|Citation||Tripp, D. 1998. Evolution of fish habitat structure and diversity at log jams in logged and unlogged streams subject to mass wasting. In: Hogan, D.L., P.J. Tschaplinski, and S. Chatwin (Editors). B.C. Min. For., Res. Br., Victoria, B.C. Land Manage. Handb. No. 41.|
|Abstract/Description or Keywords||Large woody or organic debris is an essential component
of most streams on the Queen Charlotte
Islands (Hogan 1986; Tripp and Poulin 1986). It is
frequently also closely linked with upslope processes,
inasmuch as debris torrents and other mass wasting
events appear to be a significant source of debris for
streams on the Queen Charlotte Islands (Schwab,
this volume). Where the gradient is steep enough,
slides or torrents may be carried down in small
streams for a considerable distance before halting in
a lower gradient reach. When the floodplain is
confined between steep hillsides, debris torrents also
enter the low gradient sections of larger streams
directly from gully failures alongside the stream.
Most of the large organic debris in medium-size
streams (15–25 m wide ) on the Queen Charlotte
Islands is organized into log jams (Hogan 1989).
These log jams physically occupy a significant portion
of the total stream length available to fish.
Because log jams also control many of the habitat
characteristics upstream of a jam as well as below a
jam, understanding how the fish habitat at log jams
develops or evolves in many streams can require
study of most of the fish habitat present.
Logging to the stream edge changes the type and
rate of debris entering a stream. In steep land areas
on the Queen Charlotte Islands, logging in upslope
areas also accelerates the amount of sediment and
debris introduced into streams (Rood 1984). Both
factors should affect the structure of the log jams,
but to what degree or how quickly is unknown. The
present study attempts to determine how log jams
and the fish habitat associated with them evolve over
time. It also attempts to determine if log jams in
logged streams show the same patterns and rates of
change as log jams in unlogged streams.
|Regional Watershed||Coast Region|
|Sub-watershed if known|