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Long-term dynamics of large wood in old-growth and second-growth stream reaches in the Cascade Mountains of Oregon
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  • Stan Gregory,
  • Linda Ashkenas,
  • Randy Wildman,
  • George Lienkaemper,
  • Ivan Arismendi,
  • Gary Lamberti,
  • Mark Meleason,
  • Brooke E. Penaluna,
  • Daniel Sobota
Stan Gregory
Oregon State University Department of Fisheries and Wildlife

Corresponding Author:[email protected]

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Linda Ashkenas
Oregon State University Department of Fisheries and Wildlife
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Randy Wildman
Oregon State University Department of Fisheries and Wildlife
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George Lienkaemper
Oregon State University Department of Fisheries and Wildlife
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Ivan Arismendi
Oregon State University Department of Fisheries and Wildlife
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Gary Lamberti
University of Notre Dame Department of Biological Sciences
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Mark Meleason
Oregon State University Department of Fisheries and Wildlife
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Brooke E. Penaluna
USDA Forest Service Pacific Northwest Region
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Daniel Sobota
Oregon Department of Environmental Quality
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Abstract

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.