State 1
Spruce - Fir Forests

This state represents the range of variability that dominates the dynamics of this site. The canopy will typically have a strong dominance of conifers, particularly red and white spruce, mixed with variable amounts of balsam fir. Scattered hardwoods may be infrequent or completely absent. The understory will have variable coverage depending on the stage of succession.

Resilience management. Silvicultural methods for these forest types include clear cutting, selective harvesting, and shelterwood cuttings. In natural systems, stand-replacing disturbances were rare and were dominated by small-scale disturbances, resulting in most forests being multi-aged.

Community 1.1
Late Successional Uneven-Aged Spruce Forest

The reference phase consists of a closed canopy (>75% closure) of spruce (>60% cover) with a minor to moderate amount of balsam fir (often up to 20% cover). Scattered hardwoods may be present but generally do not make up much cover (

Resilience management. Group selection or irregular shelterwood harvest methods may assist with advanced spruce regeneration to maintain a multi-aged stand that minimizes forest disturbance as well as promoting spruce over other softwood species. This will establish new cohorts of red spruce and expose residual overstory trees to promote wind-firmness.

Forest overstory.The canopy is dominated by some combination of red spruce, white spruce, and balsam fir. Associates include yellow birch (Betula alleghaniensis), eastern hemlock (Tsuga canadensis), white pine (Pinus strobus), tamarack (Larix laricina), red maple (Acer rubrum), black cherry (Prunus serotina), or northern white cedar (Thuja occidentalis). Balsam fir is often found in open gaps or in younger stands.

Forest understory. The forest understory is often sparse or patchy, consisting of mostly tree regeneration. Shrubs are typically dwarfed and sparse to absent. Herbaceous species will often be less than 10% cover. Conifer litter is present in moderate to high amounts on the ground surface, with bryophytes forming partial to full cover beneath. These bryophytes provide good nurse habitats for tree regeneration and low forbs. Characteristic species may include Schreber’s big red stem moss (Pleurozium schreberi), stair-step moss (Hylocomium splendens), knights plume moss (Ptilium crista-castrensis), greater whipwort (Bazzania trilobata), windswept moss (Dicranum spp), and species of Sphagnum.

Community 1.2
Early Successional Herbaceous Phase (Temporary Dominance)

This phase occurs after large scale disturbances such as heavy logging or a stand replacing natural event such as windstorm damage, fire, insect damage, disease, etc. resulting in an open stand. Remnant living overstory species, standing dead snags, understory downed woody debris, and remaining groundcover may vary depending on the nature and severity of the disturbance. Large accumulations of slash and the development of heavy herbaceous cover may inhibit natural regeneration, perpetuating this phase.

Forest overstory.The canopy will often be sparse to absent, with leave trees or standing dead trees remaining for wildlife habitat.

Forest understory. Annual grasses and forbs and perennial shrubs take temporary dominance while tree regeneration occurs. Saplings will tend to be less than 1.5 feet in height, whereas shrubs can range up to 15 feet in some areas but will often be less than 6 feet. The once dominant groundcover of bryophytes is likely to be all but replaced with herbaceous litter of these species.

Community 1.3
Early Successional Even-Aged Spruce-Fir Forest (Doghair Forest)

This phase consists of spruce and balsam fir saplings that are the dominant species growing extremely close together. This forested phase will often be extremely dense and greater than 1.5 feet but less than 15 feet in height, with average diameters less than 1.6 inches at breast height (DBH). As these trees grow, competition will weed out individual trees until a balanced density is achieved. Mixed in with the highly dense spruce-fir forest will often be other early successional forest species such as paper birch, aspen, and pine. As the ground surface becomes more shaded and more deposits of downed woody debris occur, bryophyte cover may begin to reestablish. Overstocked areas of spruce and / or fir may result in slow growth rates, resulting in overtopping by faster growing hardwood species that can suppress conifer growth, resulting in a temporary hardwood or mixed forest.

Resilience management. Applying herbivore browse protection (e.g. snowshoe hare) for seedlings using tree tubes may assist in the regeneration and establishment of regenerative spruce-fir forests.

Community 1.4
Mid Successional Even-Aged Spruce-Fir Forest

Figure 8. Red spruce forest in the Nullhegan Basin of Silvio O. Conte National Fish and Wildlife Refuge near Brighton, VT. Closed canopy overstory of red spruce prior to any preparatory or establishment cuts. NASIS Vegetation Plot ID .....

