bluuebunny/crossref_metadata_2025 huggingface dataset:
Endonuclease III and endonuclease IV protect Escherichia coli from the lethal and mutagenic effects of near-UV irradiation
Authors: Serafini David M , Schellhorn Herb E
Published: April 2011

In contrast to the DNA damage caused by far-UV (λ < 290 nm), near-UV (290 < λ < 400 nm) induced DNA damage is partially oxygen dependent, suggesting the involvement of reactive oxygen species. To test the hypothesis that enzymes that protect cells from oxidative DNA damage are also involved in preventing near-UV mediated DNA damage, isogenic strains deficient in one or more of exonuclease III (xthA), endonuclease IV (nfo), and endonuclease III (nth) were exposed to increasing levels of far-UV and near-UV. All strains, with the exception of the nth single mutant, were found to be hypersensitive to the lethal effects of near-UV relative to a wild-type strain. A triple mutant strain (nth nfo xthA) exhibited the greatest sensitivity to near-UV-mediated lethality. The triple mutant was more sensitive than the nfo xthA double mutant to the lethal effects of near-UV, but not far-UV. A forward mutation assay also revealed a significantly increased sensitivity for the triple mutant compared to the nfo xthA deficient strain in the presence of near-UV. However, the triple mutant was no more sensitive to the mutagenic effects of far-UV than a nfo xthA double mutant. These data suggest that exonuclease III, endonuclease IV, and endonuclease III are important in protection against near-UV-induced DNA damage.Key words: near-UV, UVA, DNA damage, DNA repair.
Environmental factors influencing the nitrogen fixation activity of free-living terrestrial cyanobacteria from a high arctic area, Spitsbergen
Authors: Liengen Turid
Published: April 2011

The influence of environmental factors on the nitrogen fixation activity of free-living, terrestrial cyanobacteria from a high arctic area were investigated using experimental manipulations with two different types of field samples, including macroscopic sheets of Nostoc commune and soil samples with a cyanobacterial crust from a Puccinellia salt marsh. In addition, a cultured Anabaena sp. previously isolated from the salt marsh was examined. Nitrogen fixation activity was measured using the acetylene reduction method. The nitrogen fixation mainly took place in the light, but even after 12 h incubation in darkness, low activities were maintained. Phosphorus fertilization stimulated the nitrogen fixation activity, and the highest activities were obtained with about 300 μM phosphate, both in the field samples and the cultured Anabaena sp. Ammonium (28 mM) immediately inhibited the nitrogen fixation activity of the cultured Anabaena sp, whereas 14 mM urea and 540 μM glutamate led to a weaker and slower inhibition of the nitrogen fixation activity, showing that the cultured Anabaena sp. was able to assimilate these combined nitrogen sources. Nitrate did not have any inhibitory effect on nitrogen fixation activity, either in the field samples or in the cultured Anabaena sp. Both the field samples and the cultured Anabaena sp. showed tolerance against sodium chloride concentrations corresponding to the concentration in seawater. The temperature optimum of the nitrogen fixation activity of the cultured Anabaena sp. was about 20°C. Key words: nitrogen fixation, cyanobacteria, Nostoc commune, Anabaena sp., high arctic.
Trichosporon guehoae sp.nov., an anamorphic basidiomycetous yeast
Authors: Middelhoven Wouter J , Scorzetti Gloria , Fell Jack W
Published: April 2011

A morphological and physiological description of an anamorphic basidiomycetous yeast species, named Trichosporon guehoae (CBS 8521T), is presented. The ability to assimilate several aliphatic and aromatic compounds as sole source of carbon and energy is reported. The phylogenetic position within the genus, based on nuclear base sequencing of the D1/D2 region of the large subunit of rDNA is discussed.Key words: basidiomycetes, taxonomy, Trichosporon guehoae sp.nov., yeasts.
Enhanced benzaldehyde formation by a monokaryotic strain of Pycnoporus cinnabarinus using a selective solid adsorbent in the culture medium
Authors: Lomascolo A , Lesage-Meessen L , Labat M , Navarro D , Delattre M , Asther M
Published: April 2011

