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A3104 Sporobolus heterolepis - Deschampsia cespitosa / Dasiphora fruticosa Alvar Grassland Alliance
Type Concept Sentence: This mesic to wet-mesic alvar grassland and pavement occurs around the eastern and central Great Lakes, on calcareous bedrock, dominated by sedges and grasses, including Deschampsia cespitosa, Schizachyrium scoparium, and Sporobolus heterolepis, with scattered short to tall shrubs, especially Dasiphora fruticosa ssp. floribunda and Juniperus horizontalis.
Common (Translated Scientific) Name: Prairie Dropseed - Tufted Hairgrass / Shrubby-cinquefoil Alvar Grassland Alliance
Colloquial Name: Great Lakes Alvar Grassland
Hierarchy Level: Alliance
Type Concept: This alliance occurs around the eastern and central Great Lakes on calcareous bedrock (dolomite or limestone). The physiognomy is dominated by sedges and grasses with scattered short to tall shrubs (<25%), and sometimes trees (<10%), growing in thin soil over calcareous bedrock. Areas of exposed bedrock pavement are common. Dwarf-shrubs such as Juniperus horizontalis and Dasiphora fruticosa ssp. floribunda may have variable cover. There are three subtypes of this alliance. The dominant species in each are as follows: subtype 1 (mesic alvar grassland) contains Carex scirpoidea, Carex spp., Schizachyrium scoparium, and Sporobolus heterolepis; subtype 2 (wet-mesic alvar grassland) contains Carex crawei, Deschampsia cespitosa, and Eleocharis compressa; subtype 3 (alvar pavement grassland) contains annual grasses such as Trichostema brachiatum, Panicum philadelphicum, Sporobolus neglectus, and Sporobolus vaginiflorus as well as various lichen spp. Windthrow can occur in alvars because of the thin soils and proximity to major streams (which often funnel windstorms) and the Great Lakes. The thin soils are also droughty, giving the potential for tree-killing drought or surface fires. Thus, stands of this alliance are maintained as primarily herb-and-dwarf-shrub-dominated communities. Flooding after spring snowmelt may also limit tree growth by creating anaerobic conditions for a few weeks.
Diagnostic Characteristics: The physiognomy is dominated by sedges and grasses with scattered short to tall shrubs (<25%), and sometimes trees (<10% cover), growing in thin soil over calcareous bedrock. Areas of exposed bedrock pavement are common. The vegetation is cool-temperate grassland and shrublands in transition with temperate / sub-boreal trees and shrubs in the eastern temperate/boreal region around the Great Lakes. The dominant and characteristic grasses include perennial grasses of Deschampsia cespitosa, Eleocharis compressa, Schizachyrium scoparium, and Sporobolus heterolepis, the annual grasses of Trichostema brachiatum, Panicum philadelphicum, Sporobolus neglectus, and Sporobolus vaginiflorus, and sedges Carex scirpoidea and Carex crawei, occasionally in sparse pavement settings with lichens (including Cladonia pocillum, Placynthium spp., Tortella tortuosa). Characteristics shrubs that intermix with these herbaceous species include Juniperus horizontalis and Dasiphora fruticosa ssp. floribunda. Less distinctive shrub and herb associates include Poa compressa, Danthonia spicata, and Juniperus communis.
Rationale for Nominal Species or Physiognomic Features: No Data Available
Classification Comments: Ordination and clustering of plots for all alvars clearly show a separation between alvar shrublands and grasslands. Further separation of alvar grasslands is not clear, but three subtypes are provisionally indicated to show patterns of both moisture and nonvascular- or annual grass-dominated pavement. Note that even pavement grasslands can be wet in spring.
Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: The physiognomy is dominated by sedges and grasses with scattered short to tall shrubs (<25%), and sometimes trees (<10%), growing in thin soil over calcareous bedrock. Areas of exposed bedrock pavement are common.
