Ecological dynamics
Frequent disturbance is essential to the persistence of the reference state for this ecological site. The primary disturbance that maintained herbaceous dominance of this site historically was fire. Though some lightning ignitions likely occurred, fire was much more frequent in this ecological site due to its use by Native American tribes across the Puget Sound region who were highly skilled at applying it to enhance and maintain resources they relied on in these open prairies. In addition to fire, soil perturbation and careful tending during the regular harvest of bulbs and rhizomes by local tribes had a strong historic influence on plant composition and soil condition. These important activities have largely been removed from this ecological site where its reference state historically occurred, resulting in the conversion to forest or to other land uses such as urban development or post-European settlement style agriculture.
Solitary and small groups of Oregon white oak and native shrubs occur naturally in the reference plant communities for this ecological site. If no disturbance occurs, these plant communities are quickly invaded by trees and shrubs, transitioning from prairie to woodland or forest rapidly. Initial native tree species to invade this site include Douglas-fir, grand fir and lodgepole pine. In some historic cases, an increase in Oregon white oak density may have preceded development of conifer forest where a large acorn mast or a dense pre-existing oak seedling layer was present at the precise time when burning cessation occurred. The further the departure from the last fire event, the more advanced the encroachment becomes, ultimately to a point where the succeeding conifer forest, typically dominated by Douglas-fir, is difficult to discern from adjacent areas where conifers are the dominant cover for the reference state. Vast areas of this ecological site exist across MLRA 002 today as mature conifer forest or have been subject to development for urban or cropland agricultural use, and the reference for lowland prairie only exists in a few carefully protected and managed sites such as at Joint Base Lewis-McChord in the South Sound.
Reestablishment of plant communities that mimic the reference state for this ecological site is possible in areas of suitable soils and where management objectives and resources allow. In places that have become conifer forest, harvest of conifer trees must precede successive restorative actions. Native prairie species must be replanted and carefully tended so that they mature and can produce seed and perpetuate themselves on the site. In all cases, fire must be used frequently to prevent re-invasion of trees. Nonnative species are typically present in this ecological site where it has not transitioned to conifer forest. Due to their inherent adaptability to fire and frequent disturbance, some of these species tend to persist despite efforts to control them with fire, chemical or mechanical treatment. Their dominance in the community is affected by the type and intensity of disturbance employed. Careful management can reduce their cover, but elimination of these species altogether is unlikely. Thus, a pathway to full recovery of the reference state for this ecological site is uncertain.
State 1
Reference Native Dry Prairie
Community 1.1
Native Dry Prairie
A native grassland community including abundant carbohydrate-rich forbs and a rich mix of native herbaceous species. Woody vegetation is limited to few scattered oaks and in some places, ponderosa pines. Shrubs and other tree species are rare. Native conifers such as Douglas fir or grand fir may occasionally be present as isolated individuals if able to escape frequent fires.
State 2
Woody Encroached Prairie
Community 2.1
Invading Conifers and Shrubs
This community consists of a dense cover of establishing young trees and shrubs throughout a native prairie. Invading woody vegetation is composed of a mixture of native trees and native and non-native shrubs species. Douglas-fir is the most common encroaching tree, but grand fir and lodgepole pine may also invade in abundance. Non-native herbaceous species are introduced to the site and quickly become well-established or dominant. Occasional oaks and ponderosa pines remain emergent above encroaching tree seedlings and shrubs. Tree seedlings and shrubs are beginning to cause declines in cover of herbaceous species.
Community 2.2
Young Conifer Forest
This community consists of dense, young conifer trees. Shrubs and herbaceous species have been largely outcompeted by establishing conifers which have substantially shaded the site. Oaks and ponderosa pines are still present in the canopy but are beginning to suffer declines in vigor and crown die-back due to competition with ascending invasive conifer trees. Only small patches of the reference herbaceous plant community remain.
Pathway 2.1A
Community 2.1 to 2.2
This pathway represents the continued absence of fire or other disturbances. This pathway occurs if disturbances that can kill or clear woody vegetation, such as fire (natural or prescribed), mowing, or grazing continue to be absent from the site. This includes intentional omission of woody vegetation clearing activities and active suppression of fire.