A monokaryotic strain of the white-rot fungus Pycnoporus cinnabarinus was shown to produce, in a 2-L bioreactor culture, 100 mg·L-1 benzaldehyde (bitter almond aroma) from L-phenylalanine with a productivity of 33 mg·L-1·day-1. The addition of HP20 resin, a styrene divinylbenzene copolymer highly selective for benzaldehyde, enabled an eightfold increase in the production of benzaldehyde and a twofold increase in productivity. In the presence of HP20 resin, the production of 790 mg·L-1 benzaldehyde was concomitant with the synthesis of cinnamic acid derivatives of high organoleptic notes such as cinnamaldehyde, cinnamyl alcohol, and methyl cinnamate.Key words : benzaldehyde, L-phenylalanine, Pycnoporus cinnabarinus, adsorbents.
β-lactam antibiotic selection of non-swarming mutants ofFlexibacter maritimus
Authors: Burchard Robert P
Published: April 2011

Non-swarming mutants of Flexibacter maritimus appeared at high frequency on β-lactam antibiotic-containing medium. Among them were several phenotypes characterized by changes in cell surface properties and cell envelope proteins, in adhesion and in resistance to β-lactams, including increased sensitivity to these antibiotics.Key words: Flexibacter, gliding, adhesion, β-lactam, antibiotic resistance.
Effect of subinhibitory concentrations of antimicrobial agents (quinolones and macrolide) on the production of verotoxin by enterohemorrhagic Escherichia coli O157:H7
Authors: Yoh M , Frimpong E K , Voravuthikunchai S P , Honda T
Published: April 2011

In Japan, antimicrobial agent therapy for patients with diarrhea due to enterovirulent organisms including enterohemorrhagic Escherichia coli (EHEC) is common, and norfloxacin (NFLX), fosfomycin, and kanamycin are recommended for EHEC treatment by the Japanese Ministry of Health and Welfare. The aim of this study was to analyze the effects of antimicrobial agents which have been used or recommended for the treatment of EHEC on the production of verotoxin (VT) in vitro. Subinhibitory concentrations of quinolones, NFLX, sparofloxacin (SPFX), and grepafloxacin (GPFX) markedly stimulated the productions of VT1 and VT2. The macrolide azithromycin (AZM), erythromycin (EM), and clarithromycin (CAM) did not stimulate the production of VT at a wide range of concentrations. These in vitro results indicate that when quinolones are prescribed for a patient infected with EHEC, the concentration of antimicrobial agents used in vivo and the susceptibility of the EHEC strains against quinolones should be taken into consideration.Key words: EHEC, O157:H7, verotoxin, quinolone, macrolide.
Combined effects of ethanol, high homogenization pressure, and temperature on cell fatty acid composition inSaccharomyces cerevisiae
Authors: Guerzoni Maria Elisabetta , Ferruzzi Marilena , Gardini Fausto , Lanciotti Rosalba
Published: April 2011

The specific aims of this research were to evaluate the combined effects of ethanol and high-pressure homogenization at different temperatures on cell viability in Saccharomyces cerevisiae and to study the induced modification of fatty acid composition. The decrease in viability was weak at 10°C while a homogenization pressure over 1000 bar (1 bar = 100 kPa) induced a significant reduction in viability when the cells were incubated at 20 and 30°C. The cell tolerance to pressure decreased with an increase in ethanol concentration and temperature. Ethanol, particularly intracellular ethanol accumulated by S. cerevisiae, played an important role in the response to homogenization pressure and in modification of the cell fatty acid composition. In fact, an unusually elevated accumulation of ethyl esters in lipid extracts of yeast cells subjected to high homogenization pressure, especially in the presence of exogenous ethanol and at 30°C, was observed. Moreover, only unsaturated and traces of short chain fatty acids were esterified with ethanol.Key words: Homogenization pressure, ethanol, fatty acids, Saccharomyces cerevisiae.
Influence of growth and environmental conditions on cell surface hydrophobicity ofPseudomonas fluorescensin non-specific adhesion
Authors: Jana T K , Srivastava A K , Csery K , Arora D K
Published: April 2011

