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Chapter 25: Background Paper: Fire in Southern Forest Landscapes 607 Chapter 25: Background Paper: Fire in Southern Forest Landscapes John A. Stanturf, Dale D. Wade, Thomas A. Waldrop, Deborah K. Kennard, and Gary L. Achtemeier Southern Research Station, USDA Forest Service and temporal variability of fire and These fires tend to have low intensity Fire as a its effects, descriptions of fire regimes because fuels are less flammable than Landscape Process are broad (Whelan 1995). The fire in ecosystems with a substantial regimes used in this chapter follow conifer component. The low-intensity the descriptions used in Brown and presettlement fires that wounded or Other than land clearing for urban Smith (2000). They include the killed many trees did not cause enough development (Wear and others 1998), understory, mixed, and stand mortality (greater than 80 percent) no disturbance is more common replacement fire regimes. to be considered stand replacement in southern forests than fire. The regimes (Wade and others 2000). pervasive role of fire predates human Fires in the understory fire regime activity in the South (Komarek 1964, generally do not kill the dominant In the stand replacement fire regime, 1974), and humans magnified that vegetation or substantially change its fires kill aboveground parts of the role. Repeating patterns of fire structure. Approximately 80 percent dominant vegetation, changing the behavior lead to recognizable fire or more of the aboveground dominant aboveground structure substantially. regimes, with temporal and spatial vegetation survives fire (Brown 2000). Approximately 80 percent or more of dimensions. Understanding these The understory fire regime occurs the aboveground dominant vegetation fire regimes is essential to examining primarily in southern pine and oak- is either consumed or dies as a result of the importance of fire in southern hickory forests, which support pine and fires (Brown 2000). Several vegetation landscapes and integrating fire into pine-oak associations such as Kuchler’s types in the Eastern United States are forest management. This chapter southern mixed forest, oak-hickory- represented by stand replacement fire has six sections: pine, and oak-hickory associations. regimes, including oak-gum-cypress (bay forests), sand pine, Atlantic white- 1. Fire regimes and fire types The severity of fire in the mixed fire regime either causes selective mortality cedar, and spruce-fir. Table Mountain 2. Fire history in the South in dominant vegetation, depending pine usually is regarded as having 3. Fire regimes of southern forests on tree species’ susceptibility to fire, a stand replacement fire regime, but a mixed regime may be more accurate 4. Prescribed fire or varies between understory and stand replacement (Brown 2000). The mixed as it produces the seedbed conditions 5. Smoke management fire regime best represents the needed for survival of seedlings. 6. Restoring fire into southern resettlement fire history for several ecosystems hardwood- and conifer-dominated Fire Types ecosystems. The conifers include pitch Three kinds of fires burn in forests Fire Regimes pine and Virginia pine of Kuchler’s when weather and fuel conditions oak-pine association (Kuchler 1964) permit ignition and sustained and Fire Types and pond pine, a dominant tree of the combustion: surface fire, ground fire, pocosin association. The conifer types and crown fire. Surface fires burn the fit the mixed fire regime because fire upper litter layer and small branches Fire Regimes intensities are generally greater than that lie on or near the ground. Surface Fire regime refers to the long-term in the understory fire regime and fires usually move quickly through an nature of fire in an ecosystem (Brown cause mortality ranging from 20 to area, and do not consume the entire 2000), including both frequency and 80 percent of the overstory. The hard- organic layer. Moisture in the organic severity of effects. The interval between wood ecosystems include mesophytic horizons often prevents ignition of the fires in southern forests may be as short hardwood, northern hardwood, and humus layer, and protects the soil and as a year or as long as centuries. The elm-ash-cottonwood forest types. soil-inhabiting organisms from heat. intensity of fire and severity of effects Although the hardwoods are prone The heat pulse generated at the burning FIRE can vary in scale from benign to to fire injury, many survive numerous front of these fast-moving fires does not catastrophic. Because of the spatial fires before eventually being girdled. normally persist long enough to 608 Southern Forest Resource Assessment damage tissue beneath the thick bark in America about 14,000 BP (before of large trees. However, it will girdle present). Hunting and gathering the root collar of small trees and Fire History of characterized their progressively more shrubs, and reduce small-diameter the South sophisticated cultures until the advent branches and other fine surface fuels. of settled societies after 3,000 BP in Ground fires smolder or creep slowly