PARENT SESSION
Organized Oral Session 4: Tropical cyclone disturbance and forest dynamics at multiple temporal scales: results from long-term studies in the new and old worlds
Organizer(s): T Lin, H King, and SP Hamburg
Monday, August 8, 8:00 AM - 11:30 AM, Meeting Room 511 B, Level 5, Palais des congrès de Montréal

The impact of hurricanes Charley, Frances, and Jeanne on net ecosystem carbon exchange of a scrub oak ecosystem in central Florida.

Powell, Thomas^*,1, Bracho, Rosvel², Hinkle, Charles³, Drake, Bert¹, ¹ Smithsonian Environmental Research Center, Edgewater, MD² National Research Council, Kennedy Space Center, FL³ Dynamac Corporation, Kennedy Space Center, FL

ABSTRACT- From 1900 to 1996, an average of 1.6 hurricanes per year struck the United States from Texas to Maine. Destructive tropical force winds (> 16 m s^-1) from these storms often extend over 300 km wide and continue for hundreds of kilometers inland, potentially affecting a wide range of ecosystems. Central Florida was hit particularly hard during the 2004 hurricane season by three different hurricanes: Charley made landfall on the west coast as a category 4 on August 13, Frances on the east coast as a category 2 on September 5, and Jeanne as a category 3 on September 25. We measured the impact of these three hurricanes and tracked recovery on leaf area, litter fall, and net ecosystem gas exchange (NEE) in the scrub oak ecosystem at our research site at the Kennedy Space Center on the east coast of central Florida. The tropical and hurricane force winds heavily defoliated the evergreen, broad-leaf, scrub oak species, reducing leaf area index by 23% and prematurely returning LAI to annual minimum levels. Defoliation caused ecosystem saturated CO₂ assimilation (A_sat), a measure of the photosynthetic capacity of the ecosystem, to decrease by 30% and soil respiration to decrease immediately after Hurricane Frances. Gross primary productivity (GPP) was reduced by 20% and ecosystem respiration (R_e) was reduced by 24% in the three months after the hurricanes (Sept. - Nov.) compared to respective averages during this period in the 3 years prior to the hurricanes, but returned to normal values by December. The reduction of both GPP and R_e had a compensatory effect on NEE, causing it to remain within the range of -27 to -88 g C m^-2 (negative means carbon uptake) measured between September - December in the 3 years prior to the hurricanes. Understanding how these component ecosystem fluxes are altered after a hurricane and their course of recovery will greatly aid in modeling C accumulation across the affected landscapes.

Key words: hurricane, disturbance, net ecosystem exchange, gross primary productivity