Ecological dynamics
The following State and Transition diagram depicts the most common plant communities found on this ecological site. It does not necessarily depict all the plant communities that can occur, but does show the most prevalent and repeatable. As more data are collected, some of these plant communities may be revised or removed, and new ones added. These descriptions capture the current knowledge and experience at the time of this revision.
State 1 Reference State
This Reference State describes the biotic communities that may become established on this ecological site if all successional sequences are completed under natural disturbance conditions. Species composition is generally dominated by mature or seral aspen community types. Shrubs are of minor importance in this state. Several seral communities are described in this reference state including those of open canopy, seedling, sapling, pole, immature forest, mature forest, and eventually to an old or overmature forest type if fire is excluded for very long periods of time.
The primary disturbance mechanisms in this state are overstory canopy density, weather fluctuations, and fire, or lack of fire. The reference state is self-sustaining and resistant to change beyond it's normal seral community types due to a good adaptation to natural disturbances and a high resilience following those disturbances. When natural disturbances such as fire do occur, the rate of recovery can be quite variable.
Feedbacks: Natural fluctuations in weather patterns that allow for a self-sustaining mix of a aspen, shrubs and native grass and grasslike community. Insect herbivory, more frequent fires, or other disturbances that may allow for the establishment of invasive species.
At-risk Community Phase: All communities are at risk when native plants are stressed and nutrients become available for non-native plants to establish.
Trigger: The establishment of non-native plant species.
Community 1.1 Mature Aspen Community Phase.
This community phase is dominated by an overstory canopy of mature aspen that have reached or are near maximal heights for the site. Average age is 80 to 120 years. Trees have developed tall, straight, clear stems with short, high rounded crowns. Tree canopy cover ranges from 20 to 40 percent. Understory vegetation is strongly influenced by tree competition, overstory shading, duff accumulation, etc. A few seedlings and/or saplings of quaking aspen occur in the understory. Shade tolerant plants dominate the understory.
Community 1.2 Aspen Seedling/ Herbaceous Community Phase.
This community phase is dominated by aspen sprouts and seedlings, and by perennial grasses and forbs under nearly full sunlight. This stage is experienced after a major disturbance such as crown fire, insect damage or disease. Any skeleton forest (dead trees) remaining have little or no affect on the composition and production of the herbaceous vegetation. Various amounts of tree seedlings 1 to 25 years old are present up to the point where they are obviously a major component of the vegetal structure. Thick duff layers are present on some sites, completely covering the forest floor with needles and twigs.
Community 1.3 Immature Aspen Forest/ Herbaceous Community Phase.
This community phase is characterized by a growing canopy of pole sized and/or immature aspen. Trees are developing tall, straight, clear stems with narrow pointed crowns. Average age is 25 to 80 years. Tree canopy cover ranges from 10 to 20 percent. Understory vegetation is somewhat influenced by tree competition, overstory shading, duff accumulation, etc. Seedlings and/or saplings of quaking aspen are common in the understory. Shade tolerant plants dominate the understory. Thick duff layers are present on some sites, completely covering the forest floor with needles and twigs.
Community 1.4 Decadent Aspen Community Phase.
This community phase is dominated by an overstory canopy of very mature and decadent aspen that have reached maximal heights for the site. Average age is 120 plus years. Trees have developed tall, straight, clear stems with high, very rounded crowns. This phase typically develops in the absence of wildfire or other naturally occurring disturbances including disease and insect damage. Tree canopy cover is at a maximum for the site and is commonly greater than 50 percent. Very old trees often show signs of disease and/or insect damage. Understory vegetation is somewhat sparse due to tree competition, overstory shading, duff accumulation, etc.
a. Nature of Forest Community
The overstory tree canopy cover is about 55 to 65 percent. Slender wheatgrass, mountain brome, Columbia needlegrass, and thurber fescue are common understory species. Understory composition by air-dry weight is about 60 percent perennial grasses and grasslike plants, 15 percent forbs, and 25 percent shrubs and young trees. Understory production ranges from 800 pounds per acre in favorable years to about 400 pounds per acre in unfavorable years. Understory production includes the total annual production of all species within 4 ½ feet of the ground surface.
Pathway 1.1B Community 1.1 to 1.2
This community pathway occurs when wildfire removes the aspen overstory. This event can be exacerbated by drought, insect damage or disease.
Pathway 1.1A Community 1.1 to 1.4
This community pathway occurs when fire is excluded from the plant community for long periods of time.
Pathway 1.2A Community 1.2 to 1.3
This community pathway occurs when fire is excluded from the plant community for long periods of time.
