Abstract:
This study was conducted to describe variation of riparian vegetation in an Oregon
Coast Range system according to geomorphic characteristics and in relation to streamflow.
Specific objectives of this study were to: I) examine if the vegetation composition and
structure of the riparian forest varied among channel-reach morphologies, 2) examine how the
composition and structure of the riparian forest changed with distance from the stream, and 3)
extract major underlying environmental gradients explaining riparian forest community from
riparian vegetation data.
A 30 m x 30 m sample site was randomly located on each side of upper Camp Creek
in each of 19 reaches, and within each site three consecutive 30 m x 10 m belt-transects
established perpendicular to the stream flow. Overstory and understory vegetation was
sampled in each belt transect. Environmental variables sampled included slope, aspect, height
above summer low flow, elevation above sea level. Non-metric Multidimensional Scaling and
Indicator Species Analysis was used to describe characteristics of riparian plant communities.
Distinct riparian vegetation patterns were observed in upper Camp Creek with
increasing distance from stream. Both overstory and understory vegetation quickly changed
with increasing distance from stream. Areas within ten meters from stream were characterized
as mesic riparian environments while areas twenty meters away from stream were
characterized as upland conifer forest environments. Vegetation composition was ordered
along an inferred moisture gradient from streamside to hillslope, and distance from stream and
height above summer low flow were almost equally correlated to the gradient. Tall shrubs
including salmonberry, sword fern and vine maple are important component of riparian
vegetation. Channel-reach morphology little differentiated riparian vegetation. A few species
were significantly abundant in a specific reach of channel morphology. However, results of
this study about relationships between channel-reach morphology and riparian vegetation were
inconclusive.
