The Longleaf Alliance 3Rd Biennial Regional Conference Proceedings
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PROCEEDINGS of the Third Longleaf Alliance Regional Conference FOREST FOR OUR FUTURE Restoration and Management of Longleaf Pine Ecosystems: Silvicultural, Ecological, Social, Political and Economic Challenges Hosted by The Longleaf Alliance, USDA Forest Service, and US Geological Survey Alexandria, Louisiana October 16-18, 2000 Longleaf Alliance Report No. 5 July 2001 THE HISTORY AND CHARACTER OF LONGLEAF PINE SYSTEMS IN THE WEST Latimore Smith (The Nature Conservancy – Louisiana Field Office Baton Rouge, LA) Longleaf pine (Pinus palustris) historically ranged from southern Virginia to east Texas, occupying mainly the sandy and silty Atlantic and Gulf Coastal Plains. In the West Gulf Coastal Plain (WGCP), longleaf pine historically occupied over 7 million acres in west Louisiana and southeast Texas, occurring on a wide variety of geologic substrates, and soil conditions, from high hills to flatwoods. It was principally found on acidic sandy loams and silt loams formed on Pleistocene-aged deposits to the south, but also on acidic clays, loams and sands of older Tertiary formations to the north. Such variation in substrates supporting longleaf pine produced a truly amazing complexity of herbaceous ground cover plant communities in the longleaf system of the WGCP, and notable variation in the structure of the virgin forests and savannas. The western range of longleaf pine of longleaf pine, west of central Mississippi, is comprised entirely of what has been generally labeled the “longleaf-bluestem” range, due to the dominance of bluestems and broomsedges (mainly little bluestem, Schizachyrium scoparium) and complete lack of wiregrass (Aristida berychiana/stricta) in the ground cover. While much emphasis has been placed on the longleaf-wiregrass system of the eastern states by many in recent years, the longleaf-bluestem range is equally worthy of attention. It supports a grand assortment of native species, both plant and animal (many rare and restricted to longleaf communities), and has been equally profoundly reduced in extent by human endeavor. As throughout the range of longleaf, frequent fire was, without question, the primary force that gave rise to and maintained the longleaf system in the western part of its range. Fires originating from lightning (long before the arrival of aboriginal peoples, e.g., Komarek 1968) are estimated to have burned through the grassy ground cover of the western forests and savannas every 1 to 5 years, mainly in the spring and early summer. There are clear indications in early written accounts (e.g., Sargent 1884, Mohr 1897) that the virgin longleaf forests of the western range were typically more heavily stocked than the majority of the forests to the east, almost certainly owing to the predominance of more fertile loams to the west. Well-drained sites in the loamy flatwoods and gently rolling hills are particularly conducive to excellent growth of longleaf pine. Despite such heavy average stocking of trees, the forest was naturally heterogeneous in stand structure, as it was to the east, typically varying over short distances from very densely stocked areas to very open areas with few, if any, trees (e.g., Schwarz 1907). The virgin forests of the west were also primarily uneven-aged, individual stands usually comprised of trees of many ages and sizes (e.g., Chapman 1909), although more-or- less even-aged stands did originate after devastating windstorms. The largest longleaf pines in the virgin forests of the west were 35 to 40 inches in diameter breast height (dbh) and about 120 feet tall, with the oldest trees averaging 200 – 300 years of age, but rarely exceeding 400 years (Mohr 1897). The two principal historic landscape settings for longleaf pine in its western range were forests (or woodlands) in rolling hills, and pine savannas and flatwoods in the flats. Although there were a variety of landscape and substrate settings on which longleaf was found in the hills, longleaf was most common on dry- mesic, acidic sandy loams, with essentially pure forests of longleaf pine stretching across the rolling hills. The most common hardwoods (yet very scattered, in general) found in these forests included southern red oak (Quercus falcata), post oak (Q. stellata), blackjack oak (Q. marilandica), mockernut hickory (Carya alba), and black hickory (C. texana). In this landscape, longleaf characteristically transitioned quickly going down major slopes to a mixed shortleaf pine (Pinus echinata)-hardwood type that formed narrow belts along upper reaches of major slopes leading to permanent streams. Down slope from the latter type was typically a mesic mixed loblolly pine (P. taeda)-hardwood type. Judging from best remaining examples, the ground cover plant communities of the dry-mesic, loamy longleaf uplands was extremely diverse. Field studies of best remnants of the type reveal that over 100 herbaceous plant species are often present on a typical acre. While grasses (particularly little bluestem), composits (sunflower family) and legumes are the most common groups, a huge assortment of other species are present. Many of these species are restricted to upland longleaf systems, or reach their greatest abundance there. It is fair to estimate that over 400 plant species are present in the loamy upland longleaf forests of the western range, and over 100 are essentially restricted to these forests in the region. 