Alvar is a Swedish term to describe barrens and grassland vegetation that grows on thin soils over level outcrops of limestone or dolomite bedrock. This community is limited to areas in Jefferson County underlain with Chaumont limestone (Galoo-Rock outcrop complex).
There are probably much less than 30 occurrences statewide. A few documented occurrences have good viability and several are protected on public land or private conservation land. This community is limited to areas in Jefferson County underlain with Chaumont limestone (Galoo-Rock outcrop complex), and there are only a few high quality examples. The current trend of this community is probably stable for occurrences on public land and private conservation land, or declining slightly elsewhere due to moderate threats that include conversion to pastureland, development, trampling by visitors, ATVs, and invasive species.
It is estimated that alvar shrubland acreage has declined 10-30% within the last 100 years.
The current acreage is estimated to be less than half of the historical acreage.
Threats to alvar shrublands include the invasion of exotic plants (in particular pale swallow-wort, buckthorn, and honeysuckles), grazing, trampling (especially ATV damage), hydrologic alterations, and development pressure in Jefferson County.
Maintain the mosaic proportional distribution of existing alvar communities by ensuring the the pavement areas and grasslands are kept open. Alvar communities seem to require seasonal flooding, and maintenance of the natural hydrologic regime is critical. Take measures to exclude use of sites by ATVs. Prescribed fire may be a useful tool to promote native plant species diversity (care should be taken in selecting sites for its introduction) and the maintanence of open site conditions (Kost et al. 2007). Develop and implement a prescribed burn plan at appropriate sites. Improve the condition of existing alvar communities by reducing and/or eliminating invasive species, such as black swallow-wort (Cynanchum louiseae), Morrow's honeysuckle (Lonicera morrowii), and buckthorn (Rhamnus cathartica). Identify and target areas with early infestations of invasive exotic plants for control and eradication. Improve the condition of the alvar communities by minimizing trail network and clearly marking existing trails. Improve the landscape context of the barrens by encouraging surrounding landowners to establish natural buffers and restore natural corridors to other larger natural landscape blocks.
Soils are very thin or lacking in and around this community and the effect of clearing and construction on soil retention and erosion must be considered during any development activities. Similarly, these pavements have wide cracks and fissures and any soil enrichment contamination (e.g., from septic leach fields and fertilized lawns) may rapidly alter the water quality of underlying aquifers as well as altering the barrens community structure and function.
The alvar communities in Jefferson County need to be inventoried and remapped using the current classification of alvar communities: 1) alvar pavement grassland, 2) alvar shrubland, 3) alvar woodland, 4) dry alvar grassland, and 5) wet alvar grassland. Survey for additional occurrences in Jefferson County and the surrounding region to advance documentation and classification of alvar shrublands. Continue searching for large sites in excellent to good condition (A- to AB-ranked). Periodic inventory of the alvar shrublands is needed, in order to keep occurrence data current. Quantitative data on composition and variability among patches within occurrences are needed from surveys throughout the growing season. Surveys for rare and characteristic invertebrate species (especially butterflies and moths, along with terrestrial molluscs) are needed for many sites.
Research the composition of alvar shrublands in Jefferson County in order to characterize variations and distinguish it from other alvar communities. Studies of the hydrology of alvar communities (a past study was conducted at Chaumont Barrens) and their immediately surrounding landscape are needed to better understand their hydrologic regimes. Continue long-term monitoring of deer browsing and grazing impacts. Establish a monitoring progam at various sites to understand and track the development of impacts from global climate change. Identify areas where fire can be implemented and evaluated as a management tool, including a flora and fauna monitoring component (Reschke et al. 1999).
Restricted to outcrops of Chaumont limestone (Galoo-Rock outcrop complex) in Jefferson County. New York's sites are at the easternmost edge of a narrow range extending across southern Ontario to the eastern edge of northern Michigan. There are about 54 square miles (34,368 acres) of Galoo-Rock outcrop complex mapped in Jefferson County in the Soil Survey Geographic (SSURGO) database for New York.
This alvar shrubland type occurs throughout the Great Lakes region of the United States and Canada, in northern New York, southern Ontario, northern Ohio, northern Michigan, and eastern Wisconsin (NatureServe Explorer 2015).
