Graduate Thesis Or Dissertation

 

Microbial ecology of an old-growth Douglas fir canopy Public Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/3197xp987

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  • Microbial populations associated with the major substrates of the canopy of a 70 m old-growth Douglas fir were studied to determine potential activities. Seasonal samples from bark, foliage, epiphytic moss, lichens, and litter accumulations were collected to i) obtain population data, ii) to isolate the major groups of microorganisms present, iii) to measure enzymatic activities associated with cellulose and xylan degradation, and iv) to examine the potential for nitrogen fixation. Five hundred sixty-two bacterial isolates were tested for utilization of 25 carbohydrates associated with the canopy substrates, and for activities in the nitrogen and sulfur cycle transformations. Total bacterial populations, reflecting seasonal temperature and moisture conditions, were lowest on bark and foliage (21 to 266 x 10³ colony forming units (CFU/gm)) on moss and lodged litter (19 to 610 x 10⁵ CFU/gm). Lichens contained intermediate numbers of bacteria (3.3 to 270 CFU/gm) while the flourescent pseudomonads and Streptomyces reflected 0.005 to 2.2 percent of the total plate counts. The majority of the organisms isolated were classifed as species of Arthrobacter, Bacillus, Flavobacterium, and Xanthomonas. Isolates of Alcaligenes (=Achromobacter), Aeromonas, Chromobacterium, Micrococcus and Pseudomonas were less common). No measurable rates of nitrogen fixation attributable to bacteria were detected by acetylene reduction. Isolates of Bacillus, Citrobacter, and Enterobacter were recovered sporadically. Eleven species in six genera of lichens containing a blue-green algal phycobiont showed positive acetylene reduction. One species, Lobaria oregana, accounted for 51 percent of the total lichen biomass of the canopy. Cellulase and xylanase activity was routinely detected in moss and litter samples, and less frequently in lichens. There was a strong correlation between the two activies for moss (r=0.94) and litter (r=0.81).
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