History and restoration of the longleaf pine-grassland ecosystem: Implications for species at risk

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Forest Ecology and Management 211 (2005) History and restoration of the longleaf pine-grassland ecosystem: Implications for species at risk David H. Van Lear a, *,
Forest Ecology and Management 211 (2005) History and restoration of the longleaf pine-grassland ecosystem: Implications for species at risk David H. Van Lear a, *, W.D. Carroll a, P.R. Kapeluck a, Rhett Johnson b a Department of Forestry and Natural Resources, Clemson University, Clemson, SC 29634, USA b Solon Dixon Forestry Education Center, Auburn University, Auburn, AL 36849, USA Abstract The longleaf pine-grassland (Pinus palustris-poaceae) ecosystem occupied over 30 million ha in the southeastern United States at the time of European discovery. Frequent low- to moderate-intensity surface fires ignited by both lightning and native Americans sustained open diverse stands in a fire climax and prevented succession to mixed hardwood forests. Disruption of prehistorical and historical fire regimes, coupled with land conversion, urbanization, and other factors, is responsible for the rapid decline of the ecosystem. Today only about 1.2 million ha remain, much in isolated fragments. Primarily because of habitat loss, many animal and plant species associated with longleaf forests are now rare or in decline. Restoration ecologists and managers face a daunting challenge recreating an ecosystem, in the face of chronic cumulative stress from human activities, that varied widely over temporal and spatial scales. Key restoration factors include: (1) development of a general understanding of the historical condition of the longleaf ecosystem, especially unusual or unique communities and habitats embedded in the general fabric of the larger ecosystem, (2) initiation and expansion of a fire regime, where feasible, similar to that which historically shaped the ecosystem, (3) maintenance/enhancement of herbaceous diversity, (4) continued research on habitat requirements and distribution of rare species, and (5) encouragement of a multi-owner partnership approach to promote conservation across the landscape. Landowners and the public must be educated about the values of the longleaf pine-grassland ecosystem and develop a conservation ethic that considers aesthetics, wildlife, and biodiversity, in addition to economics, if the ecosystem is to be restored. Most forestry practices used to manage and restore longleaf forests are of low short-term risk to rare species in this ecosystem. The benefits of active management usually far outweigh the long-term risks associated with no management. # 2005 Elsevier B.V. All rights reserved. Keywords: Fire-dependent ecosystems; Prescribed burning; Endangered and threatened species; Historical and pre-historical fire regimes 1. Introduction At the time of European settlement, longleaf pine (Pinus palustris) was dominant on about 30 million ha and occurred on another 7 million ha in mixed stands * Corresponding author. Tel.: ; fax: address: (D.H. Van Lear). (Frost, 1993). From southeastern Virginia to eastern Texas, it dominated the Coastal Plain but also extended into the Piedmont, Cumberland Plateau, Ridge and Valley, and Blue Ridge physiographic regions (Boyer, 1990; Outcalt and Sheffield, 1996). Although upland pine-grassland communities were most characteristic of this expansive ecosystem, communities of numerous rare habitats, such as sinks and other depressional /$ see front matter # 2005 Elsevier B.V. All rights reserved. doi: /j.foreco D.H. Van Lear et al. / Forest Ecology and Management 211 (2005) Fig. 1. Estimated area in the longleaf pine ecosystem from 1500 A.D. to 2004 A.D. Data from Frost (1993), Wahlenberg (1946), and U.S. Fish and Wildlife Service (2003). wetlands, hammocks, and upland/wetland ecotones, were also important components. Man and lightning combined over the millennia to make frequent fire the dominant ecological process shaping the vast longleaf pine-grassland ecosystem. However, today only about 1.2 million ha of the ecosystem remain (Outcalt and Sheffield, 1996; U.S. Fish and Wildlife Service, 2003), a 97% loss from its original extent (Fig. 1). Noss et al. (1995) ranked longleaf pine forests the third most endangered ecosystem in the United States. In this review, we discuss the pre-historical and historical role of fire in this ecosystem and the effects of almost a century of fire exclusion, which coupled with rampant development, land conversion, and other factors, account for the loss of habitat and biodiversity. The consequences of this altered fire regime on forest succession, forest structure, and species at risk will be contrasted with the short-term risks of active management to restore ecosystem composition, structure, and function. The term species at risk is a comprehensive term that includes all species whose long-term survival is questionable because of habitat loss in the longleaf pine-grassland ecosystem. For conciseness, the term longleaf ecosystem will replace longleaf pine-grassland ecosystem. 