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 historic reference plant community phase of this site is perceived to be an uneven-aged mixing of temperate deciduous and northern boreal species, called the “Acadian Forest.” This forest consisted of long-lived, shade-tolerant species with small gaps and relatively infrequent severe disturbances. Due to the multiple (8) biophysical regions involved and the history of land use and management, which involved over 95 percent of the MLRA land area, a least disturbed, mature, plant community phase will be considered the reference state for this ecological site description. The least disturbed, mature community phase is a mixed conifer-hardwood forest that has grown up from cleared open fields and pastures that were abandoned approximately 70 or more years ago.

Before European settlement, which occurred in the early 1600s, the plant community phase on this site consisted of an uneven-aged mixing of southern temperate deciduous and northern boreal species. This forest consisted of long-lived, shade-tolerant species with small gaps and relatively infrequent severe disturbances, from 0.6 to 1.0 percent of the land area per year. Three forested areas of similar composition occurred at the broad scale with even more variation at the local scale within each area. In the southern area of the state, forests contained more oak and pine. In the central area of the state, the dominant forest type was mixed hardwoods with some conifers. In the coastal areas, there were higher numbers of spruce in forest stands (Barton et al. 2012). Dominant tree species were hemlock and spruce with a scattering of pines and cedar with some ash and oak according to early settlement survey records (Barton et al. 2012). In forested wetlands along the mid- and eastern coast, dominant tree species included spruce, birches, and alder with smaller amounts of pine, fir, maple, oak, beech, and hemlock, which is similar to present-day vegetation composition (Barton et al. 2012). These forest stands were not especially filled with old trees either, being almost entirely less than 400 years old, and generally between 104 to 203 years old in the oldest stands.

Presettlement natural disturbances were usually small, single-tree mortality events caused by wind or insect damage, rather than stand replacing events. Stand replacing events include extensive fires on average every 1,461 years and major windstorms, such as hurricanes, on average every 3,289 years. Extensive insect outbreaks, such as the spruce budworm infestation, were recorded as occurring every 60 to 70 years (Barton et al. 2012). During present day times, these natural disturbances still occur within these intervals of time.

There appears to be only one plant community phase in the reference state. Because of the continual harvesting of the forest and the composition of the data collected from representative sites, it was not possible to differentiate between a possible more mature and a younger phase. The reference plant community phase has many of the same attributes, including species composition and structure, as the historic reference plant community phase. The site has a dense canopy cover, 85 to 99 percent, of a stratified mixture of even-aged conifer and northern hardwood tree species. Large eastern white pine (Pinus strobus) or quaking aspen (Populus tremuloides) or a mixture of both, form a super-canopy over other co-dominant or intermediate softwood and hardwood species which form the main canopy.

Even though white pine and quaking aspen are upland (Facultative Upland wetland status or FACU), shade-intolerant species, they have taken advantage of wetter cleared areas that provide drier spots where they can out-compete other species for light and space. Thus, they are a relic of a previously cleared state. The actual reference state can be described predominantly as a mixture of either spruce-fir-red maple in the eastern part or red maple-hemlock in more southern parts of the MLRA. Hemlock and red spruce occurred on drier spots in plots as they both have a wetland status of FACU, similar to white pine and quaking aspen.

The understory is very sparse due to the dense overstory cover except for very small open areas, less than 0.1 of an acre, where a wide variety of forbs, grasses, sedges, ferns, shrubs, and tree regeneration grow. Under the dense overstory, only small, scattered shade-tolerant and moisture-loving plants grow, especially mosses, liverworts, and hornworts. In addition, trees have several different types of lichen growing on them, including Lungwort (Lobaria pulmonaria), which occur on older hardwood trees. Tall shrubs are virtually non-existent in this dense, shady, understory.

White pine and quaking aspen regeneration is conspicuously absent from the understory because of their shade intolerance.

Natural disturbances include ice and windstorms, and insect infestations that cause small gaps in the canopy. These small open areas in the forest provide an abundance of small herbs, grasses, sedges, and shrubs as well as tree regeneration for a brief period of time. Many species of medium and small-sized mammals, birds, and insects may have an influence on the plant community composition in terms of pollination, herbivory, seed dispersal, and creation of local disturbance patches, all of which contribute to plant species diversity.

Human disturbances include timber harvesting and land clearing. Harvesting of this reference state has been continuous over the years since European settlement, with most harvesting occurring in the winter months due to the poorly drained nature of the soil. Spruce and pine were the desirable species to harvest, mainly for timber up until about 10 years ago. Presently, all types of trees, including standing dead trees, are harvested for their best use depending on their size and grade. Best use includes timber, pulp, cordwood, firewood, and biomass. A typical harvested alternative state consists of young red maple and gray birch with some fir, hemlock, poplar, and ash. Any larger trees remaining are of poor grade and some younger looking trees are actually older suppressed trees that may not respond to release.

Some sites in agricultural areas have been cleared and maintained as pasture, hayland, and cropland. Small areas are cleared for silage corn or other row crops in order to “square off the field,” as part of a larger cleared upland cropped field. A cropland state may be drained or undrained. Larger cleared areas are used mainly for hay and pasture. In these hay fields, harvest is delayed or not completed if wet weather prevents access and pastures can become quite compacted from livestock.

Timber harvest areas and/or cleared areas may become infested with invasive plants such as European buckthorn in the overstory and bush honeysuckle and Japanese barberry in the understory.

A state-and-transition model diagram for the Marine Terrace Flat Ecological Site (F144BY001ME) follows this narrative. Thorough descriptions of each state, transition, plant community, and pathway follow the model. Experts base this model on available experimental research, field observations, professional consensus, and interpretations. It is likely to change as knowledge increases.

Plant communities will differ across the MLRA because of the naturally occurring variability in local weather events, small inclusions of other soils, and microrelief. The reference plant community is not necessarily the management goal. The biological processes on this site are complex. Therefore, representative values are presented in a land management context. The species lists are representative and are not botanical descriptions of all species occurring, or potentially occurring, on this site. They are not intended to cover every situation or the full range of conditions, species, and responses for the site.