CO2 effects on plant nutrient concentration depend on plant functional group and available nitrogen: a meta-analysis (original) (raw)

Elevated CO 2 is expected to lower plant nutrient concentrations via carbohydrate dilution and increased nutrient use efficiency. Elevated CO 2 consistently lowers plant foliar nitrogen, but there is no consensus on CO 2 effects across the range of plant nutrients. We used meta-analysis to quantify elevated CO 2 effects on leaf, stem, root, and seed concentrations of B, Ca, Cu, Fe, K, Mg, Mn, P, S, and Zn among four plant functional groups and two levels of N fertilization. CO 2 effects on plant nutrient concentration depended on the nutrient, plant group, tissue, and N status. CO 2 reduced B, Cu, Fe, and Mg, but increased Mn concentration in the leaves of N 2 fixers. Elevated CO 2 increased Cu, Fe, and Zn, but lowered Mn concentration in grass leaves. Tree leaf responses were strongly related to N status: CO 2 significantly decreased Cu, Fe, Mg, and S at high N, but only Fe at low N. Elevated CO 2 decreased Mg and Zn in crop leaves grown with high N, and Mn at low N. Nutrient concentrations in crop roots were not affected by CO 2 enrichment, but CO 2 decreased Ca, K, Mg and P in tree roots. Crop seeds had lower S under elevated CO 2 . We also tested the validity of a ''dilution model.'' CO 2 reduced the concentration of plant nutrients 6.6% across nutrients and plant groups, but the reduction is less than expected (18.4%) from carbohydrate accumulation alone. We found that elevated CO 2 impacts plant nutrient status differently among the nutrient elements, plant functional groups, and among plant tissues. Our synthesis suggests that differences between plant groups and plant organs, N status, and differences in nutrient chemistry in soils preclude a universal hypothesis strictly related to carbohydrate dilution regarding plant nutrient response to elevated CO 2 .