State 3
Conifer Converted Prairie
Community 3.1
Mature Conifer Forest
Large, mature, Douglas-fir dominates the community by shading nearly all the understory and forming a continuous canopy. Other encroaching conifers may be present. Forbs and grasses are severely constrained to very few spots where there are gaps in the canopy or are eliminated from the site. Overstory oaks are overtopped, and many have died from lack of access to sunlight. Ponderosa pines may rival encroaching conifers in height but struggle to compete for light due to side-shading from adjacent conifers and many of these have also died. If any oaks and ponderosa pines remain, they are very few and are in poor health with very little living crown remaining. Shade tolerant shrubs and ferns may begin to establish.
Community 4.1
Timber Plantation
This community is the management-controlled climax condition for a Douglas-fir plantation. The overstory is even-aged and exclusively or near exclusively Douglas-fir. Trees are usually less than 100 years old. Trees are relatively evenly spaced, owing to their having been artificially established on a tight grid; there are typically no significant canopy gaps and little complexity in canopy structure. Stock used for planting is skewed to heavily favor Douglas-fir. Other conifers may be included in planting or occur naturally from adjacent seed sources depending on management objectives. Hardwoods such as maple, madrone and oak are typically less abundant due to efforts to control them and increase space for and growth of desired conifers. The understory may be somewhat sparse to relatively well-vegetated with a mix of highly shade-tolerant shrubs and herbaceous species, especially western sword fern or salal (Gaultheria shallon). Large snags are very few or absent.
Community 4.2
Regenerating Douglas-fir Plantation
Structure is single story small trees and shrubs.
This community consists of regenerating conifer forest over a large area that has been opened by timber harvest. Species composition is strongly controlled by management actions. The site is typically planted with Douglas-fir. Non-timber shrubs and trees are controlled to facilitate planted seedling survival, resulting in a dense, young conifer forest. Shrubs and mixed herbaceous species typically occupy space between planted saplings. These may include oceanspray, salal, red huckleberry, western sword, salmonberry and mixed native and non-native grasses and forbs. Introduced Himalayan blackberry (Rubus armeniacus) and Scotch broom (Cytisus scoparius) are often present and may be abundant, usually at the expense of native shrubs or planted trees. Snags are very few or absent. Downed woody debris may be abundant or limited depending on thoroughness of its reduction during the prior timber harvest.
Community 4.3
Stem Exclusion Douglas-fir Plantation
Structure is single story forest of even-aged conifer trees.
This community phase is the interim point in a Douglas-fir plantation between regeneration and the mature state. Composition is exclusively or near exclusively Douglas-fir, and the stand is very dense, having been artificially established on a grid and tended with weed control methods to maximize conifer survival. The conifers may be present at a lower frequency. A pre-commercial thin may be applied at or shortly before this phase to reduce inter-tree competition and maintain high growth rates. The understory is often very sparse, particularly if pre-commercial thinning is not performed, owing to the very limited light that reaches the forest floor. Only highly shade tolerant species occur, if present at all. Snags are very few or absent. Downed woody debris may be abundant or limited depending on thoroughness of its reduction during the prior timber harvest.
Pathway 4.1A
Community 4.1 to 4.2
This pathway represents even-aged harvest of a mature Douglas-fir plantation followed by conifer planting. This pathway may also result from a stand-replacing fire followed by a salvage harvest and replanting. Site preparation and removal of woody material to limit fire hazard is usually performed prior to planting.
Pathway 4.2A
Community 4.2 to 4.3
This pathway represents growth of an even-aged Douglas-fir plantation alongside active weed controls to limit competition with undesired species. Thinning of conifer saplings and pruning may or may not occur, depending on stand density or fire hazard concerns. Disturbances, such as fire, pests, and disease, are discouraged and controlled if possible.
Pathway 4.3A
Community 4.3 to 4.1
This pathway represents growth of an even-aged Douglas-fir plantation that is maturing and dominates the overstory. Light thinning may or may not occur, depending on stand density or fire hazard concerns. Disturbances, such as fire, pests, and disease, are discouraged and controlled if possible.
Pathway 4.3B
Community 4.3 to 4.2
This pathway results from a stand-replacing fire or a major pest or disease event that kills all or nearly all trees, followed by replanting of conifers. Salvage harvesting may occur if there is sufficient commercially viable material in the stand. Site preparation and removal of woody material to limit fire hazard is usually performed prior to planting.
State 5
Developed Cropland
Community 5.1
Cropland or Hayland
Structure is annual or perennial non-native species monoculture.
This community consists of a range of crops, including annually planted species, short-lived perennial species, and more permanent perennial crops. Hay and grasses and legumes for silage are included in this community.
Community 6.1
Native and Introduced Grasses and Forbs
Structure is annual and perennial grasses and forbs, few scattered trees.
