Preliminary Studies of the Long-Term CO2 Response of Mediterranean Vegetation Around Natural CO2 Vents

One of the major concerns about the effect of increasing carbon dioxide concentration in the atmosphere is for the long-term response of photosynthesis and biomass accumulation in natural vegetation. Knowledge about this response is critical while attempting to predict the effect of global change on primary production, on vegetation spatial distribution, and on potential sinks for carbon which may be provided by terrestrial ecosystems. Some recent experiments suggested that carbon sequestering, water use efficiency, and nutrient capture of terrestrial ecosystems will be enhanced by increasing atmospheric CO2 concentrations (Long and Drake, 1991), but some other studies showed that growth stimulation did not occur in some natural (Grulke et al., 1990) and artificial (Korner, 1992) ecosystems under elevated CO2. Whatever the case, it has been recently suggested that small spatial-scale community experiments which simulate a future greenhouse climate will be hardly capable of predicting ecosystem functioning and nutrient and water cycling under global change because the necessary range of natural disturbances and relevant information about the long-term response of the system are lacking (Woodward, 1992).