PARENT SESSION
Poster Session #42: Carbon Storage.
Thursday, August 9, 2001. Presentation from 3:30 PM to 5:00 PM. Exhibition Hall

Net exchange of carbon dioxide, water, and energy for a mature uneven-aged pine flatwoods forest.

Powell, Thomas¹, Starr, Gregory¹, Martin, Timothy¹, Clark, Kenneth¹, Gholz, Henry¹, ¹

ABSTRACT- Pine flatwoods comprise 50% of terrestrial ecosystems in Florida. Uneven-aged management is increasingly being looked at as an alternative silvicultural model on non-industrial flatwoods forests. However, it is uncertain how this management strategy would affect regional carbon, water and energy budgets. From July 2000 to June 2001, we used eddy covariance to estimate carbon, water and energy exchanges for an open canopy, 40-to-70-yr-old, naturally regenerated, slash (Pinus elliottii) and longleaf pine (Pinus palustris) flatwoods in north central Florida. Maximum daytime CO₂ exchange rates were -10 mol CO₂m^-2s^-1 at 1300 mol PPFDm^-2s^-1 and were not affected by seasonal differences in LAI (all-sided 2.6 in the summer to 2.0 in the winter). Nighttime exchanges averaged 3 mol CO₂m^-2s^-1 during both the summer and winter. Latent energy fluxes were linearly related to net radiation, with summer maximum rates of 330 Wm^-2 and winter maximum rates of 170 Wm^-2. The average Bowen ratio, 1.1, remained stable between the summer and winter seasons. The lack of seasonal differences seen across the study is likely attributable to a prolonged drought affecting the region. The energy budget (latent + sensible + soil energy fluxes vs. net radiation) balanced to within 19%. The net annual carbon balance of this system indicates that it is a net carbon sink, suggesting that flatwoods forests managed under uneven-aged silviculture could play an important role in long-term regional carbon sequestration.

KEY WORDS: carbon exchange, latent energy , slash pine, eddy covariance