Pathway 1.3A Community 1.3 to 1.1
This community pathway occurs when fire is excluded from the plant community for long periods of time.
Pathway 1.3B Community 1.3 to 1.2
This community pathway occurs when wildfire removes the growing aspen overstory. This event can be exacerbated by drought, insect damage and/or disease.
Pathway 1.4A Community 1.4 to 1.1
This community pathway occurs when insect damage or disease kills old trees and allows the community to return to a community phase 1.1 type with snags present.
Pathway 1.4B Community 1.4 to 1.2
This community pathway occurs when wildfire removes the aspen overstory. This event can be exacerbated by drought, insect damage or disease.
State 2 Current Potential State
The current potential state is similar to the reference state, however minor amounts of non-native species may now be present in all community phases. This condition has not been well documented and so community phases in this state are based on possible community dynamics and not documented facts. This state describes the biotic communities that may become established on this ecological site if all successional sequences are completed under natural disturbance conditions. Species composition is generally dominated by mature or seral aspen community types. Shrubs are of minor importance in this state.
Several seral communities are described in this reference state including those of open canopy, seedling, sapling, pole, immature forest, mature forest, and eventually to an old or overmature forest type if fire is excluded for very long periods of time.
The primary disturbance mechanisms in this state are overstory disturbance, canopy density, weather fluctuations, and fire, or lack of fire. The current potential state is still self-sustaining and resistant to change beyond it's normal seral community types due to a good adaptation to natural disturbances and a high resilience following those disturbances. When disturbances such as fire do occur, the rate of recovery can be quite variable.
Current Potential State: Plant communities influenced by Aspen canopy density, long term weather fluctuations, and periodic fire.
Feedbacks: Natural fluctuations in weather patterns that allow for a self-sustaining mix of a aspen, shrubs and native grass and grasslike community. Insect herbivory, more frequent fires, or other disturbances that may allow for the increase of non-native species.
At-risk Community Phase: All communities are at risk when native plants are stressed and nutrients become available for non-native plants to increase.
Trigger: The increase of non-native plant species.
Community 2.1 Mature Aspen, Non-Native Herbaceous Community Phase.
This community phase is dominated by an overstory canopy of mature aspen that have reached or are near maximal heights for the site. Trees have developed tall, straight, clear stems with short, high rounded crowns. Tree canopy cover ranges from 20 to 40 percent. Understory vegetation is strongly influenced by tree competition, overstory shading, duff accumulation, etc. A few seedlings and/or saplings of quaking aspen occur in the understory. Shade tolerant plants dominate understory species. Non-native species oncluding smooth brome, orchardgrass, and Kentucky bluebrass may now be present in the community. Thick duff layers are present on some sites, completely covering the forest floor with needles and twigs.
Community 2.2 Aspen Seedling/ Non-Native Herbaceous Community Phase.
This community phase is dominated by aspen sprouts and seedlings, and by perennial grasses and forbs under nearly full sunlight. This stage is experienced after a major disturbance such as crown fire, insect damage or disease. Any skeleton forest (dead trees) remaining have little or no affect on the composition and production of the herbaceous vegetation. Various amounts of tree seedlings 1 to 25 years old are present up to the point where they are obviously a major component of the vegetal structure. Non-native including smooth brome, orchardgrass, and Kentucky bluegrass may also occur on the site. Thick duff layers are present on some sites, completely covering the forest floor with needles and twigs.
Community 2.3 Immature Aspen Forest/Non-Native Herbaceous Community Phase.
This community phase is characterized by a growing canopy of pole sized and/or immature aspen. Trees are developing tall, straight, clear stems with narrow pointed crowns. Average age is 25 to 80 years. Tree canopy cover ranges from 10 to 20 percent. Understory vegetation is somewhat influenced by tree competition, overstory shading, duff accumulation, etc. Seedlings and/or saplings of quaking aspen are common in the understory. Shade tolerant plants dominate understory. Non-native species including smooth brome. orchardgrass anf Kentucky bluegrass are present in the community. Thick duff layers are present on some sites, completely covering the forest floor with needles and twigs.
Community 2.4 Decadent Aspen, Non-Native Herbaceous Community Phase.
This community phase is dominated by an overstory canopy of very mature and decadent aspen that have reached maximal heights for the site. Average age is 120 plus years. Trees have developed tall, straight, clear stems with high, very rounded crowns. This phase typically develops in the absence of wildfire or other naturally occurring disturbances including disease and insect damage. Tree canopy cover is at a maximum for the site and is commonly greater than 50 percent. Very old trees often show signs of disease and/or insect damage. Understory vegetation is somewhat sparse due to tree competition, overstory shading, duff accumulation, etc. Minor amounts of non-native species including smooth brome, orchardgrass and Kentucky bluegrass may be present on the community. Thick duff layers are often present, completely covering the forest floor with needles and twigs.
