Mycorrhizal colonization and nutrient supply rate influence elemental and isotopic tracers of calcium cycling in plant-substrate systems

Intraplant (root-foliage) fractionation of Ca isotopes and Ca/Sr were determined in Pinus sylvestris seedlings grown at different nutrient supply rates with or without ectomycorrhizal colonization. Foliar 44Ca/40Ca and Ca/Sr are uniformly higher than those of roots in individual seedlings, and these ratios in both foliage and roots differed significantly from those of nutrient sources. The measured offsets indicate that isotopic and trace element ratios can identify relative contributions from distinct calcium pools in terrestrial ecosystems. Furthermore, the results clearly show that fractionation of calcium isotopes and calcium from strontium in plants must be assessed in ecosystem-scale budgets and large watershed models. A second experiment similar to the first but with the addition of a second tree species, Acer saccharum and its arbuscular fungal associate was setup and completed. Two types of bedrock were also added to investigate the effect of fungal weathering on the calcium cycle