Semi-desert Saline Terraces (Gardner's saltbush/ Bluebunch wheatgrass)
Scenario model
Current ecosystem state
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Management practices/drivers
Select a transition or restoration pathway
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Transition T1A
The simultaneous introduction of exotic species, both plants and animals, and possible extinctions of native flora and fauna, along with year long heavy livestock grazing and climate change
More details -
Transition T2A
Trigger causing transition: sustained heavy grazing especially during the growing season
More details
Restoration pathway: not apparent at this time. -
Restoration pathway R3A
Reseeding with tall wheatgrass
More details -
No transition or restoration pathway between the selected states has been described
Target ecosystem state
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Description
The Reference State is a description of this ecological site just prior to Euro-American settlement but after centuries of use by Native Americans. The description of the Reference State was determined by NRCS Soil Survey Type Site Location information and the familiarity of rangeland relict areas where they exist. Before Euro-American settlement these areas would have been sparsely vegetated by the suffrutescent (half-shrubs) Gardner’s Saltbush (Atriplex gardneri) and bud sagebrush (Picrothamnus desertorum). Scattered among these would have been clumps of native perennial bunchgrasses including bottlebrush squirreltail (Elymus elymoides) and Indian ricegrass (Achnatherum hymenoides) with minor amounts of Bluebunch wheatgrass (Pseudoroegneria spicata) and needleandthread (Hesperostipa comata) (1.1). A more complete list of species by lifeform for the Reference State is available in the accompanying tables in the “Plant Community Composition by Weight and Percentage” section of this document.
Submodel
Description
State 2 is a description of the ecological site shortly following Euro-American settlement, which is dominated by Gardner’s Saltbush. Perennial bunch grasses and bud sagebrush has been removed because of historic heavy grazing. Negative feedbacks that maintain state resiliency are: ground cover provided by both grasses and leaf litter which help maintain soil stability, and retention of water at the site. Positive feedbacks that reduce state resiliency are: reduction in perennial grass cover which puts this plant community and state at-risk to further degradation from lack of soil stabilization and reduced soil moisture retention. These feedbacks can be reversed with release from grazing pressure, especially during spring.
Submodel
Description
Once halogeton was introduced to these sites, livestock grazing became much more limited due to the poisonous qualities of this exotic species, nevertheless Halogeton continued to usurp space and resources and pump salts to the soil surface (Eckert and Kinsinger, 1960) impeding establishment of other herbs. Negative feedbacks that maintain state resiliency are: the absence of perennial grass seed source, and the establishment of exotic poisonous species. Halogeton also pumps sodium to the soil surface (Eckert and Kinsinger, 1960) causing surface slacking which impedes establishment of more desirable herbs.
Submodel
Mechanism
Transition T1a: from State 1 to State 2 (Reference State to Gardner’s Saltbush Monoculture/ Introduced Herbs State)
The simultaneous introduction of exotic species, both plants and animals, and possible extinctions of native flora and fauna, along with year long heavy livestock grazing and climate change, will cause State 1 to transition to State 2, the current potential. Reversal of such historic changes (i.e. a return pathway) back to State 1 is not practical. Additionally, historic year around livestock grazing (T1a) quickly reduced the perennial grass and bud sagebrush components. This quickly led to a near monoculture of Gardner’s saltbush, the only major perennial able to reproduce vegetatively. Little recovery of other species occurred following reduction of livestock grazing pressure beginning in the 1930s because of local extinction of seed sources for the original companion species.
Mechanism
Transition T2a: from State 2 to State 3 (Gardner’s Saltbush Monoculture/ Introduced Herbs State to Gardner’s Saltbush /Halogeton State)
The Gardner’s Saltbush Monoculture/ Introduced Herbs State will transition to the Gardner’s Saltbush / Halogeton Co-dominant State following heavy continuous growing season-long grazing. In 1943, the introduction of halogeton (Halogeton glomeratus) (T2a) resulted in the first important exotic entering this habitat. Halogeton’s poisonous nature caused further reduction of livestock grazing.
Key indicators of approach to transition: loss of perennial grass understory; introduction of exotic, poisonous species
Trigger causing transition: sustained heavy grazing especially during the growing season
Restoration pathway: not apparent at this time.
Mechanism
Restoration Pathway R3a: From State 3 to State 2 (Gardner’s Saltbush/Halogeton co-dominant state to Gardner’s Saltbush Monoculture/Introduced Herbs State)
Very few feasible alternatives for improving cover or forage production have emerged. Reseeding with tall wheatgrass (Thinopyrum ponticum) may offer opportunities for re-establishment of a palatable herbaceous understory.
Model keys
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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.