14 - Carbon Metabolism and Plant Growth under Elevated CO2 in a Natural Quercus ilex L. “Macchia” Stand

Publisher Summary This chapter examines the impact of long-term exposure to elevated CO2 concentration in a natural Mediterranean community dominated by Quercus ilex (high "macchia"). The research emphasizes on measurements of carbon metabolism and light energy utilization by the leaves to assess the physiological responses that subtend growth rather than just measuring short-term biomass increments at the tree level alone. Given the relevance of the Mediterranean woodland communities from an economical and environmental perspective, it is critical to be able to predict the possible effects of global change on these ecosystems and to eventually adopt adequate mitigation strategies. The interaction between carbon metabolism and biomass partitioning in woody plants is also regulated by nutrient availability. In the nutrient-limited Mediterranean environment, a CO2 increase may in part relieve this limitation by a greater efficiency of nutrient utilization, especially in tree species, characterized by a large proportion of their biomass allocated to components with low nutrient cost. These limitations are likely to moderate the responses of plants and communities to a global change, particularly to increases in atmospheric CO2 and biosphere warming. After a three-year period, the community responses to elevated CO2 indicate a wide range of acclimation processes by tree and shrub species in relation to their different ecological strategies.