Comparative carbon dioxide efflux rates from respiration of coarse woody debris among three mangrove species in Thailand

Coarse woody debris (CWD) is an important component in forest ecosystems. A knowledge of CWD respiration, in addition to its storage, is necessary to clarify the carbon dynamics in a forest ecosystem. However, data on CWD respiration in mangrove forests is still scarce. We measured the carbon dioxide (CO2) efflux rates from the CWD respiration of three mangrove species (Avicennia alba, Rhizophora spp. and Xylocarpus granatum) using gas chromatography (GC) and sodalime (SL) methods. The results revealed that the CO2 efflux rates obtained by the SL method were not significantly different to those obtained by the GC method for all three species. Therefore, the CO2 efflux rate from CWD respiration of the three mangrove species was measured by the SL method without calibration. The CO2 efflux rate of A. alba CWD was significantly higher than the other two species, whereas the CO2 efflux rates of Rhizophora spp. and X. granatum were not different. The differences in the CO2 efflux among the species was likely to be due to their different wood densities and water contents, and the interaction of these terms. Although, the CO2 efflux rate from CWD respiration showed a relatively low value in a comparison to that from soil respiration, the CO2 efflux rates from CWD respiration should still be measured for clarifying the carbon dynamics in a mangrove ecosystem, especially those with a high CWD mass.