Strontium isotope composition aided strontium and calcium sourcing in a cool temperate ecosystem, South Korea

Atmospheric deposition and mineral weathering are important sources of base cations in vegetated ecosystems. To assess plant preferences for weathering-fed versus atmospheric-fed mineral nutrition during different growth stages (sapling to mature), we have studied 87Sr/86Sr isotope ratios, and Ca and Sr concentrations in the vegetation, litter, organic matter and mineral soils from five functionally different species: Korean red pine, Korean chestnut, black locust, annual fleabane, and silvergrass. Isotope values of vegetations (0.7124–0.7162) closely matched with that of litter (0.7143–0.7161), soil (0.7126–0.7165), and parent material (0.7161). Plant height (as a proxy for maturity) and plant functional forms did not show discriminating effect on the variation in the Sr isotope ratio. An assessment of the relative contribution of the in-situ weathering input versus the ex-situ atmospheric input using a mixing equation suggests that vegetation, irrespective of maturity, is dependent on the weathering supplied elements as a primary source of nutrients. At all the sites, the 87Sr/86Sr ratio of organic layers and mineral soil were similar to the isotopic values of the vegetation, suggesting an active recycling pool and suggesting that vegetation in the region conservatively extracts nutrients from weathered parent materials, which are then internally recycled via organic layers.