PARENT SESSION
Oral Session #70: Riparian Ecology. Presiding: R. Cosgriff.
Thursday, August 9, 2001. 1:00 PM to 4:45 PM. Hall of Ideas I.

Effects of marine-derived nutrients on riparian forest structure in southwest Alaska.

BARTZ, KRISTA¹, NAIMAN, ROBERT¹, ¹

ABSTRACT- Spawning Pacific salmon (Oncorhynchus spp.) contribute marine-derived nutrients to freshwater and terrestrial ecosystems. The dispersal of these nutrients through aquatic food webs and the ensuing effects on instream productivity have been well documented, yet parallel impacts to streamside systems have been reported only recently. The goal of this study was to investigate the effect of marine-derived nutrients on the structure of riparian forest communities in southwest Alaska. Eleven spawning streams spanning three major watersheds were examined during the summer of 2000. Each stream had a natural barrier to upstream salmon migration but limited geomorphologic differences across the barrier, enabling comparisons between reaches with and without salmon. Structural characteristics were measured in the overstory, understory and shrub layers of above- and below-barrier transects. Foliage and soil samples were also collected for stable isotope analysis. Results revealed significant differences in both the community characteristics and ¹⁵N signatures of above- and below-barrier transects. Generally, overstory basal area and stem density were greater below the barrier, while shrub basal area and stem density and understory species richness and evenness were greater above the barrier.

KEY WORDS: marine-derived nutrients, riparian ecology, boreal forest structure