The effect of disturbance by Phellinus weirii on decomposition and nutrient mineralization in a Tsuga mertensiana forest

Summary Microbial biomass in the upper 7 cm of soil and needle decomposition on the forest floor were measured seasonally for 10 months in a mountain hemlock (Tsuga mertensiana) old-growth forest and in a regrowth forest after Phellinus weirii, a root-rot pathogen infection, had caused disturbance. The microbial biomass was higher in the old-growth forest soil than in the regrowth forest soil. However, T. mertensiana needle decomposition rates were higher in the regrowth than in the old-growth forest. Total N, Ca, Fe, Cu, and Zn concentrations in needles increased during the 1st year of decomposition in both the old and the regrowth forests, but P, K, Mg, Mn, and B concentrations decreased. N, P, K, Mg, Cu, and Zn concentrations were lower in regrowth than in old-growth decomposing needles. During mineralization, needles in the regrowth forests released more N, P, and K as a result of higher needle decomposition rates. Our results suggest that higher needle decomposition rates increased the mineralization of N, P, and K, which may lead to increased soil fertility and faster tree growth rates in the regrowth forest.     

Reciprocal transfer effects on denitrifying community composition and activity at forest and meadow sites in the Cascade Mountains of Oregon

In order to examine the effects of disturbance, vegetation type, and microclimate on denitrification and denitrifier community composition, experimental plots were established at the H. J. Andrews Experimental Forest in the Cascade Mountains of Oregon. Soil cores were reciprocally transplanted between meadow and forest and samples were collected after 1 and 2 years. Denitrifying enzyme activity (DEA) was measured using the acetylene block assay and terminal restriction length polymorphism profiles were generated with nosZ primers that target the gene coding for nitrous oxide reductase. Nitrate concentrations, C mineralization, and water content were measured to gain additional insights into soil properties controlling DEA. Meadow soils were significantly higher in DEA than forest soils, and the highest DEA levels were observed in cores transferred from the meadow into the forest. Nitrate concentrations were also different between forest and meadow soils, but did not correlate to DEA. DEA was higher in open versus closed cores, suggesting an association between denitrification and the rhizosphere. Denitrifier communities of undisturbed forest and meadow soils shifted through a 4-year period but remained distinct from each other. Similarly, denitrifier communities clustered by vegetation type of origin regardless of manipulation, suggesting that the overall denitrifier communities are well buffered against environmental changes.     

Calcium oxalate accumulation and soil weathering in mats of the hypogeous fungus Hysterangium crassum

Fungal mats of Hysterangium crassum (Tul. and Tul.) Fischer occupied a mean of 9.6% of the upper 10 cm of soil developed under a 40–65 yr old stand of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) in Oregon. This hypogeous basidiomycete exudes large amounts of oxalic acid, some of which precipitates with Ca in microscopic crystals of calcium oxalate, resulting in a mean CaC₂O₄ content of 82g m^?2 for the entire soil. Soil oxalate concentration was significantly greater within fungal mats (P < 0.01) and soil pH was significantly lower (P < 0.01) than in soil adjacent to mats. The quantity of Ca present as CaC₂O₄ is 0.5 the amount of exchangeable Ca in the soil and exceeds the mass of Ca lost annually in runoff. Scanning electron micrographs show intense chemical weathering, attributable to oxalate attack, in the immediate vicinity of hyphae. X-ray diffraction patterns of clay indicate bulk weathering is more intense within the fungal mats than in adjacent uncolonized soil.     

The effect of Armillaria attack on the nutrient status of Inland Douglas-fir

Nutrient status, sapwood basal area (SBA) and sapwood to heartwood basal area (S/H) were measured on second growth Pseudotsuga menztesn trees in western Montana. Armillaria-infected trees had significantly lower S/H ratios, growth, and foliar N and S concentrations than noninfected trees. Our results indicate a general influence of Armillaria infection on nutrient content and physiological status of P. menziesü trees. However, these measurements are not a reliable method to determine the extent of infection.     

The influence of carbon nutrition on Armillaria ostoyae growth and phenolic degradation

Concentrations of 1, 5 and 25 g C L^?1 as glucose, fructose and sucrose were added to basal media containing 0 or 1.0 mM catechol orwa-hydroxybenzoic acid. Media were poured in petri dishes and inoculated with one of three isolates of Armillaria ostoyae(Romagn.) Herink. Armillaria ostoyae isolates usually had greater colony size and biomass yield when glucose was the carbon source as compared to fructose or sucrose. When compared to A. ostoyae growth on basal media alone, 1.0 mM catechol and /wvi-hydroxybenzoic acia added to basal media inhibited A. ostoyae growth. In a second experiment, catechol andpara-hydroxybenzoic acid degradation by three A. ostoyae isolates growing on 1, 5 and 25 g C L^?1 glucose, fructose or sucrose were measured radiometrically. Carbon source and concentration had no effect on the degradation of pzra-hydroxybenzoic acid or catechol by Armillaria ostoyae. Results of these experiments suggests that A. ostoyae can grow faster when at high carbon concentration but cannot more effectively degrade catechol or para-hydroxybenzoic acid.     

