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Integration of carbon dynamics from leaf to landscape in Florida pine forest.
Starr, Gregory 1, Martin, Timothy1, Binford, Michael2, Gholz, Henry1, 3, Genc, Levent*,2, 1 School of Forest Resources and Conservation, Gainesville, FL, USA2 Department of Geography, Gainesville, FL, USA3 National Science Foundation, Arlington, VA, USA
ABSTRACT- In recent years Florida AmeriFlux studies have shown that managed plantations of Pinus elliottii have the capacity to rapidly sequester carbon (maximum annual NEE approximately 800 g C m-2 year-1). However, from 1999 to 2001 a severe drought reduced rainfall in the north central Florida region by 60%. Maximum canopy leaf area index remained relatively stable over the drought with minor changes in temporal display occurring due to early leaf senescence. Midday stomatal limitations reduced leaf-level photosynthetic capacity of pines by 30%. At the ecosystem level, daytime net ecosystem exchange (NEE) of CO2 showed an approximately 30% reduction, with similar reductions in night ecosystem respiration rates as the drought persisted. Because of these compensating effects of decreased GEP and decreased ecosystem respiration, NEE on longer time scales in our P. elliottii flatwoods systems appears to be relatively stable in the face of extreme soil water deficits. A collaborative effort between the Florida AmeriFlux project and a UF NASA-funded project is currently attempting to estimate integrated NEE over time for a 15 km x 15 km landscape in north-central Florida. This effort combines eddy-covariance and mensurational measurements of NEE with land-use and stand-developmental classifications made from Landsat images. Preliminary results suggest that NEE of this forested landscape remains relatively stable over decadal time scales. At this same scale NDVI decreases over the severe drought, indicating a lack of relationship between NDVI and NEE. A more relative relationship appears to exist between GEP and NDVI at the landscape level within these coniferous forests. The study of these relationships between NDVI, NEE, and GEP are currently being expanded beyond the conifer forests of the regions and into riparian and agricultural areas with the intentions of developing a better understanding of the regions carbon dynamics.
Key words: NEE, NDVI, Carbon Cycling, GEP