1 Other significant longleaf types in the rolling hills of the western longleaf range included xeric longleaf woodlands on deep sands, and xeric to mesic longleaf woodlands on acid clays. Xeric longleaf woodlands of the WGCP support a significant component of scrub oaks, such as bluejack oak (Quercus incana), sand post oak (Q. margarettiae), and blackjack oak, and probably burned less frequently than the typical dry-mesic longleaf forest of the loamy uplands due to sparser grassy fuels. Although overall species richness is not as great in the deep sandy uplands as the loamy uplands, numerous specialized herbaceous species are restricted to the sandy xeric uplands of the WGCP longleaf range such as scarlet catch-fly (Silene subciliata) and Winkler’s Indian blanket (Gaillardia aestivalis var. winkleri). Analogous sandhill longleaf sites in much of the East Gulf Coastal Plain support Gopher tortoise (Gopherus polyphemus), but this animal does not range west of the central Florida Parishes of southeastern Louisiana. Sandstone glades supporting scattered, stunted longleaf pine and scrub oaks and a specialized flora are locally common (yet rare overall) in portions of the western longleaf range. Such glades arise on outcrops of sandstone “pavement”, mainly on the Catahoula formation in central and western Louisiana. Inclusional areas of calcareous clays within the longleaf range of the WGCP supported mixed forest types (lacking longleaf), and calcareous prairie grasslands. In transitional areas between acid loams or sands with longleaf and calcareous clays supporting other vegetation types, there was typically a fairly dramatic transition in types over short distances. At the edges of the longleaf range in the west, pure longleaf forests often gave way to mixed forests of longleaf, shortleaf, loblolly and a variety of hardwoods. While transitions to other types were typically abrupt and transitional mixed forests including longleaf pine were never extensive in Louisiana, such forests apparently were prominent at the western edge of the longleaf range in Texas (Paul Harcombe, pers. comm.). Hillside seepage bogs are embedded within frequently burned, sandy upland longleaf forests of the western range, being particularly abundant in west central Louisiana. This region may support the highest density of hillside seepage bogs found anywhere in the southeastern United States. In the heart of this “bog country”, dozens of seepage bogs are present per square mile. While hundreds of bogs are known from this area, each is usually less than 2 acres in size (though much larger ones exist), and the total acreage of hillside seepage bogs in the WGCP probably does not exceed 3,000 acres. These special wetlands are floristically closely related to the acidic, wet longleaf pine flatwood savannas of the region, sharing many species in common, but differ markedly from savannas in the WGCP by the presence and sheer abundance of insectivorous yellow pitcher-plants (Sarracenia alata; the only species in the genus found in the WGCP). These fascinating plants are completely and inexplicably absent from the flatwood savannas of the WGCP. Hillside seepage bogs support at least one regional endemic, Bog brown-eyed Susan (Rudbeckia scabrifolia). Longleaf pine flatwood savannas dominated the youngest and flattest Pleistocene terraces of the outer coastal plain of western Louisiana and east Texas (north of the coastal prairie zone), and were found further inland on “relict” flats on higher parts of older Pleistocene terraces and certain Tertiary formations. Soils of the flatwoods of the WGCP are overwhelmingly acidic silt loam alfisols, although a very rare and unusual savanna type is found on sodic silt loams. Flatwood savannas are actually closely intermingled wetlands (generally called “savannas”) and non-wetlands (generally called “flatwoods”), produced by close-proximity variations in topography that greatly influence microsite hydrology. Wet pine savannas and non-wet flatwoods in the WGCP are tightly co-mingled in a landscape studded with “pimple mounds” (also called mima mounds), which are small, rounded knolls or hillocks, usually a few feet higher than the intermound areas, and that are more or less regularly distributed across the flats. In this unique landscape, “savannas” occupy the wet intermound areas and “flatwoods” occupy the well-drained pimple mounds, but the entire complex is usually referred to as a savanna. The federally-listed (“Endangered”) plant, American chaffseed (Schwalbea americana), was recently rediscovered in southwest Louisiana, after a near 100-year hiatus, growing on pimple mounds in the longleaf pine flatwoods. The flatwood savannas of the west, as those in the east, are very rich in native herbaceous species, dominated by grasses and sedges, but a multitude of other groups are represented.