances the competitive advantage of native grass and forb species. This may include: (1) early spring grazing when exotic cool-season grasses are actively growing and native cool-season grasses are dormant; (2) applying proper deferment periods allowing native grasses to recover and maintain or improve vigor; (3) adjusting overall grazing intensity to reduce excessive plant litter (above that needed for rangeland health indicator #14 – see Rangeland Health Reference Worksheet); (4) incorporating early heavy spring utilization which focuses grazing pressure on exotic cool-season grasses and reduces plant litter provided that livestock are moved when grazing selection shifts from exotic cool-season grasses to native grasses.
Prescribed burning should be applied in a manner that maintains or enhances the competitive advantage of native grass and forb species. Prescribed burns should be applied as needed to adequately reduce/remove excessive plant litter and maintain the competitive advantage for native species. Timing of prescribed burns (spring vs. summer vs. fall) should be adjusted to account for differences in annual growing conditions and applied during windows of opportunity to best shift the competitive advantage to the native species.
Submodel
Description
This state is similar to State 1.2: Thin-Reference State but has now been invaded by exotic cool-season grasses (e.g., Kentucky bluegrass, smooth brome, quackgrass). Other exotic plants (e.g., leafy spurge) may are also known to invade the site. But due to soil chemistry (high sodicity and pH) and soil structure (claypan at or near the surface), exotic species may remain as a minor component,
Characteristics and indicators
The presence of trace amounts of exotic cool-season grasses indicates a transition from State 1 to State 2. The presence of exotic biennial or perennial leguminous forbs (i.e., sweet clover, black medic) may not, on their own, indicate a transition from State 1 to State 2 but may facilitate that transition.
Resilience management
To slow or limit the invasion of these exotic grasses, it is imperative that managerial techniques (e.g., prescribed grazing, prescribed burning) be carefully constructed, monitored, and evaluated with respect to that objective. Grazing management should be applied that enhances the competitive advantage of native grass and forb species. This may include: (1) early spring grazing when exotic cool-season grasses are actively growing and native cool-season grasses are dormant; (2) applying proper deferment periods allowing native grasses to recover and maintain or improve vigor; (3) adjusting overall grazing intensity to reduce excessive plant litter (above that needed for rangeland health indicator #14 – see Rangeland Health Reference Worksheet); (4) incorporating early heavy spring utilization which focuses grazing pressure on exotic cool-season grasses and reduces plant litter provided that livestock are moved when grazing selection shifts from exotic cool-season grasses to native grasses.
Prescribed burning should be applied in a manner that maintains or enhances the competitive advantage of native grass and forb species. Prescribed burns should be applied as needed to adequately reduce/remove excessive plant litter and maintain the competitive advantage for native species. Timing of prescribed burns (spring vs. summer vs. fall) should be adjusted to account for differences in annual growing conditions and applied during windows of opportunity to best shift the competitive advantage to the native species.
Submodel
State 4
Thick-Invaded State
Description
This state is the result of invasion and dominance by the exotic cool-season grasses (e.g., Kentucky bluegrass, smooth brome, quackgrass) on sites with thick surface. They often form monotypic stands. As these exotic cool-season grasses increase, both forage quantity and quality become increasingly restricted to late spring and early summer due to the monotypic nature of the stand, even though annual production may increase.
These exotic cool-season grasses can invade the site and are particularly well adapted to heavy grazing. Native forbs generally decrease in production, abundance, diversity, and richness compared to that of State 1: Reference State. Common forbs often include black medic, red clover, and sweetclover. Shrubs, such as prairie sagewort and wild rose, show marked increases. Leafy spurge may also invade the site. Once the state is well established, prescribed burning and grazing techniques have been largely ineffective in suppressing or eliminating these species, even though some short-term reductions may appear successful.
Annual production of this state may vary widely, in part due to variations in the extent of invasion by exotic cool-season grasses.
Characteristics and indicators
This site is characterized by exotic cool-season grasses constituting greater than 30 percent of the annual production and native grasses constituting less than 40 percent of the annual production.
Resilience management
Light or moderately stocked continuous, season-long grazing or a prescribed grazing system which incorporates adequate deferment periods between grazing events and proper stocking rate levels will maintain this State. Application of herbaceous weed treatment, occasional prescribed burning and/or brush management may be needed to manage noxious weeds and increasing shrub (e.g., western snowberry) populations.