The relative cell surface hydrophobicity (CSH) of 18 soil isolates of Pseudomonas fluorescens, determined by phase exclusion, hydrophobic interaction chromatography (HIC), electrostatic interaction chromatography (ESIC), and contact angle, revealed large degrees of variability. Variation in the adhesion efficiency to Macrophomina phaseolina of the hyphae/sclerotia of these isolates was also examined. Two such isolates with maximum (32.8%; isolate 12-94) and minimum (12%; isolate 30-94) CSH were selected for further study. Early- to mid-log exponential cells of these isolates were more hydrophobic than those in stationary phase, and the CSH of these isolates was also influenced by fluctuations in temperatures and pH. Isolate 12-94 exhibited high CSH (32.3%) at 30°C, compared to lower values (28-24%) in the higher temperature range (35-40°C). Increasing concentrations of either Zn2+, Fe3+, K+, and Mg2+in the growth medium were associated with the increased CSH. Trypsin, pepsin, and proteinase K (75 to 150 μg·mL-1) reduced the CSH of isolate 12-94 cells. CSH was reduced, following exposure to DTT, SDS, Triton X-100, or Tween 80. Prolonged exposure of cells to starvation (60 days) also caused a significant decline in CSH. Several protein bands (18, 21, 23, 26 kDa) of the outer cell membrane were absent in 60-day starved cells compared to unstarved cells. In conclusion, our findings demonstrate that CSH of P. fluorescens isolates may contribute to non-specific attachment/adhesion onto M. phaseolina hyphae/sclerotia, and the efficiency of adhesion is regulated by growth and other environmental conditions. Key words: adhesion, hydrophobicity, Pseudomonas fluorescens, Macrophomina phaseolina
Diversity in the yeast Cryptococcus albidus and related species as revealed by ribosomal DNA sequence analysis
Authors: Fonseca Álvaro , Scorzetti Gloria , Fell Jack W
Published: April 2011

Evidence accumulated from studies based on physiological, biochemical, and molecular characteristics has pointed to the heterogeneity of the ubiquitous anamorphic basidiomycetous yeast species Cryptococcus albidus (Saito) Skinner, with its current varieties and synonyms. The taxonomic status of this species has not been reappraised because different studies, mostly involving limited numbers of strains, have not been integrated. To assess species diversity within the clade containing Cryptococcus albidus and other phylogenetically related Cryptococcus and Filobasidium species, we determined ribosomal DNA (rDNA) sequences of 69 strains from the 5prime end of the 26S gene, D1/D2 region, and in some cases, the non-coding ITS2 region. Analysis of the sequence data together with available physiological, biochemical, and molecular characteristics, showed the segregation of C. albidus into at least 12 species, leading to the elevation of former varieties to the rank of species (C. aerius, C. diffluens), the reinstatement of synonyms (C. liquefaciens, C. terricola), and the proposal of new species (C. arrabidensis, C. chernovii, C. cylindricus, C. oeirensis, C. phenolicus, C. saitoi, C. uzbekistanensis, C. wieringae). The overall analyses of the results argue in favour of the use of rDNA sequence data to improve species delineation when integrated with other available physiological and molecular characteristics.Key words: basidiomycetous yeasts, taxonomy, Cryptococcus albidus, ribosomal DNA, molecular systematics.
Hydrocarbon-degrading filamentous fungi isolated from flare pit soils in northern and western Canada
Authors: April T M , Foght J M , Currah R S
Published: April 2011

Sixty-four species of filamentous fungi from five flare pits in northern and western Canada were tested for their ability to degrade crude oil using gas chromatographic analysis of residual hydrocarbons following incubation. Nine isolates were tested further using radiorespirometry to determine the extent of mineralization of model radiolabelled aliphatic and aromatic hydrocarbons dissolved in crude oil. Hydrocarbon biodegradation capability was observed in species representing six orders of the Ascomycota. Gas chromatography indicated that species capable of hydrocarbon degradation attacked compounds within the aliphatic fraction of crude oil, n-C12- n-C26; degradation of compounds within the aromatic fraction was not observed. Radiorespirometry, using n-[1-14C]hexadecane and [9-14C]phenanthrene, confirmed the gas chromatographic results and verified that aliphatic compounds were being mineralized, not simply transformed to intermediate metabolites. This study shows that filamentous fungi may play an integral role in the in situ biodegradation of aliphatic pollutants in flare pit soils.Key words: bioremediation, filamentous fungi, flare pits, hydrocarbon degradation, petroleum.
Chemical components and their locations in the Verticillium fungicola cell wall
Authors: Calonje M , Novaes-Ledieu M , Bernardo D , Ahrazem O , Mendoza C García
Published: April 2011

