Research
PNW
Funded Projects
2001
2000
1999
1998
1997
1996
1995
PNW Project Overview 2000
Influences of Riparian Red Alder (Alnus Rubra) on Nutrient Dynamics, Energy Flow, Food Webs and Salmon Production in Small, Forested Watersheds
Principal
Investigator:
Dr.
Peter
M. Kiffney, University of Washington, College of Forest Resources
Awarded: $44,850
Project
Description:
One
legacy of clearcut logging in the Pacific Northwest is that many
watersheds are now dominated by riparian stands of red alder (Alnus
rubra). This species
colonizes disturbed areas quickly and can limit the establishment of
coniferous forest species. Aquatic
ecosystems with riparian stands of red alder may be more productive than
ecosystems dominated by other species such as conifers.
Data collected during 1999-2000 from two streams on the Olympic
Peninsula suggests that a stream with red alder as the dominant riparian
species was more productive (higher inputs of litterfall, periphyton
biomass, and insect abundance) than a stream bordered by old-growth
conifers. A management
practice becoming more common in the Pacific Northwest is to remove red
alder bordering streams and replant with conifers, because conifers
provide a more stable supply of large woody debris to streams, and thus
form important fish habitat. Understanding
links between red alder and stream productivity may be critical to
recovery of salmon stocks. Red
alder litter, which is rich in nitrogen, may provide a critical source of
nutrients to streams as inputs of nutrients from decaying salmon carcasses
have declined with declining salmon runs.
This nitrogen-rich leaf litter may therefore, provide an important
subsidy of nutrients and carbon to Pacific Northwest stream food webs
contributing to recovery of threatened salmon stocks.
This research tests the hypothesis that streams bordered by red
alder are more productive than streams bordered by coniferous species.
Researchers will examine litter inputs, stream water nutrient
chemistry, periphyton biomass, stream invertebrate and vertebrate
abundance and biomass, and elemental dynamics (carbon, nitrogen and
phosphorous content) of these compartments in small streams on the Olympic
Peninsula (Skokomish and Hoh River drainages) with contrasting riparian
forests. Riparian vegetation
at one set of streams (n = 3-4) is dominated by stands of red
alder. This project will also
conduct experiments to examine the response to stream food webs, including
juvenile coho salmon (Onchorhynchus kisutch) to different litter
types (i.e., alder verses conifer needles).
Results from our comparative and experimental studies will provide
information on the influences of litter type on nutrient dynamics and
ecosystem productivity in streams of the Olympic Peninsula; this
information is essential for designing ecologically effective management
strategies for riparian forests, their streams and recovery of depressed
salmon stocks.
Project Status:
Project work has begun with the allocation of funds in Fall 2000.