Submodel
Description
This state is highly variable depending on the level and duration of disturbance related to the T6A transitional pathway. Annual tillage, in most cases, does not redistribute sodium between the Thick-Reference and Thin- Reference State. The main factor determining plant growth and restoration is the depth to the restrictive root zone (claypan) and soil chemistry (high SARs and alkalinity). In this MLRA, the most probable origin of this state is plant succession following cropland abandonment. This plant community will initially include a variety of annual forbs and grasses, some of which may be noxious weeds and need control. Over time, the exotic cool-season grasses (e.g., Kentucky bluegrass, smooth brome, quackgrass) will likely predominate. Common forb and shrub associates may include black medic, sweetclover, red clover, curly dock, lambsquarters, plantain, Canada thistle, and wild rose.
Resilience management
Continued tillage will maintain the state. Control of noxious weeds will be required.
Submodel
Mechanism
This is the transition from the 1.0 Mosaic State, 1.1 Thick-Reference State to the State 2: Thick-Native/Invaded State resulting from the introduction and establishment of exotic cool-season grasses (e.g., Kentucky bluegrass, smooth brome, quackgrass). Other exotic plants (e.g., leafy spurge) may are also known to invade the site. This transition was inevitable and corresponded to a decline in native warm-season and cool-season grasses. It may have been exacerbated by chronic season-long or heavy late season grazing or long-term annual haying. Complete rest from grazing and suppression of fire could also have hastened the transition. The threshold between states was crossed when Kentucky bluegrass, smooth brome, quackgrass, or other exotic plants became established on the site.
Constraints to recovery
Current knowledge and technology will not facilitate a successful restoration to Reference State.
Mechanism
This is the transition from the 1.0 Mosaic State, 1. 2 Thin-Reference State to the State 3: Thin-Native/Invaded State resulting from the introduction and establishment of exotic cool-season grasses (e.g., Kentucky bluegrass, smooth brome, quackgrass). Other exotic plants (e.g., leafy spurge) may are also known to invade the site. This transition was inevitable, but due to the increased sodicity and shallow claypan, exotic cool- season grasses may not increase beyond a minor component.
Constraints to recovery
Current knowledge and technology will not facilitate a successful restoration to Reference State.
Mechanism
This is the transition from the State 2: Thick-Native/Invaded State to State 4: Thick-Invaded State due to heavy grazing or long-term non-use or very light grazing and no fire. Exotic cool-season grasses (e.g., quackgrass, Kentucky bluegrass, smooth brome) become the dominant graminoids. Soil conditions related to thick surface (depth to claypan) and soil chemistry of the surface layer (low sodicity, salinity, and pH) allow these exotic cool-season grasses to exceed the threshold. This transition may occur under other managerial conditions, including annual haying. Studies indicate that a threshold may exist in this transition when both the exotic cool-season grasses exceed 30% of the plant community and native grasses represent less than 40% of the plant community composition.
Constraints to recovery
Variations in growing conditions (e.g., cool, wet spring) will influence effects of various management activities on exotic cool-season grass populations.
Mechanism
This restoration pathway from State 4: Thick-Invaded State to Thick-Native/Invaded State 2: Thick Native/Invaded State may be accomplished with the implementation of long-term prescribed grazing and prescribed burning, assuming there is an adequate component of native grasses to respond to the treatments.
Both prescribed grazing and prescribed burning are likely necessary to successfully initiate this restoration pathway, the success of which depends upon the presence of a remnant population of native grasses in Community Phase 4.1. That remnant population, however, may not be readily apparent without close inspection. The application of several prescribed burns may be needed at relatively short intervals in the early phases of this restoration process, in part because some shrubs may sprout profusely following one burn. Early season prescribed burns have been successful; however, fall burning may also be an effective technique to favor native warm-season grasses. The results of the timing and intensity of burns has been mixed as to the impacts on exotic cool-season grasses.
The prescribed grazing should include adequate recovery periods following each grazing event and stocking levels which match the available resources. If properly implemented, this will shift the competitive advantage from the exotic cool-season grasses to the native cool-season grasses.
Context dependence
Grazing management should be applied in a manner that enhances/maximizes the competitive advantage of native grass and forb species over the exotic species. This may include the use of prescribed grazing to reduce excessive plant litter accumulations above that needed for rangeland health indicator #14 (see Rangeland Health Reference Worksheet). Increasing livestock densities may facilitate the reduction in plant litter provided length and timing of grazing periods are adjusted to favor native species.
