Cool Wet Conifer Mountains and Plateaus (ABGR/VAME/LIBO)
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
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Transition T1A
Long term fire exclusion
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Transition T1B
Widespread stand replacing fire
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Restoration pathway R2A
Treatment practices to reduce excessive ladder fuels
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Transition T2A
Time elapsed without major disturbance
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Transition T2B
Time elapsed without major disturbance
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Restoration pathway R3A
Conifer planting
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Restoration pathway R4A
Significant time elapsed, and forest restoration efforts
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Transition T4A
Widespread catastrophic fire
More details -
No transition or restoration pathway between the selected states has been described
Target ecosystem state
Select a state
Description
The historical reference state existed across the landscape as a spatially complex forest mosaic of plant communities in various stages of development and with varying composition. The most common expression was the mature closed canopy stand (community 1.2), yet young closed canopy stands (community 1.5) were also common. Open canopy conditions were less common (1.1 and 1.4) due to conditions favoring long intervals between mixed or high severity fire.
At the landscape scale, these historic stand structures were represented by a combination of patch openings, clumpy (dense or overstocked) tree groups which were often pole size or smaller, and as well-spaced mature overstory trees encompassing larger stand groups. A wide range of conifer establishment and expression was possible due to the influence of a mixed fire regime. Following a disturbance in which large representatives of individual conifers were eliminated, the key to conifer re-establishment in the reference state relied on the recruitment of seed from adjacent sites, or from the few remnant surviving seed bearing sources. In a replacement fire of an older, mature stand, the trees that did survive tended to be the mature and over-mature early seral species because they have the most resistance to fire induced mortality.
Submodel
States 2 and 5 (additional transitions)
1.2. Mature forest, Closed canopy
1.5. Young forest, closed canopy
Description
Conditions favorable to the development of this alternative state began to occur within the Reference State around the turn of the twentieth century. The impacts of fire exclusion, a management goal of post-European settlers and land managers, allowed many stands to progress without the natural occurrence of any fire, including frequent surface fires. Fire suppression shifted the age expression and density of the younger stands and changed the composition of understory vegetation, leading to reduced spatial variation. Fuel levels and fuel stratum layers increased, shifting the fire regime/condition class toward a greater likelihood of stand replacement fire episodes.
The overall consequences of the changes to the forest structure and function due to the combined management actions in the last century are:
INCREASED
• Stand Density
• Shift towards mid and late seral species
• Amount of understory and secondary stand levels of conifers
• Fuel loads and risk of catastrophic high severity fires
DECREASED
• Large old pine and other fire adapted early seral species
• Regeneration of early seral species
• Habit for species of open stands of old pine forests
• Decreased levels of snags and large organic debris
• Reduction in soil quality due to loss of soil wood and organic matter
• Decrease in genetic variation of early seral species
Description
State 3 represents conditions immediately following a stand replacement fire. Short- and long-term detrimental impacts to wildlife, hydrology and soil quality begin to occur immediately due to the abnormally high intensity of the catastrophic burn. Microbial populations, organic matter levels, soil hydrophobicity and other structural elements of the native soil resources are negatively impacted. These types of fires, when they occurred within the historic context of the reference state, transitioned the stand to this alternative state if and when the vast majority of the cone producing conifers were eliminated by the fire, and when other sources of conifer recruitment are also absent (i.e. resulting in unstocked stand conditions). State 3 would infer a much longer post-fire stand recovery period compared to situations that normally existed in the reference state (where older relict, seed producing early and mid-seral seed sources existed). The basic natural resource values (especially soil quality) were generally preserved or quickly restored in these instances.
State 3 could also result from catastrophic stand replacement fires that originate from conditions found in alternative state 2.1 and 4.1 (as shown on the state and transition diagram by the T2A and T4A transition symbols). The destructive heat generated impacts of these events are much greater than naturally occurring replacement fires, and in these instances the basic natural resource values (plants, animals, hydrology and especially soil quality elements) have been degraded and are very slow to recover. Natural sources for conifer recruitment are absent.
Description
This state may seem to mimic the conditions of Alternative state 3 in that forest stocking is virtually non-existent, but the underlying cause leading to the unstocked condition and the recovery options are vastly different. In this state, immediate restoration by planting is not feasible because the root mass is still active in the soil, and young developing conifer seedlings will succumb to root disease mortality in a short period of time. Poorer quality sites are at greater risk of root disease occurrence and impacts, and species such as grand fir and Douglas-fir are most susceptible.
Note that Alternative State 4 is at risk of catastrophic wildfire while fuel levels are in excess, which would transition the site to Alternative State 3 (by way of T4A.).
Mechanism
Long term fire exclusion (50-100+) years (resulting in Alternative State 2).
Mechanism
A widespread stand replacing fire event occurs as a natural event in any phase of the reference state. Approximately ¾ or more of the cone producing age conifer species are killed across all age/size classes. There is a potential of a long-term deficiency of seed source(s) necessary for the re-establishment of the early, mid and late seral species (this results in Alternative State 3).
Mechanism
Treatment practices that reduce excessive ladder fuels (low thinning) and reduce overstory bulk density and continuity (crown and selective thinning) may provide immediate benefits in terms of reducing the potential of catastrophic wildfire. Other practices which reduce overstocking, or which shift species towards early seral species (pre-commercial and commercial thinning, tree planting), as well as introducing understory prescribed burning as a maintenance practice, can contribute to increased resiliency and will improve the ecologic function of the stand if done properly.
Mechanism
In the absence of catastrophic fire, the long-term build-up of mid to late seral Douglas-fir and grand-fir leads to increased levels of root disease, especially on poor quality sites (i.e. lower fertility soils or soils with depth/water holding limitations, sites with late summer excessive heat and drought). The eventual loss of all conifer species results in the development of long-term persistent brush fields.
Mechanism
In the absence of catastrophic fire, the long-term build-up of mid to late seral Douglas-fir and grand-fir leads to increased levels of root disease, especially on poor quality sites (i.e. lower fertility soils or soils with depth/water holding limitations, sites with late summer excessive heat and drought). The eventual loss of all conifer species results in the development of long-term persistent brush fields.
Mechanism
Conifers are planted in order to overcome the virtual lack of adequate seed source of surviving Ponderosa pine, larch, or Douglas-fir of any size or age class. Natural recovery will be extremely long without tree planning efforts, up to many 100’s of years as trees may slowly re-establish perimeter areas and migrate inwards by natural reproduction and under favorable circumstances. It is likely that persistent brush or grass/brush cover would exist for hundreds of years if un-planted. Soil quality is slow to respond to pre-fire levels, especially with the lack of soil organic wood input and other contributors to soil health.
Mechanism
These impacted stands will need to be left alone for a long period of time, up to 100’s of years (where they remain protected from erosion by grass/shrub vegetation) until the sub-surface level of fungi naturally declines as infected roots decompose. At that time, forest restoration efforts similar to those described in Restoration Pathway 3A can be applied. Early seral species (Ponderosa pine, western larch and blister resistant western white pine) are most resistant to lingering root disease root threats and are also well adapted to establishing in full sunlight conditions. These species also acquire fire resistance attributes as they establish and grow. Site preparation will need to be done prior to planting.
Model keys
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