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.
One of the most pervasive themes in ecology is that biological diversity stabilizes ecosystem processes and the services they provide to society, a concept that has become a common argument for biodiversity conservation.
Watersheds are complex mosaics of habitats whose conditions vary across space and time as landscape features filter overriding climate forcing, yet the extent to which the reliability of ecosystem services depends on these dynamics remains unknown. We quantified how shifting habitat mosaics are expressed across a range of spatial scales within a large, free-flowing river, and how they stabilize the production of Pacific salmon that support valuable fisheries.