Acidic Grand Fir Mosaic 30-45" PZ Frigid Clearwater Mountains
Scenario model
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- Transition T1A More details
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No transition or restoration pathway between the selected states has been described
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Description
These are climax plant communities that persist within a matrix of overmature grand fir (Abies grandis) and western redcedar (Thuja plicata) forests and tree islands. There are few wildfires, so natural succession has reduced the occurrence of seral conifers such as lodgepole pine (Pinus contorta), Douglas-fir (Pseudotsuga menziesii), western white pine (Pinus monticola), and western larch (Larix occidentalis). Late successional, shade-tolerant species like grand fir, western redcedar, Pacific yew (Taxus brevifolia), and sometimes mountain hemlock (Tsuga mertensiana) and subalpine fir (Abies lasiocarpa), are common along with mid-successional Engelmann spruce (Picea engelmannii). Regeneration of conifers in forest canopy openings is a slow and unreliable process in these low pH volcanic ash-cap soils that have abundant populations of pocket gophers (Thomomys talpoides). Disjunct and rare plant species occur in and near these forests, including evergreen synthyris (Synthyris platycarpa), Oregon bluebell (Mertensia bella), Dasynotus (Dasynotus daubenmirei), and Case’s corydalis (Corydalis caseana). Reoccurring severe fires in the can cause expansion of the glades into formerly forested areas. Fire exclusion for long periods allows the forest composition to move to late successional, shade-tolerant species like grand fir, western redcedar, Pacific yew (Taxus brevifolia), and sometimes mountain hemlock (Tsuga mertensiana) and subalpine fir (Abies lasiocarpa). However, succession does not lead to a reduction in size of glade areas
Submodel
Description
Severe fires or other historic disturbance creates glade openings. Successional plant communities in the GFM are dominated by bracken fern and western coneflower. Bracken fern is usually present in low densities under forest canopies, but rapidly expands following disturbance. Once established these communities are very persistent. They appear to be maintained by a combination of allelopathy, pocket gopher activity and changes in soil minerology and chemistry due to increased organic matter contribution
Submodel
Mechanism
Severe burns kill regeneration and allow for invasion and expansion of glade assemblage species. Presence of bracken fern and other glade species in pre-fire understory provides opportunity for rapid site colonization. Pocket gopher activity increases with proliferation of bracken fern.
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