Long-term dynamics of large wood in old-growth and second-growth stream
reaches in the Cascade Mountains of Oregon
We quantified temporal dynamics of wood storage, input, and transport in
a third-order stream over a 23-year period in adjacent old-growth and
second-growth forested reaches in the Cascade Mountains of Oregon.
Numbers and volumes of large wood (i.e., standing stock) in the old
growth reach were more than double and triple, respectively, than those
in the second growth. Annual inputs of large wood were highly variable.
Wood numbers delivered into the old-growth reach were 3X higher and wood
volume 10X greater than that of the second growth. Movement of number
and volume of logs did not differ significantly between the two reaches.
Less than 3% of the logs moved in most years, and the highest
proportion moved in the year of the 1996 flood (9% in old growth and
17% in second growth). The majority of wood occurred in accumulations
(i.e., jams) in both reaches. The second-growth reach lacked major jams,
but 29% of the logs in the old growth were in full-channel spanning
jams. Long-term observations of annual storage, input, and movement best
reveal the dynamics of wood rather than static representations of the
characteristics of wood. Input events and transport of wood in Mack
Creek were episodic and varied greatly over the 23-yr study, which
illustrates one of the major challenges and opportunities for
understanding the cumulative dynamics of wood in streams.