High Mountain Loam 25-35 PZ ACSAG2/PHMA5/BRCA5
Scenario model
Current ecosystem state
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Management practices/drivers
Select a transition or restoration pathway
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Transition T1a
introduction of exotic species, climate change, and the advent of intense season-long livestock grazing
More details -
Transition T2a
elective harvest of stems, wildfire, excessive livestock grazing, brush management
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Restoration pathway R3a
Heavy, continuous, season-long grazing, fire control
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 familiarity with rangeland relict areas where they exist. Shorter trees and shrub forms of bigtooth maple (Acer grandidentatum), quaking aspen (Populus tremuloides), and Rocky Mountain juniper (Juniperus scopulorum) would have made up the upper canopy. Other shrubs would have included mallow ninebark (Physocarpus malvaceus) and mountain snowberry (Symphoricarpos oreophilus). Understory shrubs would have been composed primarily of creeping barberry (Mahonia repens), Oregon boxleaf (Paxistima myrsinites), Woods' rose (Rosa woodsii). Grasses would have included blue wildrye (Elymus glaucus), mountain brome (Bromus marginatus), and slender wheatgrass (Elymus trachycaulus). Forbs would have included tall ragwort (Senecio serra), western coneflower (Rudbeckia occidentalis), silvery lupine (Lupinus argenteus), and nettleleaf giant hyssop (Agastache urticifolia) among others. The average fire return interval would have ranged from approximately 50 to 60 years, which would have been the driving factor behind changes in relative abundance and size of trees and associated understory richness. Shorter trees and shrubs with an understory rich in forbs and grasses (1.1) would have been found following recent wildfire events (1.2a). As the length of time elapsed since the fire lengthened (1.1a), trees would have increased both in height and density, while the understory would have lessened (1.2). A more complete list of species by lifeform for the Reference State is available in accompanying tables in the “Plant Community Composition by Weight and Percentage” section of this ESD document.
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 some native species, and a different climate. State 2 is a description of the ecological site shortly following Euro-American settlement and should be considered the current potential. Heavy season-long livestock grazing was prevalent on these sites starting in the 1860s up through the 1950s, which had its most noticeable impact on diminishing the understory.
Submodel
Description
Tree and brush removal by chemical, fire, or fuel wood cutting, helped to thin the tree canopy and provide for the re-establishment of the understory shrubs, forbs, and grasses.
Submodel
Mechanism
The simultaneous introduction of exotic species, both plants and animals, possible extinctions of native flora and fauna, climate change, and the advent of intense season-long livestock grazing has 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
This transition occurred where there was selective harvest of stems for fuel wood and tapping the maple for sugar. Unburned slash with abundant leaf fall makes this vegetation susceptible to wildfire. The root sprouting of maple and other dominants makes it resilient.
Excessive livestock grazing has been the major agent of positive feedback to accelerated soil erosion and vegetational change. Reduction of livestock numbers and season of use result in a rapid recovery of the perennial dominance. Brush management, whether by chemical means (e.g. 2,4-D, tebuthiron) or prescribed fire, will cause State 2 to transition to State 3.
Cutting the trees for use as fuel wood was prevalent in some areas, which opened up the canopy allowing the understory components to re-establish abundantly if not excessively grazed.
Model keys
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Ecological sites
Major Land Resource Areas
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.