In the present study, the high-resolution stable carbon ( 13 C/ 12 C) and oxygen ( 18 O/ 16 O) isotope ratio profiles in the wood of the mangrove Rhizophora mucronata Lam., a tropical tree species lacking distinct growth rings, were investigated. Variations of both isotope ratios revealed a remarkable annual cyclicity with lowest values occurring at the latewood/earlywood boundary (April-May) and highest values during the transition from earlywood to latewood (October-November). Based on the current knowledge of the physiology of this mangrove species, as well as on the current literature available on high-resolution profiles of stable isotope ratios in tree rings, possible driving forces responsible for this seasonal pattern are discussed. The annual cyclicity, together with a conspicuous isotope pattern appearing in the El-Niño year 1997, promises great potential for tropical dendrochronology.

Own experiments and literature data point at a strong correlation between mineralization processes in soils i.e. the corresponding CO2 release and temperature variations. This seems to be important with regard to the global CO2 problem, since it implies that due to the global temperature increase over 80 years large additional amounts of CO2 were released to the atmosphere. These additional quantities seem to have been at least as important as the anthropogenic release of CO2 from the burning of fossil fuels.

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