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G515 Carex aquatilis - Carex lasiocarpa - Sphagnum spp. Rocky Mountain Acidic Fen Group

Type Concept Sentence: This group occurs infrequently throughout the Rocky Mountains from Colorado north into Canada. It is confined to specific environments defined by groundwater discharge, soil chemistry, and peat accumulation of at least 40 cm. It is dominated by Carex aquatilis, Carex livida, Carex lasiocarpa, Carex limosa, Dulichium arundinaceum, Ledum glandulosum, Trichophorum cespitosum, and many others.

Common (Translated Scientific) Name: Water Sedge - Woolly-fruit Sedge - Peatmoss species Rocky Mountain Acidic Fen Group

Colloquial Name: Rocky Mountain Acidic Fen

Hierarchy Level:  Group

Type Concept: This group occurs infrequently throughout the Rocky Mountains from Colorado north into Canada. Fens usually occur as a mosaic of several plant associations dominated by Carex aquatilis, Carex livida, Carex lasiocarpa, Carex limosa, Dulichium arundinaceum, Ledum glandulosum, and Trichophorum cespitosum. The surrounding landscape may be ringed with other wetland systems, e.g., riparian shrublands, or a variety of upland systems from grasslands to forests. This group is confined to specific environments defined by groundwater discharge, soil chemistry, and peat accumulation of at least 40 cm. Fens form at low points in the landscape or on slopes where groundwater intercepts the soil surface. Groundwater inflows maintain a fairly constant water level year-round, with water at or near the surface most of the time. Acidic fens are restricted to areas where bedrock is noncalcareous (e.g., sandstone, basalt, quartzite, granite). Constant high water levels and cold winter temperatures lead to accumulation of organic material. In addition to peat accumulation and perennially saturated soils, soil chemistry is acidic and nutrients are low. Iron fens are the exception where the pH is low (acidic) but nutrients are high.

Diagnostic Characteristics: Saturated year-round organic soils with >40 cm peat, acidic soil water pH and dominated by wetland indicator plants Carex aquatilis, Carex livida, Carex lasiocarpa, Dulichium arundinaceum, Ledum glandulosum, and Trichophorum cespitosum. Ground cover is dominated by Sphagnum mosses.

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: Nutrient-rich alkaline fens are not included here, they belong to ~Rocky Mountain Alkaline Fen Group (G516)$$. Acidic fens in Alaska are placed into either ~Western North American Boreal Bog & Acidic Fen Group (G360)$$ or ~North Pacific Acidic Open Bog & Fen Group (G284)$$.

Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: Wetlands dominated by bryophytes and low-statured graminoids. Woody cover, if present, is very sparse.

Floristics: Acidic fens associated with peatlands more closely resemble the vegetation of bogs, with Sphagnum mosses and ericaceous shrubs. Dominant species include Carex aquatilis, Carex livida, Carex lasiocarpa, Dulichium arundinaceum, Ledum glandulosum, and Trichophorum cespitosum (Cooper 1986b, Windell et al. 1986, Steen and Coupe 1997).

Dynamics:  Mountain fens act as natural filters cleaning ground and surface water. Fens also act as sponges by absorbing heavy precipitation, slowly releasing it downstream, minimizing erosion and recharging groundwater systems (Windell et al. 1986). The persistent groundwater and cold temperatures allow organic matter to accumulate (forming peat) which allows classification of wetlands within this group as fens. Fens produce peat that accumulates at the rate of 20 to 30 cm (8-11 inches) per 1000 years, making peatlands a repository of 10,000 years of post-glacial history (Windell et al. 1986).
Environmental Description:  Soil/substrate/hydrology: Fens are wetlands that develop where a relatively constant supply of groundwater maintains saturated conditions and the water chemistry reflects the mineralogy of the local soils and geological materials (Bedford and Godwin 2003). Organic soil of partially decomposed peat has a minimum depth of 40 cm (although some authors use 30-cm depth criteria). Acidic fens arise either because the groundwater accounts for only a small fraction of the annual water budget or because groundwater inputs move through materials with low solubility and are non-calcareous (e.g., basalt gneiss, granite) or low buffering capacity (e.g., sand, quartz) (Bedford and Godwin 2003).
Geographic Range: This group occurs infrequently throughout the mountains of the interior west, the Sky Islands of Arizona and high mountains and plateaus of Nevada and Utah, and the Rocky Mountains of Utah, Colorado, Wyoming, Montana, Idaho, and north into interior Canada, where it is known from interior (non-coastal) British Columbia and Alberta.

