The evolution of pine plantation silviculture in the Southern United States

In the 1950s, vast acreages of cutover forest land and degraded agricultural land existed in the South. Less than 2 million acres of southern pine plantations existed at that time. By the end of the 20th century, there were 32 million acres of southern pine plantations in the Southern United States, and this region is now the woodbasket of the world. The success story that is southern pine forestry was facilitated by the application of research results generated through cooperative work of the U.S. Department of Agriculture Forest Service, southern forestry schools, State forestry agencies, and forest industry. This chapter reviews the contributions of applied silvicultural research in land classification, tree improvement, nursery management, site preparation, weed control, and fertilization to plantation forestry in the South. These practices significantly increased productivity of southern pine plantations. Plantations established in the 1950s and 1960s that produced < 90 cubic feet per acre per year have been replaced by plantations established in the 1990s that are producing > 400 cubic feet per acre per year. Southern pine plantations are currently among the most intensively managed forests in the world. Growth of plantations managed using modern, integrated, site-specific silvicultural regimes rivals that of plantations of fast-growing nonnative species in the Southern Hemisphere. Additional gains in productivity are likely as clonal forestry is implemented in the South. Advances in forest biotechnology will significantly increase growth and quality of future plantations. It appears likely that the South will remain one of the major wood-producing regions of the world. INTRODUCTION P ine (Pinus spp.) plantation silviculture in the Southern United States is one of the major success stories for forestry in the world. In 1952, there were only 1.8 million acres of pine plantations in the South (fig. 8.1), containing 658 million cubic feet of timber (U.S. Department of Agriculture, Forest Service 1988). At the turn of the 21st century, there are 32 million acres of pine plantations in the South that contain 23.9 billion cubic feet of timber (Wear and Greis 2002). Perhaps more remarkable is the significant increase in productivity that occurred during this period (fig. 8.2). Mean annual increment of pine plantations has more than doubled, and rotation lengths have been cut by > 50 percent. The success of pine plantation silviculture has turned the South into the woodbasket of the United States (Schultz 1997). These remarkable changes in the last 60 years were the result of a variety of factors that came together at the end of World War II. Economic factors, including a declining agricultural economy coupled with a rapidly expanding pulp and paper industry based on southern pine, combined to provide the impetus for the large increase in southern pine plantations. The success of this effort was due in large part to the cooperative research and technology transfer efforts of many organizations, including the U.S. Department of Agriculture Forest Service (Forest Service), State forestry agencies, forestry programs at southern universities, and forest industry. The objectives of this chapter are to describe the evolution of southern pine plantation silviculture over the last 50 years and to outline our view of the current state of the art of pine plantation silviculture in the South. Rather than present an exhaustive review of the literature, 1 Associate Professor of Forestry, Virginia Polytechnic Institute and State University, Department of Forestry, Blacksburg, VA 24061; Professor of Forestry, University of Florida, School of Forest Resources and Conservation, Gainesville, FL 32611; and C.A. Schenck Distinguished Professor of Forestry, North Carolina State University, Department of Forestry, Raleigh, NC 27695, respectively. So ut he rn F or es t Sc ie nc e: Pa st , P re se nt , a nd F ut ur e Pr od uc ti vi ty 64 0 5 10 15 20 25 30 35 1952 1962 197