Research
PNW
Funded Projects
2001
2000
1999
1998
1997
1996
1995
PNW Project Overview 1998
The Ecology of Aquatic and Riparian Ecosystems Under Alternative Management Regimes: a Retrospective Analysis
Principal
Investigators:
Dr. Peter
A. Bisson, USDA Forest Service,
PNW Research
Station, Olympia, Wa
Dr. Martin G. Raphael, USDA Forest Service, PNW Research
Station, Olympia, Wa
Dr. Lawrence
L.C. Jones, USDA Forest Service, PNW Research
Station, Olympia, Wa
Dr. Robert Bilby, Weyerhaeuser
Company, Technology Center, Tacoma, WA
Awarded: $20,000
Project
Description:
Despite
the acknowledged importance of riparian zones to fish and wildlife and the
current regulatory requirements for protecting riparian areas in forested
landscapes, relatively few studies have examined the response of riparian
ecosystems to active management for commodity production, or for riparian
protection and restoration.
This project is a continuation of an ongoing study of the response
of riparian-associated plants, fishes, and terrestrial vertebrates to
alternative riparian management strategies, including variation of buffer
width and thinning within streamside zones. The null hypothesis is that
aquatic and riparian plant and animal assemblages are unaffected by the
condition of riparian forests or the characteristics of forest buffers.
The alternative hypothesis is that the occurrence and abundance of fish
and wildlife species is influenced by riparian forest composition and
buffer width. A retrospective approach to this investigation will be used
by sampling streams and streamside environments that represent a variety
of conditions (buffer widths, forest age and density, and understory plant
communities) that have resulted from past forest management activities.
It is expected that this study will increase our understanding and
refine our hypotheses about relationships between plant and animal species
and riparian conditions. It is also expected that this knowledge will help
design planned experiments to eventually test these refined hypotheses
through direct manipulation of riparian vegetation.
Project Status:
A
poster display of this work is on display at ONRC.
A manuscript is expected by the end of the year 2001.
Project Summary:
The
study was conducted at 62 federal, state and private land stream sites
around the Olympic Peninsula, excluding the northeast (rain shadow)
portion, which harbors a dissimilar biotic community.
Riparian forest stands adjacent to the stream study sites were
assigned to one of six types:
second-growth buffers bounded by clearcuts, old-growth buffers
bounded by clearcuts, young forests less than 25 years old, second growth
commercially thinned, mature second growth (no recent logging), and
old-growth forests with no timber harvest.
Preliminary results of amphibian survey findings indicate that
stream-associated amphibians are good biological indicators of riparian
condition, and that species diversity and densities are greater in
unlogged stands.
The mean density of cutthroat trout is fairly consistent among
riparian habitat types.
Sculpin however, were more numerous in older riparian types with
lower channel slopes.
Mean abundance of avian species varied among riparian types, mature
stands with buffers supported the greatest abundance for many species.
The number of mammal species was greatest in mature, commercially
thinned forest.
Researchers consider controlled riparian manipulation experiments (silviculture)
a next logical step to further test these emerging relationships from
highly variable data.