The chemical structure of cell walls and fractions of Verticillium fungicola, a pathogen of Agaricus bisporus, as well as their corresponding ultrastructures were studied. There are at least three chemically distinct types of carbohydrate polymers: one yielding mannose with lower amounts of galactose and glucose (glucogalactomannan), another one composed mainly of glucose (glucan), and a third one containing only N-acetylglucosamine (chitin). Attempts were made to locate these materials in situ by comparing electron micrographs of shadowed and sectioned cell walls, and also by indirect immunofluorescence. It was shown that none of these polymers constituted a completely physically distinct layer, but there seem to be different solubility properties in the outer, inner, and intermediate layers. It was also shown that fibrillar material (chitin) embedded in cementing glucan constituted the residual inner fraction of the original wall material. Indirect immunofluorescence showed the location of a significant amount of glucogalactomannan on the surface of the walls in which rodlet structures were visualized by electron microscopy.Key words: cell walls, polysaccharides, Verticillium fungicola.
Studies on the interactions of immunostimulated macrophages andYersinia enterocoliticaO:8
Authors: Ivanova E , Yanchev I , Najdenski H , Toshkova R , Dimitrova P , Manov V
Published: April 2011

Immunological and electron microscopy investigations of the phagocytic and killing activities of peritoneal macrophages from rats and mice against Yersinia enterocolitica serotype O:8 cells were performed. The effect of in vivo application of cytoplasmic membranes (CM) from the stable Escherichia coli WF+ L-form on macrophage activity was also studied. It was established that rat macrophages more actively phagocytosed the plasmidless pYV(-) Y. enterocolitica cells, compared to the plasmid-bearing pYV(+) Y. enterocolitica cells. The killing ability against both variants of the Y. enterocolitica strain was significantly enhanced in macrophages from CM-treated rats after 2 h, 4 h, and 24 h incubation. The CM treatment enhanced the phagocytic activity of the macrophages. The in vitro interaction of normal and immunostimulated rat macrophages with both pYV(+) and pYV(-) variants of Y. enterocolitica did not lead to any additional apoptotic and necrotic changes in macrophages compared to control macrophages, which were cultivated without Y. enterocolitica. Electron-microscopic investigation showed that mouse macrophages eliminated Y. enterocolitica pYV(+) cells in vivo after 24 h. No engulfed or digested bacterial cells were observed. Activation of cell surfaces and vacuolization of macrophage cytoplasm, both of CM-treated non-infected and infected mice, were observed. The experimental results showed that Y. enterocolitica pYV(+) cells could be eliminated by peritoneal macrophages.Key words: Yersinia enterocolitica, immunostimulation, electron microscopy, bacterial L-forms, macrophages.
Ribosomal DNA, species structure, and biogeography of the cactophilic yeastClavispora opuntiae
Authors: Lachance Marc-André , Starmer William T , Bowles Jane M , Phaff Herman J , Rosa Carlos A
Published: April 2011

The ribosomal DNA of the cactophilic yeast species Clavispora opuntiae was studied in order to clarify the global distribution of the yeast. Over 500 strains, including isolates from several new localities worldwide, were characterized by rDNA restriction mapping. An unusual restriction pattern previously encountered only in one strain, from Conception Island in the Bahamas, was found in several Brazilian isolates. Sequences of the D1/D2 and D7/D8 divergent domains of the large subunit (LSU) and of the intergenic spacers (IGS) confirmed that these strains represent a genetically distinct variety of Clavispora opuntiae. This divergence had previously been hypothesized on the basis of reduced genetic recombination in inter-varietal crosses and the presence of a polymorphic ApaI restriction site located in the LSU. The exact position of the ApaI site in the D8 divergent domain and the nature of the variation that it reveals were determined. The complete sequences of 12 intergenic spacers clarified the significance of the species-wide variation uncovered by restriction mapping. Most of the polymorphic sites occur in the IGS1 and IGS2 regions, on either side of the 5S gene, and the variation is largely due to differences in the numbers and the sequences of internal repeats. Two other polymorphic sites are located in the external transcribed spacer (ETS) region. The reliability of various sites as indicators of overall spacer sequence divergence differed from one case to another. Variety-specific probes were devised and used to screen 120 strains for the presence of recombinant rDNA spacers. Three strains gave ambiguous results, but these did not constitute evidence that inter-varietal recombination has taken place in nature. The hypothesis that the global movement of Clavispora opuntiae has been influenced by the worldwide biological control of prickly pear with Cactoblastis cactorum, a moth of Argentinian origin, has received additional support from the demonstration that Argentinian strains have rDNAs similar to those found where the moth has been introduced. A dramatic founder effect was identified in a yeast population collected in cacti (Maui, Hawaii) in a site where the moth had been recently introduced.Key words: Clavispora, ribosomal DNA, biogeography, speciation.
Ca2+fluxes in developingTrichoderma viridemycelium
Authors: imkovič Martin , Krytofová Svetlana , Varečka L'udovít
Published: April 2011

