Name:
Juniperus communis - Picea glauca Alvar Shrubland Alliance
Reference:
NatureServe Biotics 2019
Description:
Shrubs dominate this juniper alvar shrubland alliance, with over 25% cover of tall, short, and dwarf-shrubs; the average is about 43% cover of shrubs, with less than 10% of that being tall shrubs. A characteristic short (0.5-2 m) to tall (2-5 m) shrub is <i>Juniperus communis</i>, often associated with scrub forms of trees such as <i>Juniperus virginiana, Thuja occidentalis</i>, and <i>Quercus macrocarpa</i>. Tree forms (>5 m tall) of these species may be present, but trees have less than 10% cover in the community. Other less common trees (>5 m tall) that may be present include <i>Carya ovata, Ulmus thomasii</i>, and <i>Fraxinus americana</i>. Characteristic short shrubs (0.5-2 m tall) include <i>Cornus racemosa, Prunus virginiana, Rhus aromatica</i>, and <i>Viburnum rafinesqueanum</i>. Some dwarf-shrubs (under 0.5 m tall) are usually present, including <i>Arctostaphylos uva-ursi</i> and <i>Symphoricarpos albus</i>. Characteristic vines include <i>Toxicodendron radicans</i> and <i>Vitis riparia</i>. The herb layer forms a dry, grassy meadow between the shrubs; average cover of herbs is about 23%. The most abundant herbs are <i>Carex eburnea, Carex umbellata, Danthonia spicata, Iris lacustris</i>, and <i>Oligoneuron album</i>. Less than 50% of the ground surface is exposed limestone bedrock, which is usually covered with lichens, mosses, and algae. Grikes (eroded cracks in the rock up to 2 m or more deep and extending 5-30 m in length) may occur, with shrubs and trees rooted in the cracks. The juniper alvar shrubland 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. Stands occur on very shallow soils (usually less than 30 cm deep) over flat limestone outcrops (pavements). Moisture varies over the season, but summer droughts are typical. Juniper - white spruce alvar shrublands often occur in a patchy landscape mosaic with other alvar communities, including tufted hairgrass wet alvar grassland, little bluestem alvar grassland, annual alvar pavement-grassland, alvar nonvascular pavement, and poverty grass dry alvar grassland.
Accession Code:
urn:lsid:vegbank.org:commConcept:38398-{670054FA-6FE3-4E87-A526-03C3BE7AF86B}
Plot-observations of this Community Concept:
0
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