Physiognomy and Structure: These are woodlands or forests that are pine-dominated, or with a mixed pine-hardwood overstory. Examples that have had recent or frequent fire will exhibit a more open structure of the canopy and an open understory with low shrubs. Stands that have experienced less fire, or with a longer fire-return time, will exhibit a more closed canopy with a greater proportion of hardwoods, a denser understory, and taller shrubs.

Floristics: These pine-oak woodlands of Pennsylvania and Maryland are dominated by some combination of Pinus rigida and Pinus virginiana, typically with hardwoods as additional components of the canopy and understory. Quercus marilandica and Quercus stellata are characteristic, in contrast to other Pinus rigida communities (Zimmerman et al. 2012). In better examples (that have had recent or frequent fire), the most characteristic overstory species include Juniperus virginiana, Nyssa sylvatica, Pinus rigida, Populus grandidentata, Quercus marilandica, Quercus stellata, and Sassafras albidum. The shrub layer may be dominated by an impenetrable tangle of Smilax glauca and Smilax rotundifolia, particularly if fire has been absent for many years. In addition, Quercus ilicifolia or Quercus prinoides may occur in the understory and in openings. The low-shrub species include Gaylussacia baccata, Vaccinium pallidum, and Vaccinium stamineum. Herbaceous species include Aralia nudicaulis, Pteridium aquilinum, and a variety of graminoids (Zimmerman et al. 2012). In addition, Robinia pseudoacacia is generally invasive in these woodlands. Stands that have experienced less fire, or with a longer fire-return time, will exhibit dominance by a mixture of Acer rubrum, Pinus virginiana, and various Quercus spp. Pinus virginiana produces denser shade and thicker litter than does Pinus rigida. Herbaceous and shrub growth under Pinus virginiana is generally more sparse than in examples dominated by Pinus rigida (Zimmerman et al. 2012). More information can be found in Podniesinski et al. (1999).

Dynamics:  This plant community is adapted to the weathering of serpentine bedrock. It was once thought that the lack of canopy cover was maintained by the unique edaphic features of the chrome series soils. This is certainly a factor, but in the last few decades, many sites have been invaded by dense Pinus virginiana (Tyndall 1992a), as well as Acer rubrum. This dramatically alters the light regime and promotes substantial soil development (up to 10 cm in 20 years). Under these conditions, an entirely different community develops as the influence of the bedrock is buffered by the soil/litter accumulation. This closed-canopy serpentine forest typically exhibits a dense understory of Smilax glauca and Smilax rotundifolia. Some of the characteristic herbaceous serpentine species apparently persist in the ground layer as scattered non-flowering individuals; other populations appear to die out but may persist in the seed bank. Selective cutting has been effective in restoring degraded sites to their previous composition and structure, but most researchers believe that without regular burning to prevent soil development the serpentine plant communities will not persist. There is substantial evidence that most of the existing areas were regularly burned by Native Americans (Marye 1920, 1955a, 1955b, 1955c) and perhaps maintained by grazing after European settlement.