SS3.07 Headwater Ecosystems in Forested Landscapes and Beyond
Date: Wednesday, June 12, 2002
Time: 11:30:00 AM
Location: View Royal
 
PiccoloJJ, Juneau Center, School of Fisheries and Ocean Sciences, Univ. of Alaska Fairbanks, Juneau, USA, ftjjp1@uaf.edu
Wipfli, M, S, Pacific Northwest Research Station, USDA Forest Service, Wenatchee, USA, mwipfli@fs.fed.us
 
EXPORT OF AQUATIC AND TERRESTRIAL INVERTEBRATES FROM UPLAND, FISHLESS HEADWATERS TO DOWNSTREAM, FISH-BEARING HABITATS IN SOUTHEAST ALASKA.
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We examined the export of invertebrates (terrestrial and aquatic) from headwaters to downstream habitats to assess the role of headwater streams in delivering prey to downstream salmonid habitats, in the coastal mountains of Southeast Alaska. Export was sampled in 90 headwater streams, upstream of fish-bearing reaches. Streams drained old growth, clearcut (< 5 years post-cut), and young-growth (40 years old) red alder and conifer forests. Invertebrates (roughly 2/3 aquatic, 1/3 terrestrial origin) were exported from headwaters throughout the year. Export averaged 165 mg dry mass per stream per day, enough to support up to 2000 young-of-the-year salmonids per kilometer of fish-bearing stream if downstream habitat is suitable. Young-growth alder sites exported four times more invertebrates than did young-growth conifer sites. These results illustrate that headwaters are sources of aquatic and terrestrial invertebrates, and suggest that riparian vegetation influences the type and amount of invertebrates delivered to fish-bearing food webs. Maintaining an alder component in upland forests following timber harvest should increase the productivity of headwater streams, and the subsequent delivery of invertebrates to fish-bearing food webs lower in the drainage.