2. The pre-historical role of fire in the longleaf ecosystem 2.1. Climate change and establishment of the longleaf pine-grassland ecosystem Although the Wisconsin ice sheet of 18,000 years ago extended southward only to the present location of the Ohio River, the massive dimensions of the glaciers and the water they contained caused a colder and drier climate in the South (Delcourt and Delcourt, 1979; Carroll et al., 2002). Longleaf pine and other southern pines found refuge mainly in coastal areas and on the exposed continental shelf from Florida to northeastern Mexico (Edwards and Merrill, 1977). As the glaciers retreated, the climate warmed and cooled periodically, vegetation patterns in the South changed rapidly, and species migrated north and westward from their Ice Age refuges. During the Hypsithermal Period ( years before present or ybp), the warmest period during the past 20,000 years, prairie grasses, aided by anthropogenic burning, expanded from the Midwest into the Southeast (Edwards and Merrill, 1977; Watts, 1980; Delcourt and Delcourt, 1985). At the same time, the longleaf ecosystem became dominant in the Coastal Plain (Culberson, 1993; Watts, 1980; Delcourt and Delcourt, 1985). Although climate, soil, and topography influence the distribution of vegetation, frequent burning was the dominant ecological process that shaped and maintained the composition, structure, and function of the longleaf ecosystem (Komarek, 1974; Noss, 1989; Landers et al., 1995). Frequent fires ignited by lightning and Native Americans sustained this ecosystem (Landers, 1991; Carroll et al., 2002; Stanturf et al., 2002), which over the millennia became one of the most floristically diverse in North America (Peet and Allard, 1993; Walker, 1993) Sources of ignition: Native Americans and lightning It is difficult to separate the effects of lightning and anthropogenic fire on vegetative patterns or determine which was the most dominant ignition source. The southeastern United States, especially the Gulf Coastal Plain, has the highest frequency of lightning strikes in North America (Komarek, 1974). However, man domesticated fire tens of thousands of years before the first Americans brought this powerful tool to the South over 12,000 ybp, and knew how to influence vegetation with fire for his benefit (Kurten, 1972; Champion et al., 1984; Carroll et al., 2002). As Native Americans advanced through different cultural periods and became more numerous, they undoubtedly 152 D.H. Van Lear et al. / Forest Ecology and Management 211 (2005) used fire more and more (Delcourt and Delcourt, 1997; Delcourt, 2002). At the time of Columbus, it is estimated that million people lived in the Southeast, mostly in the Coastal Plain (Dobyns, 1983). Fire was their primary tool for managing the landscape for their benefit. Native Americans burned locally around their settlements to reduce fuels and protect themselves from wildfires (Williams, 1989; Johnson and Hale, 2002). They also influenced the character of the broader landscape by using fire to enhance wildlife habitat and increase wildlife populations, aid in hunting, favor berry- and nut-producing plants and other palatable forage, maintain open landscapes for ease of travel, and protect themselves from ambush by predators and enemy tribes (Hudson, 1976; Williams, 1989; Pyne et al., 1996; Bonnicksen, 2000; Carroll et al., 2002). Frequent burning reduced biting insects like blackflies, ticks, fleas, mosquitos, and other pests, improving the quality and health of their lives (Bonnichsen et al., 1987). The early hunter-gatherers of the Clovis and Late Paleo Period cultures (12, ybp) initiated a burning pattern that would dominate the Southeast until approximately 500 ybp (Pyne et al., 1996; Bonnicksen, 2000; Carroll et al., 2002). Although lightning fires were common during the growing season (Komarek, 1974; Noss, 1989), Native Americans set fires in all seasons. In all likelihood, a combination of Native American- and lightningcaused fire helped genetically fix fire-adapted characteristics in species in this ecosystem (Masters et al., 2003). Frequent fire shaped vegetative communities in the longleaf ecosystem, possibly by acting as an ecological filter that permitted access only to species compatible with this disturbance regime (Bond and Van Wilgen, 1996, p. 147) and by controlling the size and distribution of less-fire adapted hardwoods (Ware et al., 1993). Fire interacted with site and disturbance to maintain a shifting mosaic of prairies, savannas, woodlands, and other community types over the landscape (Peet and Allard, 1993; Landers et al., 1995). In recent decades, the major role of Native Americans in shaping the Southern landscape, although controversial, has been more widely acknowledged, especially by historical geographers, historians, paleoecologists, anthropologists, and resource managers (Delcourt and Delcourt, 1985; Williams, 1989; Pyne et al., 1996; Bonnicksen, 2000; Carroll et al., 2002). Man