WATER SOURCES AND CARBON-ISOTOPE COMPOSITION (DELTA-C-13) OF SELECTED TREE SPECIES OF THE ITALIAN ALPS

Selected species of the Italian Alpine region (Picea abies (L.) karst., pinus sylvestris L., pinus cembra L., and Larix decidua L.) have been investigated in terms of water-source utilization and carbon fixation estimated by the analysis of hydrogen and carbon stable isotopes composition at two sites of differing altitude (1000 and 1500 m above sea level). Larix decidua is the species most dependent on groundwater in both sites, while pinus sylvestris utilizes rainwater to a greater extent. Concurrently,Pinus sylvestris displayed the highest value of the carbon isotopic ratio (delta(13)C=-25.9+/-0.6 parts per thousand), while Larix decidua had the most negative one (delta(13)C=-29.0+/-0.4 parts per thousand). A relationship was found between water-source utilization and carbon-isotope discrimination.