MODELLING THE EFFECTS OF GLOBAL TEMPERATURE INCREASE ON THE GROWTH OF SALT MARSH PLANTS

Gradual increases in temperature and atmospheric CO2 concentrations have resulted from the increased human use of fossil fuels since the beginning of industrial activity. In coastal wetland ecosystems, salt marshes constitute important habitats because they play important ecological roles, acting as carbon sinks by capturing atmospheric CO2 and storing it in living plant tissue. Ecological models are important tools for understanding the results of anthropogenic impacts on a global scale. Global warming poses threats to salt marshes through different effects, e.g., increases in sea level. The objectives of this study were i) to assess how temperature increases will influence the growth of salt marsh plants, ii) to infer the carbon budget of salt marshes under temperature increase scenarios and iii) to predict how salt marsh plants will keep pace with increases in sea level. These goals were achieved by developing growth models of three different plants (Spartina maritima, Scirpus maritimus and Zostera noltei) found in the Mondego estuary. Models were developed for C-3 and C-4 plant species. The results suggest that a temperature increase enhances the aboveground biomass of salt marsh plants. According to the predictions of the models, the sedimentation rate of S. maritima and Z. noltei can keep pace with increases in sea level, but this is apparently not the case for S. maritimus. If S. maritimus disappears from the Mondego estuary, the carbon sequestration ability of the system should decrease due to the loss of active plant tissue. This conclusion is based on the fact that S. maritimus accumulated more than 80% of the total carbon sequestered in the tissues by the three studied species.