Fertilization Increases Below-ground Carbon Sequestration of Loblolly Pine Plantations

The extent of fertilization of southern pine forests is increasing rapidly; industrial fertilization increased from 16,200 ha per year in 1988, to 344,250 ha in 1998. Fertilization increases stand productivity and can increase carbon (C) sequestration by: 1) increasing above-ground standing C; 2) increasing C stored in forest products; and 3) increasing below-ground C pools. This talk will concentrate on the latter and will present summary data from five experiments spatially ranging from the Virginia Piedmont to the Alabama Coastal Plain, and ranging in age from one to 17 years. Fertilization has increased pine growth in all of these studies. In two other studies, fertilization has significantly decreased C losses from the soil as measured via an automated CO2 efflux system using an infrared gas analyzer. In two more of these studies, soil CO2 efflux did not differ significantly between control and fertilized plots (means under fertilization were lower though), although below-ground biomass was increased. And in the last study, fertilization increased soil CO2 efflux by approximately 18%; however, fertilization increased below-ground biomass by more than 250%. Combined, these studies indicate forest fertilization increases below-ground C sequestration. As forest industry is firmly established in the Southeastern United States, and since soil nutrition is a major limiting factor to tree growth, increasing forest fertilization represents a realistic method to sequester atmospheric C in the shortto long-term.