SREL Reprint #2117
Characterization of riparian species
and stream detritus
using multiple stable isotopes
McArthur, J.V. and K.K. Moorhead. 1996
Abstract:
Multiple stable isotopes were used to determine the effectiveness
of distinguishing among several dominant riparian species and
aquatic macrophytes both spatially (three sites) and temporally
(three seasons) along an 8 km reach of a blackwater stream. The
differences in isotopic composition were used to assess
contributions of various organic matter sources to the detrital pool
of the stream. Samples of riparian and aquatic macrophyte
vegetation and detritus were collected at three times to represent
early leaf-out (April), mid-summer (August), and just prior to
abscission (October). Each sample was analyzed for stable
isotopes of carbon ( 13 C), nitrogen (d15 N), and sulfur (d34 S)
Within a site and sampling date, d13 C-values were significantly
different among certain riparian species and detritus samples.
Species differences persisted between seasons. d34 S-values
were the most variable of the three elements examined although
they remained fairly constant through time within each species and
site. The results suggest that temporal changes in isotopic
composition of riparian species and aquatic macrophytes are
site-specific. Discriminant analysis dissimilarity plots (based on all
three isotopes) demonstrated that the contribution of species to
the detrital pool depended on the site and season. At the upper
site, detritus was isotopically most similar to Quercus laurifolia
and Sparganium americanum in April, and the aquatic
macrophytes (S. americanum and Potamgeton spp.) in August
and October. At the middle site, detritus was most similar to
Carpinus caroliniana and Quercus nigra in April but no single
source was similar to detritus in August or October. At the lower
site, detritus was most similar to Taxodium distichum for all three
seasons.
SREL Reprint #2117
McArthur, J.V. and K.K. Moorhead. 1996. Characterization of riparian species and stream detritus using multiple stable isotopes. Oecologia 232-238.