Pathway 2.1B Community 2.1 to 2.2
This community pathway occurs when wildfire removes the growing aspen overstory. This event can be exacerbated by drought, insect damage and/or disease.
Pathway 2.1A Community 2.1 to 2.4
This community pathway occurs when fire is excluded from the plant community for long periods of time.
Pathway 2.2A Community 2.2 to 2.3
This community pathway occurs when fire is excluded from the plant community for long periods of time.
Pathway 2.3A Community 2.3 to 2.1
This community pathway occurs when fire is excluded from the plant community for long periods of time.
Pathway 2.3B Community 2.3 to 2.2
This community pathway occurs when wildfire removes the growing aspen overstory. This event can be exacerbated by drought, insect damage and/or disease.
Pathway 2.4B Community 2.4 to 2.1
This community pathway occurs when insect damage or disease kills old trees and allows the community to return to a community phase 2.1 type with snags present.
Pathway 2.4A Community 2.4 to 2.2
This community pathway occurs when wildfire removes the growing aspen overstory. This event can be exacerbated by drought, insect damage and/or disease.
State 3 Logged/Disturbed State
The logged or disturbed state is similar to the current potential state, however merchantable timber composed mostly of mature and old aspen have been removed. Various amounts of invasive species may also now be present in all community phases. This condition has not been well documented and so community phases in this state are based on possible community dynamics and not documented facts. Species composition is generally dominated by an immature canopy of aspen. Shrubs are of minor importance in the understory. A wide diversity of perennial forbs and grasses are also present. Non-native species including orchard grass, Kentucky bluegrass and smooth brome may also be present. These species could have been seeded as part of the site rehabilitation following the logging process.
Logging will release younger aspen trees and will give the site the look of an immature forest. Site will return to a mature, and finally an old or over-mature forest type if fire is excluded for very long periods of time.
The primary disturbance mechanisms are logging, road building or other man caused activities, weather fluctuations and fire or lack of fire. The logged state is still self sustaining but has a lower resistant to change due to a reduced resistance to disturbances. When disturbances do occur, the rate of recovery can be highly variable.
Logged/disturbed State: Plant communities influenced by man caused activities, wildlife browsing, insect herbivory, weather fluctuations, fire periods and surface disturbances.
Indicators: A community dominated by immature aspen with an understory of aspen reproduction, shrubs, grasses and forbs. The density of the overstory canopy determines the amount and composition of the other native perennial grasses, grasslikes and forbs that may be present.
Feedbacks: Natural fluctuations in weather patterns that allow for a self-sustaining mix of a aspen, shrubs and native grass and grasslike community. Insect herbivory, more frequent fires, or other disturbances that may allow for the increase of non-native species.
At-risk Community Phase: All communities are at risk when native plants are stressed and nutrients become available for non-native plants to increase.
Trigger: The increase of non-native plant species.
Community 3.1 Logged Aspen Forest Community Phase.
This community phase is typically found following logging or other man caused activity such as road building or pipeline construction. It is characterized by a partial canopy of aspen. Pole and/or immature sized trees are present and are beginning to once again dominant the community. Shrubs are a minor component in the understory as well as native perennial grasses and forbs. Non-native species including orchard grass, Kentucky bluegrass and smooth brome may potentially also be found on the site. Understory vegetation is somewhat influenced by tree competition, overstory shading, duff accumulation, etc. Seedlings and/or saplings of quaking aspen are common in the understory. Thick duff layers are present on some sites, completely covering the forest floor with needles and twigs.
Transition T1A State 1 to 2
This transitional pathway occurs when various disturbances such as road building, pipeline construction or fenceline clearing provides and opportunity for non-native species to become established. Seeding of these species could be a normal part of these activities. Once non-native species are established, a threshold has been crossed.
Transition T2A State 2 to 3
This transitional pathway occurs when timber logging and its associated activities, including road building and skid trail development, removes mature and over-mature aspen trees from the site and provides an opportunity for non-native species to increase. Seeding species such as orchardgrass and smooth brome would often be a normal part of these activities. Once the site is logged, a threshold has been crossed.
Restoration pathway R3A State 3 to 2
This restoration pathway occurs following logging activities when the site is allowed to recover naturally. Pole sized and immature aspen trees are increasing in dominance. Seeded, non-native herbaceous species where present, are well established.
