PARENT SESSION
Poster Session #59: Fire Ecology II.
Thursday, August 8. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC

Productivity and biodiversity patterns: Controls in a southeastern coastal plain landscape.

Wilson, Carlos^*,1, Mitchell, Robert¹, Boring, Lindsay¹, Kirkman, Kay¹, ¹ J.W. Jones Ecological Research Center, Newton, GA

ABSTRACT- Recent studies conducted at Ichauway have demonstrated how fire, hydrology and N availability play important, albeit complex, roles in the determining the structure and function of longleaf pine (Pinus palustris) ecosystems. Experiments conducted in 1994 and 1995 revealed that, on average, greater than 90% of N in understory biomass pools was lost to volatilization during experimental burns, roughly translating into 27.3 and 36.9 kg N/ha lost for typical two and three year burning cycles, respectively. While fire may result in significant losses of N, frequent fire also encourages the development of abundant, diverse and ubiquitous populations of perennial legumes (> 43 native species identified) and preliminary work has demonstrated that some species of legumes fix between 70-90% of the N in their tissue. Although recent reports have suggested that gradients in southern pine forest productivity may be more nutrient-limited than water-limited, overstory and understory ANPP at Ichauway were found to be positively correlated with soil moisture yet negatively related to N mineralization, suggesting that water is the dominant resource in these systems. Understanding how ecosystem structure and function respond to hydrologic variation and periodic disturbance (i.e., fire) has been limited by the lack of manipulative experiments that investigate regulating mechanisms. The next phase of research at Ichauway will include a series of long-term (> 15 yrs.), inter-related experiments that use manipulative approaches in both natural hydrologic gradients across the landscape and in young planted stands of longleaf pine. Briefly, they are: 1) an experimental manipulation of resources (water and N) and fire; 2) an experiment examining how N manipulation and fire exclusion interact in regulating plant distribution and biodiversity; 3) a "common garden" experiment investigating the influence of N, P and fire on legumes and symbiotic N₂-fixation. The following discussion is an overview of this work-in-progress.

KEY WORDS: pinus palustris , fire