Oak - Hickory Woodlands and Savannas
Piedmont military base training areas ("impact areas") that have been subject to frequent incendiary fires for at least 50 years support the deciduous woodlands that constitute this group. As currently defined, these communities are endemic to Virginia and are now found only at Quantico Marine Base in the northern Piedmont (Fauquier, Prince William, and Stafford Counties) and Fort Pickett in the southern Piedmont (Dinwiddie and Nottoway Counties), where they cover hundreds of hectares. Habitats at both sites are rolling uplands underlain by granitic rocks. Soils are generally sandy and range from extremely to strongly acidic, with relatively low base cation levels. However, in a small (20-25 ha) area of Fort Pickett that is underlain by a sill of intrusive Triassic diabase, soils are dark, slightly acidic to circumneutral loams with relatively high calcium and magnesium levels.
Stand physiognomy encompasses semi-closed woodlands with little understory; graminoid-rich savannas with widely spaced trees; and dense thickets of small, sprout-origin trees. Variable mixtures of white oak (Quercus alba), black oak (Quercus velutina), southern red oak (Quercus falcata), scarlet oak (Quercus coccinea), post oak (Quercus stellata), and mockernut hickory (Carya tomentosa) form the woodland overstories. Understories are highly variable in both density and composition. Dense herb layers are rich in both grasses and legumes. Abundant species include little bluestem (Schizachyrium scoparium var. scoparium), indian grasses (Sorghastrum nutans and Sorghastrum elliottii), broomsedges (Andropogon virginicus var. virginicus) and (Andropogon gyrans), poverty oatgrass (Danthonia spicata), silver plumegrass (Saccharum alopecuroides), tick-trefoils (Desmodium spp.), and bush-clovers Lespedeza spp.). Goldenrods (Solidago spp.), thoroughworts (Eupatorium spp.), and other composites are characteristic of the diverse late-flowering flora of the woodlands. Stands on basic soil have a more species-rich herbaceous flora characterized by forbs, including nettle-leaf sage (Salvia urticifolia), glade wild quinine (Parthenium auriculatum), naked-flowered tick-trefoil (Hylodesmum nudiflorum), green-and-gold (Chrysogonum virginianum var. virginianum), perfoliate bellwort (Uvularia perfoliata), sunflowers (Helianthus strumosus and (Helianthus divaricatus), small white snakeroot (Ageratina aromatica), skunk meadow-rue (Thalictrum revolutum), and hog-peanut (Amphicarpaea bracteata).
Although communities of this group are strongly influenced by an artificial disturbance regime, they are Virginia's only extant examples of vegetation that is shaped by random burns of a size, frequency, and intensity comparable to those of putative pre-settlement fire regimes. Thus, they may provide important clues about the probable composition and environmental dynamics of woodlands that burned under a regime of natural fires and fires intentionally set by native Americans beginning in the early Holocene. The largest known population in the world of the globally rare, federally listed shrub Michaux's sumac (Rhus michauxii) is associated with the fire-influenced woodlands at Fort Pickett.References: Fleming (2002a), Fleming et al. (2001), Maxwell (1910).
Click on the images below to open a larger image in a separate window.
|Nettle-leaf sage (Salvia urticifolia , flowering), woodland sunflower (Helianthus divaricatus), and hickory (Carya sp.) saplings in a Basic Oak-Hickory Woodland / Savanna on diabase at Fort Pickett Military Reservation, Dinwiddie County. Gary P. Fleming / © DCR Natural Heritage.|
|Fire-maintained, graminoid-rich Acidic Oak-Hickory Woodland / Savanna at Quantico Marine Base, Fauquier County.Gary P. Fleming / © DCR Natural Heritage.|
|A frequently burned savanna dominated by oaks (Quercus spp.), hickories (Carya spp.), and little bluestem (Schizachyrium scoparium var. scoparium) at Fort Pickett Military Reservation, Dinwiddie County.Photo: Caren Caljouw.|
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