Ecological dynamics
[Caveat: The vegetation information contained in this section and is only provisional, based on concepts, and future projects support validation through field work. *] The vegetation groupings described in this section are based on the terrestrial ecological system classification and vegetation associations developed by NatureServe (Comer et al., 2003) and localized associations provided by the New York Natural Heritage Program (Edinger et al., 2014), Maine Natural Areas Program (Gawler and Cutko, 2010), New Hampshire Natural Heritage Program (Sperduto and Nichols, 2011), and Massachusetts Division of Fisheries and Wildlife (Swain, 2020).
The reference state is a boreal softwood dominated forest where red spruce (Picea rubens) often makes up a dominant component in the canopy. Other trees may include black spruce, tamarack, balsam fir, red maple, and / or white pine, but will often only be present in small amounts. The understory is diverse with sphagnum moss, cinnamon fern, creeping snowberry, and three-seed sedge common.
Large scale logging is common on this site and will set the stand through a series of phases but will revert to a spruce dominant forest within 100 years. Due to the wetness of this site, limiting harvesting to very dry years or during the winter months should be prioritized so soil and ground disturbances may be minimized. Logging operations can significantly alter the structure and function of these swamps, causing shifts in vegetative composition, hydrologic function, and ecosystem services. Selective harvesting, thinning, and shelterwood cuts will not generally shift the site to a different state but may help promote forest regeneration and result in a temporary increase in understory shrubs and herbs. Clear cutting may have the largest impact on these communities, with potential disruption of water retention, soil surface cover and altered groundwater flow. In some cases, clearcutting can be used as a surrogate to fire, promoting rapid growth of seedlings after the disturbance. Draining and ditching along with tree cover removal can convert the site to hayfield and pasture with varying degrees of ponding, depending on the extent of hydrological alteration.
Red spruce is relatively free from insects and diseases until it is mature, where it can become susceptible to spruce budworm (Choristoneura fumiferana), eastern spruce beetle (Dendroctonus rufipennis), European spruce sawfly (Diprion hercyniae), yellowheaded spruce sawfly (Pikonema alaskensis), and eastern spruce gall adelgid (Adelges abietis).
Fire is typically not a dominant risk in these communities due to their inherent wetness and general lack of ladder fuels. It has been suggested that the increase of dead fuels following insect or disease outbreaks (such as spruce budworm) increased the likelihood of fire (Sullivan 1993). Red spruce is easily killed by fire and can cause serious damage to the roots if it consumes the litter and organic layers but may assist seed germination. Postharvest/postfire restocking by red spruce is extremely slow where the organic layers are destroyed by severe fire (particularly where harvest has been heavy).
State 1
Red Spruce Swamp
These are softwood dominated boreal forests most often comprised of mature red spruce (Picea rubens) found on shallow organic over mineral soils. The canopy is often a pure stand of red spruce that is often closed to broken but may be mixed with black spruce (Picea mariana) or red-black spruce hybrids. Other trees that are found in the canopy include balsam fir (Abies balsamea) or red maple (Acer rubrum). Tall shrubs are often well developed, and forbs and graminoids are well expressed in the understory. Bryophytes are the dominant groundcover, covering both hummocks and hollows. Natural disturbances by wind create tip-ups of individual trees or small groups of trees that are attributed to the hummock and hollow microtopography. Changes in light availability and soil wetness are the dominant drivers for these communities, with logging being the main factor attributable to large scale changes.
Dominant plant species
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red spruce (Picea rubens), tree
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black spruce (Picea mariana), tree
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balsam fir (Abies balsamea), tree
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red maple (Acer rubrum), tree
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blueberry (Vaccinium), shrub
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holly (Ilex), shrub
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white meadowsweet (Spiraea alba), shrub
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gray alder (Alnus incana), shrub
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sedge (Carex), grass
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bunchberry dogwood (Cornus canadensis), other herbaceous
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osmunda (Osmunda), other herbaceous
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sensitive fern (Onoclea sensibilis), other herbaceous
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eastern marsh fern (Thelypteris palustris), other herbaceous
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sphagnum (Sphagnum), other herbaceous
Community 1.1
Late Successional Spruce Forest
The reference phase consists of a closed to partly open (ranging from greater than 20 to over 65% closure) of red and black spruce with a minor to moderate amount of red maple. Other trees such as yellow birch, northern white cedar, balsam fir, and occasionally eastern hemlock may be present. Tall shrubs are often well developed and will be inversely related to canopy closure. The herbaceous layer will often be dominated by species adapted to wet conditions and will have a groundcover of mosses and other bryophytes. This site is often resilient to small disturbances, most commonly single tree tip ups, which creates a microtopography of hummocks and hollows. These will often reflect even-age structures likely result from the past influences of insects, fire, blowdowns, harvesting, or a combination of those factors.
Within the Northeast US, this community type correlates to Maine’s “Spruce – Fir – Wet Flat” concept (Gawler and Cutko 2010), Massachusetts’ “Red Spruce Swamp” (Swain and Kearsley 2001), New Hampshire’s “Red Spruce Swamp” concept (Sperduto and Nichols 2012), New York’s “Spruce-fir Swamp” concept (Edinger et al. 2014), and Vermont’s “Red Spruce – Cinnamon Fern Swamp” concept (Thompson, Sorenson, and Zaino 2019). This correlates with NatureServes ‘Picea rubens - Acer rubrum / Ilex mucronata Swamp Forest’ Association (CEGL006198).
