Prescribed burning and productivity in southern pine forests: a review

Fire is an ancient tool but still widely used in the management of southern pine forests. Fire is a relatively inexpensive tool and has a number of beneficial uses such as removing logging debris, reducing wildfire risk, increasing the abundance of certain understory species, and maintaining or restoring certain ecological conditions. However, recent studies demonstrate that fire can play a significant role in regulating the productivity of certain ecosystems. Burning releases large quantities of carbon and essential nutrients to the atmosphere as gases and particulates. The adverse impact of these releases on air quality is widely recognized, but the potential impact of nutrient losses and changes in soil productivity have received less attention from southern pine managers. The effect of fire on nitrogen (N) pools is especially significant since N availability is one of the most common limiting factors in forest productivity. The amount of N lost during the burning of forest fuels is directly related to fuel consumption and ranges from 3 to 6 kg N Mg^-1 of fuel consumed. The combined losses of N and other elements through harvesting and burning appear to exceed considerably the rate of replacement by natural processes, and may necessitate the regular application of fertilizer to maintain the nutrient capital of the site. Burning results in a short-term increase in soil available N and other nutrients immediately after burning, which stimulates the growth of understory vegetation; a desirable effect in some settings but also a source of competition for newly planted pine seedlings. A more thorough understanding of the biogeochemical effects of prescribed fire of varying frequencies and severities is needed to make optimum use of this tool in sustainable forest management.