CO2 Exchange in soil algal crusts occurring in the trachypogon savannas of the Orinoco Llanos,Venezuela |
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Authors: | J J San José C R Bravo |
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Institution: | (1) Centro de Ecología y Ciencias Ambientales, Instituto Venezolano de Investigaciones Científicas, (San Martin), Apdo. 21827 Caracas, Venezuela |
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Abstract: | 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. |
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Keywords: | CO2 exchange soil algal crust Trachypogon savannas water potential |
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