Effects of annual fertilization and competition control treatments on loblolly pine growth through age 25.This article is part of a larger document. View the larger document here.
Loblolly pine (Pinus taeda L.) plantations represent the largest surface of managed forest in the Southern United States. Over the last 3 decades, forest productivity has been increased as a result of intensive management and improved genetics. Many studies have shown the effects of fertilization and competition control in early ages (1 through 10) on yield of intensively managed loblolly pine stands. However, few studies have looked at the long-term effects of these practices on the inherent site productivity and carrying capacity. The Consortium for Accelerated Pine Plantation Studies (CAPPS), through the Plantation Management Research Cooperative (PMRC), tested if carrying capacity could be increased over the life of the stands in an experimental design with treatments of complete competition control, annual fertilization, and interaction between them. Nine study sites were distributed throughout the Piedmont, Upper Coastal Plain, and Lower Coastal Plain in Georgia, with four replications at each site and tree-level measurements collected each growing season. Results showed higher growth rates on sites receiving annual fertilization and herbicide treatments relative to the control for the first 10 to 15 years. Subsequently, growth rates for this combination treatment diminished at a greater rate than the untreated plot and competition control only. As a result, mortality rates remained fairly constant for all treatments until age 10, after which fertilized treatments showed greater annual mortality. Volume growth rates remained high for treatments without fertilization, showing no evident decline, indicating an increase in site inherent productivity.