부산대학교 도서관

CO₂ exchange between the atmosphere and soil algal crusts of the Trachypogon savannas of the Orinoco Llanos has been analyzed using an open gas exchange system. These savannas encompass a wide range of physiognomic types, from herbaceous communities to savanna woodlands. A maximum CO₂ flux of 0.207 mg m⁻² s⁻¹ was measured in the crusts of the Guanipa savannas, while in the other examined crusts (0.035-0.105 mg m⁻² s⁻¹) the flux was similar to values reported for terrestrial algae. The CO₂ flux data were statistically fitted to the photosynthetically active radiation by a logarithmic relationship, and the photosynthetic efficiencies of the crusts were compared. The activation energy calculated for the CO₂ fixation indicates that limitations by diffusion and photochemical processes were excluded in the Guanipa crusts (above 12 kcal mole⁻¹), whereas they were evident in the other crust studied. An optimum CO₂ incorporation as a function of the crust water potential was established and carbon gain strategies were proposed on the basis of the results and characteristics of the habitats.