Great Lakes Alkaline Fen

EVT 9114Laurentian-Acadian Alkaline Fen
CES201.585GNRShrubRiparian
Summary
These fens, distributed across glaciated eastern and central North America, develop in open basins where bedrock or other substrate influence creates circumneutral to calcareous conditions. They are most abundant in areas of limestone bedrock, and widely scattered in areas where calcareous substrates are scarce. Shore fens, which are peatlands that are occasionally flooded along stream and lakeshores, are also included here because flooding tends to create moderately alkaline conditions. The vegetation may be graminoid-dominated, shrub-dominated, or a patchwork of the two; Dasiphora fruticosa ssp. floribunda is a common diagnostic shrub. The herbaceous flora is usually species-rich and includes calciphilic graminoids and forbs. Sphagnum dominates the substrate in many sites though in Michigan a patchy to continuous carpet of brown mosses is more typical; Campylium stellatum is an indicator bryophyte. The edge of the basin may be shallow to deep peat over a sloping substrate, where seepage waters provide nutrients.
Source: NatureServe Explorer
Environment
This system usually occurs where there is flat, highly calcareous bedrock near the surface. Water slowly moves along this bedrock and, where it comes to the surface, fens can form in the cold, mineral-rich, anoxic water. Soils are organic and saturated most or all of the growing season. Waterflow through this system is slow but greater than in bogs (Schwintzer and Tomberlin 1982). Some fens in this system occur on the shore of lakes or ponds where wave action is low.
Source: NatureServe Explorer
Dynamics
The presence of cold, mineral-rich, alkaline groundwater which promotes the formation of peat and marl is key to the formation and maintenance of this system. Where cold, mineral-rich groundwater emerges as diffuse seeps, decomposition of plant matter is slowed and peat can accumulate. Marl forms under sustained flow of calcium- and magnesium-rich water. Peat can form hummocks which have microenvironments that are drier and more acidic than the bulk of the fen. The hummock-and-hollow microtopography, which generates small-scale gradients in soil moisture and chemistry, contributes to fen floristic diversity. The high pH of the bulk of the fens strongly shapes the floristic composition.
Source: NatureServe Explorer
Threats
Alterations in wetland hydrology and physical destruction of sites are the prime threats to this system. These can occur due to ditching, road construction, or quarrying/mining that affect groundwater or surface waterflows into sites. Both reductions and increases in groundwater or surface water input can negatively affect this system. Partial drainage of a site can lead to increased fertility as peat decomposes; this allows species typical of richer swamps or uplands to colonize. Increased surface waterflow can flood the peatland and transform it to an inundated wetland rather than a saturated peatland and can transport sediment and higher nutrient loads. Logging of adjacent forests can negatively impact this system through increased water runoff and sedimentation. This system is slow to recover from perturbation so disturbance can accumulate over time. Invasive species that can reduce diversity and alter vegetative structure in fen systems include Frangula alnus (= Rhamnus frangula), Lythrum salicaria, Phragmites australis, and Typha angustifolia.
Source: NatureServe Explorer
Distribution
Scattered locations from New England and adjacent Canada west to the Great Lakes and northern Minnesota.
Source: NatureServe Explorer
Ecologically Associated Plant Species

Plant species that characterize this ecosystem type, organized by vegetation stratum. These are species ecologically associated with the ecosystem, not confirmed present in any specific area.

Tree canopy

Thuja occidentalis

Shrub/sapling (tall & short)

Dasiphora fruticosa ssp. floribunda, Myrica gale

Herb (field)

Carex heleonastes ssp. heleonastes, Carex livida, Carex schweinitzii, Cladium mariscoides, Lobelia kalmii, Oligoneuron houghtonii, Platanthera leucophaea, Poa paludigena, Polemonium lacustre, Sarracenia purpurea ssp. venosa, Trichophorum alpinum, Trollius laxus

Nonvascular

Campylium stellatum
Source: NatureServe Ecological System assessment
Ecologically Associated Animals (5)

Animal species ecologically associated with this ecosystem type based on NatureServe assessment. These are species whose habitat requirements overlap with this ecosystem, not confirmed present in any specific roadless area.

Butterflies & Moths (2)

Common NameScientific NameG-Rank
Swamp MetalmarkCalephelis muticumG3
Dorcas CopperTharsalea dorcasG5

Insects (1)

Common NameScientific NameG-Rank
Scrub Palmetto Flower Scarab BeetleTrigonopeltastes floridanusG3

Molluscs (1)

Common NameScientific NameG-Rank
Pleistocene CatinellaMediappendix exilisG3?

