Riparian soil nitrogen cycling and isotopic enrichment in response to a long-term salmon carcass manipulation experiment

To test the long-term importance of salmon subsidies to riparian ecosystems, we measured soil nitrogen cycling in response to a 20-yr manipulation where salmon carcasses were systematically removed from one bank and deposited on the opposite bank along a 2-km stream in southwestern Alaska. Surprisingly, despite 20 years of salmon supplementation, the presence of marine derive nitrogen did not cause a long-term increase in soil nitrogen availability. This finding indicates the importance of MDN to ecosystem nitrogen biogeochemistry, and riparian vegetation may be overestimated for some systems.