Ecological dynamics

Legend
State 1.0: This represents the historic state in which there are no weedy species present at the site. The community is the same composition as currently but without any weedy species.
Community Phase 1.1: This represents mature black cottonwood in the overstory with a significant presence of shorter statured water birch present. The understory is multistoried with medium statured shrubs common snowberry and rose species and forbs and grasses. Cowardin Classification: Paustrine: Class=forested wetland; subclass=broad-leaved deciduous; Water regime= temporarily flooded to intermittently flooded.


State 2.0: This represents the current reference state in which the same dominant species exist as in State 1.0 but there is a low presence of weedy species.
Community Phase 2.1: This represents the reference state in which tall, mature black cottonwood dominate the overstory with a minor amount of water birch. The understory has a mixture of shrubs including: redosier dogwood (Cornus sericea ssp. sericea), common snowberry (Symphoricarpos albus), and Rocky mountain maple (Acer glabrum). There is a mixture of herbaceous forbs. There can be small gap dynamics in which one or two trees die, opening the canopy and allowing sunlight into the forest floor. Cowardin Classification: Paustrine: Class=forested wetland; subclass=broad-leaved deciduous; Water regime= temporarily flooded to intermittently flooded.

Community Phase 2.2: This represents the community post disturbance from flooding or fire. It represents an early seral stage. If the flooding event or fire is substantial, than the site will not have trees. The mineral soil will allow for re-establishment by herbaceous forbs, grasses and resprouting shrubs. Tree species, especially black cottonwood, will become established on the mineral soil. Over time, the trees will over-top the shrubs and herbaceous species, and dominate. This phase is very susceptible to flooding and may be eliminated after just a year or two of growth. Ice can also damage this phase by mechanical damage (bending, shearing or pulling out of young stems or tilting or pushing over of mature trees) or flooding. Seedlings and sapling black cottonwoods are particularly susceptible to fire since their bark is thin and the root system shallow. Young black cottonwoods are very susceptible to defoliation by livestock, wildlife and beaver use, and can be eliminated. Cowardin: System=palustrine; Class=forested wetland; Subclass=broad-leaved deciduous; Water Regime (nontidal) = seasonally flooded.

Community Phase 2.3: This represents the community in competitive exclusion phase in which the tree seedlings have grown to sapling and pole sized trees and are competing with each other for resources. The canopy cover is very high, shading out the forest floor and limiting the understory to shade-tolerant species. Cowardin Classification: Paustrine: Class=forested wetland; subclass=broad-leaved deciduous; Water regime= temporarily flooded to intermittently flooded.

Community Phase 2.4: This site is directly adjacent to the active floodplain that is slightly higher and drier and sustains a ponderosa pine overstory with an understory of shrubs, forbs and perennial bunchgrasses. The mature trees are able to access the subsurface water and grow very large.

State 3.0: This community has sustained a long period of heavy utilization grazing in which the native community has been impacted and increaser species, such as baltic rush are dominant. There is increased hummocking and trailing throughout the site, which can impact roots of the native plant community and cause a decrease in productivity of the site.

State 4.0 Native with introduced annuals state:
4.1: This represents the community after heavy grazing resulting in a decrease of shrubs species except western snowberry and rose species and an introduction of weedy species such as timothy and Kentucky bluegrass. This represents a moderately disturbed secondary successional stage. Cowardin Classification: Paustrine: Class=forested wetland; subclass=broad-leaved deciduous; Water regime= temporarily flooded to intermittently flooded.

4.2: This represents the community after severe grazing in which all shrub species have been eliminated and the cover of weedy species has increased dramatically. Secondary successional state. This depauperate state has only an overstory of black cottonwood and an understory of wood’s rose, common timothy and Kentucky bluegrass. Cowardin Classification: Paustrine: Class=forested wetland; subclass=broad-leaved deciduous; Water regime= temporarily flooded to intermittently flooded.

Community Phase Pathway 2.1.A: This pathway represents flooding disturbance intense enough to kill trees and set the site back to mineral soil and colonizing herbaceous species, resprouting shrubs and tree seedlings.


Community Phase Pathway 2.2A: This pathway represents time without disturbance.


Community Phase Pathway 2.3A: This pathway represents time without disturbance.


Community Phase Pathway 2.3B: This pathway represents flooding disturbance intense enough to kill trees and set the site back to mineral soil and colonizing herbaceous species, resprouting shrubs and tree seedlings.

Transition 1: This represents the pathway from the historic state 1.0 without any weedy species present in the vegetation community to State 2.0 in which there are very low covers of weedy species present in the vegetation community.

Transition 2: This represents the pathway from the current state to one in which increaser species such as baltic rush dominate the vegetation community due to sustained, heavy grazing.

Transition 3: This represents the pathway from State 2.0 the current reference state in which the cover of weedy species is very low to State 4.0 in which there has been a dramatic increase of weedy species through heavy continuous livestock grazing.

Community Phase Pathway 4.1.A: This pathway represents the community after heavy grazing with a concomitant loss of shrub species except western snowberry and rose species.

Community Phase Pathway 4.2A: This pathway represents the community after cessation heavy grazing or establishment of prescribed grazing methods in which there is an increase of shrub species such as serviceberry, redosier dogwood and western snowberry and a decrease in shrub species such as western snowberry and rose species.