This savanna community is typically characterized by scattered jack pines (Pinus banksiana), or less commonly, red pines (Pinus resinosa), sometimes mixed with scrubby northern pin and bur oaks. The scattered trees or groves are interspersed with openings in which shrubs such as hazelnuts (Corylus americana and C. cornuta), sand cherry (Prunus pumila), and prairie willow (Salix humilis) are prominent, along with prairie grasses and forbs. The groundlayer often contains species characteristic of "heaths", such as blueberries (Vaccinium angustifolium and V. myrtilloides), bearberry (Arctostaphylos uva-ursi), and sweet-fern (Comptonia peregrina). Other characteristic plants include dry sand prairie species such as June grass ( Koeleria macrantha), little bluestem (Schizachyrium scoparium), silky and azure asters (Symphyotrichum sericeum and S. oolentangiense), wild lupine (Lupinus perennis), blazing-stars (Liatris aspera and L. cylindracea), and western sunflower (Helianthus occidentalis). Pines may now be infrequent, even absent, in some stands in northern Wisconsin and elsewhere due to past logging, altered fire regimes, and an absence of seed source. In extreme cases, the pines have been virtually eliminated and oak sprouts and shrubs are now the dominant woody species.
The pine and oak barrens communities described by Curtis (1959) share many similarities. In general, there is a loss in the number and abundance of prairie species from south to north, and pine was more characteristic of the northern stands. However, jack pine is an important component of some of Wisconsin's southernmost barrens occurrences (e.g., Gotham Jack Pines on the Wisconsin River in Richland County), and both red pine savanna and jack pine barrens were described in the Public Land Survey notes for Juneau County in central Wisconsin. Maintaining pine in some of the managed stands has been challenging for managers. Frequent fires can cause the local elimination of species like the pines that don't sprout from the root collar. Also, in some parts of Wisconsin, jack pine does not have serotinous cones, which open under the intense heat generated by wildfire, and can then reseed burned areas in which the adult pines have been killed.
The pine barrens community occurs on landforms that include outwash plains, glacial lakeplains, and broad sandy terraces that flank some of the major rivers in southern Wisconsin. Soils are almost always dry and sandy, of low nutrient status, and in topography that is often nearly level, but can be gently rolling. Similar communities include oak barrens, bracken grassland, sand prairie, northern dry forest, central sands pine-oak forest, and bedrock glade.
