Element Pool Changes within a Scrub-Oak Ecosystem after 11 Years of Exposure to Elevated CO 2

The effects of elevated CO₂ on ecosystem element stocks are equivocal, in part because cumulative effects of CO₂ on element pools are difficult to detect. We conducted a complete above and belowground inventory of non-nitrogen macro- and micronutrient stocks in a subtropical woodland exposed to twice-ambient CO₂ concentrations for 11 years. We analyzed a suite of nutrient elements and metals important for nutrient cycling in soils to a depth of ∼2 m, in leaves and stems of the dominant oaks, in fine and coarse roots, and in litter. In conjunction with large biomass stimulation, elevated CO₂ increased oak stem stocks of Na, Mg, P, K, V, Zn and Mo, and the aboveground pool of K and S. Elevated CO₂ increased root pools of most elements, except Zn. CO₂-stimulation of plant Ca was larger than the decline in the extractable Ca pool in soils, whereas for other elements, increased plant uptake matched the decline in the extractable pool in soil. We conclude that elevated CO₂ caused a net transfer of a subset of nutrients from soil to plants, suggesting that ecosystems with a positive plant growth response under high CO₂ will likely cause mobilization of elements from soil pools to plant biomass.