Figure 9. Managed red spruce forest in the White Mountain National Forest near Five Corners, NH. Partially open overstory of red spruce to allow for understory regeneration of spruce, fir, and pine. NASIS Vegetation Plot ID 2024NH009023.

Figure 10. Managed even-age red spruce forest canopy view from the ground in Groton State Forest near Peacham, VT. Spruce is the dominant canopy species and makes up the dominant age and heigh class. NASIS Vegetation Plot ID 2025VT005003.

This phase consists of variable canopy closure in which spruce and fir are mixed with early successional and other hardwood species (often less than 25% cover) in a similar age class (typically less than 150 years). The understory will often range from sparse to absent in natural stands to having large amounts of regeneration in managed stands. This community may slightly reflect the microtopography of the reference state caused by tip ups. These even age stands will often have one to two distance age classes present, often seen as regeneration and pole (immature trees) or sawtimber (mature trees) wood.

Resilience management. In natural settings, as the larger early successional species become removed, canopy gaps will allow for the development of a multi-aged stand of dominantly spruce, with some fir and hardwood species being present in under lower canopy layers (transition to 1.5). In managed settings, preparatory and establishment cuts (extended / irregular shelterwood methods) can be used to increase the vitality and health of the intended residual trees while simultaneously open growing space in the canopy to encourage the establishment of regrowth in the understory before removal of the remaining overstory species.

Forest overstory.The forest overstory will generally consist of a monoculture or mixed stand of red spruce, white spruce, and / or balsam fir that are part of a similar height and age class. In natural stands, these will often be growing close together and will create a shaded understory with minimal development. In managed stands, these will often be more evenly spaced to allow light to reach the understory and promote regeneration. <br /> <br /> Less common are hardwoods, often mature early succession species, including as red maple (Acer rubrum), quaking aspen (Populus tremuloides), bigtooth aspen (P. grandidentata), paper birch (Betula papyrifera), yellow birch (Betula alleghaniensis), or black cherry (Prunus serotina).

Forest understory. In natural settings or stands prior to preparatory or establishment cuts the understory will often be highly shaded with little to no understory species or regeneration. In managed stands (post preparatory or establishment cuts), the understory will often consist of large amounts of spruce regeneration. Beneath the tree regeneration bryophytes may make a large portion of the ground cover with scattered forbs.

Community 1.5
Mid Successional Even-Aged Mixedwood Forest

Figure 11. Even-aged stand of red maple, balsam fir, and red spruce in Groton State Forest near Peacham, VT. The understory is dominantly leaf litter and the overstory is mostly deciduous with some mature softwood canopy trees. NASIS Vegetation Plot ID 2025VT005002.

Figure 12. Even-aged mixedwood forest canopy view from the ground in Groton State Forest near Peacham, VT. Maple, spruce, and fir are the dominant canopy species and makes up the dominant age and heigh class. NASIS Vegetation Plot ID 2025VT005002.

Repetitive harvesting of softwoods for pulp may exhaust the natural conifer seedbank and allow for a higher density of hardwood species, particularly those representative of a mixed northern hardwoods forest. Eventually softwood regeneration, dominantly spruce and fir, may occur and return to a place of dominance, but this process is thought to take a long time. The ground surface will often lose the bryophyte cover and be replaced with herbaceous leaf litter. Shrubs and forbs may become more dominant in the understory during this time.

Pathway 1.1A
Community 1.1 to 1.2

This may occur through intensive harvesting practices such as clearcutting for pulp and lumber. Immediate loss of mature canopy trees increases light availability for understory vegetation and disturbs the seedbank, shifting dominant species composition and structure. Natural mortality from windstorms, insects, diseases, ice or snow damage may also reflect a similar transition, opening the canopy and allowing for the temporary dominance of grasses and forbs, but will leave behind large pieces of woody material for nurse logs. Loss of characteristic groundcover mosses is common as more light availability and altered soil conditions favor faster-growing species. Harvesting during winter months is recommended to prevent extensive rutting and hydrologic instability that may lead to issues such as erosion, loss of moisture retention, and changes in groundwater flow.

Pathway 1.2A
Community 1.2 to 1.3

This transition can occur if the basic requirements for tree regeneration are met, primarily an adequate seed supply, proper seedbed, and light, temperature, and moisture conditions are conductive for seed germination and survival. This transition will often occur in less than but no greater than 20 years post-canopy disturbance. Planting spruce can help accelerate the restoration of the natural vegetation of harvested areas.

