| Carbon (C) storage and fluxes were investigated for the Missouri Ozark Forest Ecosystem Project (MOFEP) in southeastern Missouri, USA, to determine the effects of timber harvesting regimes (non-harvest management: NHM, uneven-age management: UAM, and even-age management: EAM) on carbon storage and related ecological processes. The central hypothesis was that harvesting regimes would alter major forest ecosystem processes and thus affect the magnitude of C sequestration within the system. I used biometric and empirical modeling approaches, quantified the C pool sizes, examined the contribution of microclimate variables to the variation of the C pool sizes. I further examined the rates of mixed leaf litter mass loss under different harvesting regimes. Finally, I measured ecosystem component respiratory C losses and examined their responses to the harvesting regimes. Total C pools were 182, 170, and 130 Mg C ha -1 for the NHM, UAM, and EAM stands, respectively. Harvest significantly reduced C pools in live tree biomass and increased the pool sizes of coarse woody debris. I found significant correlations between C pools and soil nitrogen, soil temperature, and canopy cover. Harvest also significantly increased mixed oak and oak-hickory leaf litter decomposition. The oak-hickory litter mixtures decay faster than that of either oak or oak-pine litter mixtures. The decay constant over the 32-month of field incubation ranged between 0.39 and 0.51 y-1 at my study sites, and it had linear relationships with initial litter nitrogen concentration, cellulose-to-nitrogen ratio, and lignin-to-nitrogen ratio. The nitrogen concentration in remaining litter had an exponential relationship to cumulative mass loss. Lastly, timber harvesting reduced by 27.7% annual ecosystem respiration in the EAM stands compared to that in the NHM stands. The annual ecosystem respiratory carbon losses were 1642, 1691, and 1285 g C m-2 y-1 in the NHM, UAM, and EAM stands, respectively. The harvesting activities affected ecosystem processes by removing biomass, and changed the magnitude of component respiration. |