Nations: CA,US

States/Provinces:  AB, AK?, AZ, BC, CA, CO, ID, MT, NV, OR, UT, WA, WY


Confidence Level: Moderate

Confidence Level Comments: No Data Available
Grank: GNR

Greasons: No Data Available
Type Name Database Code Classification Code
Class 2 Shrub & Herb Vegetation Class C02 2
Subclass 2.C Shrub & Herb Wetland Subclass S44 2.C
Formation 2.C.2 Temperate to Polar Bog & Fen Formation F016 2.C.2
Division 2.C.2.Na North American Bog & Fen Division D029 2.C.2.Na
Macrogroup 2.C.2.Na.1 Leatherleaf - Small Cranberry - Few-seed Sedge Bog & Acidic Fen Macrogroup M876 2.C.2.Na.1
Group 2.C.2.Na.1.c Water Sedge - Woolly-fruit Sedge - Peatmoss species Rocky Mountain Acidic Fen Group G515 2.C.2.Na.1.c
Alliance A3437 Woolly-fruit Sedge - Livid Sedge - Threeway Sedge Acidic Graminoid Fen Alliance A3437 2.C.2.Na.1.c
Alliance A3438 Western Labrador-tea Acidic Shrub Fen Alliance A3438 2.C.2.Na.1.c
Concept Lineage: No Data Available

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available
Synonomy: No Data Available
Concept Author(s): J. Rocchio, D. Cooper, B. Bedford, in Faber-Langendoen et al. (2011)

Author of Description: G. Kittel

Acknowledgements: No Data Available

Version Date: 11-23-15
  • Bedford, B. L., and K. S. Godwin. 2003. Fens of the United States: Distribution, characteristics, and scientific connection versus legal isolation. Wetlands 23(3):608-629.
  • Cooper, D. J. 1986b. Community structure and classification of Rocky Mountain wetland ecosystems. Pages 66-147 in: J. T. Windell, et al. An ecological characterization of Rocky Mountain montane and subalpine wetlands. USDI Fish & Wildlife Service Biological Report 86(11). 298 pp.
  • Faber-Langendoen, D., J. Drake, S. Gawler, M. Hall, C. Josse, G. Kittel, S. Menard, C. Nordman, M. Pyne, M. Reid, L. Sneddon, K. Schulz, J. Teague, M. Russo, K. Snow, and P. Comer, editors. 2010-2019a. Divisions, Macrogroups and Groups for the Revised U.S. National Vegetation Classification. NatureServe, Arlington, VA. plus appendices. [in preparation]
  • Rondeau, R. 2001. Ecological system viability specifications for Southern Rocky Mountain ecoregion. First edition. Colorado Natural Heritage Program, Colorado State University, Fort Collins, CO. 181 pp.
  • Steen, O. A., and R. A. CoupĂ©. 1997. A field guide to forest site identification and interpretation for the Cariboo Forest Region. Land Management Handbook No. 39. Parts 1 and 2. British Columbia Ministry of Forests Research Program, Victoria, BC.
  • Windell, J. T., B. E. Willard, D. J. Cooper, S. Q. Foster, C. F. Knud-Hansen, L. P. Rink, and G. N. Kiladis. 1986. An ecological characterization of Rocky Mountain montane and subalpine wetlands. USDI Fish and Wildlife Service Biological Report 86(11). 298 pp.