Pathway 1.2B
Community 1.2 to 1.5

This transition may occur if there is no longer a viable seedbank of spruce or fir present in the system and it has not been replanted. This may occur as the result of repetitive harvesting of spruce and fir for pulpwood. This may also occur following extensive clearcutting, as spruce and balsam fir seedlings are commonly rooted in the upper part of the organic layer, which dries out after heavy logging, resulting in extensive seedling mortality (Pothier and Prevost, 2006). These species are also sensitive to full light and to temperature extremes at their juvenile stage, causing mortality of seedlings and can result in rapid hardwood establishment with spruce and balsam fir in the regeneration stratum beneath a low, closed density canopy.

Pathway 1.3A
Community 1.3 to 1.2

This may occur through intensive harvesting practices such as clearcutting for pulp and lumber. Immediate loss of mature canopy trees increases light availability for understory vegetation and disturbs the seedbank, shifting dominant species composition and structure. Natural mortality from windstorms, insects, diseases, ice or snow damage may also reflect a similar transition, opening the canopy and allowing for the temporary dominance of grasses and forbs, but will leave behind large pieces of woody material for nurse logs. Loss of characteristic groundcover mosses is common as more light availability and altered soil conditions favor faster-growing species. Harvesting during winter months is recommended to prevent extensive rutting and hydrologic instability that may lead to issues such as erosion, loss of moisture retention, and changes in groundwater flow.

Pathway 1.3B
Community 1.3 to 1.4

This transition will occur over time, typically greater than 20 years but less than 100 years into a stand’s lifecycle. The early successional stand will thin in density either naturally (treefall, disease, etc.) and with human interference (forest stand improvement [FSI]). This will lead to an even-aged stand in which spruce is typically the dominant species. Selective cuts and thinning through FSI methods can allow for the regeneration of understory vegetation, including saplings, while encouraging the growth of the desired species. FSI during winter months is recommended and will differ from clearcutting or selecting harvesting methods through the limited disturbance to the local hydrology.

Pathway 1.4A
Community 1.4 to 1.1

This transition will over time, often greater than 150 years, in which the main stand remains relatively undisturbed. This will allow the spruce stand to mature in its size, age, and height classes, creating a more uneven aged stand with a well-developed overstory and a dark, cool understory that limits regeneration. Balsam fir and other mixed in hardwoods will reach the end of their natural life expectancy and will revert the canopy to spruce dominance. This transition may be assisted with forest stand improvement (FSI) practices, often seen as single tree removal. Red spruce will become the dominant canopy, and the understory will reflect more variation in microtopography (hummocks and hollows) due to natural disturbance tip ups.

Pathway 1.4B
Community 1.4 to 1.2

This may occur through intensive harvesting practices such as clearcutting for pulp and lumber. Immediate loss of mature canopy trees increases light availability for understory vegetation and disturbs the seedbank, shifting dominant species composition and structure. Natural mortality from windstorms, insects, diseases, ice or snow damage may also reflect a similar transition, opening the canopy and allowing for the temporary dominance of grasses and forbs, but will leave behind large pieces of woody material for nurse logs. Loss of characteristic groundcover mosses is common as more light availability and altered soil conditions favor faster-growing species. Harvesting during winter months is recommended to prevent extensive rutting and hydrologic instability that may lead to issues such as erosion, loss of moisture retention, and changes in groundwater flow.

Pathway 1.4C
Community 1.4 to 1.3

This is often seen in shelterwood systems and used to release the established seedlings by removing the remaining overstory to allow the understory more growing space. This will revert the forest back to a doghair forest phase where tree regeneration is abundant with the absence of an overstory component.

Pathway 1.5A
Community 1.5 to 1.1

This transition will over time, often greater than 150 years, in which the main stand remains relatively undisturbed. This will allow any spruce in the overstory to mature in its size, age, and height classes and seed in new saplings, creating a more uneven aged stand with a well-developed overstory and a dark, cool understory that limits regeneration. Balsam fir and other mixed in hardwoods will reach the end of their natural life expectancy and will revert the canopy to spruce dominance. This transition may be assisted with forest stand improvement (FSI) practices, often seen as single tree removal. Red spruce will become the dominant canopy, and the understory will reflect more variation in microtopography (hummocks and hollows) due to natural disturbance tip ups.

