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Scientific Name: Great Lakes Alvar
Unique Identifier: CES201.721
Classification Confidence: 1 - Strong
Image 21951
© New York Natural Heritage Program
Summary: Alvars are natural systems of humid and subhumid climates, centered around areas of glaciated horizontal limestone/dolomite (dolostone) bedrock pavement with a discontinuous thin soil mantle. These communities are characterized by distinctive flora and fauna with less than 60% tree cover that is maintained by associated geologic, hydrologic, and other landscape processes. In particular, all forms of alvar tend to flood each spring, then experience moderate to severe drought in summer months. They include open pavement, grassland, and shrubland/woodland types. Alvar communities occur in an ecological matrix with similar bedrock and hydrologically influenced communities. Almost all of North America's alvars occur within the Great Lakes basin, primarily in an arc along the Niagaran Escarpment from northern Lake Michigan across northern Lake Huron and eastern Ontario and northwestern New York state.

Classification Approach: International Terrestrial Ecological Systems Classification (ITESC)

Component Associations
Association Unique ID Association Name
CEGL005059 Acer saccharum - Ostrya virginiana - Carya ovata - Quercus rubra Limestone Woodland
CEGL005100 Danthonia spicata - Poa compressa - (Schizachyrium scoparium) Grassland
CEGL005110 Deschampsia cespitosa - (Sporobolus heterolepis, Schizachyrium scoparium) - Carex crawei - Packera paupercula Grassland
CEGL005122 Juniperus virginiana / Ranunculus fascicularis Woodland
CEGL005126 Pinus banksiana - Thuja occidentalis - Picea glauca / Juniperus communis Woodland
CEGL005132 Thuja occidentalis - Pinus banksiana / Dasiphora fruticosa / Clinopodium arkansanum Wooded Grassland
CEGL005192 Tortella tortuosa - Cladonia pocillum - Placynthium spp. Sparse Vegetation
CEGL005211 Picea glauca - Thuja occidentalis - Juniperus communis / Iris lacustris - Carex eburnea Shrubland
CEGL005212 Juniperus communis - (Juniperus virginiana) - Rhus aromatica - Viburnum rafinesqueanum / Oligoneuron album Shrubland
CEGL005230 Carya ovata / Zanthoxylum americanum / Panicum philadelphicum - Carex pensylvanica Open Woodland
CEGL005234 Sporobolus heterolepis - Schizachyrium scoparium - (Carex scirpoidea) / (Juniperus horizontalis) Grassland
CEGL005235 Sporobolus neglectus - Sporobolus vaginiflorus - Trichostema brachiatum - Panicum philadelphicum - (Poa compressa) Alvar Grassland
CEGL005236 Juniperus horizontalis - Dasiphora fruticosa / Schizachyrium scoparium - Carex richardsonii Dwarf-shrubland


Land Cover Class: Steppe/Savanna
Spatial Pattern: Large patch
Natural/Seminatural: No
Vegetated ( > 10% vascular cover):
Upland: Yes
Wetland: Yes
Isolated Wetland: Partially Isolated

Non-diagnostic Classifiers
Primary Classifier Secondary Classifier
Glaciated uplands  
Rock Outcrops/Barrens/Glades  
Extensive Wet Flat Lakeshore
Isolated Wetland Partially Isolated
Very Shallow Soil  
Intermittent Flooding  

At-Risk Species Reported for this Ecological System
Scientific Name
  (Common Name)
NatureServe Global Status U.S. Endangered Species Act Status
Catinella exile
  (Pleistocene Catinella)
Erynnis martialis
  (Mottled Duskywing)
Iris lacustris
  (Dwarf Lake Iris)
G3 LT: Listed threatened
Pyrgus wyandot
  (Appalachian Grizzled Skipper)
Sistrurus catenatus
  (Eastern Massasauga)
G3 LT: Listed threatened

Vegetation Composition (incomplete)
Species Name Rounded Global Status Growth Form Stratum Char-
Domi-nant Con-stant
Cover Class %
Juniperus communis G5 Needle-leaved tree Tree canopy    
Dasiphora fruticosa ssp. floribunda T5 Broad-leaved evergreen shrub Shrub/sapling (tall & short)    
Carex scirpoidea G5 Graminoid Herb (field)    
Danthonia spicata G5 Graminoid Herb (field)    
Deschampsia caespitosa G5 Graminoid Herb (field)    
Schizachyrium scoparium G5 Graminoid Herb (field)    
Sporobolus heterolepis G5 Graminoid Herb (field)    