Dominant plant species
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red spruce (Picea rubens), tree
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black spruce (Picea mariana), tree
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balsam fir (Abies balsamea), tree
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red maple (Acer rubrum), tree
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catberry (Ilex mucronata), shrub
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common winterberry (Ilex verticillata), shrub
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gray alder (Alnus incana), shrub
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highbush blueberry (Vaccinium corymbosum), shrub
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white meadowsweet (Spiraea alba), shrub
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threeseeded sedge (Carex trisperma), grass
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greater bladder sedge (Carex intumescens), grass
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sphagnum (Sphagnum), other herbaceous
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bunchberry dogwood (Cornus canadensis), other herbaceous
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parasol whitetop (Doellingeria umbellata), other herbaceous
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starflower (Trientalis borealis), other herbaceous
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cinnamon fern (Osmunda cinnamomea), other herbaceous
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royal fern (Osmunda regalis), other herbaceous
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sensitive fern (Onoclea sensibilis), other herbaceous
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eastern marsh fern (Thelypteris palustris), other herbaceous
Community 1.2
Early Successional Herbaceous Phase
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. Annual species may have important temporary dominance as woody perennial shrubs and trees become reestablished. Trees 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. 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 (Viburnums, Rubus, Vaccinium, etc.) may inhibit natural regeneration, perpetuating this phase.
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.
Community 1.4
Mid Successional Even Aged Spruce-Fir Forest
This successional phase consists of a variable canopy in which spruce and fir are mixed with early successional hardwood species in a similar age class (less than 100 years).
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 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.
The understory will often be sparse to absent and will not 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.
Community 1.5
Mid Successional Uneven Aged Mixed Conifer Forest
This successional phase consists of a closed canopy in which spruce and fir are mixed with early successional hardwood species of different age classes. As the larger early successional species become removed, canopy gaps will allow for the development of a multi-aged stand of dominant spruce. Lower canopy layers are often variable and will begin to reflect the reference condition, but rarely extensive, composed of tree regeneration and sparse shrubs and herbaceous species where gap dynamics occur. Extensive repetitive harvesting of spruce may cause the seedbank to become exhausted and will reflect a forest with a greater hardwood dominance than spruce dominance.
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 black spruce can help accelerate the restoration of the natural vegetation of the swamp.
Pathway 1.3A
Community 1.3 to 1.2
This may occur through intensive harvesting practices such as clearcutting for pulp. Immediate loss of regenerating 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 1.3C
Community 1.3 to 1.5
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 naturally (treefall, disease, etc.) and often without human interference. This will lead to an uneven aged stand in which spruce and fir may be mixed in with hardwood species such as red maple.
Pathway 1.4A
Community 1.4 to 1.1
This transition will over time, often greater than 100 years, in which the main stand remains relatively undisturbed. This will allow the spruce stand to mature in its size and height classes, creating a more uneven aged stand with a well-developed overstory and a dark, cool understory that limits regeneration. Balsam fir will reach the end of its natural life expectancy and will revert the canopy to spruce dominance. This transition may be assisted with forest stand improvement practices. 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 regenerating 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 overstory to allow the understory more growing space.
Pathway 1.4D
Community 1.4 to 1.5
This may occur over time, typically greater than 20 years but less than 100 years into a stand's lifecycle, where the even-aged forest will undergo changes in canopy structure, resulting in multiple age classes, often seen as regeneration, pole (immature trees), and sawtimber (mature trees) wood. The even aged stand will thin in density either naturally (treefall, disease, etc.) or via human interference (irregular shelterwood cuts, forest stand improvement [FSI]). 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 1.5A
Community 1.5 to 1.1
This transition will over time, often greater than 100 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 1.5B
Community 1.5 to 1.2
This may occur through intensive harvesting practices such as clearcutting for pulp and lumber. Immediate loss of regenerating 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.
State 2
Converted Cultural State
This state represents a once forested area now cleared for pasture. This will typically only occur on gentler slopes (<15 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. In these systems, water control structures may be used to prevent excess water in the fields and historical drainage and cultivation of this site may lead to the loss of the mucky organic surface texture.
Community 2.1
Improved Pasture Grasses and Legumes
This community phase represents commonly planted forage species on pastureland and hayland. 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 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.
Dominant plant species
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timothy (Phleum pratense), grass
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sweet vernalgrass (Anthoxanthum odoratum), grass
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Kentucky bluegrass (Poa pratensis), grass
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orchardgrass (Dactylis glomerata), grass
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smooth brome (Bromus inermis), grass
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red fescue (Festuca rubra), grass
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sheep fescue (Festuca ovina), grass
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perennial ryegrass (Lolium perenne), grass
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redtop (Agrostis gigantea), grass
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festulolium (×Festulolium), grass
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alfalfa (Medicago sativa), other herbaceous
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red clover (Trifolium pratense), other herbaceous
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milkvetch (Astragalus), other herbaceous
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bedstraw (Galium), other herbaceous
Community 2.2
Herbaceous and Shrubby “Old Field”
This phase represents a more degraded phase for livestock. While some utilization of desirable pasture plants will occur, undesirable species are prolific. As undesirable pasture species grow, desirable pasture grasses and forbs will decrease in cover. Small trees representative of the reference condition (often early successional species) is often present but do not form great amounts of canopy cover.
Pathway 2.1A
Community 2.1 to 2.2
This transition may occur through the absence or mismanagement of pasture or haylands may result with the increase in undesirable species and decrease in desirable species.
Pathway 2.2A
Community 2.2 to 2.1
This transition may occur through management practices via mechanical, chemical, or biological means may be used to remove undesirable pasture or hayland species.
Transition T1A
State 1 to 2
The reference state transitions to the managed grassland state with the clearing of woody vegetation and the establishment of pasture grasses and legumes.
Transition T2A
State 2 to 1
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.