Community 6.1 is a livestock grazed grassland dominated by a mix of perennial grasses and forbs. Introduced weedy species may be present on the site, and desired non-native forage grasses may be abundant. Native species are often intermixed and can be abundant in some areas. Oaks and pines are typically retained, although regeneration of these is limited by grazing activity or intentional suppression to retain open conditions for forage species. The site is grazed, mowed or burned often enough to prevent re-establishment of forest. Dominant shrubs are typically invasive rhizomatous species that form thickets such as Himalayan blackberry (Rubus armeniacus) or those that develop a robust seedbank and flourish in open conditions such as Scotch broom (Cytisus scoparius). Some tougher native shrub species such as California blackberry (Rubus ursinus) and salmonberry may be interspersed. Areas where ponding or brief inundation occurs commonly support non-native rhizomatous grasses. Between shrub thickets introduced pasture species such as tall fescue (Schedonorus arundinaceus), orchardgrass (Dactylis glomerata), redtop (Agrostis gigantea) and red fescue (Festuca rubra) are common. Native Roemer’s fescue (Festuca idahoensis ssp romeri) and other prairie reference species may be found but are usually not dominant.
Transition T1A
State 1 to 2
This transition represents the absence of fire or other disturbances. It occurs if disturbances that can kill or clear woody vegetation, such as fire (natural or prescribed), mowing, or grazing continue to be absent from the site. This includes intentional omission of woody vegetation clearing activities and active suppression of fire. Historically, this transition occurred primarily due to the cessation of Native American burning and root resource harvesting and tending.
Transition T1C
State 1 to 4
Transition T1B
State 1 to 5
This transition represents a shift of land use from the reference native prairie state to a cropland agriculture state. Trees are cleared and the site is tilled to support cropping activity. Amendments are added to soil and the site is irrigated, as needed. Crops grown may be perennial or annual.
Transition T1D
State 1 to 6
This transition is caused by the addition of livestock to the site and intentional establishment of mixed grass and forb species that support a grazed grassland system. Living oaks and pines may be retained for shade for livestock. Soil amendments and irrigation may or may not occur.
Restoration pathway R2A
State 2 to 1
This restoration transition represents a disturbance, such as fire, selective cutting or mowing, or herbicide treatment (or a mix of those) that removes encroaching woody vegetation, allowing herbaceous species to recover and dominate the site. The restoration of complete cover of native species is unlikely as non-native herbaceous species are likely to persist despite efforts to eradicate them. Overstory oaks and pines are minimally affected by disturbances, but a majority native cover can be attained by intensive, frequent management. This transition can be initiated from any community phase in state 2.
Transition T2A
State 2 to 3
This transition represents the continued absence of fire or other disturbances. This transition occurs if disturbances that can kill or clear larger woody vegetation, such as fire (natural or prescribed), mechanical harvesting of trees or chemical treatment continue to be absent from the site or are not employed. This includes intentional omission of woody vegetation clearing activities and active suppression of fire. This transition can be initiated from community 2.2 in state 2.
Transition T2B
State 2 to 5
This transition is caused by development of an intensive cropping or haying agricultural management system. Trees are cleared and the site is tilled to support cropping activity. Amendments are added to soil and the site is irrigated, as needed. Crops grown may be perennial or annual. This transition can be initiated from any community in state 2.
Transition T2C
State 2 to 6
This transition is caused by the removal of young conifers, brush and shrubs to restore open space, followed by the establishment of mixed grass and forb species that support a grazed grassland system. Living oaks may be retained for shade for livestock. Soil amendments and irrigation may or may not occur.
Restoration pathway R3A
State 3 to 1
This restoration represents invading conifer tree removal followed by planting of native prairie forbs and grasses. Oaks and ponderosa pines also require planting to be restored to the site. Conifer tree removal consists of a timber harvest or chemical or girdling treatments which kill conifers in place. Activities to restore the original plant community include removal of non-native grass, forb, and shrub species and prescribed fire, brush control, invasive plant control, mowing, thatching, grazing, and soil aeration and reseeding. The restoration of complete cover of native species is unlikely as non-native herbaceous species are likely to persist despite efforts to eradicate them, but a majority native cover can be attained by intensive, frequent management.
Transition T3A
State 3 to 4
This transition represents a shift of land use from an unmanaged, conifer converted prairie to a managed conifer plantation. A rotation of timber harvest and regeneration is implemented, and prairie oaks and pines are further reduced by intention or as casualties of heavy competition in a heavily shaded timber management system and collateral damage from harvesting actions and equipment.
