A Retrospective Ecological Analysis of Riparian Restoration Treatments in Western Washington Primary Support from Pacific Northwest Research Station, U.S. Forest Service

Pete Bisson, USFS; Scott Elliott, UW Forestry; Robert Naiman, UW Fisheries

Suspended particulate matter (seston) plays an important role in the trophic ecology of forested streams. Silvicultural activities in and along the riparian corridor may alter the existing levels of allochthonous and autochthonous contributions to the lotic system, ultimately changing the food quality of the seston. We sampled seston at baseflow from 19 sites on the Olympic Peninsula of Washington State. The condition of each site was characterized by harvest history and successional condition of the canopy. We used concentration of chlorophyll a (a predictor of primary production), percent organic matter, and the C:N ratio as indices of seston food quality. Scanning electron microscopy (SEM) was employed to assay seston composition and particle origin. Chlorophyll a was found to be correlated to canopy closure within stream order groups. C:N values were typically higher in unimpacted systems, and SEM analysis is currently showing a trend toward increased particle diversity in more natural sites. Percent organic matter was not significantly related to any parameter we measured. Our results, although still in progress, describe a link between the condition of the riparian ecotone and the trophic ecology of the stream in question. Seston shows some potential as an indicator for riparian condition and recovery.