Characteristic tall shrubs (2 to 5 m tall) are scrub forms of trees such as eastern red cedar (Juniperus virginiana), northern white cedar (Thuja occidentalis), and bur oak (Quercus macrocarpa). Tree forms (over 5 m tall) of these species may be present, but trees have less than 10% cover in the community. Other less common trees (over 5 m tall) that may be present include shagbark hickory (Carya ovata), rock elm (Ulmus thomasii), and white ash (Fraxinus americana). Characteristic short shrubs (0.5 to 2 m tall) include common juniper (Juniperus communis), gray dogwood (Cornus foemina ssp. racemosa), fragrant sumac (Rhus aromatica), chokecherry (Prunus virginiana), and downy arrow-wood (Viburnum rafinesquianum). Some dwarf shrubs (under 0.5 m tall) are usually present, including bearberry (Arctostaphylos uva-ursi) and snowberry (Symphoricarpos albus). Characteristic vines include poison ivy (Toxicodendron radicans) and riverbank grape (Vitis riparia). The herb layer forms a dry, grassy meadow between the shrubs; average cover of herbs is about 23%. The most abundant herbs are poverty grass (Danthonia spicata), upland white aster (Oligoneuron album), and hidden sedge (Carex umbellata).
This community is a shrubland community that has over 25% cover of dwarf, short, and tall shrubs (less than 0.5 to 5 m); the average is about 43% cover of shrubs, with less than 10% of that being tall shrubs. Alvar shrublands occur on Chaumont limestone (Galoo-Rock outcrop complex).
Characteristic shrubs of this community can be seen thoughout the growing season. Most of them bloom from spring through early summer and fruit from late summer into fall.
This New York natural community encompasses all or part of the concept of the following International Vegetation Classification (IVC) natural community associations. These are often described at finer resolution than New York's natural communities. The IVC is developed and maintained by NatureServe.
This New York natural community falls into the following ecological system(s). Ecological systems are often described at a coarser resolution than New York's natural communities and tend to represent clusters of associations found in similar environments. The ecological systems project is developed and maintained by NatureServe.
Fraxinus americana (white ash)
Quercus macrocarpa (bur oak)
Thuja occidentalis (northern white cedar, arbor vitae)
Ulmus thomasii (rock elm)
Arctostaphylos uva-ursi (bearberry)
Cornus racemosa (gray dogwood, red-panicled dogwood)
Vitis riparia (river grape, frost grape)
Carex umbellata (parasol sedge)
Danthonia spicata (poverty grass)
This figure helps visualize the structure and "look" or "feel" of a typical Alvar Shrubland. Each bar represents the amount of "coverage" for all the species growing at that height. Because layers overlap (shrubs may grow under trees, for example), the shaded regions can add up to more than 100%.
Edinger, G. J., D. J. Evans, S. Gebauer, T. G. Howard, D. M. Hunt, and A. M. Olivero (editors). 2014. 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. http://www.dec.ny.gov/docs/wildlife_pdf/ecocomm2014.pdf
Edinger, Gregory J., D.J. Evans, Shane Gebauer, Timothy G. Howard, David M. Hunt, and Adele 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. 136 pp.
Gilman, B. 1998. Alvars of New York: a site summary. Finger Lakes Community College. Canadaigua, NY.
NatureServe. 2015. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia. Available http://www.natureserve.org/explorer.
New York Natural Heritage Program. 2020. New York Natural Heritage Program Databases. Albany, NY.
Reschke, C., R. Reid, J. Jones, T. Feeney, and H. Potter. 1999. Conserving Great Lakes Alvars: final technical report of the International Alvar Conservation Initiative. The Nature Conservancy, Great Lakes Program, Chicago, IL.
Reschke, Carol. 1990. Ecological communities of New York State. New York Natural Heritage Program, New York State Department of Environmental Conservation. Latham, NY. 96 pp. plus xi.
This guide was authored by: Gregory J. Edinger
Information for this guide was last updated on: March 2, 2017
Please cite this page as:
New York Natural Heritage Program. 2020. Online Conservation Guide for Alvar shrubland. Available from: https://guides.nynhp.org/alvar-shrubland/. Accessed April 7, 2020.