Original Articles

WETLANDS AS ACCRETING SYSTEMS: ORGANIC CARBON

DOI: 10.1080/03779688.1983.9632861
Author(s): K.H. RogersCentre for Resource Ecology, Department of Botany, South Africa

Abstract

Accretion of organic carbon in a wetland occurs when inputs of allochthonous organic matter and primary production exceed losses by heterotrophic respiration and export via the outflow. Although both dissolved and particulate organic matter (DOM, POM) are produced, most accretion is of POM and occurs in the sediments. In general, rates of accretion are highest in permanently flooded swamps and marshes where emergent plant production dominates and decomposition is reduced by a combination of low pH, low redox potential and a reduced detritivore component. Wetlands which experience frequent wetting and drying such as floodplains and tidal basins show least accretion as losses via the grazing food chain and exports are large, and decomposition is rapid under the more oxidised conditions. Methods for measuring the fluxes of organic carbon between different pools in a wetland are poorly developed and present day accretion rates have only been estimated in a few instances. Improved methods are particularly required for estimating underground primary production, microbial conversion of DOM to POM, grazing of periphyton and decomposition. The probable effects of management practices (manipulation of hydrological regime, fire, grazing, harvesting and the use of wetlands for wastewater treatment) on organic matter accretion are discussed.

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