Pathway 1.5B
Community 1.5 to 1.2

This may occur through intensive harvesting practices such as clearcutting for pulp and lumber. Immediate loss of mature canopy trees increases light availability for understory vegetation and disturbs the seedbank, shifting dominant species composition and structure. Natural mortality from windstorms, insects, diseases, ice or snow damage may also reflect a similar transition, opening the canopy and allowing for the temporary dominance of grasses and forbs, but will leave behind large pieces of woody material for nurse logs. Loss of characteristic groundcover mosses is common as more light availability and altered soil conditions favor faster-growing species. Harvesting during winter months is recommended to prevent extensive rutting and hydrologic instability that may lead to issues such as erosion, loss of moisture retention, and changes in groundwater flow.

Pathway 1.5C
Community 1.5 to 1.4

Mid Successional Even-Aged Mixedwood Forest

Mid Successional Even-Aged Spruce-Fir Forest

Softwood release through hardwood thinning methods (cutting, ringing, or herbicide application) can assist in the restoration of a softwood dominated forest, as well as creating scarified seedbeds for its establishment.

State 2
Agricultural Row Crops

This state represents a once forested area now cleared for cropland. This will typically only occur on gentler slopes (less than15 percent) due to potential for water erosion. Corn and potatoes are the dominant agricultural row crop on this site.

Community 2.1
Conventionally Tilled Row Crops

This phase consists of cleared and cultivated fields for annual or perennial crops that are heavily managed with regular soil disturbances.

Community 2.2
Conservation Till Row Crops

This phase consists of cleared and cultivated fields for annual or perennial crops that are managed with a conservation focus on tilling practices. These methods include strip till, vertical till, or no till systems. These methods may improve soil ecosystem function over time.

Pathway 2.1A
Community 2.1 to 2.2

This transition can occur through the reduction or elimination of conventional tillage practices and the implementation of conservation practices. Conservation strategies may vary depending on local site conditions and should be addressed with management planners. Through the long term conservation practices, soil physical and chemical properties should improve and pose less of a risk with land management issues.

Pathway 2.2A
Community 2.2 to 2.1

This transition can occur through the use of intensive, regular mechanical soil disturbances.

State 3
Managed Grassland

This state represents a once forested area now cleared and managed as pasture or hay fields. This will typically only occur on gentler slopes (less than15 percent) due to potential for water erosion. Pasture vegetation can consist of grasses, legumes, other forbs, shrubs or a mixture. Many of these forages are introduced, having originally come from areas in other states or continents. Overgrazed pastures can lead to soil compaction and numerous bare spots, which may then become focal points of accelerated erosion and colonization sites of undesirable plants or weeds.

Community 3.1
Desirable Pasture Conditions

This community phase represents commonly planted forage species on pastureland and hay land. The suite of plants established on any given site may vary considerably depending upon purpose, management goals, and usage (e.g., horse vs. cattle). Most systems include a mixture of non-native cool-season grasses and legumes that provide forage throughout the growing season. Several additional plants and/or species combinations maybe present depending on the objectives and management approaches of the land manager/owner. This may also be the result of bare soil after cessation of agriculture, and will be short-lived without annual mowing, but can persist indefinitely when actively managed.

Resilience management. Mechanical mowing, at least annually but ranging up to four times during the growing season, helps maintain these areas as dominant grasslands

Community 3.2
Undesirable Pasture ("Old Field") Conditions

This phase represents a more degraded phase for livestock. While some utilization of desirable pasture plants will occur, undesirable species are prolific and will make up more than 50 percent cover. As undesirable pasture species grow, desirable pasture grasses and forbs will decrease in cover. Small trees and shrubs are often present but do not form great amounts of canopy cover. As time progresses if left neglected, these fields become colonized by pioneer tree species, often white pine, but may include species such as eastern redcedar, birch, or spruce. These abandoned fields can persist for many years and may remain for up to 30 years before reverting to forested conditions.

Pathway 3.1A
Community 3.1 to 3.2

This may occur when grassland management operations are reduced or eliminated, allowing for succession to predominately undesirable and incursive forbs, grasses, shrubs, and trees. Desirable species may remain but will often be less than 50 percent total cover.

