Graduate Thesis Or Dissertation
 

Storage dynamics of fine woody debris for two low-order streams in southeast Alaska

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/5425kf09f

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  • The characteristics and associated storage dynamics of approximately 2000 pieces of fine woody debris (FWD; 2.5 cm <diameter<10 cm and 0.3 m<length<10 m) was evaluated over a three-year period in two undisturbed salmonid nursery streams in Southeast Alaska. To index a given reaches propensity to capture and store FWD over time, 100 survey stakes (diameter=2.9 cm, length=44 cm) were introduced at one-year intervals to the head of four reaches with distinct coarse woody debris (CWD; diameter>10 cm, length>1 m) loadings, and their downstream dispersal monitored. Between 1987 and 1989, storage of FWD was temporally and spatially variable and not suggestive of steady-state conditions. In the 1987-1988 stormflow period, the total resident FWD volume (cm³ per meter of reach) declined 43%. This was followed by a resident volume increase of 9% in the 1988-1989 period. These changes in FWD storage occurred despite maximum peak flows which differed between periods by only 10%. These annual changes in FWD storage indicate that factors and processes in addition to magnitude of peak flow were important in FWD storage dynamics. Factors important in describing the observed storage fluctuations might include the effects of an unusually low peak flow regime (20% of nine-year average) in the year prior to the study's commencement, as well as variable rates of FWD recruitment from the riparian environment. The majority of FWD was shorter (66-102 cm) than bankfull width (3.8-5.6 in), approximately 4.7 cm in diameter, geometrically simple in form, and in moderate to advanced states of decay. Shorter pieces were generally entrained more frequently than longer pieces, resulting in selective retention of longer pieces through time. The data strongly suggest FWD loadings are positively correlated with the amount of CWD in the reach. Retention of stakes was generally highest in a reach with high CWD loading (0.47 m³/m), intermediate in two reaches with moderate CWD loading (0.13 m³/m and 0.11 m³/m), and lowest in a reach with low CWD loading (0. 0082 m³/m). Distinct spatial and temporal stake dispersal patterns were noted between reaches. The retention of stakes declined most dramatically during the first stormflow (1.31 m³/s) following their introduction, while succeeding storms of equal or greater magnitude had less of an effect.
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  • Master files scanned at 600 ppi (256 Grayscale) using Capture Perfect 3.0 on a Canon DR-9080C in TIF format. PDF derivative scanned at 300 ppi (256 B+W), using Capture Perfect 3.0, on a Canon DR-9080C. CVista PdfCompressor 3.1 was used for pdf compression and textual OCR.
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