Restoration pathway R4A
State 4 to 1
This restoration represents a change in land management system from timber plantation to an open prairie. It is achieved through plantation conifer tree removal followed by planting of native prairie forbs and grasses. Oaks and ponderosa pines also require planting to be restored to the site. Conifer tree removal most often consists of a timber harvest, though in rare cases chemical or girdling treatments which kill conifers in place may be used. Activities to restore the original plant community include removal of non-native grass, forb, and shrub species and prescribed fire, brush control, invasive plant control, mowing, thatching, grazing, and soil aeration and reseeding. The restoration of complete cover of native species is unlikely as non-native herbaceous species are likely to persist despite efforts to eradicate them, but a majority native cover can be attained by intensive, frequent management.
Restoration pathway T4B
State 4 to 3
This transition represents the cessation of timber management after the site has been managed previously for timber. This transition retains the conifer dominance of the site, and the forest is allowed to persist and continue to age beyond what is typical in a timber management rotation in the absence of actions that would open the site for prairie species, such as fire, mechanical treatment or chemical treatments. This transition can be initiated from any community phase in state 4.
Transition T4A
State 4 to 5
This transition is caused by an intentional clearing of land, or a stand replacing fire in state 4, followed by development of an intensive cropping or haying agricultural management system that prevents trees from re-establishing. This transition can be initiated from any community phase in state 4.
Transition T4C
State 4 to 6
This transition is caused by an intentional clearing of trees, followed by establishment of mixed grass and forb species that support a grazed grassland system. Improvements including soil amendments or irrigation may or may not be utilized. This transition can be initiated from any community in state 4.
Restoration pathway R5A
State 5 to 1
This restoration represents a change in land management system from cropland agriculture to prairie. It is achieved through cessation of conventional tilling and crop rotation management, and planting of native prairie forbs and grasses. Oaks and ponderosa pines also require planting to be restored to the site. Activities to restore the original plant community include removal of non-native grass, forb, and shrub species and prescribed fire, brush control, invasive plant control, mowing, thatching, grazing, and soil aeration and reseeding. The restoration of complete cover of native species is unlikely as non-native herbaceous species are likely to persist despite efforts to eradicate them, but a majority native cover can be attained by intensive, frequent management.
Restoration pathway T5C
State 5 to 2
This transition is caused by a cessation of cropland agriculture and lack of disturbance activities. Various native and non-native trees, herbaceous plants, and shrubs naturally establish throughout the site due to lack of significant disturbance or control.
Restoration pathway T5B
State 5 to 4
This transition represents a shift of land use from a cropland state to a managed conifer plantation. Conifer trees are intentionally established by planting throughout cropped site. A rotation of timber harvest and regeneration is implemented, and species composition is heavily controlled to favor conifers.
Transition T5A
State 5 to 6
This transition is caused by establishment of mixed grass and forb species that support a grazed grassland system.
Restoration pathway R6A
State 6 to 1
This restoration represents an effort to restore the native prairie plant community and control invasive and other non-natives species. It is achieved through planting of native prairie forbs and grasses, and suppression of non-native species. Oaks and ponderosa pines also require planting to be restored to the site if they were previously removed. Activities to restore the original plant community include removal of non-native grass, forb, and shrub species and prescribed fire, brush control, invasive plant control, mowing, thatching, grazing, and soil aeration and reseeding. The restoration of complete cover of native species is unlikely as non-native herbaceous species are likely to persist despite efforts to eradicate them, but a majority native cover can be attained by intensive, frequent management. It may be possible to continue grazing on the site if carefully controlled to prevent decline of native species.
Restoration pathway T6B
State 6 to 2
This transition is caused by a cessation of grazing and lack of other disturbance activities. Various native and non-native trees, herbaceous plants, and shrubs naturally begin to establish throughout the site due to lack of significant disturbance or control.
Restoration pathway T6C
State 6 to 4
This transition represents a shift of land use from a grazed grassland state to a managed conifer plantation. Conifer trees are intentionally established by planting throughout cropped site. A rotation of timber harvest and regeneration is implemented, and species composition is heavily controlled to favor conifers.
Restoration pathway T6A
State 6 to 5
This transition is caused by development of an intensive cropping or haying agricultural management system. Trees and shrubs are cleared and the site is tilled to support cropping activity. Amendments are added to soil and the site is irrigated, as needed. Crops grown may be perennial or annual.
