Fall-line Sandhills Longleaf Pine Woodland

This system occurs in the Fall-line Sandhills region of central North Carolina south and west into central Georgia. It is the predominant system in its range, covering most of the natural landscape of the region. It occurs on upland sites ranging from gently rolling, broad ridgetops to steeper sideslopes, as well as locally in mesic swales and terraces. Most soils are well-drained to excessively-drained. The vegetation is naturally dominated by Pinus palustris. Most associations have an understory of scrub oaks (Quercus laevis, Quercus marilandica, Quercus incana, and Quercus margarettae). The herb layer is generally well-developed and dominated by grasses. Wiregrasses (Aristida stricta in the north, Aristida beyrichiana in the south) dominate in most of the range, but other grasses dominate where these are absent. Forbs, including many legumes and composites, are also abundant. Frequent, low-intensity fire is the dominant natural ecological force.

Vegetation is a set of associations naturally dominated by longleaf pine (Pinus palustris). Scrub oaks (Quercus laevis, Quercus marilandica, Quercus incana, and Quercus margarettae) form an understory in most associations, all but the mesic ones. Low shrubs, most ericaceous, may be abundant. In most of the range, wiregrass (Aristida stricta or in the south Aristida beyrichiana) is the dominant herb. In central South Carolina both species are absent and various other grass species dominate. Most associations have abundant legumes, as well as composites and other forbs. The abundance of legumes distinguishes this system from Atlantic Coastal Plain Upland Longleaf Pine Woodland (CES203.281), where most associations have few legumes. Many associations have moderate to high species richness, with most of the species in the herb layer. Some mesic associations have among the highest species richness values measured at the 1/10-hectare scale. Associations on deep, coarse sands may have low species richness but have a distinct set of xerophytic herbs and dwarf-shrubs.

This system occurs on upland sites in the Fall-line Sandhills region (Ecoregion 65c of EPA (2004); 232Bq of Keys et al. (1995)). It covers the gently rolling, ancient eolian sands and the steeper side slopes in older formations that make up most of the dissected landscape in this region. Shallow swales, drier stream terraces, and rock outcrops also may support this system. Substrates include interbedded sands and clays, deep sands, and occasional loamy sediments. Soils are generally well- to excessively drained and infertile, though local richer, mesic sites occur. All soil types are underlain by a thick clay layer that impedes drainage and creates innumerable headwater creeks; the depth from the surface to this clay layer is very variable. Non-wetland conditions and frequent fire unify this system within the Fall-line Sandhills region. Soil texture appears to be the most important driver of differences among associations within the system, with biogeography also important.

Frequent fire is the predominant natural disturbance in this system. Component communities naturally burned every few years, many averaging as often as every 3 years. Fires are naturally low to moderate in intensity. They burn above-ground parts of herbs and shrubs, but have little effect on the fire-tolerant Pinus palustris trees. Vegetation recovers very quickly from fires, with live herbaceous biomass often restored in just a few weeks during the growing season. Many plants have their flowering triggered by burning. Fire is important in creating the structure of the vegetation. In the absence of fire, less fire-tolerant species increase and others invade the system. The scrub oaks and shrubs, kept to low density and mostly reduced to shrub size, become tall and dense and can suppress Pinus palustris tree regeneration. Herb layer density and diversity decline. Only on the most excessively drained coarse sands does the vegetation not undergo substantial structural alteration and reduction in species richness after just a few years without burning. The often patchy nature of natural fires (and controlled burns) results in part from the abundance of streamheads that lace the Sandhills region and which tend to restrict fires from sweeping across large acreages.

Canopies are believed to naturally be multi-aged, consisting of a fine mosaic of small even-aged groves driven by gap-phase regeneration. Pinus palustris is shade-intolerant and slow to reach reproductive age, but is very long-lived. Most plants in these systems appear to be conservative, living a long time and only rarely sexually reproducing or colonizing new sites. Similar conservatism is shown by some of the vertebrates, such as red-cockaded woodpecker (Picoides borealis). Different dynamics occur in many insect populations, whose individuals are not resilient to fire and must recolonize burned areas from nearby unburned patches.

Lack of fire is a big threat for all Pinus palustris ecosystems, even on conservation lands. The development of a closed forest canopy and lack of fire can lead to declines, and eventual loss, of the native herbaceous ground cover vegetation. For unprotected examples, the greatest threat is destruction by commercial and residential development, conversion to intensively managed pine plantation, and other land uses. Logging without deliberate conversion (such as high grading) is also a serious threat, because it can destroy the natural vegetation structure, and because Pinus palustris often fails to regenerate at all if not carefully managed, for instance by retaining enough Pinus palustris seed trees, and using prescribed fire to prepare the seed bed for Pinus palustris regeneration. The collecting of snakes by putting gasoline or kerosene in gopher tortoise burrows is a real threat, as it pollutes the tortoise burrow which is habitat for many species. Fragmentation of habitat by roads and commercial or residential development is also a serious threat, because the ability to manage remaining Pinus palustris sites with fire is limited in urban interface areas and near roads. These threats limit prescribed burning due to urban interface, safety and smoke management concerns. Invasive exotic species are threats, including Imperata cylindrica (Brewer 2008), Lespedeza bicolor or Lespedeza cuneata, and feral pigs (Sus scrofa), which root up Pinus palustris seedlings (Wahlenberg 1946) and herbaceous plants with thick roots. Pinus palustris woodlands have declined due to conversion to intensively managed pine plantations.

This system ranges from central North Carolina to central Georgia, in the Fall-line Sandhills region (Ecoregion 65c of EPA (2004); 232Bq of Keys et al. (1995)).