Animal Species Reported for this Ecological System
Scientific Name
  (Common Name)
Global Status U.S. Endangered Species Act Status Charact-
Ammodramus savannarum
  (Grasshopper Sparrow)
Bartramia longicauda
  (Upland Sandpiper)
Callophrys polios
  (Hoary Elfin)
Catinella exile
  (Pleistocene Catinella)
Erynnis martialis
  (Mottled Duskywing)
Lanius ludovicianus
  (Loggerhead Shrike)
Oeneis chryxus strigulosa
  (Chryxus Arctic)
Phyciodes batesii
  (Tawny Crescent)
Pipilo erythrophthalmus
  (Eastern Towhee)
Pyrgus centaureae
  (Grizzled Skipper)
Pyrgus wyandot
  (Appalachian Grizzled Skipper)
Sistrurus catenatus
  (Eastern Massasauga)
G3 LT: Listed threatened    

Color legend for Distribution Map
Nation: United States
United States Distribution: MI, NY, OH, WI
Nation: Canada
Canadian Province Distribution: ON
Global Range: Alvars occur within the Great Lakes basin.

Biogeographic Divisions
Division Code and Name Primary Occurrence Status
201-Laurentian-Acadian C: Confident or certain

The Nature Conservancy's Conservation Ecoregions
Code Name Occurrence Status
48 Great Lakes Confident or certain
64 St. Lawrence-Champlain Valley Confident or certain

MRLC 2000 Mapzones
Code Name Occurrence Status
41 Northern Lake Country Confident or certain
50 Central Great Lakes Uplands Confident or certain
51 Great Lakes Plains Confident or certain
52 Eastern Till Plains Confident or certain
62 Allegheny Plateau Never was there
63 Finger Lakes Predicted or probable
64 Northeastern Highlands Confident or certain

National Mapping
ESLF Code (Ecological System Lifeform): 5458
ESP Code (Environmental Site Potential): 1409
EVT Code (Existing Vegetation Type): 2409

West Landfire Legend: No
East Landfire Legend: Yes

Element Description Edition Date: 14Jan2014
Element Description Author(s): C. Reschke, S.C. Gawler and J. Drake

Ecological data developed by NatureServe and its network of natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).

  • Albert, D. 1990. Drummond Island Alvar. Michigan Natural Features Inventory, Lansing, MI.

  • Comer, P., D. Faber-Langendoen, R. Evans, S. Gawler, C. Josse, G. Kittel, S. Menard, C. Nordman, M. Pyne, M. Reid, M. Russo, K. Schulz, K. Snow, J. Teague, and R. White. 2003-present. Ecological systems of the United States: A working classification of U.S. terrestrial systems. NatureServe, Arlington, VA.

  • Edinger, G. J., D. J. Evans, S. Gebauer, T. G. Howard, D. M. Hunt, and A. M. Olivero, editors. 2014a. Ecological communities of New York state. Second edition. A revised and expanded edition of Carol Reschke's ecological communities of New York state. New York Natural Heritage Program, New York State Department of Environmental Conservation, Albany, NY.

  • Eyre, F. H., editor. 1980. Forest cover types of the United States and Canada. Society of American Foresters, Washington, DC. 148 pp.

  • Kost, M. A., D. A. Albert, J. G. Cohen, B. S. Slaughter, R. K. Schillo, C. R. Weber, and K. A. Chapman. 2007. Natural communities of Michigan: Classification and description. Report No. 2007-21, Michigan Natural Features Inventory, Lansing. 314 pp. []

  • LANDFIRE [Landfire National Vegetation Dynamics Database]. 2007a. Landfire National Vegetation Dynamics Models. Landfire Project, USDA Forest Service, U.S. Department of Interior. (January - last update) [] (accessed 8 February 2007).

  • ONHD [Ohio Natural Heritage Database]. No date. Vegetation classification of Ohio and unpublished data. Ohio Natural Heritage Database, Division of Natural Areas and Preserves, Ohio Department of Natural Resources, Columbus.

  • Reschke, C., R. Reid, J. Jones, T. Feeney, and H. Potter, on behalf of the Alvar Working Group. 1998. Conserving Great Lakes Alvars. Final Technical Report of the International Alvar Conservation Initiative. The Nature Conservancy, Great Lakes Program, Chicago, IL. 119 pp. plus 4 appendices.

  • WDNR [Wisconsin Department of Natural Resources]. 2015. The ecological landscapes of Wisconsin: An assessment of ecological resources and a guide to planning sustainable management. PUB-SS-1131 2015. Wisconsin Department of Natural Resources, Madison. []

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Citation for Bird Range Maps of North America:
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Version 7.1 (2 February 2009)
Data last updated: March 2019