The properties of both Ca2+influx and efflux in the mycelium during the life cycle of Trichoderma viride were studied by means of45Ca2+and by X-ray fluorescence spectroscopy measurements. The properties of the45Ca2+influx and effluxes indicate that they are mediated by different transport systems. The Ca2+influx could be mediated by an electrogenic Ca2+/nH+antiport, or by an Ca2+uniport system. Both Ca2+influx and efflux were stimulated by the uncouplers (and the treatment leading to the suppression of energy metabolism) and by azalomycin F, an antifungal agent. Salicylate stimulated the Ca2+efflux, but inhibited the Ca2+influx. In the isolated preparation of crude vacuolar/mitochondrial fraction, salicylate induced the Ca2+release, as did A23187. Azalomycin F moderately released Ca2+from the microsomal fraction. On the other hand, uncouplers did not release Ca2+from the isolated organelles, but inhibited to a different extent the ATP-dependent and -independent Ca2+influx. The results could be explained in terms of the capacitative Ca2+influx mechanism. The rate of45Ca2+influx, or of the40Ca2+content, was maximal after about 30 h of submerged cultivation, and then decreased. The results show that loading of internal Ca2+stores occurs in the early stages of the development of mycelium only, and the Ca2+influx mechanism is developmentally down-regulated, being almost nonexistent during its later stages. In older mycelium, growth seems to be autonomous of the extracellular Ca2+until the onset of conidiation.Key words: Trichoderma viride, development, Ca2+influx, Ca2+efflux, salicylate, uncoupler, azalomycin F.
Oral immunization of mice with a glycoconjugate vaccine containing the O157 antigen ofEscherichia coliO157:H7 admixed with cholera toxin fails to elicit protection against subsequent colonization by the pathogen
Authors: Conlan J Wayne , KuoLee Rhonda , Webb Ann , Cox Andrew D , Perry Malcolm B
Published: April 2011

It has been postulated that a humoral immune response directed against the O157 antigen of Escherichia coli O157:H7, and expressed in the intestine, might afford protection from colonization and consequent infection by this enteric pathogen. The present study was conducted to determine whether such an immune response can be experimentally generated in mice. To this end, mice were orally immunized with a glycoconjugate vaccine consisting of horse serum albumin and the O157 polysaccharide admixed with the mucosal adjuvant, cholera toxin. Mice consistently developed robust local and systemic immune responses to the cholera toxin adjuvant, but were far from uniformly reactive to the test vaccine. Moreover, vaccinated mice were as susceptible to transient intestinal colonization following challenge with an isolate of E. coli O157:H7 as unvaccinated control mice. These results indicate that this vaccination approach is unlikely to be straightforward in target bovine or human hosts.Key words: Escherichia coli O157:H7, glycoconjugate vaccine, mucosal immunity, mice.
Plant growth-promoting bacteria that decrease heavy metal toxicity in plants
Authors: Burd Genrich I , Dixon D George , Glick Bernard R
Published: April 2011

Kluyvera ascorbata SUD165 and a siderophore-overproducing mutant of this bacterium, K. ascorbata SUD165/26, were used to inoculate tomato, canola, and Indian mustard seeds which were then grown in soil for 25-42 days in the presence of either nickel, lead, or zinc. The parameters that were monitored included plant wet and dry weight, protein and chlorophyll content in the plant leaves, and concentration of heavy metal in the plant roots and shoots. As indicated by a decrease in the measured values of these parameters, in all instances, plant growth was inhibited by the presence of the added metal. Both bacterial strains were effective, although not always to a statistically significant extent, at relieving a portion of the growth inhibition caused by the metals. In most cases, the siderophore overproducing mutant K. ascorbata 165/26 exerted a more pronounced effect on plant growth than did the wild-type bacterium K. ascorbata SUD165. The data suggest that the ability of these bacteria to protect plants against the inhibitory effects of high concentrations of nickel, lead, and zinc is related to the bacteria providing the plants with sufficient iron.Key words: phytoremediation, heavy metals, siderophores, Kluyvera ascorbata.
Characterization of high density monolayers of the biofilm bacteriumCaulobacter crescentus: Evaluating prospects for developing immobilized cell bioreactors
Authors: Smit John , Sherwood Christopher S , Turner Robin FB
Published: April 2011

