Streamside vegetation provides
nutrition that fuels food chains in terrestrial and aquatic riparian
habitats. Although different tree species vary widely in their nutritional
quality, riparian management strategies tend to focus on conifer management
as a way to promote recruitment of woody structure for streams. However,
little is known about the relative use by invertebrates and vertebrates of
nutrient contributions by red alder- versus conifer-dominated systems.
If red alder-dominated reaches support greater numbers of organisms or
provide habitat for different species, the conversion of riparian systems
from alder to conifer could have unexpected effects on these populations.
Naturally occurring stable isotopes have been used to follow
nutrient flows through aquatic and terrestrial food webs
with
varying degrees of success. This study is designed to assess
the suitability of stable isotope analysis as a tool to
examine
food chains in red alder- and Douglas-fir-dominated riparian
areas. In the process, we will also document some of the
variability
in the naturally occurring 15N and 13C isotope signatures
of foliage from red alder and Douglas-fir in parts of the
Oregon Coast Range. 
To address isotope variation, we are asking two broad questions:
1) what is the level of isotope variability within tree
species
and 2) what is the isotope variation among riparian stands
dominated by red alder or Douglas-fir? Our results will
provide
an initial basis for determining whether naturally occurring
stable isotopes can be used as an effective ecological tool
for tracking food sources through food chains in riparian
areas dominated by red alder or Douglas-fir.
For additional information about this research study see
the 2003 CFER
Annual Report. (2.2 MB)
