Graduate Thesis Or Dissertation
 

Fungal and bacterial associations in heart rots of Abies concolor (Gord. and Glend.) Lindl. and techniques for estimating damage in southwestern Oregon

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  • Infection courts for microorganisms invading white fir heartwood were determined to be primarily branches and basal wounds. Of 11 hymenomycetes isolated from infected trees, only four: Echinodontiurn tinctorium, Phellinus chrysoloma, Pholiota adiposa, and Hericium abietis were of major significance in terms of frequency of infection and damage caused. Two or more hyrnenomycetous fungi were commonly isolated from a single decay column. Where this occurred decay was more extensive than that caused by a single hymenomycete. Hericium abietis was a common associate of F. tinctorium and other hymenomycetes. Decay columns in white fir were typically cylindrical in shape and had three distinct zones of discoloration and deterioration. These included advanced, incipient and early decay. The progression of decay stages horizontally across the grain and vertically at the lower and upper ends of columns was from the advanced zone at the center through incipient to early decay to sound wood. Results of cultural isolation of microorganisms from the decay zones indicated that a succession of microorganisms occurs as decay progresses in white fir heartwood. Bacteria were the primary organisms isolated from the early decay zone. A consistent microflora of bacteria and fungi was isolated from the incipient and advanced stages of decay. Bacteria apparently are the initial colonizers of heartwood followed by the fungi. The hymenomycetous fungi responsible for causing 173 of the 513 decay columns were either unidentifiable in culture or in most cases they were not isolated. These decay columns were small, the causal fungi appeared to have died or become inactive. Limiting factors are thought to be competition by other microorganisms or unfavorable air or moisture conditions accompanying healing of infection courts. Non-hymenomycetes identified included: Phialophora fastigiata and Phialophora spp., Cladosporium herbarum, Gliocladium roseum, and Rhinocladiella atrovirens. No successional pattern was detected among those identified. Most bacteria were Enterobacteriaceae and Pseudomonas spp. A few Bacillus species were found. Species of nitrogen-fixing bacteria were isolated from decay in 31 white fir trees distributed among 16 areas. Evidence of N2- fixation by these bacteria was initially obtained by acetylene reduction then confirmed by use of 15N2 and by total nitrogen analyses. Bacteria fixing N2 were associated with the major decay fungi during all stages of attack on the white firs. High populations (1O^5 to 10^6/ml expressed sap) of N2-fixing bacteria were associated with the early and incipient stages of decay caused by P. chrysoloma and H. abietis, but not E tinctorium Population data are considered preliminary because of the limited sample. Many of these bacteria were identified as typical or atypical isolates of Enterobacter agglomerans, E. aerogenes, E. cloacae and Kiebsiella pneurnoniae. Identifications based on phenotypic properties were confirmed by percent guanine plus cytosine base composition analyses of selected isolates. Phenotypic properties of many N2-fixing bacteria did not conform with published descriptions. Since most differences were negative responses none of the aberrant strains were considered new species. Two methods were developed for estimating defect in standing white fir trees in southwestern Oregon (1) Defect percentages of gross merchantable volumes (Scribner and International board-foot and cubic-foot) are tabulated by d.b.h and age. Then constant defect percentages are added for various indicators. Multiple regression equations used to derive the indicator defect percentage tables are given. (2) Average length deductions below and above various indicators are given along with flat percentage factors for hidden defect. The first method was considered to be the most accurate and objective. Statistical analysis indicated that the first method can be used to estimate defect in white fir in three cover types in which this species occurs in southwestern Oregon.
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