Caulobacters are biofilm-forming members of the natural flora of soil and aquatic environments, which exhibit several characteristics that make them attractive for development of high surface area microbial bioreactors or biosensors. Although caulobacters are well characterized genetically, little is known about their biofilm-forming characteristics as a monoculture, or their tolerance of bioreactor-like conditions. Here we investigated the ability of caulobacters to spontaneously form high-density monolayers on artificial surfaces under a variety of environmental conditions, using phase contrast image analysis to assess biofilm density, and epifluorescence with the vital stain DiBAC(tm) to assess viability. With adequate nutrition, extremely dense monolayers formed within 24-48 h, and maintained near 100% viability in experiments ranging up to 22 days. When areas were abraded to remove cells, repopulation occurred rapidly with characteristics similar to the population of a clean surface. When established monolayers were starved for nutrients, a significant fraction of the cells detached from the surface, and cells remaining on the surface no longer tested as viable. Within 4-6 h of nutrient restoration, however, cells in the monolayer again appeared normal and tested as 100% viable. This is the first demonstration that Caulobacter crescentus is stable and amenable to high density monolayer growth and resists starvation, though some cells may express a programmed response to detach from the surface under severe nutrient limitation.Key words: Caulobacter crescentus, biofilm characterization, image analysis, phase contrast, epifluorescence, vital stains.
Climatic signal in annual growth variation of Norway spruce (Picea abies) along a transect from central Finland to the Arctic timberline
Authors: Mäkinen Harri , Nöjd Pekka , Mielikäinen Kari
Published: April 2011

Regional and temporal growth patterns of Norway spruce (Picea abies (L.) Karst.) were evaluated in 40 stands along a transect of over 500 km running from central Finland to the Arctic spruce timberline. Standard deviation of the ring-width series increased from south to north, but the geographical differences in mean sensitivity and first-order autocorrelation were small. The high degree of similarity in growth variation between stands indicated similar growth responses of trees to weather variation despite different environmental conditions along the transect. The most pronounced differences in the regional increment chronologies were found between the southernmost and northernmost stands. Growth variation was most strongly correlated with current June mean temperature, and correlation between growth and July temperature increased from south to north. In addition, negative correlation was observed between winter temperatures, particularly February temperature, and growth variation. Growth was more weakly correlated with precipitation than with temperature.
Elevated atmospheric CO2 and species mixture alter N acquisition of trees in stand microcosms
Authors: Friend Alexander L , Jifon John L , Berrang Paul C , Seiler John R , Mobley Juanita A
Published: April 2011

The potential for elevated atmospheric CO2 to increase forest growth depends on how it affects plant acquisition of soil nitrogen (N) in realistic competitive settings. We grew seedling microcosms in large (0.6-m2) boxes of forest soil placed outdoors in CO2-controlled open-top chambers. Loblolly pine (Pinus taeda L.) and sweetgum (Liquidambar styraciflua L.) were grown as single-species stands (monocultures) and as 50:50 pine:sweetgum mixtures, with a factorial combination of CO2 (ambient, twice ambient) and soil water (dry, moist) for two growing seasons. We added N, enriched with 15N, 2 months after planting and used N and 15N content of microcosm components to evaluate treatment effects. Under ambient CO2, species mixture decreased biomass and N accumulation of pine compared with pine in monoculture. Elevated CO2 partially to fully ameliorated this negative effect of species mixture for pine by increasing its biomass and N accumulation irrespective of competitive setting. Sweetgum biomass and N accumulation were improved in mixed culture (compared with monoculture) under moist conditions. However, only sweetgum biomass (not N) responded positively to increasing CO2. Our study suggests that increasing atmospheric CO2 concentration may provide a competitive advantage to pine growing in mixture with sweetgum in low fertility forest soils.
Recovery of15N-labelled nitrate applied to a small upland boreal forest catchment
Authors: Lamontagne Sébastien , Schiff Sherry L , Elgood Richard J
Published: April 2011

