Northeastern Pine Barrens

These pine barrens occur on glacial sandplains of the inland regions of the northeastern U.S., with a disjunction to the distinctive till plain shrublands in the Poconos of eastern Pennsylvania. Substrates include outwash plains, stabilized sand dunes, and glacial till. The soils are consequently coarse-textured, acidic, mostly well-drained to xeric, and low in nutrients. Pinus rigida is the usual dominant, and cover may range from closed-canopy forest to (more typically) open woodlands. Quercus rubra, Pinus strobus, and Betula populifolia are common associates. A tall-shrub layer of Quercus ilicifolia and/or Quercus prinoides is commonly present, although portions of some barrens (or occasionally the entire barrens) lack the scrub oak component. A well-developed low-shrub layer is typical, with lowbush Vaccinium spp., Gaylussacia baccata, and Comptonia peregrina characteristic, with Rhododendron canadense characteristic on the slightly more mesic microsites of the Poconos. The system is often a physiognomic patchwork, ranging from nearly closed-canopy forest to open pine woodlands, to scrub oak shrublands, to herbaceous/dwarf-shrub frost pockets. Grassy areas dominated by Schizachyrium scoparium with Lupinus perennis, Lespedeza capitata, and other forbs provide habitat for several rare invertebrates. Small changes in elevation can create pockets with saturated soil, where shrubs such as Corylus americana, Cephalanthus occidentalis, Vaccinium corymbosum, and Alnus spp. form dense cover. These barrens always have a history of recurrent fires, and fire is required to maintain them.

This system is confined to flat to gently rolling plains with sandy soils that are coarse-textured, acidic, mostly well-drained to xeric, and low in nutrients.

Fire regime includes frequent stand-replacing events and lower intensity surface fires. Periodic severe wildfires with 40- to 100-year intervals have produced oak-pine mixtures over extensive areas of uplands, while more frequent severe fires have created mixtures of pitch pine and shrub oaks. Pitch pine younger than 20-40 years may produce stump sprouts after top-killing fire (Andresen 1959). If not top-killed, pines may recover from fire by sprouting from branches and trunk. Pitch pine has. Additionally, pitch pine is quick to maturity and to produce seeds. Frequent fires of moderate to high intensity/severity eventually eliminate all other tree species except for scrub oak and pitch pine, which has thick, fire-resistant bark and is a prolific seed producer. Fires, especially large wildfires, have been a major factor in the development of the present differences among forest stands on similar sites in the Pine Barrens. Abandoned upland sites generally progress from a grass or shrubland (MFRI of 2-3? years) to pitch pine/scrub oak woodland (5-25 years) to pure pitch pine forest with heath/oak scrublands (30-60 years) to pitch pine/tree-sized oak forest (60-100 years) to oak-hickory forest (100-200 years) (Landfire 2007a).

This system has faced widespread conversion to agriculture. Motzkin et al. (1999) note that areas currently occupied by pitch pine - scrub oak communities in central Massachusetts likely represent less than 10% of the area that supported this vegetation in the early historical period. Agricultural activity has been documented since the mid-19th century at Waterboro Barrens in Maine (Copenheaver et al. 2000), in addition to other land uses such as logging, charcoal production, and sand mining. Urban and commercial development continues to be a threat to this system, and as remaining patches become smaller and surrounded by development, they can no longer support the fire regime required to maintain the mosaic of vegetation types that make up this system. Other threats include invasive species and irresponsible recreation activities (Gray and Dawson 2004). Another threat is the degradation in ecological integrity that results from re-establishment of barrens following cessation of agriculture. Motzkin et al. (1999) note that those barrens with soils that have been plowed are depauperate and differ in their composition and structure. [Note: With increasing temperatures and decreased drying projected in the coming decades, it is possible that these effects of climate change may foster continued existence of pine barrens if sufficient protection measures are put in place.]

This system is restricted to interior south-central New England; Colchester, Vermont; eastern New York; and the Pennsylvania Poconos.