biologia plantarum

Biologia plantarum 46:411-418, 2003 | DOI: 10.1023/A:1024342606329

Nitrogen and Carbon Concentrations, and Stable Isotope Ratios in Mediterranean Shrubs Growing in the Proximity of a CO₂ spring

R. Tognetti¹, J. Peñuelas²

¹ Dipartimento di Scienze Animali, Vegetali e dell'Ambiente (SAVA), Universitá degli Studi del Molise, Campobasso, Italy

² Unitat Ecofisiologia CSIC - Centre de Recerca Ecològica i Aplicacions Forestals (CREAF), Facultat de Ciències, Universitat Autònoma, Bellaterra (Barcelona), Spain

Seasonal changes in foliage nitrogen (N) and carbon (C) concentrations and δ¹⁵N and δ¹³C ratios were monitored during a year in Erica arborea, Myrtus communis and Juniperus communis co-occurring at a natural CO₂ spring (elevated [CO₂], about 700 μmol mol^-1) and at a nearby control site (ambient [CO₂], 360 μmol mol^-1) in a Mediterranean environment. Leaf N concentration was lower in elevated [CO₂] than in ambient [CO₂] for M. communis, higher for J. communis, and dependent on the season for E. arborea. Leaf C concentration was negatively affected by atmospheric CO₂ enrichment, regardless of the species. C/N ratio varied concomitantly to N. Leaves in elevated [CO₂] showed lower δ¹³C, and therefore likely lower water use efficiencies than leaves at the control site, regardless of the species, suggesting substantial photosynthetic acclimation under long-term CO₂-enriched atmosphere. Leaves of E. arborea showed lower values of δ¹⁵N under elevated [CO₂], but this was not the case of M. communis and J. communis foliage. The use of the resources and leaf chemical composition are affected by elevated [CO₂], but such an effect varies during the year, and is species-dependent. The seasonal dependency and species specificity suggest that plants are able to exploit different available water and N resources within Mediterranean sites.

Keywords: elevated CO₂; Erica arborea; global change; Juniperus communis; Mediterranean ecosystems; Myrtus communis; water stress

Subjects: C/N ratio; carbon, stable isotopes (δ¹³C, ¹⁴CO₂ fixation); CO₂ spring, elevated CO₂ concentration, growth; Erica arborea; global change of climate; growth analysis, biomass production; growth near to CO₂ spring, Mediterranean shrubs; Juniperus communis; Mediterranean ecosystems, natural CO₂ spring; Myrtus communis; δ¹⁵N/δ¹³C ratio; nitrogen, stable isotope ratios; seasonal variations, δ¹⁵N and δ¹³C; stable isotope ratios, δ¹⁵N and δ¹³C; water stress, growth near to CO₂ spring

Prepublished online: April 1, 2003; Published: November 1, 2003  Show citation