Longleaf pine  (Pinus palustris)

Classified as Vulnerable (VU) on the IUCN Red List (1).

The longleaf pine is an attractive medium to large evergreen, with long needles that distinguish it from other pines, and give this tree its name (2) (3) (4). The trunk is straight, and the relatively fire-resistant, orange-brown bark is made up of scaly, rectangular plates (2). Despite sometimes living for hundreds of years, and growing to heights of almost 50 metres, the girth of this pine is relatively modest, with few trees attaining a trunk diameter of much more than one metre (4). The male cones are cylindrical and purplish, and range in size from 3 to 8 cm, while the dull brown female cones are more ovoid in shape, and range in size from 15 to 25 cm (2). A particularly distinctive feature of the longleaf pine is the new-growth buds, which are characteristically silvery-white during the winter (2) (3) (5).

The longleaf pine is native to the southeastern United States (1), where its natural range includes most of the Atlantic and Gulf Coastal Plains, from southeastern Virginia to eastern Texas (6) (7).

The longleaf pine is most commonly found in fairly pure stands, with an understorey dominated by wiregrass (Aristida stricta) (8).

The longleaf pine has evolved for millions of years in a fire dominated realm, and consequently exhibits superb adaptations to frequent fires. In particular seedlings are able to withstand fire by going through a distinctive ‘grass stage’ for the first two to ten years. During this stage, the seedlings develop a deep tap root that stores energy and nutrients, whilst a bushy spray of needles is all that is visible above ground (9). This allows the seedlings to lose foliage during a fire, yet still survive low intensity burns (8) (9). Once the tap root is sufficiently developed, the sapling will shoot up rapidly, rising above the fire zone within two years (9). Mature trees regularly shed the highly flammable needles, twigs and bark, ensuring that low-intensity ground fires occur relatively frequently. Not only does this make it difficult for less fire-adapted trees to compete, but it also prevents the accumulation of large amounts of deadwood with the potential to generate very hot fires that the longleaf pines are unable to withstand (8) (9).

Prior to European settlement, the longleaf pine grew in extensive pure stands throughout the coastal plains of the southeastern United States (4). Today, however, the distribution of pine savannas dominated by the longleaf pine is less than three percent of its original extent. The dramatic decline in its distribution is attributable to over harvesting, particularly during the 19th century, as well as clearance for urban development, agriculture and pine plantations (6). Furthermore, the fragmentation and mismanagement of the remaining stands has resulted in the suppression of wildfires, allowing non-fire tolerant hardwood species to outcompete the longleaf pine (2) (6) (8) (9). Consequently, broadleaved hardwood forests in the region are now far more extensive than they were in pre-settlement times (9).

Pine savannas dominated by the longleaf pine also characteristically support high levels of biodiversity (6). Thus the loss of the longleaf pine ecosystem is putting many other plants and animals at a high risk of extinction. In particular, old-growth longleaf pine stands are the preferred habitat of the endangered red-cockaded woodpecker (8) (9).

Considerable efforts are being made to restore longleaf pine across its natural range. Organisations such as the Longleaf Alliance are bringing together private landowners, forest industries, state and federal agencies, conservation groups and researchers, to determine the most appropriate means for revitalising this threatened ecosystem. Given that the vast majority of forested land in the southeastern United States is privately owned, much of the effort is focused on restoration on private land (10).

To find out more about the conservation of longleaf pine, visit:

• The Longleaf Alliance:
  http://www.longleafalliance.org
• America's Longleaf Initiative:
  http://www.americaslongleaf.net/