Population growth and the decline of natural Southern yellow pine forests

Population growth has created social and economic pressures that affect the sustainability of naturally regenerated southern yellow pine forests. Major causes of this decline include (1) a shift in public attitudes regarding woods burning (from one favoring it to one that favors fire suppression) and (2) an increase in land values (especially near urban centers). The increase in land values reduces the chance of farmland abandonment, which was common in the first half of the 20th century. Abandoned farmlands provided many of the sites for the naturally regenerated pine stands that are being harvested today. Also, higher land values and higher taxes put pressure on landowners to subdivide their land for development or to establish more profitable tree plantations. These population-related factors and outbreaks of the southern pine bark beetle have resulted in a decline in naturally regenerated southern pines of more than 38 million acres since 1953. As population pressures reduce the incidence of wildfire, prescribed burning, and the abandonment of old fields, the decline in naturally regenerated southern yellow pine will continue. By 2030, only 23 million acres of natural southern yellow pine may remain. INTRODUCTION Population growth is the principal factor placing pressure on forest lands (Barlow and others 1998; Wear and others 1998, 1999). In some cases, the effect is immediate as when naturally regenerated forests are converted to developments, pastureland, rangeland, cropland, plantations, or other uses. In the United States, 11.7 million acres of forests were converted to developed land during the period from 1982 to 1997 (fig. 29.1). Population growth also influences forests in subtle ways that take place over decades. The public generally overlooks gradual changes in species composition, even when millions of acres are affected. Naturally established southern yellow pines2 are disappearing over Eastern North America. This trend is exacerbated by southern pine bark beetle (Dendroctonus frontalis Zimmermann) epidemics. With the exception of spruce pine (Pinus glabra Walt.), southern yellow pines are intolerant of shade, and exposed mineral soil is generally required for their successful establishment. Pines were often the primary tree cover over much of the Southeast when the first historians recorded plant names. However, during the second half of the 20th century, the combined effects of fire 1 Professor, Auburn University, School of Forestry and Wildlife Sciences, Auburn, AL 36849; and Professor Emeritus, The University of Tennessee, Department of Forestry, Wildlife and Fisheries, Knoxville, TN 37996, respectively. 2 For the purpose of this chapter, the southern yellow pines are defined as eight members of the genus Pinus (subsection Australes Loud.) plus sand pine and Virginia pine. “Natural” stands of pine are those that are regenerated by seedfall and not by direct seeding or planting. Figure 29.1—The conversion of forested land to other land uses in the United States from 1982 to 1997 (U.S. Department of Agriculture, Forest Service 2001). So ut he rn F or es t Sc ie nc e: Pa st , P re se nt , a nd F ut ur e Bi od iv er si ty 348 196