Ephemeral Drainageways
Scenario model
Current ecosystem state
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Management practices/drivers
Select a transition or restoration pathway
- Transition T1A More details
- Transition T1B More details
- Restoration pathway R2A More details
- Transition T2A More details
- Transition T2B More details
- Restoration pathway R3A More details
- Transition T3A More details
- Restoration pathway R4A More details
- Restoration pathway R4B More details
- Restoration pathway R4C More details
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No transition or restoration pathway between the selected states has been described
Target ecosystem state
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Description
Grasses are the primary plant species in the reference state. The main species are western wheatgrass, blue grama, vine mesquite, galleta, alkali sacaton, ring muhly and creeping muhly. The typical shrubs likely encountered in this state include fourwing saltbush, fringed sage, and broom snakeweed.
A temperature gradient across the LRU also plays a role in the presence or abundance of some species, and is generally seen as an eastward trend of lowering elevation with rising average annual temperatures. In the easternmost part of this LRU, a greater presence of warm-season plants such as buffalograss is expected. Western parts of this LRU will have a higher prevalence of cool-season grasses such as western wheatgrass and bottlebrush squirreltail as well as fringed sage.
Submodel
Description
This site has been grazed continuously for several years, if not decades or longer. Annuals and shrub species have increased in coverage, while several grass species including vine mesquite, western wheatgrass, sideoats grama and the shrub fourwing saltbush have decreased or are no longer present. Blue grama, buffalograss, mat (creeping) muhly, ring muhly and sleepygrass will dominate the grass species while shrubs and succulents such as plains pricklypear, stick cholla, broom snakeweed, fringed sage, and rubber rabbitbrush will increase. In warmer, easterly parts of this site’s range, cholla, buffalograss, and silver bluestem are more likely to increase whereas, in the west, plains pricklypear, ring muhly and fringed sage will be more prominent.
As shrubs and forbs increase, they gain a competitive advantage, primarily by out-competing the grass for water and nutrients, especially during periods of short- and long-duration drought. Fire had been the natural event in the Great Plains that thwarts shrub species from gaining a competitive advantage and facilitates greater colonization by grasses. Historic continuous grazing has prevented the fuel loads in these grasslands from being able to carry a fire, therefore giving shrubs and annuals their advantage.
As shrubs increase, root density and turnover in the soil begins to lessen causing a decrease in decomposition rates which are a source of nutrient supply to plants. In return, storage of labile and sequestered carbon pools decline causing a decrease in soil organic matter. Soil organic matter decline coincides with lower infiltration capacity, water holding capacity, and higher bulk density, all which lead to decreased resiliency to drought and heat stress. It also increases erosion rates and may lead to gully formation.
Submodel
Description
The degradation in this state is severe, with significant damage to the soil profile that alters its ability to produce a viable plant community for wildlife or agricultural uses on its own. The grass component is dominated by sod-bound blue grama and/or creeping muhly with minor amounts of western wheatgrass, bottlebrush squirreltail, and buffalograss. This condition usually results in a compromised soil surface that is highly susceptible to gully erosion.
Submodel
Description
This state occurs where significant salts (particularly gypsum) have accumulated in soils as a result of the net upward movement of water into a given Playa (see Water Features above). Given enough data, this state could probably be divided into multiple phases, as plant communities and channel morphology vary widely in response to grazing regime, hydrology, and construction activities.
Submodel
Mechanism
Grazing pressure, or severe flooding events, coupled with or following a single drought event, can cause a state shift to the degraded condition.
Mechanism
Landscape hydrology is altered such that the drainageway becomes a site of elevated groundwater discharge. This is most often the result of the addition of irrigation water to landforms above the stretch of drainageway in question, but could theoretically occur in response to changes in weather patterns. Slow variables: In periods between flooding events, capillary action draws groundwater to the surface of the soil. Evapotranspiration leaves behind the salts (particularly gypsum) that were dissolved in the groundwater. Since the water table is elevated, flooding no longer flushes these salts from soils. Thus, over a number of years under the new hydrologic regime, significant amounts of salts accumulate in the drainageway soils.
Mechanism
Where the condition of the range is degraded without significant formation of gullies, a simple changing of management strategies may lead to restoration. This involves relying on techniques that value plant production and diversity over herd size, using systems such as deferred grazing with periods of rest, especially during drought periods. Use of burning strategies, following a period that allows fuels to accumulate, may be necessary to allow grasses to re-dominate. Some reseeding or shrub removal measures may need to accompany this management shift. Where gully formation is present and significant, more intensive restoration techniques need to be employed. The installation of small rock grade control structures, or other engineered methods (Zeedyke, 2009), along with brush control and, depending on viability of seedbank, reseeding.
Burning can be a useful tactic to control shrubs and possibly exotic species. Since the production is generally higher in this site compared to surrounding uplands, a shorter period of grazing rest, relative to adjacent upland sites, may be sufficient to build the fuel load required to carry a fire hot enough to kill snakeweed and cholla.
Mechanism
Installation of a watering facility, either in ground or above ground, magnifies the trampling traffic in the area. Corrals or other high use structures can have the same effect. These areas typically have a preponderance of bare ground, with only small patches of grass and annuals. They now act as a source for concentrated overland flow and this will impact areas downstream by applying great erosive cutting power to the bottomland, usually to the effect of significant gully formation.