Other Invertebrates (1)

Common NameScientific NameG-Rank
Bog TurtleGlyptemys muhlenbergiiG2G3
Source: NatureServe Ecological System assessment
At-Risk Species Associated with this Ecosystem (11)

Species with conservation concern that are ecologically associated with this ecosystem type. G-Rank indicates global conservation status: G1 (critically imperiled) through G5 (secure). ESA status indicates U.S. Endangered Species Act listing.

Common NameScientific NameG-RankESA Status
Swamp MetalmarkCalephelis muticumG3--
Hudson Bay SedgeCarex heleonastes ssp. heleonastesG4T3T4--
Schweinitz's SedgeCarex schweinitziiG3G4--
Bog TurtleGlyptemys muhlenbergiiG2G3Threatened; Threatened due to similarity of appearance
Pleistocene CatinellaMediappendix exilisG3?--
Houghton's GoldenrodOligoneuron houghtoniiG3Threatened
Eastern Prairie White-fringed OrchidPlatanthera leucophaeaG2G3Threatened
Bog BluegrassPoa paludigenaG3G4--
Great Lakes Jacob's-ladderPolemonium lacustreG1G2--
Scrub Palmetto Flower Scarab BeetleTrigonopeltastes floridanusG3--
Spreading GlobeflowerTrollius laxusG3--
Source: NatureServe Ecological System assessment
Component Associations (15)

Plant community associations that occur within this ecological system. Associations are the finest level of the U.S. National Vegetation Classification (USNVC) and describe specific, repeating assemblages of plant species. Each association represents a distinct community type that may be found where this ecosystem occurs.

NameG-Rank
Betula pumila - Alnus incana - Salix spp. / Chamaedaphne calyculata Fen NatureServe
Betula pumila / Chamaedaphne calyculata / Carex lasiocarpa Fen NatureServe
Betula pumila - Dasiphora fruticosa / Carex lasiocarpa - Trichophorum alpinum Fen NatureServe
Carex (interior, hystericina, flava) - Trichophorum alpinum / Campylium stellatum Fen NatureServe
Carex lasiocarpa - Calamagrostis spp. - (Eleocharis rostellata) Fen NatureServe
Carex lasiocarpa - Carex buxbaumii - Trichophorum cespitosum Boreal Fen NatureServe
Carex lasiocarpa - (Carex rostrata) - Equisetum fluviatile Fen NatureServe
Carex lasiocarpa - Trichophorum cespitosum - Rhynchospora capillacea / Andromeda polifolia Fen NatureServe
Chamaedaphne calyculata - Myrica gale / Carex lasiocarpa FenG4 NatureServe
Dasiphora fruticosa / Carex lasiocarpa / Campylium stellatum Fen NatureServe
Dasiphora fruticosa / Carex (sterilis, hystericina, flava) Fen NatureServe
Myrica gale - Dasiphora fruticosa / Carex lasiocarpa - Cladium mariscoides Fen NatureServe
Prunus virginiana - Acer spicatum - Ribes triste / Angelica atropurpurea - Heracleum maximum Seepage Shrubland NatureServe
Thuja occidentalis - Abies balsamea / Ledum groenlandicum / Carex trisperma Swamp Woodland NatureServe
Thuja occidentalis - (Myrica gale) / Trichophorum alpinum / Drepanocladus spp. Fen NatureServe
State Conservation Ranks (8)

Subnational conservation status ranks (S-ranks) assigned by Natural Heritage Programs in each state where this ecosystem occurs. S1 indicates critically imperiled at the state level, S2 imperiled, S3 vulnerable, S4 apparently secure, and S5 secure. An ecosystem may be globally secure but imperiled in specific states at the edge of its range.

StateS-Rank
MASNR
MESNR
MISNR
MNSNR
NHSNR
NYSNR
VTSNR
WISNR
Methodology and Data Sources

Ecosystem classification: Ecosystems are classified using the LANDFIRE 2024 Existing Vegetation Type (EVT) layer, mapped to NatureServe Terrestrial Ecological Systems via a curated crosswalk. Each EVT is linked to the USNVC (U.S. National Vegetation Classification) hierarchy through pixel-level co-occurrence analysis of LANDFIRE EVT and NatureServe IVC Group rasters across all roadless areas.

Vegetation coverage: Coverage percentages and hectares are derived from zonal statistics of the LANDFIRE 2024 EVT raster intersected with roadless area boundaries.

Ecosystem narratives and community species: Sourced from the NatureServe Explorer API, representing professional ecological assessments of vegetation composition, environmental setting, dynamics, threats, and characteristic species assemblages.

IVC hierarchy: The International Vegetation Classification hierarchy is sourced from the USNVC v3.0 Catalog, providing the full classification from Biome through Association levels.

Component associations: Plant community associations listed as components of each NatureServe Ecological System. Association data from the NatureServe Explorer API.

State ranks: Conservation status ranks assigned by NatureServe member programs in each state where the ecosystem occurs.