Seven streams, one of them permanent, were studied in
western Oregon, USA. The research was designed to assess
the value of summer-dry headwaters for conservation
oriented landscape management. Streams were categorized
primarily according to exposure (forest versus meadow
sites) and secondarily according to flow duration
(ephemeral = short-flow versus temporary = long-flow
sites). Ephemeral streams have discontinuous flow and last
less than three months annually. Temporary streams have
continuous flow for more than five months each season.
Ephemeral forest streams were highly efficient at
filtering road-generated sediment. Uptake lengths for
suspended sediment were short (36 m-105 m) at moderately
elevated input concentrations. As a result of the
filtration mechanism, filtration efficiency is expected to
increase as annual flow duration decreases.
Injection experiments yielded nitrate uptake rates of
almost 1% per m of temporary stream channel. Exchange with
subsurface flow was the most important route for nitrate
removal from the water column. Biological uptake was
insignificant in a light-limited forest stream, whereas a
considerable amount of nitrate was retained by the biota
a nutrient-limited meadow channel.
At least 207 insect species were collected from the
summer-dry streams. Species richness recorded from
temporary forest streams exceeded that in an adjacent
permanent headwater and there was high overlap between the
fauna of the permanent and the temporary streams. Species
richness in ephemeral channels was only 1/4 to 1/3 of that
in long-flow forest streams.
Multivariate analysis of community structure revealed
flow duration and microhabitat pattern (riffle-pool) as
the most important environmental factors determining faunal
composition in temporary forest streams. Summer drought
conditions at the sample sites also were important.
By providing habitat and contributing to water quality
in permanent downstream reaches, summer-dry streams have
the potential to serve multiple purposes in conservation
management. Their value from a conservation perspective is
unexpectedly high. Landscape management therefore should be
directed toward the preservation and protection of
ephemeral and temporary streams. / Graduation date: 1993
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/35758 |
| Date | 07 December 1992 |
| Creators | Dieterich, Martin |
| Contributors | Anderson, N. H. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
Page generated in 0.0017 seconds