This rare community consists of areas of thin, discontinuous soil overlying horizontal beds of limestone or dolomite in the vicinity of Great Lakes shorelines. These communities support an unusual blend of boreal and prairie species, which appear to be relicts of the cold period following the last glaciers and of the warmer, drier period that followed. They are characterized by relatively low tree cover and a distinctive biota which includes elements of rock pavement, prairie, savanna and boreal forest communities. Among these are regional endemics, some of which are globally very rare. This community type is much more common and better developed in Michigan and Ontario than in Wisconsin.
Small coniferous and deciduous trees such as northern white-cedar (Thuja occidentalis), balsam fir (Abies balsamea), pines (Pinus spp.), oaks (Quercus spp.), aspens (Populus spp.), and paper birch (Betula papyrifera) are scattered among an assemblage of species that can include big bluestem (Andropogon gerardii), little bluestem (Schizachyrium scoparium), Indian grass (Sorghastrum nutans), and wood lily (Lilium philadelphicum), as well as shoreline plants such as silverweed (Potentilla anserine) and dwarf lake iris (Iris lacustris). Alvars are home to an unusual set of wildlife species as well, including the Loggerhead Shrike and a large number of distinctive invertebrates such as leafhoppers and terrestrial snails.
