Salt Additions Alter Short‐term Nitrogen and Carbon Mobilization in a Coastal Oregon Andisol

Deposition of sea salts is commonly elevated along the coast relative to inland areas, yet little is known about the effects on terrestrial ecosystem biogeochemistry. We examined the influence of NaCl concentrations on N, C, and P leaching from a coastal Oregon forest Andisol in two laboratory studies: a rapid batch extraction (∼1 d) and a month‐long incubation using microlysimeters. In the rapid extractions, salt additions immediately mobilized significant amounts of ammonium and phosphate but not nitrate. In the month‐long incubations, salt additions at concentrations in the range of coastal precipitation increased nitrate leaching from the microcosms by nearly 50% and reduced the mobility of dissolved organic carbon. Our findings suggest that coupled abiotic–biotic effects increase nitrate mobility in these soils: exchange of sodium for ammonium, then net nitrification. Changes in sea salt deposition to land and the interactions with coastal soils could alter the delivery of N and C to sensitive coastal waters.