Abstract ID: 242

Carbon balance and dynamics in an Amazonian forest: a synthesis of top down and bottom up studies in LBA

The fate and dynamics of the large stores of organic carbon in Amazonian forests has global significance. We analyze 6 years of combined eddy-flux and field-based ecological measurements of carbon flux in the Tapajós National Forest (TNF), Pará, Brazil. Eddy-flux measurements showed initial net carbon loss of ~ 1 MgC•ha-1•yr -1 from 2000 to 2002 followed by a shift toward neutral carbon balance from 2002 to 2006, with mean net loss of - 0.89 ± 0.22 MgC•ha-1•yr -1, and a range of - 0.22 ± 0.45 (C uptake) to + 2.68 ± 0.49 (C loss) MgC•ha-1•yr -1. Eddy flux data showed greater carbon uptake in the dry season, with uptake rates largely controlled by phenology and light. There was virtually no indication of seasonal water limitation during the 5-month dry season. The shift from net carbon release towards near neutral carbon balance implies recovery from prior disturbance. This trend was supported by ground-based biometric measurements, which showed rapid accrual of carbon in live biomass (3.23 ± 0.11 MgC•ha-1•yr -1), combined with an excessive pool of necromass (40.1 ± 3.9 MgC•ha-1). The estimated respiration from the large pool of necromass more than offset carbon uptake in live biomass, resulting in estimated net carbon losses of ~ -1.5 MgC•ha-1•yr -1 from 1999 to 2001, and - 0.81 ± 0.47 MgC•ha-1 from 2001 to 2005. Reconstruction of current forest demography and dynamics indicated that ongoing shifts of biomass among tree size classes and reduction of necromass would likely continue. We infer that net loss of carbon from the TNF likely persists 10-15 years after a disturbance (controlled by the rate of decay of coarse woody debris), followed by uptake of carbon as the forest size class structure and composition continue to shift. Overall, our LBA studies indicate a dynamic and resilient forest recovering from a probable disturbance.

Session:  Carbon - What has been learned and what further can be learned from a network of eddy covariance towers in Amazonia?.

Presentation Type:  Oral