the eastern woodlands (Fagan 2000). To appreciate the pervasive role of Beginning about 6,000 BP (Middle through the litter and humus layers, fire in shaping southern forests requires consuming all or most of the organic Holocene), warmer climates and final an understanding of the dynamic wastage of the Laurentide Ice Sheet cover, and exposing mineral soil or response of southern ecosystems to underlying rock. These fires usually (Delcourt and Delcourt 1981, 1983) climate change since the retreat of translated into increased food resources occur during periods of protracted the Laurentide Ice Sheet, which began drought when the entire soil organic and rapid population growth. By around 18,000 years ago, and the 5,000 BP, sea level had stabilized, layer may dry sufficiently. They extent of human influence, which likely may burn for weeks or months until and vegetation patterns were essentially began about 14,000 years ago. Humans as we find them today. precipitation extinguishes them exert an influence by igniting or After this rapid population growth, or fuel is exhausted. suppressing fires. Native Americans more or less permanent settlements Crown fires occur when stand used fire extensively for thousands appeared, primarily in river valleys and structure, weather, and ladder fuels of years. The early European settlers rich bottomland soils from the Coastal (heavy accumulations of understory continued and to a degree expanded Plain to the mountains (Fagan 2000). material such as slash piles, shrubs, the use of fire. In the last century, After 3,000 BP, population pressures led and lower branches of standing trees, however, human influence over fire to cultivation of native plants typical of often draped with fallen needles) allow in the South changed markedly. disturbed habitats. After 1,000 BP, corn surface or ground fires to ignite tree We have divided the long history crowns and spread to other crowns. cultivation was widespread (Hudson of fire since humans arrived in the 1982) and bean cultivation by 800 Crown fires occur in forests during South into five periods: periods of drought and low relative BP (Smith 1994), but hunting and ■ humidity, particularly in areas with a From the earliest appearance of gathering were still prominent activities. dense, volatile understory. Crown fires humans in North America around Population density was probably greater generate tremendous heat that rises in 14,000 years ago (Fagan 2000) until in the southern than in the northern a strong convection column, drawing European contact 500 years ago, part of the eastern woodlands and in surface winds that fan the flames the first period was one of increasing greater on the coast than inland, even more. Heated air blowing across human population level and more but higher densities extended inland the flames warms and dries the fuel extensive use of fire. along major rivers (Driver 1961). ahead of the fire, and releases volatile ■ For the first 400 years after their Judging the extent to which forests gases from vegetation in the path of the arrival, the early European settlers and other vegetation were influenced flaming front. Crown fires kill all trees continued to use fire in much the by Native American use of fire requires and shrubs in their path and consume same way as Native Americans, often knowledge of the typical pattern of land most of the surface organic layers. reoccupying and farming land cleared use and the population levels before The shorter the interval between fires, by Native Americans and expanding European contact (Kemmerer and the more likely that fires kill only small burning of woodlands to provide Lake 2001). Williams (1992, p. 40, fig. trees or particularly susceptible species, forage for livestock (Williams 1992). 2.8) presented a concept of a typical such as thin-barked hardwoods, ■ At the end of the 19th century southern woodland village. Located on resulting in an understory fire regime. and extending into the 20th century, the a stream or river, the clearing for the This regime usually perpetuates fire- remaining southern forests were village and surrounding fields of mostly adapted species (Mutch 1970). As fire extensively logged to support economic corn, beans, and squash extended for frequency decreases, fuel accumulates, expansion; wildfires were common 4 miles. Girdling larger trees and increasing the probability of a fire in the slash left behind. burning the undergrowth cleared this area originally, and burning kept it intense enough to kill nearly all trees. ■ In reaction to these widespread Fires in forests regenerated by a stand open, in much the way that swidden and destructive wildfires, the fourth agriculture occurs in the tropics today. replacement fire regime come at period of fire suppression started in frequencies of 25 to 100 years and The field zone was buffered by a further the early 1900s. 1.25-mile-wide zone that was burned probably maintain high levels of ■ diversity in the landscape (Waring The current period is one of fire annually for defense (visibility), where and Schlesinger 1985).

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