Name:
Tortella tortuosa - Cladonia pocillum - Placynthium spp. Sparse Vegetation
Reference:
NatureServe Biotics 2019
Description:
Alvar nonvascular pavement is a rock outcrop community that occurs throughout the Great Lakes region of the United States and Canada, from central and southern Ontario to northern parts of Michigan, Ohio, and New York. Stands occur on flat limestone and dolostone outcrops (pavements). Soils of alvar nonvascular pavement are either lacking or very shallow (usually less than 10 cm deep). This community typically has a soil moisture regime characterized by severe summer drought, as well as high summer temperatures. Alvar nonvascular pavements usually occur in a patchy landscape mosaic with other alvar communities, including annual alvar pavement-grassland, creeping juniper - shrubby-cinquefoil alvar pavement, little bluestem alvar grassland, tufted hairgrass wet alvar grassland, and juniper alvar shrubland. Alvar nonvascular pavement consists of exposed, flat limestone or dolostone pavement that is sparsely vegetated with a mosaic of mossy patches and exposed bedrock that is covered with crustose and foliose lichens. In the mossy patches, characteristic mosses are <i>Tortella tortuosa</i>, other <i>Tortella</i> spp., and <i>Tortula ruralis</i>; a characteristic lichen is <i>Cladonia pocillum</i>. On exposed pavement patches, characteristic lichens are <i>Placynthium nigrum</i> and <i>Dermatocarpon cf. miniatum</i>. Very small herbs (under 15 cm [6 inches] tall), grow in the mossy patches, including <i>Saxifraga virginiensis, Penstemon hirsutus, Potentilla norvegica, Trichostema brachiatum, Fragaria virginiana, Minuartia michauxii var. michauxii</i>, and <i>Houstonia longifolia</i>. Some taller herbs and low shrubs grow primarily in slightly deeper soils of rock crevices that crisscross the pavement, including <i>Solidago nemoralis, Symphoricarpos albus, Vitis riparia, Aquilegia canadensis</i>, and <i>Hieracium piloselloides</i>. There is usually less than 15% cover of herbs. Usually a few trees and shrubs are rooted in deep crevices of the pavement; characteristic trees and shrubs that occur sparsely include <i>Thuja occidentalis, Juniperus communis, Betula papyrifera, Juniperus virginiana, Juglans cinerea</i>, and <i>Picea glauca</i>. There is less than 10% total cover of trees, and less than 10% total cover of shrubs. There is a lot of exposed bedrock, and much of it is covered with lichens and mosses (average cover of lichens and mosses is about 55%).
Accession Code:
urn:lsid:vegbank.org:commConcept:33956-{56771EDF-09BC-48B8-B823-DBA70AB80F98}
Plot-observations of this Community Concept:
5
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