Land use effects on groundlayer composition and regeneration of mixed pine hardwood forests in the Fall Line Sandhills, S.E. USA

Abstract

We surveyed groundlayer vegetation from 2000 to 2004 and longleaf pine regeneration before and after a change in the prescribed fire interval in 32 mixed pine hardwood stands at Fort Benning, Georgia, to determine if combinations of fire and military training maintain or shift groundlayer composition of stands on sandy or clayey soil. The stands have been managed using prescribed fire at ca. 3 year intervals since 1980. They were equally divided between: lighter (infantry only) or heavier (mechanized) military training; sandy or clayey soil; and a 2-year (2002, 2004) or 4-year (2004) (except for two stands, which burned after 3 years) fire interval. One site (clayey soil, light military use, and 2-year fire interval) was logged in 2001 and was excluded from the analysis. NMDS ordination was used to visualize variation in groundlayer communities among sites and trends in groundlayer composition over time. The first axis separated sites with sandy and clayey soil. A second ‘degree of disturbance’ dimension separated sites with heavier military use and 2-year fire interval from those with lighter military use and 4-year fire interval. Differences between soil texture and military use were significant in all years, but differences between fire treatments developed after the 2nd year. Mortality of tagged woody seedlings was greater after fire in burned compared to unburned sites and in clayey compared to sandy sites. The results suggest prescribed fire can maintain desirable ground layer composition, especially in sites with heavier military use, but frequent fire may not allow adequate establishment of longleaf pine.