Leaf mineral concentrations of Erica arborea, Juniperus communis and Myrtus communis growing in the proximity of a natural CO2 spring

Leaf mineral concentrations of co-occurring Erica arborea, Juniperus commun is and Myrtus communis were measured at bimonthly intervals throughout a ye ar in a natural CO2 spring and in a nearby control site with similar soil c hemistry in a Mediterranean environment. There were different responses to the elevated [CO2] (C. 700 muL L-1) of the spring site plants depending on the element and the species. In the CO2 spring site K, Ca, Mg, Mn, Al, Fe, and Ti leaf concentrations and the ratio C/N showed significant greater val ues in at least one or two of the three species. Leaf S concentration were greater in all three species. Leaf concentrations of N, Sr, Co, and B were lower in at least one or two species, and those of C and Ba were lower in a ll the three studied species near the CO2 spring. P, Na, Zn, Si, Cu, Ni, Cr , Pb, Mo, V and Cd leaf concentrations and the specific leaf area (SLA, mea sured in Myrtus communis) did not show any consistent or significant patter n in response to the elevated [CO2] of the spring site. There was a slight trend towards maximum concentrations of most of these elements during autum n-winter and minimum Values during the spring season, especially in Myrtus communis. Multivariate principal component analyses based on the leaf eleme ntal concentrations clearly differentiated the two sites and the three spec ies. Lower concentrations at the spring site were not the result of a dilut ion effect by increased structural or nonstructural carbon. In contrast to most experimental studies of CO2 enrichment, mainly conducted for short per iods, several of these elements had greater concentrations in the CO2 sprin g site. Nutrient acclimation and possible causes including decreased nutrie nt export, increased nutrient uptake capacity, photosynthetic down-regulati on, Mediterranean water stress, and higher H2S concentration in the spring site are discussed.