Semi-desert Shallow Clay (Early sagebrush)
Scenario model
Current ecosystem state
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Management practices/drivers
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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 climate change
More details -
Transition T2A
A reduction in livestock grazing, especially some deferment during the growth season for herbs,
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 long after the arrival of 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. The least modified plant community would have been an early sagebrush-dominated (Artemisia arbuscula ssp. longiloba) site with scattered winterfat (Krascheninnikovia lanata) and other associated shrubs, with various caespitose perennial forbs such as milkvetch (Astragalus spp.) and stemless mock goldenweed (Stenotus acaulis), and a grassy understory composed mainly of Western wheatgrass (Pascopyrum smithii) (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. This ESD is related to R034AY2iiUT, but where clayish soils are shallow, usually at the tops of slopes where clay parent materials are exposed, and occasionally in low swales, early sagebrush prevails. Herbaceous production would have been less than adjacent ecological sites not on clayish soils because of the Inverse Texture Principle (Noy-Meir, 1973). In deserts and semi-deserts, finer textured soils are effectively drier and thus typically have lower production potential than coarser textured soils. The herbage also dried out earlier than adjacent ecological sites.
Submodel
Description
State 2 is a description of the ecological site shortly following Euro-American settlement. Early sagebrush is the dominant species, with a much reduced native perennial understory and evidence of accelerated soil erosion in some areas due to the heavy utilization by livestock. Accelerated soil erosion will reduce state resiliency, while a reduction of livestock grazing will maintain state resiliency.
Submodel
Description
This state is characterized by a dominance of early sagebrush with a bunchgrass understory, and can result from reduction of livestock grazing especially some deferment during the growth season for herbs. It should be considered the current reference community. Because of the lower forage production in State 2 and 3, many will be tempted to try to improve the situation with chemical or mechanical reductions of brush to enhance the grasses. When that doesn’t work, some will attempt to plow and re-seed with Eurasian grasses. These manipulations are much less successful than on adjacent ecological sites with coarser textured soils, and are not recommended. Resuming heavy livestock grazing, especially during the growth season of desirable herbs will reduce state resiliency. State resilience will be maintained with moderate livestock use, especially during the growth periods of desirable herbs.
Submodel
Mechanism
Transition T1a: from State 1 to State 2 (Reference State to Early Sagebrush/ Depauperate Understory/ Introduced Non-natives State)
The simultaneous introduction of exotic species, both plants and animals, and possible extinctions of native flora and fauna, along with climate change, causes State 1 to transition to State 2. The heavy continuous livestock grazing that occurred on these sites not only depleted the herbaceous component, but triggered accelerated soil erosion especially on steeper locations, permanently lowering site potential.
Mechanism
Transition T2a: from State 2 to State 3 (Early Sagebrush/ Depauperate Understory/ Introduced Non-natives State to Early Sagebrush/ Re-established Bunchgrass State)
Relaxation of the grazing pressure, especially deferment during the growing season of the grasses will allow some recovery of the grasses. However, they will be mostly bunch form and short-lived, namely bottlebrush squirreltail (Elymus elymoides) and Sandberg bluegrass (Poa secunda). A key indicator of the approach to this transition is an increase in desirable native perennial herbs. A reduction in livestock grazing, especially some deferment during the growth season for herbs, will trigger this transition.
Model keys
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