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 relict areas where they exist. At the time of European colonization, what would have been observed on these sites would have primarily depended on the time since the last wildfire occurred. If fire had not occurred for about 100 years, a stand of mixed conifers including Engelmann Spruce (Picea engelmannii), subalpine fir (Abies lasiocarpa), Douglas-fir (Pseudotsuga menziesii), and white fir (Abies concolor), and lodgepole pine (Pinus contorta) would have been the dominant species occupying the site (1.1). The understory would have been relatively sparse under mature trees due to tree competition, overstory shading, and duff accumulation. Wildfire or insect outbreaks on particular tree species would have replaced these stands with a rich diversity of herb-dominated vegetation. In the absence of any major disturbance, the vegetation would have progressed into more of a shrub-herb co-dominance, followed by the increasing presence of aspen (Populus tremuloides) first as seedlings and saplings, and later as mature aspen with mixed conifer seedlings. Ultimately the conifers would have outcompeted aspen, returning the climax vegetation. Wildfire would have been the primary disturbance factor prior to colonization, although periodic outbreaks of insects destroying particular tree species could reset the successional clock. Early successional stages were shorter in duration.
State 2 is 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, a different climate, and a secondary stand of trees. State 2 is a description of the ecological site following Euro-American settlement. This state can be regarded as the current potential. With the least amount of disturbance or manipulation of the fire regime, a mature stand of subalpine fir, white fir, and Douglas fir with a sparse understory component is expected at this site (2.1). As with the Reference State, time since last wildfire remains the key factor in determining what vegetation will be encountered on these sites. Wildfire, particularly crown fires, or complete harvesting of the forest will replace these stands with a rich diversity of herb-dominated vegetation. In the absence of any major disturbance, the vegetation will progress into more of a shrub-herb co-dominance, followed by the increasing presence of aspen, first as seedlings and saplings, and later as mature aspen with immature conifers. Ultimately the conifers will outcompete aspen, returning to a semblance of climax vegetation. In some areas where wildfire has been prevented, the conifers may become over-mature and consequently are more susceptible to infestation by insects and pathogens. The resiliency of this State can be maintained by moderating human uses of the forest for timber and grazing.
The simultaneous introduction of exotic species, both plants and animals, and possible extinctions of native flora and fauna, along with climate change, has caused State 1 to transition to State 2. Europeans further altered this vegetation largely through logging, livestock grazing, trapping of beaver, and changing the fire regime. Continued impacts could prevent the recovery toward potential conifer dominance (State 2, various phases). The reversal of these changes (i.e. a return pathway) back to State 1 is not impractical.
Model keys
Briefcase
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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.
) icon wherever it occurs. Drag and drop items to reorder. Cookies are used to store briefcase items between browsing sessions. Because of this, the number of items that can be added to your briefcase is limited, and briefcase items added on one device and browser cannot be accessed from another device or browser. Users who do not wish to place cookies on their devices should not use the briefcase tool. Briefcase cookies serve no other purpose than described here and are deleted whenever browsing history is cleared.
