Headwater Streams in Southeast Alaska: Why Do We Care?

• Headwater streams may comprise more than 70% of the area of a watershed and until recently, they have been largely over-looked by managers and ecologists in Southeast Alaska and elsewhere. However, their importance in shaping downstream processes isbecoming more widely recognized. Recently, a series of studies were completed in Southeast Alaska that examined the physical and biological features of headwater streams. We review and synthesize these studies to define headwater stream characteristics in Southeast Alaska, describe some processes that occur in these streams, and discuss their importance to watersheds. Alterations in large wood abundance anddistribution have predictable effects on sediment storage and transport in headwater streams. Legacy wood remaining in streams more than 25 yrs after logging was an important structural component. Invertebrate populations captured in drift samples arediverse, and more than 60 % of the taxa were aquatic. Downstream transport of invertebrate drift from reaches without fish may be an important to juvenile fish residing in the lower reaches. Drift density is inversely related to stream discharge, so smallstreams may provide better foraging and growth potential. Resident and anadromous fish live and spawn in headwater reaches with gradients > 10 % and occupied small step pools formed by large woody debris. Dolly Varden were the dominant species in higher gradient reaches, but juvenile coho were also present. Steelhead were seasonal residents. Headwater streams link hill slope processes to watersheds and can have important consequences for salmonid populations throughout a watershed

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NATURVETENSKAP  -- Biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences (hsv//eng)

Nyckelord

Biology

Biologi

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