Nitrate labelled with15N was added for 2 years to a small Boreal Shield forested catchment to evaluate where new nitrogen (N) inputs are stored in this system in the short term. The landscape in the study catchment is a mosaic of Pinus banksiana Lamb. - Picea mariana (Mill.) BSP "forest islands" surrounded by "pillows" of lichens, mosses, and grasses on exposed bedrock surfaces. After the second year of N addition, 10% of the added15N was found in aboveground biomass, 27% in organic horizons, 6% in forest island mineral soil, 3% in "soil" underneath pillows, and 16% was lost through runoff. Despite covering a smaller proportion of the catchment and having only slightly larger N stocks, forest islands stored more15N (31%) than pillows (15%). Preferential routing of water towards forest islands and a greater potential for biotic and abiotic N immobilization are hypothesized to favor N retention in forest islands. Thirty-eight percent of the15N could not be accounted for. The comparison of a mass-balance analysis with the15N recovery suggests a missing sink for the15N in forest islands, possibly woody detritus. In the short term (~2 years), organic horizons are the main sinks for elevated N inputs in the boreal forest.
Climatic response ofCedrus deodaratree-ring parameters from two sites in the western Himalaya
Authors: Pant G B , Kumar K Rupa , Borgaonkar H P , Okada N , Fujiwara T , Yamashita K
Published: April 2011

Cores of Cedrus deodara D. Don from two different sites of western Himalaya were subjected to densitometric analysis to obtain data for earlywood, latewood, minimum, maximum, and mean densities and total ring width. Most of these variables show moderately high values of common variance and signal to noise ratio except latewood and maximum densities. These analyses suggest density parameters of this species may be useful in dendro climatic studies. Response function analyses indicate significant relationships between pre-monsoon (March-April-May) summer climate and earlywood density parameters, as well as total ring width. Based on the relationships derived from response function analyses, the potential of tree-ring chronologies from this species to provide reconstructions of the pre-monsoon climate in western Himalayan region has been established.
The importance of forest floor disturbance in the early regeneration patterns of the boreal forest of western and central Quebec: a wildfire versus logging comparison
Authors: Nguyen-Xuan Thuy , Bergeron Yves , Simard Dan , Fyles Jim W , Paré David
Published: April 2011

The nonvascular and vascular plant composition of the early regenerating vegetation present following wildfires and clear-cut logging has been compared separately in three areas of the black spruce (Picea mariana (Mill.) BSP) - feathermoss (Pleurozium schreberi (Brid.) Mitt.)) forest of western and central Quebec. In each area, a detrended correspondence analysis successfully differentiated the burned and logged stands along the first ordination axis. This separation mainly resulted from the greater abundance of pioneer species or lichens after fire and the greater abundance of residual species after clear-cutting. Spearman's correlation coefficients were calculated to relate variables characterizing physical disturbance of the forest floor and general site conditions to the two first differentiating axes. Variables characterizing forest floor disturbance severity were strongly associated with the first ordination axis in two of the study areas but not in the third one. The interpretation of compositional differences in the light of plant reproductive strategies led to the identification of regeneration patterns that illustrated the influence of disturbance type and severity on post-disturbance vegetation composition. These results suggest that certain forestry practices such as careful logging with the protection of regeneration and soil, scarification, and prescribed burning may differ in their capability to address sustainable forest management issues.
Understorey competition affects tree growth and fate of fertilizer-applied 15N in a Coastal British Columbia plantation forest: 6-year results
Authors: Chang Scott X , Preston Caroline M
Published: April 2011

Growth of planted seedlings in cutovers dominated by salal (Gaultheria shallon Pursh) is poor largely because of low N availability and understorey competition. In this paper, the response of tree growth and fertilizer recovery to understorey competition was studied. The trees were four years old when (15NH4)2SO4 (200 kg N/ha, 3.38004% enrichment) was applied in 1991 to single-tree plots, with either understorey removed from (treated) or left (control) in the plots. Half of the plots were either sampled after two (1992) or six (1996) growing seasons. Understorey competition continued to significantly reduce height and diameter growth between 1992 and 1996, except diameter growth for western redcedar (Thuja plicata Donn.). Nitrogen and 15N concentration in both tree and understorey components decreased from 1992 to 1996 and N concentration in 1-year-old foliage in 1996 (but not in 1992) was significantly lower in the control than in the treated plots, indicating that the site was low in N supply and the effect of fertilizer application on tissue N concentration did not last for 6 years. Results strongly indicated that the trees or understorey vegetation had no net uptake of fertilizer N beyond the second growing season. Understorey vegetation components played a significant role in the uptake and recycling of fertilizer N in this forest ecosystem.
An econometric analysis of output supply and input demand in the Canadian softwood lumber industry
Authors: Latta Gregory S , Adams Darius M
Published: April 2011