Floristics: There are three subtypes of this alliance. The dominant species in each are as follows: : subtype 1 (mesic alvar grassland) contains Carex scirpoidea, Carex spp., Schizachyrium scoparium, and Sporobolus heterolepis; subtype 2 (wet-mesic alvar grassland) contains Carex crawei, Deschampsia cespitosa, and Eleocharis compressa; subtype 3 (alvar pavement grassland) contains annual grasses such as Trichostema brachiatum (= Isanthus brachiatus), Panicum philadelphicum, Sporobolus neglectus, and Sporobolus vaginiflorus as well as various lichen spp. (Reschke et al. 1998).
Dynamics: At some New York/Ontario sites there is a distinctive soil moisture regime of alternating wet and dry seasons; they are often saturated in early spring and late fall, and they are subject to severe summer drought in most years (except unusually wet years). Due to the very shallow soils, and often saturated conditions during freeze-thaw cycles in early and late winter, needle ice often forms in the soils, causing frost-heaving of the shallow soils. Windthrow can occur in alvars because of the thin soils and proximity to major streams (which often funnel windstorms) and the Great Lakes. The thin soils are also droughty, giving the potential for tree-killing drought or surface fires. Thus, stands of this alliance are maintained as primarily herb-and-dwarf-shrub-dominated communities. Flooding after spring snowmelt may also limit tree growth by creating anaerobic conditions for a few weeks.
Environmental Description: Within these sites, there are mosaic patches, including drier places where there is a soil layer of about 15 cm over bedrock and in areas where soil is present only in crevasses in bedrock, and moist places where soils are mildly to moderately alkaline (pH 7.2-8.0) sandy loams or loamy sands less than 25 cm deep. Although saturated to varying degrees by water in the spring, sites are very droughty in the summer. Lower areas can be more moist and therefore often develop loam. Alvar is found over calcareous bedrock (dolomite or limestone) of Middle and Late Ordovician and Early Silurian origin.
Geographic Range: This alliance is found in lower Michigan, southern New York, Ohio, and in Canada, in southern Ontario and possibly Quebec.
Nations: CA,US
States/Provinces: MI, NY, OH, ON, QC?
Plot Analysis Summary:
http://vegbank.org/natureserve/ELEMENT_GLOBAL.2.899234
Confidence Level: Moderate
Confidence Level Comments: No Data Available
Grank: GNR
Greasons: No Data Available
Concept Lineage: A.1402 Sporobolus heterolepis - (Deschampsia caespitosa, Schizachyrium scoparium) Herbaceous Alliance is a core old alliance, but needs to be expanded to include Danthonia spicata and Alvar Pavement associations.
Predecessors: No Data Available
Obsolete Names: No Data Available
Obsolete Parents: No Data Available
Synonomy: = Alvar Grassland (Faber-Langendoen 2001)
? Alvar grassland (Edinger et al. 2002)
? Alvar pavement grassland (Edinger et al. 2002)
? Alvar grassland (Edinger et al. 2002)
? Alvar pavement grassland (Edinger et al. 2002)
- Edinger, G. J., D. J. Evans, S. Gebauer, T. G. Howard, D. M. Hunt, and A. M. Olivero, editors. 2002. Ecological communities of New York state. Second edition. A revised and expanded edition of Carol Reschke''s ecological communities of New York state. (Draft for review). New York Natural Heritage Program, New York State Department of Environmental Conservation, Albany, NY.
- Faber-Langendoen, D., J. Drake, M. Hall, G. Kittel, S. Menard, C. Nordman, M. Pyne, M. Reid, M. Russo, K. Schulz, L. Sneddon, K. Snow, and J. Teague. 2013-2019b. Screening alliances for induction into the U.S. National Vegetation Classification: Part 1 - Alliance concept review. NatureServe, Arlington, VA.
- Faber-Langendoen, D., editor. 2001. Plant communities of the Midwest: Classification in an ecological context. Association for Biodiversity Information, Arlington, VA. 61 pp. plus appendix (705 pp.).
- 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.