s use of fire allowed him to influence the landscape far out of proportion to his numbers (Hudson, 1976). Indeed, it can be argued that, at least in some places, the southeastern Coastal Plain prior to its discovery by Europeans was a cultural artifact largely molded and manipulated by Native Americans through their use of fire (Williams, 1989, p. 49; Pyne et al., 1996, pp ; Carroll et al., 2002) Disturbances and site factors The pre-historical fire regime, i.e., prior to 500 ybp, in the longleaf ecosystem was characterized by frequent burning which produced fires of low-to moderate-intensity and severity. In this fire regime of frequent understory burning (Brown, 2000), fires were generally non-lethal to the dominant vegetation and did not change the existing structure of woody and herbaceous components. Because the interval between fires was short, fuels did not accumulate to levels that would allow stand-replacing fires. Fire-dependent plant communities developed that not only required fire for their maintenance, but encouraged future understory fires. Fine tinder provided by long, linear, and often overlapping leaves of bunch grasses (Aristida spp., Andropogon spp., Sorghastrum spp., Schizachyrium spp., and others) and the long, resinous needles of longleaf pine ensured that fires ignited readily and spread quickly across the open landscape (Noss, 1989; Clewell, 1989; McGuire et al., 2001). Without fire at 1 3 year intervals, there would have been invasion and replacement by communities of less fire-adapted species (Ware et al., 1993; Engstrom et al., 2001). Combinations of disturbances and site factors contributed to the high biodiversity of the longleaf ecosystem (Hardin and White, 1989; Walker, 1993; Peet and Allard, 1993). Frequent lightning strikes, tree falls, and various animals have local influences, while tropical storms and hydrologic extremes affect larger areas and long temporal scales. These disturbances, acting over soils and sites ranging from bogs to xeric sand ridges, interacted with fire and provided temporary habitat features (coarse woody debris, hardwood thickets, etc.) and more stable features (old trees, treeless places, etc.) over the landscape. D.H. Van Lear et al. / Forest Ecology and Management 211 (2005) Following major disturbances to the upper canopy from hurricanes and other wind events, more intense fires undoubtedly developed in the complex mix of fine and coarse fuels. These higher intensity fires would have had relatively long residence times burning in large and heavy fuels and probably killed many trees that may have survived the high winds (Outcalt and Wade, 2004). Intensely burned areas, if followed by frequent burning by Native Americans and lightning over long periods of time, would have expanded prairies and savannas (Doolittle, 1992; Gremillion, 1987; Myers and Van Lear, 1997) and contributed to this shifting vegetative mosaic that characterized the longleaf ecosystem for millennia. 3. Transition from Native American to European culture 3.1. Decline of the Native American population European and African diseases were brought to the Caribbean around 1500 A.D. and advanced to Central America, Mexico, and the southern United States prior to the arrival of the Spanish in the region (Verano and Ubelaker, 1992). When the explorer DeSoto marched his army of 600+ men across the South in , he found villages of Native Americans already decimated by disease. Mortality rates as high as 90 95% have been attributed to smallpox, typhoid, bubonic plague, influenza, mumps, measles, hepatitis, and other diseases that spread rapidly in the Americas in the century after Columbus (Dobyns, 1983; Smith, 1987; Lovell, 1992). The Mississippian Culture collapsed by 1600 A.D. as a result of European intrusion and diseases. The arrival of the English in the early 17th century continued the pandemics that decimated Native Americans for another century (Hudson, 1976; Smith, 1987; Carroll et al., 2002). With the decline in the Native American population and the still small European/African population in the southeastern United States, fire became a less common practice and was confined to smaller areas. Prairies and open savannas gradually succeeded to dense mixed hardwood forests reversing the process by which Native Americans had created them (Rostlund, 1957) European settlement and impacts Woods burning in the longleaf ecosystem became common once again as European settlers and their African slaves replaced Native Americans. Immigrants were primarily from western England, Scotland, and Ireland, where burning and open range herding was customary (Johnson and Hale, 2002). These new settlers burned to achieve many of the same goals of Native Americans. They burned frequently, often annually, to keep the woods open and for improved grazing and hunting. Now, however, wildlife competed with domestic livestock for palatable forage and exotic species were introduced into the ecosystem. Especially damaging to longleaf pine regeneration, feral hogs (Sus scrofa) saturated tidewater Virginia