The effect of elevated CO2 and temperature on nutrient uptake by plants grown in basaltic soil

Mineral weathering is an important process in soil formation. The interactions between the hydrologic, geologic and atmospheric cycles often determine the rate at which weathering occurs. Elements and nutrients weathered from the soil by water can be removed from soils in the runoff and seepage, but they can also remain in situ as newly precipitated secondary minerals or in biomass as a result of plant uptake. Here we present data from an experiment that was conducted at the controlled environment facility, Ecotron Ile-de-France (Saint-Pierre-les-Nemours, France) that studied mineral weathering and plant growth in granular basaltic material with high glass content that is being used to simulate soil in large scale Biosphere 2 Landscape Evolution Observatory (LEO) project. The experiment used 3 plant types: velvet mesquite (Prosopis velutina), green spangletop (Leptochloa dubia), and alfalfa (Medicago sativa), which were grown under varying temperature and CO2 conditions. We hypothesized that plants grown under warmer, higher CO2 conditions would have larger nutrient concentrations as more mineral weathering would occur. Results of plant digestions and analysis showed that plant concentrations of lithogenic elements were significantly influenced by the plant type and were different between above- and below-ground parts of the plant. Temperature and CO2 treatment effects were less pronounced, but we observed significant temperature effect on plant uptake. A number of major and trace elements showed increase in concentration with increase in temperature at elevated atmospheric CO2. Effect was observed both in the shoots and in the roots, but more significant differences were observed in the shoots. Results presented here indicate that climate change would have strong effect on plant uptake and mobility of weathered elements during soil formation and give further evidence of interactions between abiotic and biological processes in terrestrial ecosystems.