The restoration of rivers and streams should be based on a
strong conceptual framework. Streams are developing systems. As
such, streams exhibit temporal behaviors that change with changing
stream environments. Underlying the dynamic development of streams is
potential capacity. Streams express this capacity as an array of
habitats over time and across the landscape. Human land uses in the
western United States have rapidly altered aquatic habitats as well as
the processes that shape habitat. As a result, the diversity of native
fishes and their habitats has been suppressed. Restoration is
fundamentally about allowing stream systems to re-express their
capacities. Four steps are provided to guide stream restoration
activities. Key tasks include: identification of the historic
patterns of habitat development; protection of the developmental
diversity that remains; local application of specific knowledge about
suppressive factors; classification of sensitive, critical or refugium
habitats; release of anthropogenic suppression; and monitoring of
biotic response to habitat change.
Applying these concepts, I describe potential habitat refugia
for aquatic organisms in the Joseph Creek basin in the Blue Mountains
of northeast Oregon. Five valley segment classes, differing in valley
corridor landforms, are described. Of these, low-gradient wide
alluvial valleys have been most altered by human land use. Riparian
vegetation has been extensively removed or altered in alluvial
valleys. Currently, stream habitats are structurally depauperate, and
warm to temperatures well above thermal tolerances of native
salmonids. Potential refugia for native coldwater fishes in these
valleys include patches of complex habitat within stream reaches.
Reaches fenced to exclude domestic livestock exhibit narrower
channels, more pools, and higher frequencies of stable vegetated banks
than nearby unfenced reaches. During summer low flow periods, cold
groundwater seeping into and accumulating in stream channels forms
"cold pools". Cold pools provide potential seasonal refuge for coldwater
fish at microhabitat scales. Cold pools are associated with
channel complexity, and are more frequent in reaches with vigorous
riparian vegetation. Seven classes of cold pools are described. Cold
pool classes differ in minimum temperature, maximum depth and volume.
Distributions of cold pool classes between valley segment classes
suggest that valley geomorphology in addition to local channel form
may influence development of certain cold pool types.
Although refugia at the microhabitat to reach scales are
important, the context within which remnant or refugium habitats and
associated relict populations are maintained may ultimately determine
the persistence of those species and habitats. In managed landscapes,
protection and restoration of habitats at many scales may be necessary
if we are to best insure the persistence of native species. / Graduation date: 1995
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/35152 |
| Date | 01 June 1994 |
| Creators | Ebersole, Joseph Lamar |
| Contributors | Liss, William J. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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