Carbon isotope discrimination as a tracer of functional traits in a mediterranean macchia plant community

Werner C, Maguas C. Carbon isotope discrimination as a tracer of functional traits in a mediterranean macchia plant community. FUNCTIONAL PLANT BIOLOGY. 2010;37(5):467-477.Characterising functional plant groups with simple robust parameters of structural and functional traits is an important tool in ecological research. The reliability of carbon isotope discrimination (Delta C-13) as an indicator of functional types was assessed in a highly diverse mediterranean macchia comprising drought semi-deciduous malacophylls, evergreen sclerophylls and a gymnosperm. Pronounced differences in Delta C-13 of 4% occurred: semi-deciduous species (Cistus sp. L.) showed the highest and the gymnosperm (Juniperus sp. L.) the lowest Delta C-13 (20.3 +/- 0.5% and 16.2 +/- 0.18%, respectively). Across all studied species, Delta C-13 was correlated with (i) phenology (length of growing period) and (ii) leaf structure (leaf mass and N per area). The correlation of Delta C-13 with leaf water potentials, an indicator of drought stress, was species-specific and only 6 out of 11 species exhibited a significant relationship. Thus, leaf phenology governs seasonal responsiveness of Delta C-13 to drought, which constrains its applicability as an indicator of water use efficiency, particularly in evergreen species with short growing periods. Principal components analysis indicated the robustness of Delta C-13 for the classification of functional groups yielding similar results based on multiple leaf traits or solely on Delta C-13. Hence Delta C-13 provides an ecological tracer of different functional types, integrating structural, functional and phenological attributes