Pathway 3.2A
Community 3.2 to 3.1

This may occur through the removal of undesirable species in a managed grassland and return to specific management practices for pasture or hay production. The amount of energy required to restore an old field is dependent on the amount of time it has been out of production, with longer periods of abandonment requiring more energy. Brush management or tilling operations may be needed to control undesirable species before reseeding with a desirable species mix using the correct rate and methods.

State 4
Post-Agricultural Successional Forests

This state represents a once cleared forest that had been under pasture or crop management that has been abandoned over long periods of time (often greater than 30 but less than 200 years).

Characteristics and indicators. Vegetative indicators typically include a young to mature forest, most often eastern white pine (<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=PIST" target="_blank" title="Open in plants.usda.gov"><i>Pinus strobus</i></a>), of a singular age and height class (at least 16 feet tall). If aged, these will often range from 30 years to over 100 years old, and will often reflect the time since abandonment. The understory is typically sparse and open due to the acidic nature of pine needles. Soil indicators include the absence of surface fragments and the presence of a plowed horizon (Ap). Physiographic identifiers often include relatively flat sloped areas with smooth microtopography, becoming more complex as the forest develops and natural tip ups occur.

Community 4.1
Even Age Eastern White Pine Stands

Following long-term agricultural abandonment, eastern white pine (Pinus strobus) typically forms an even aged monoculture, being the dominant overstory species. Understory vegetation will often be sparse but may support scattered forbs and woody regeneration reflective of the reference condition. The height and age of a stand will be dependent on time since abandonment. These stands are commonly seen throughout New England, where early European settlements previously cleared an area but has since been abandoned.

Resilience management. These forests are typically not seen as the climax, or reference, community, and rather classified as disturbance-dependent. Over time, species representative of the reference conditions, such as spruce and fir, may begin to form in the subcanopy under the tall pines if a seed source is present and conditions are optimal.

Transition T1A
State 1 to 2

Converted forested communities have often undergone the clearing of native vegetation and site preparation before conversion to agricultural fields is complete. Due to the complex microtopography of the native site, land smoothing and / or leveling may be required, as well as undergoing practices such as tilling for the field to be ready to plant. Planting of desired crops can be done by hand or machine at desired spacing and intervals. Historically cleared land may have had water control structures installed to manage seasonal high water tables.

Transition T1B
State 1 to 3

Converted forested communities have often undergone the clearing of native vegetation and site preparation before conversion to a managed grassland state is complete. Due to the complex microtopography of the native site, land smoothing and / or leveling may be required. Planting of desired mixtures of grasses and / or legumes can be done by hand or machine at desired densities. Historically cleared land may have had water control structures installed to manage seasonal high water tables.

Transition T2A
State 2 to 3

Cropland can be converted to managed grasslands following the removal of the crop and the planting of desired mixtures of grasses and / or legumes at the desired density. Short term abandonment of crop fields may also give rise to ruderal shrublands and undesirable grasses and forbs that, if managed correctly, can be converted into a persistently managed grassland.

Transition T2B
State 2 to 4

This state transitions to a post-agricultural successional forest following the long-term abandonment of converted fields. While short-term abandonment of fields may allow for dominance of undesirable species they can revert to a commodity field with proper management. Long-term abandonment is accepted as the establishment of a single age stand of closed canopy forest.

Transition T3A
State 3 to 2

Managed grassland can be converted to agricultural fields following the removal of the grasses / legumes (typically achieved by tilling) and planting the desired crop at the desired spacing and intervals.

Transition T3B
State 3 to 4

This state transitions to a post-agricultural successional forest following the long-term abandonment of converted fields. While short-term abandonment of fields may allow for dominance of undesirable species they can revert to a commodity field with proper management. Long-term abandonment is accepted as the establishment of a single age stand of closed canopy forest.

Transition T4A
State 4 to 1

Following the establishment of post-agricultural successional forests the system is expected to increase in physical and chemical stability as the stand age increases. Over time as more natural disturbances occur and the forest soils are stable, species representative of the reference community can become dominant as pine mortality occurs. Individual mortality and tip ups will reform the complex microtopography (pit and mound) seen in the reference conditions.

Constraints to recovery.Forest operations, such as thinning and selective harvesting, can be used to assist in recreating reference conditions. Natural mortality from insects (pine weevil [Hylobius abietis]) or tree throw can serve to open the canopy and promote new growth. Available seedbanks must be present for spruce and fir regeneration.