Changes in Ca, Fe, Mg, Mo, Na, and S content in a Mediterranean shrubland under warming and drought

In an evergreen Mediterranean shrubland we conducted a 6-year field experiment simulating the warming and drought projected by general circulation models and ecophysiological models for the next decades: 20% reduction of soil moisture and 1 degrees C of temperature increase. We tested whether warming and drought have effects on Ca, Fe, Mg, Mo, Na and S availability, concentrations and accumulation patterns in the three dominant plant species and in soil. Warming increased concentrations of Ca and Mo in leaves in Erica multiflora (42% and 65%, respectively) and in Dorycnium pentaphyllum (38% and 60%, respectively). Warming increased Mo accumulation in leaves and aboveground biomass in Globularia alypum (0.07 and 0.40 g ha(-1)) and in E. multiflora (0.12 and 0.4 g ha(-1)), and increased Fe accumulation in stem biomass of G. alypum (600 g ha(-1)), increasing the capacity to retain these nutrients in the ecosystem. The increase of Fe and Mo capture capacity under warming conditions was greater in G. alypum than in E. multiflora coinciding with its greater increases in photosynthetic capacity. Warming decreased soil total-Fe concentration by 24% and increased Mg accumulation in soil exchange complex by 19%. Drought increased Na leaf and stem concentrations (93% and 50%, respectively) and accumulation in leaf and aboveground biomass (780 and 800 g ha(-1), respectively) in G. alypum, allowing an increase of osmotic pressure which helps to prevent water losses and is related to its capacity to resist drought. Drought reduced S leaf and Mg leaf-litter concentrations of G. alypum and increased them in leaves of E. multiflora and also increased Mo and Na concentrations in leaves of D. pentaphyllum. Drought increased Fe soil solubility by 65%. The results indicate different effects of climate change on nutrient status in the ecosystem depending on whether the main change is warming or drought. The changes in concentration and biomass accumulation were different depending on the nutrient and the species, changing the stoichiometry among these nutrients and modifying the nutritional quality of plant tissues.