Mechanism
Landscape hydrology is altered such that the drainageway becomes a site of elevated groundwater discharge. This is most often the result of the addition of irrigation water to landforms above the stretch of drainageway in question, but could theoretically occur in response to changes in weather patterns. Slow variables: In periods between flooding events, capillary action draws groundwater to the surface of the soil. Evapotranspiration leaves behind the salts (particularly gypsum) that were dissolved in the groundwater. Since the water table is elevated, flooding no longer flushes these salts from soils. Thus, over a number of years under the new hydrologic regime, significant amounts of salts accumulate in the drainageway soils.
Mechanism
The goal here is to increase the residence time of water on the landscape following a precipitation event. The focus should be on areas where water is concentrating, and methods that will work to spread the runoff over the largest extent of bottomland as possible. Success will be determined by whether the areas can be simultaneously revegetated, and all before the next significant erosive event. It would also be wise to guarantee appropriate amounts of moisture are available to ensure success of plant establishment under any possible weather condition.
Intensive remediation of the site via landform restoration techniques will be required following the removal of tanks, filling in of pits, or reclaiming gullies. It might be strategic to first address compaction of surrounding upland areas by encouraging annuals that deploy penetrating taproots. Eventually the site can be seeded with a more native blend of grasses and forbs. In cases of severe compaction, where plants cannot establish on their own, an initial deep plowing may be required to break up the dense surface. Other methods such as adding amendments like mulch or gravel may be required to help restore infiltration and root penetrability. Following this, gullies can be treated using methods to encourage sediment aggradation in smaller incremental steps. Additional sediment retention steps can be added sequentially over time to elevate the grade of the gullies to a level even with the historic bottomland. Many techniques and methods exist to handle a variety of restoration situations (Zeedyke, 2009).
Mechanism
Landscape hydrology is altered such that the drainageway becomes a site of elevated groundwater discharge. This is most often the result of the addition of irrigation water to landforms above the stretch of drainageway in question, but could theoretically occur in response to changes in weather patterns. Slow variables: In periods between flooding events, capillary action draws groundwater to the surface of the soil. Evapotranspiration leaves behind the salts (particularly gypsum) that were dissolved in the groundwater. Since the water table is elevated, flooding no longer flushes these salts from soils. Thus, over a number of years under the new hydrologic regime, significant amounts of salts accumulate in the drainageway soils.
Mechanism
R4A, R4B, R4C: Each restoration pathway from State 4 will necessarily involve a change in landscape hydrology which effectively lowers the water table below the stretch of drainageway in question. In most cases, this will involve a reduction or cessation of irrigation activities higher in the watershed. The result is that water effectively percolates through the soils of the floodplains and drainageway bottoms. Highly soluble salts such as sodium chloride and sodium bicarbonate are removed rapidly—perhaps in a matter of years. Gypsum, having only moderate solubility and often being quite concentrated in State 4, will require decades to be markedly reduced, and perhaps centuries to be removed entirely. Which of the three restoration pathways the plant community takes will depend on a number of factors.
R4A will occur if the stream channel is not incised, and the area lacks head-cuts or lateral gullies. Re-introduction of plants may require the initial removal of salts (a slow process), followed by seeding activities.
Mechanism
R4A, R4B, R4C: Each restoration pathway from State 4 will necessarily involve a change in landscape hydrology which effectively lowers the water table below the stretch of drainageway in question. In most cases, this will involve a reduction or cessation of irrigation activities higher in the watershed. The result is that water effectively percolates through the soils of the floodplains and drainageway bottoms. Highly soluble salts such as sodium chloride and sodium bicarbonate are removed rapidly—perhaps in a matter of years. Gypsum, having only moderate solubility and often being quite concentrated in State 4, will require decades to be markedly reduced, and perhaps centuries to be removed entirely. Which of the three restoration pathways the plant community takes will depend on a number of factors.
R4B will occur in stretches containing head-cuts or radiating gullies. Again, re-introduction of plants may require the initial removal of salts (a slow process), followed by seeding activities.
Mechanism
R4A, R4B, R4C: Each restoration pathway from State 4 will necessarily involve a change in landscape hydrology which effectively lowers the water table below the stretch of drainageway in question. In most cases, this will involve a reduction or cessation of irrigation activities higher in the watershed. The result is that water effectively percolates through the soils of the floodplains and drainageway bottoms. Highly soluble salts such as sodium chloride and sodium bicarbonate are removed rapidly—perhaps in a matter of years. Gypsum, having only moderate solubility and often being quite concentrated in State 4, will require decades to be markedly reduced, and perhaps centuries to be removed entirely. Which of the three restoration pathways the plant community takes will depend on a number of factors.
R4C will occur in areas that remain affected by heavy use, such as corrals, stock tanks, 2-tracks; and nearby stretches of the drainageway.
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The Ecosystem Dynamics Interpretive Tool is an information system framework developed by the USDA-ARS Jornada Experimental Range, USDA Natural Resources Conservation Service, and New Mexico State University.