Document: KEN-3-59-51

Partitioning carbon fluxes during ecosystem develoment following a disturbance.

CLARK, K.L.* ¹, H.L.GHOLZ ¹ and M.CASTRO ²

University of Florida, Gainesville, FL 32611, USA ¹
University of Maryland ²

Abstract:
Respiration is the largest carbon flux from terrestrial ecosystems after gross primary production (GPP), with the difference between them termed net ecosystem production (NEP). We obtained estimates of NEP and ecosystem respiration using eddy covariance for a chronosequence of Pinus elliottii plantations in north-central Florida: A recent clearcut, a mid-rotation (10-yr-old) stand, and a mature (24-yr-old) stand. We also measured soil respiration in static chambers at all three sites. NEP and ecosystem respiration was estimated at -393 and 1040 g C m^-2 yr^-1 during the first year following clearcutting (1998). After three years, NEP was again positive. NEP and ecosystem respiration reached 645 and 1659 g C m^-2 yr^-1 at the mid-rotation stand, and 670 and 2108 g C m^-2 yr^-1 at the mature stand. The proportion of ecosystem respiration attributable to belowground processes decreased over time, from more than 95 % at the clearcut to less than 60% at the mature stand. GPP was estimated at 647, 2304, and 2778 g C m^-2 yr^-1 at the clearcut, mid-rotation, and mature stands, respectively, and was related to the increases in leaf area and respiring biomass. The carbon dynamics of these intensively managed plantations contrast highly to those of natural ecosystems in this landscape.

Keywords: Carbon cycle, Ecosystem respiration, Florida

This abstract is being presented at: 11:00 AM in session:
Oral Session #25: Organic Matter Dynamics in Ecosystems.