Impacts of salmon-borne nutrients on riparian soils and vegetation in Southwest Alaska
Bartz KK. 2002. Impacts of salmon-borne nutrients on riparian soils and vegetation in Southwest Alaska. University of Washington
Spawning Pacific salmon (Oncorhynchus spp.) comntribute marine-derived nutrients to riparian communities, potentially impacting characteristics of the associated soils and vegetation. I address these potential impacts by comparing soil and vegetation characteristics upstream and downstream of natural migratory barriers on spawning streams in southwest Alaska. O horizon and surface mineral soils were measured for total nitrogen (N) and phosphorus (P) concentrations and nitrogen stable isotope ratiao, and indiactor of salmon-born N. Total N and P pools were calculated from consentrations with each soil layer. Foliage from three dominant plant species (Picea glauca, Salix alaxensis and Arctagrostis latifolia) was analyzed for total N and P concentrations and isotop ratio. In addition, structural and complistional charateristics were measured in the overstory, understory and ground layer vegetation. Results indicate that soil and vegetative characteristics differ between downstream (salmon-bearing) and upstream (non salmon-bearing) reaches. O horizon and surface mineral sil isotope ratio values are significantly higher downstream than upstream, as are foliar isotope ratio values for all species tested. The surface mineral soil total P pool size is also higher downstream, though the total N concentration of this layer is higher upstream. Of the structural and compositional characteristics measured, overstory stem density is 99% higher downstream, primarily due to fivefold increase in the number of large-diamter willows (Salix spp.). Understory stem density is 87% higher upstream, with all commmon genera but Viburnum contributing ot the difference. Ground layer species richnes is 19% higher upstream, while non-vascular and dwarf shrub species cover are 38% and 276% higher upstream, respectively. Though many characteristics differ upstream to downstream, few differences correlate with spawning density. These resutls suggest, on the one hand, that salmon-borne nutrients impact riparian soils and vegetation and, on the other, that factors unrelated to salmon are responsible for the ultimate expression of community characteristics.
- Type
- Academic
- Authors
- Bartz, Krista
- Date of Issue
- 2002
- Publisher
- University of Washington
- Units
- KATM , LACL
- Keywords
- Alaska, Fertilization, Fish, Nitrogen, Phosphorus, riparian community characteristics, salmon-borne nutrients, Soils, stable isotope analysis, Thesis, Vegetation