Ecological dynamics

Ecological Dynamics
[Caveat: The vegetation information contained in this section is only provisional, based on concepts, not yet validated with 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). Terrestrial ecological SYSTEMS are specifically defined as a group of plant community types called ASSOCIATIONS that tend to co-occur within landscapes with similar ecological processes, substrates, and/or environmental gradients. They are intended to provide a classification unit that is readily mappable, often from terrain and remote imagery, and readily identifiable by conservation and resource managers in the field. A given system will typically manifest itself in a landscape at intermediate geographic scales of tens-to-thousands of hectares and will persist for 50 or more years. A vegetation association is a plant community that is much more specific to a given soil, geology, landform, climate, hydrology, and disturbance history. It is the basic unit for vegetation classification and recognized by the US National Vegetation Classification (FDGC, 2008; USNVC, 2017). Each association will be named by the diagnostic and often dominant species that occupy the different height strata (represented by tree, shrub, and herb layers). Within the NatureServe Explorer database, ecological systems are numbered by a community Ecological System Code (CES) and individual vegetation associations are assigned an identification number called a Community Element Global Code (CEGL).

Th maritime Coastal Dune ecological site is characterized by a mix of xeric plant communities coinciding Northern Atlantic Coastal Plain Dune and Swale system (CES203.264). The prevailing ecological processes are due to the exposed maritime environment, including frequent salt spray, wind exposure, sand abrasion, high light intensity, overwash, and sand movement. Other disturbances considered as threats include: development and fragmentation, barriers to connectivity to the open ocean, off-road vehicles, trampling, occasional fire, and accelerated sea-level rise. Invasive plants include rugosa rose (Rosa rugosa) and beach wormwood (Artemisia stelleriana).

Plant community succession on the site coincides with coastal dune succession. Young, active foredunes, are nearest the ocean in the most exposed environments. Interspersed with small to large areas of bare sand, the vegetation on the young dunes is a Northern Beach Dune (CEGL006274) dominated by American beachgrass (Ammophila breviligulata). A mid-seral are plant community occurring on more stabilized dunes is the Northern Bayberry Dune Shrubland (CEGL006295) dominated by northern bayberry (Morella pensylvanica) and the rare but diagnostic, beach plum (Prunus maritima). On older and more stabilized backdunes or secondary dunes, occurs the Pitch Pine Maritime Dune Woodland (CEGL006117) dominated by pitch pine (Pinus rigida) and woolly beach heather (Hudsonia tomentosa) and northern bayberry (Morella pensylvanica).

Additional and more localized vegetation information can be provided by the various State Heritage Programs. Additional insights to the vegetation were provided by Natural Landscapes of Maine: A Guide to Natural Communities and Ecosystems (Grawler and Cutko, 2010).

Beyond the reference state, other ecological states, a Semi-natural State and a Cultural State are often recognized. The Semi-natural State would expect plant communities where ecological processes primarily operate with some conditioning by land management, e.g., managed forests, or plant communities that are an artifact of land management e.g., predominately invasive plants. The Cultural State is a completely converted or transformed state; heavily or completely conditioned by land management, e.g., cultivated lands, pasture/haylands, vineyards, and plantations, etc. Generally, the form of vegetation in the Semi-natural State or the Cultural State is not able to be specified until field work is conducted.

[*Caveat] The vegetation information presented is representative of complex plant communities. Key indicator plants and ecological processes are described to help inform land management decisions. Plant communities will differ across the MLRA because of the naturally occurring variability in weather, soils, and geography. The reference plant community is not necessarily the management goal. The drafts of species lists are merely 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.