Grazing prescriptions designed to address exotic grass invasion and favor native species may involve earlier, short, intense grazing periods with proper deferment to improve native species health and vigor. Fall (e.g., September, October) prescribed burning followed by an intensive, early spring graze period with adequate deferment for native grass recovery may shift the competitive advantage to the native species, facilitating the restoration to State 2: Native/Invaded.
Prescribed burning should be applied in a manner that enhances the competitive advantage of native grass and forb species over the exotic species. Prescribed burns should be applied at a frequency which mimics the natural disturbance regime, or more frequently as is ecologically (e.g., available fuel load) and economically feasible. Burn prescriptions may need adjustment to: (1) account for change in fine fuel orientation (e.g., “flopped” Kentucky bluegrass); (2) fire intensity and duration by adjusting ignition pattern (e.g., backing fires vs head fires); (3) account for plant phenological stages to maximize stress on exotic species while favoring native species (both cool- and warm-season grasses).
Mechanism
This restoration pathway from State 5: Go-Back State to State 3: Thick-Native/Invaded State may result from a successful range planting. Site-specific seeding mixes need to be developed; refer to the plant community table. A highly diverse seed mix will more than likely be necessary with species adapted to both thick and thin soil conditions.
Context dependence
A successful range planting will include proper seedbed preparation, weed control (both prior to and after the planting), selection of adapted native species representing functional/structural groups inherent to the State 1, and proper seeding technique. Management (e.g., prescribed grazing, prescribed burning) during and after establishment must be applied in a manner that maintains the competitive advantage for the seeded native species. Adding non-native species can impact the above and below ground biota. Elevated soil nitrogen levels have been shown to benefit smooth brome and Kentucky bluegrass more than some native grasses. As a result, fertilization, exotic legumes in the seeding mix, and other techniques that increase soil nitrogen may promote smooth brome and Kentucky bluegrass invasion.
The method or methods of herbaceous weed treatment will be site specific to each situation; but generally, the goal would be to apply the pesticide, mechanical control, or biological control - either singularly or in combination - in a manner that shifts the competitive advantage from the targeted species to the native grasses and forbs. The control method(s) should be as specific to the targeted species as possible to minimize impacts to non-target species.
Mechanism
This restoration pathway from State 5: Go-Back State to State 3: Thin-Native/Invaded State may result from a successful range planting. Seeding mixes need to be developed accordingly, refer to plant community table. A highly diverse seed will more than likely be necessary with species adapted to both thick and thin soil conditions.
Context dependence
A successful range planting will include proper seedbed preparation, weed control (both prior to and after the planting), selection of adapted native species representing functional/structural groups inherent to the State 1, and proper seeding technique. Management (e.g., prescribed grazing, prescribed burning) during and after establishment must be applied in a manner that maintains the competitive advantage for the seeded native species. Adding non-native species can impact the above and below ground biota. Elevated soil nitrogen levels have been shown to benefit smooth brome and Kentucky bluegrass more than some native grasses. As a result, fertilization, exotic legumes in the seeding mix, and other techniques that increase soil nitrogen may promote smooth brome and Kentucky bluegrass invasion.
The method or methods of herbaceous weed treatment will be site specific to each situation; but generally, the goal would be to apply the pesticide, mechanical control, or biological control - either singularly or in combination - in a manner that shifts the competitive advantage from the targeted species to the native grasses and forbs. The control method(s) should be as specific to the targeted species as possible to minimize impacts to non-target species
Mechanism
This restoration pathway from 5: Go-Back State to State 4: Thick-Invaded State may result from a failed range planting and/or secondary succession. A failed restoration is more likely if the Go-Back State has a thin surface over the claypan. It is unclear whether a failed range planting on an eroded Go-Back State would lead to State 4: Thick-Invaded State. The exotic cool-season grasses may not be able to out-compete the native grasses. The failed range planting would then lead to State 3: Thin-Native/Invaded State.
Context dependence
Failed range plantings can result from many causes, both singularly and in combination, including drought, poor seedbed preparation, improper seeding methods, seeded species not adapted to the site, insufficient weed control, herbicide carryover, poor seed quality (purity & germination), improper management.
Mechanism
This transition is from any plant community to State 6: Go-back State. It is most commonly associated with the cessation of cropping without the benefit of range planting, resulting in a “go-back” situation. Soil conditions can be quite variable on the site, in part due to variations in the management/cropping history (e.g., development of a plowline, erosion, fertility, and/or herbicide/pesticide carryover). Thus, soil conditions should be assessed when considering restoration techniques.
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