SS3.07 Headwater Ecosystems in Forested Landscapes and Beyond
Date: Wednesday, June 12, 2002
Time: 10:15:00 AM
Location: View Royal
 
VolkCJ, University of Washington, Seattle, USA, cvolk@u.washington.edu
Kiffney, P, M, National Marine Fisheries Service, Northwest Fisheries Science Center, Seattle, USA, peter.kiffney@noaa.gov
Edmonds, R, L, University of Washington, Seattle, USA, bobe@u.washington.edu
 
ROLE OF RIPARIAN RED ALDER IN SHAPING THE NUTRIENT DYNAMICS AND AQUATIC COMMUNITIES OF HEADWATER STREAMS
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In the Pacific Northwest, natural disturbances and clearcutting have contributed to the predominance of red alder (Alnus rubra) in riparian corridors. Current management supports the removal of nitrogen-fixing red alder and replacement with conifers to provide a stable supply of large woody debris to streams and form important fish habitat. Our previous research has shown water, seston, leaf litter, and periphyton from red alder-dominated streams to have higher biomass and macronutrient concentrations; these food resources may provide critical sources of nutrients for fish and amphibians. To compare the structure and resource derivation of red alder and conifer food webs, we collected vegetation, periphyton, invertebrates, and amphibians for 13C and 15N stable isotope analyses from four streams: two dominated by red alder and two by old-growth conifers. Preliminary analyses have shown vegetation and invertebrate shredders from alder sites to have higher delta 15N content than conifer-dominated sites. In addition, the delta 13C signature of invertebrates (grazer, filter feeder, and predator benthic samples) from alder streams was higher compared to conifer-dominated systems, suggesting differences in invertebrate food source derivation between stream systems.