Effects of vegetation control on nutrient removal and Fagus orientalis, Lipsky regeneration in the western Black Sea Region of Turkey

Dense Rhododendron ponticum (L.) understories of eastern beech (Fagus orientalis Lipsky) stands in the Black Sea Region (BSR) of Turkey create challenging forest vegetation management problems relative to beech regeneration. Rhododendron traditionally is controlled in Turkish forests with grubbing and bulldozing. The effects of these practices on nutrient removal and natural beech regeneration have not been quantitatively studied. Two woody vegetation control treatments (bulldozing and hand-grubbing) were installed during late summer, 2002 in three mature beech stands with dense rhododendron understories in the Düzce Forest Management Directorate, in the Turkish western BSR. Aboveground biomass of each vegetation component, total aboveground vegetation biomass, nutrient concentrations, organic matter (OM) removal, and total amount of OM nutrients were determined for each woody vegetation control treatment. Soil bulk density and nutrient content, and beech seedling biomass, nutrient content, and natural regeneration also were studied. One year after treatment, the machine site preparation by bulldozing (MSP) that removed understory vegetation and attached roots, reduced mean forest floor OM content by about 84%, when compared to hand-grubbing. Mean soil C, N, K and Mg concentrations on the bulldozed sites were 36, 27, 50 and 55% less, respectively, than those on the grubbed sites. Total C and Mg amounts at the 5–10 cm soil depth were 24 and 47% lower, respectively, for mechanical site preparation (MSP) sites, when compared to grubbed sites. Overall, soil bulk density did not differ significantly between the grubbing and MSP treatments. Frequent passes on designated transects on MSP sites resulted in a significant (P < 0.01) one-third increase in bulk density of the first 20 cm soil depth, when compared to grubbed sites. No natural beech regeneration occurred on untreated control sites. Mineral soil exposure on the MSP sites increased beech seedling germination substantially. One year after treatment, the mean number of naturally regenerated seedlings for MSP sites was 2.5 times greater than for grubbed sites. Woody control treatments had significant effects upon beech seedling chemistry, with N, P, K, Ca and Mg concentrations averaging 35, 47, 12, 33 and 25% lower, respectively, for MSP sites, when compared to grubbed sites. However, mean seedling biomass and nutrient content were significantly greater (P < 0.05) on MSP sites. Long-term effects from windrowing on MSP site residues, associated topsoil and nutrients need to be evaluated.     

Influence of ectomycorrhizal mat soils on lignin and cellulose degradation

Summary The ectomycorrhizal fungus Hysterangium setchellii (Fisher) forms extensive hyphal mats at the soillitter interface with the roots of the host tree Douglas fir Pseudotsuga menziesii [(Mirb.) Franco]. Microbial biomass, and lignin and cellulose decomposition rates were measured seasonally for 1 year, using ¹⁴C techniques in ectomycorrhizal mat soils and adjacent non-mat soils in a second-growth Douglas fir forest. The microbial biomass and cellulose degradation rates were 3–6 times higher in ectomycorrhizal mat soils than in adjacent nonmat soils. Lignin degradation rates were higher in ectomycorrhizal mat soils than adjacent non-mat soils. Our data suggest that the ectomycorrhizal fungus H. setchellii provides a microenvironment with increased microbiological activity which results in faster lignin and cellulose decomposition.     

Microbial characteristics of ectomycorrhizal mat communities in Oregon and California

Summary Specialized ectomycorrhizal fungi form dense mats in forest soils that have different enzyme levels, higher respiration rates, more biomass, different soil fauna, and different soil chemistry compared with adjacent soils not obviously colonized by these mats. In this study, mats formed by two genera of fungi collected in three locations were compared with a wide range of measurements. Per cent moisture, pH, chloroform fumigation-flush C, anaerobic N mineralization, exchangeable ammonium, and respiration, N₂ fixation, and denitrification rates were compared between soils or litter colonized by ectomycorrhizal mat-forming fungi and adjacent non-mat material. Significant differences were observed between the two genera of mat-forming fungi and also between mats formed primarily in mineral soil and those formed in litter. These differences suggest that different mat-forming fungi perform different functions in forest soils and that these fungi function differently in mineral soil compared with litter.Published as Technical Paper 9496, Oregon Agricultural Experiment Station     

Effect of nitrogen and carbon sources on lignin and cellulose degradation by Armillaria ostoyae

Lignin has been hypothesized to be the primary mechanism of resistance to fungal pathogens in plant tissue. Degradation of lignin and cellulose by Armillaria ostoyae cultured for six weeks in Melin-Norkrans medium containing various nitrogen and carbon sources was measured radiometrically. No consistent pattern of lignin or cellulose degradation was found, regardless of A. ostoyae isolate, nitrogen source and concentration, or carbon concentration. More lignin was degraded as the concentration of glucose and fructose increased but not when the concentration of sucrose increased.     

Properties of protein powders from arrowtooth flounder (Atheresthes stomias) and herring (Clupea harengus) byproducts

Functional, nutritional, and thermal properties of freeze-dried protein powders (FPP) from whole herring (WHP), herring body (HBP), herring head (HHP), herring gonad (HGP), and arrowtooth flounder fillets (AFP) were evaluated. The FPP samples have desirable nutritional and functional properties and contained 63-81.4% protein. All FPP samples had desirable essential amino acid profiles and mineral contents. The emulsifying and fat adsorption capacities of all FPP samples were higher than those of soy protein concentrate. The emulsifying stability of WHP was lower than that of egg albumin but greater than that of soy protein concentrate. Thermal stability of the FPP samples is in the following order: HGP > HBP > WHP > HHP > AFP.