Semi-desert Shallow Loam (Black sagebrush)
Scenario model
Current ecosystem state
Select a state
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 climate change
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Transition T2A
fire return intervals are 3 to 4 decades long and/or when continuous spring grazing is allowed.
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Restoration pathway R3A
conservative grazing practices
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Transition T3A
Heavy livestock grazing, especially during the spring growth period
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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 familiarity with rangeland relict areas where they exist. Before Euro-American settlement, the Reference plant community (1.1) would have been characterized by scattered black sagebrush (Artemisia nova) and abundant perennial herbs. The major grasses would have included Indian ricegrass (Achnatherum hymenoides), needle-and-thread (Hesperostipa comata), bluebunch wheatgrass (Pseudoroegneria spicata), and Western wheatgrass (Pascopyrum smithii). Primary forbs would have included cushion buckwheat (Eriogonum ovalifolium), scarlet globemallow (Sphaeralcea coccinea), longleaf phlox (Phlox longifolia), and several possible species of milkvetch or locoweed (Astraglus spp). 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. The productivity would have been relatively lower than the similar, but stonier loam sites (e.g. R034AY2qqUT Semi-desert Stony Loam Ecological Site) 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 phases of this State would have depended on the time since last fire, starting with a perennial herb-dominated phase (1.1) immediately following fire (1.3a, 1.2b), with yellow rabbitbrush (Chrysothamnus viscidiflorus) becoming temporarily dominant (1.2) approximately 5 to 15 years post-fire (1.1a), and finally the re-establishment of black sagebrush (1.3) approximately 20 to 30 years post-fire (1.2a).
Submodel
Description
State 2 is very similar to State 1 in form and function, with the exception of the presence of non-native plants and animals, possible extinctions of native species, and a different climate. State 2 is a description of the ecological site immediately following Euro-American settlement, and is considered the current potential for this site. The phases of this State vary between a native bunchgrass dominated phase (2.1), to a yellow rabbitbrush/ black sagebrush invaded phase (2.2), to a black sagebrush with native perennial understory phase (2.3), which develop according to the time since last wildfire (2.3a or 2.2b, 2.1a, 2.2a, respectively). The resiliency of this state is maintained by the availability of native seed sources for both the herbaceous species and for black sagebrush, and by wildfire. The resiliency of this State can be negatively impacted by heavy livestock and big game grazing.
Submodel
Description
A prolonged absence of fire and continuous heavy grazing during the growing season will moderately reduce the perennial herbaceous understory, allowing black sagebrush to increase (3.1). Employing more conservative grazing practices by avoiding the growing season of the herbaceous component (R3a), may help to restore this plant community back the Black Sagebrush/ Introduced Non-natives State. Increases in grazing, especially during the spring growth period, will reduce the resiliency of this State.
Submodel
Description
Black sagebrush and unpalatable forbs such as granite prickly phlox (Linanthus pungens) and/or poisonous locoweed/milkvetch species (4.1) will increase on sites where heavy continuous season-long grazing has taken place. The resiliency of this State can be maintained through a reduction in livestock grazing; increases in livestock grazing will reduce the resiliency of this State. Mechanical and chemical treatments are not recommended at these sites because the low responses by native perennial herbs after reseeding make them economically inadvisable. Additionally, these soils are too shallow for successful conversion to crested wheatgrass.
Submodel
Mechanism
Transition T1a: from State 1 to State 2 (Reference State to Black Sagebrush/ 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, have caused State 1 to transition to State 2. Reversal of such historic changes (i.e. a return pathway) back to State 1 is not practical.
Mechanism
Transition T2a: from State 2 to State 3 (Black Sagebrush/ Introduced Non-natives State to Moderately Grazed Remnants State)
The Black Sagebrush/ Introduced Non-natives State will transition to the Moderately Grazed Remnants State when fire return intervals are 3 to 4 decades long and/or when continuous spring grazing is allowed. This will result in black sagebrush beginning to dominate the site at the expense of the associated perennial herbs. The approach of this transition is indicated by an increase in black sagebrush and native perennial forbs.
Mechanism
Restoration Pathway R3a: from State 3 to State 2 (Moderately Grazed Remnants State to Black Sagebrush/ Introduced Non-natives State)
Restoration back to the Black Sagebrush/ Introduced Non-natives State is possible when more conservative grazing practices are used such as by avoiding the growing season of the understory component.
Mechanism
Transition T3a: from State 3 to State 4 (Moderately Grazed Remnants State to Dense Black Sagebrush/ Unpalatable Forbs State)
The Moderately Grazed Remnants State will transition to the Dense Black Sagebrush/ Unpalatable Forbs State following heavy continuous season-long grazing. This transition is indicated by increases in size, density, and cover of black sagebrush, and an increase in the proportion of unpalatable forbs. Heavy livestock grazing, especially during the spring growth period, will trigger this transition.
Model keys
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