and northeastern North Carolina by 1750 (Frost, 1993). Row crop farming and pasturing gradually broke the tradition of open-range burning in much of the South, although burning continued in the extensive pine-woods of the Coastal Plain. However, wealthy northerners bought plantations after the Civil War for hunting retreats and stopped extensive burning on their lands (Frost, 1993; Johnson and Hale, 2002). Northern attitudes about woods burning did not blend well with the Southern custom of firing the woods for hunting and grazing purposes. Between 1850 and 1870, steam technology for logging developed and proliferated as logging began in earnest in the southern Coastal Plain (Frost, 1993). By 1930, most of the large longleaf pine, except those protected on hunting plantations, had been cut (Croker, 1987). Annual burning of the cutover lands continued, but fires following logging were initially more intense as a result of heavier fuel loads from logging slash (Wade and Lundsford, 1989; Johnson and Hale, 2002). In many cases, the longleaf ecosystem did not regenerate following harvest. Not even longleaf pine can regenerate in a regime of annual fire because small seedlings ( 0.8 cm diameter at the root collar) are easily killed by fire (Boyer and Peterson, 1983) and feral hogs destroyed the occasional seedlings that had become successfully established. In addition, harvests were usually so extensive and complete that no seed source was available. Quail populations declined on the large fireprotected plantations as understory hardwoods gra- 154 D.H. Van Lear et al. / Forest Ecology and Management 211 (2005) dually developed. Fire was gradually reintroduced on these plantations, thanks largely to the efforts of Herbert L. Stoddard, whose 1931 classic book on bobwhite quail (Colinus virginianus) identified lack of fire as a primary cause of the regional decline of quail (Johnson and Hale, 2002). During the last half of the 20th century, quail-hunting plantations, with their large contiguous blocks of land and tradition dating from Stoddard of burning, remained one of the last strongholds where the historical nature of the longleaf ecosystem was preserved. 4. Fire exclusion policy and development of an uncharacteristic fire regime From the early decades of the 20th century, forest policy makers attempted to implement a new fire policy on the nation s forests a policy of fire exclusion. The U.S. Forest Service and state forestry agencies were leaders in this anti-fire campaign, which followed disastrous wildfires throughout the northern tier of the country, especially in 1910 (Pyne, 2001). The American Forestry Association sponsored teams of Dixie Crusaders who preached fire prevention throughout the South from 1927 to Eventually, the public accepted the fervently delivered anti-fire message and a nation-wide policy of fire exclusion was established (Pyne et al., 1996; Pyne, 2001). In the South, however, the use of fire to promote grazing, enhance hunting, and clear agricultural fields was deeply ingrained in the over-whelmingly rural population (Frost, 1993; Pyne et al., 1996; Johnson and Hale, 2002). As the young U.S. Forest Service (USFS) gained experience in the region, it grudgingly accepted the role of prescribed fire as a management tool. It had to, because early Chiefs of the Forest Service Pinchot and Graves recognized fire s role as researchers revealed its importance in this ecosystem (Wahlenberg, 1946; Croker, 1987; Wade et al., 2000). By the 1940s, the USFS was using prescribed fire to reduce hazardous fuels (Pyne et al., 1996). Today, in addition to hazard reduction, resource managers use prescribed fire to prepare sites for seeding and planting, improve wildlife habitat, manage competing vegetation, control disease, improve forage for grazing, enhance aesthetic appearance, and perpetuate Fig. 2. Area treated with prescribed fire and area burned by wildfire on the Carolina Sandhills Wildlife Refuge (from Pyne, 1997). fire-dependent and endangered species (Wade and Lundsford, 1989). However, prescribed burning is done on a relatively small portion of this once vast ecosystem. Only about 3.2 million ha are currently prescribe burned in the entire southern United States (Wade et al., 2000). Under the policy of fire exclusion, an uncharacteristic fire regime has replaced, in many places, the frequent, low- to moderate-intensity fire regime that sustained the longleaf ecosystem for millennia. Longer intervals between fires produced a much higher fire intensity, as witnessed by the 1998 Florida wildfire season (Outcalt and Wade, 2004). It is well established that wildfire acreage declines when prescribed burning is used to control fuel buildup (Fig. 2). Instead of the historically frequent, non-lethal understory burns that characterized the fire regime prior to 1900, the current fire regime has been one of mixed severity (Brown, 2000), where less frequent, but more severe, fires are representative. Hardwood understory species became too large
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