Few studies have examined the own-price elasticity of Canadian softwood lumber supply or output-adjusted factor demand elasticities over the past two decades, despite the utility of these measures in understanding producer response to tariffs, to market shifts (such as the decline in U.S. public harvest), and to changes in domestic forest policies. The present analysis employs a normalized, restricted quadratic profit function approach to estimate lumber supply and Marshallian factor demand elasticities for three Canadian regions. Results indicate that the lumber supply elasticity in the British Columbia coast region may be twice as large as that in the interior or eastern regions. Comparison of Hicksian factor demand elasticities with earlier studies suggests that the own price elasticity of labor demand may be two or more times larger than that for wood. Results also indicate differential time trends in Marshallian lumber output and wood demand elasticities across regions, rising in the British Columbia coast and falling elsewhere over the past two decades. Morishima elasticities of substitution from the present and past studies indicate that the wood for labor factor intensity is more sensitive to changes in labor price than is the labor for wood intensity to changes in wood price.
A retrospective early test ofPinus sylvestrisseedlings grown at wide and dense spacing
Authors: Jonsson Alena , Eriksson Gösta , Ye Zhi-hong , Yeh Francis C
Published: April 2011

Stored seeds from 30 open-pollinated families that had been field tested for 28 years provided a retrospective opportunity to assess the efficiency of early testing in Scots pine (Pinus sylvestris L.). Seedlings height at the end of first (HGP1), second (HGP2) and third growth period (HGP3), and in the third growth period, leader length (LEADER3), basal stem diameter (DIA3), number of stem units (NSU3), mean stem unit length (MSUL3), aboveground fresh weight (AGFWT3), stem dry weight (STDWT3), and shoot and needle dry weight (SHNDWT3) were studied under wide and dense spacing. Families differed at the 1 or 0.1% level of probability. Differences between spacing were significant at the 0.01% level of probability for all traits measured in the third growth period. Families interacted significantly with spacing for HGP2, HGP3, LEADER3, AGFWT3, SHNDWT3 and MSUL3. Interactions were due to rank changes and the interaction component of variance varied from 26 to 96% of the family variance. Estimates of hi2over wide and dense spacing ranged between 0.23 ± 0.11 (HGP2) and 0.51 ± 0.14 (NSU3). Spacing did not alter the variance structure, hi2for each trait under wide or dense spacing were similar. However, spacing affected the phytotron-field genetic correlations. The average of 80 genetic correlation estimates was 0.52 under wide spacing and 0.29 under dense spacing. Averaged over eight field traits, the efficiency of indirect juvenile selection for the field traits indirect-direct selection percentage ranged from -15% for NSU3 under dense spacing to 99% for HGP3 under wide spacing.
Distribution of foliar fungal endophytes of Pinus strobus between and within host trees
Authors: Deckert Ron J , Peterson R. Larry
Published: April 2011

The distribution of foliar fungal endophytes within and between needles and trees of Pinus strobus L. (white pine) is largely unknown. In this study, needles were collected in Muskoka, Ontario, plated, and scored for hyphal outgrowth of endophytes to observe distributional patterns. Individual trees displayed different levels of infection but branches within those trees had similar levels. There was a large difference in the infection levels between the two extant needle age-classes, with the youngest needles being virtually endophyte-free. Needles divided into four sections exhibited the most hyphal outgrowth from the distal portion and the least from the medial-proximal portion. Cultural morphotypes were primarily of the Lophodermium and Hormonema morphologies. Lophodermium occurred at all positions along the needle but Hormonema was restricted to the proximal and distal portions. Infrequently occurring fungi of diverse morphotypes were found at all four needle positions. A separate experiment compared levels of endophyte infection between Muskoka trees and trees growing in an urban area (Guelph, Ontario). Needle pieces from Guelph hosts had low rates of infection (0.02%) compared with needle pieces from Muskoka hosts (66.5%). Thus, for white pine, foliar endophyte distribution is patchy within and between needles, trees, and locations, possibly reflecting differences in microhabitat or infection success.
A simple technique to measure stem respiration using a horizontally oriented soil chamber
Authors: Xu Ming , DeBiase Terry A , Qi Ye
Published: April 2011

This paper introduces a simple technique, the horizontally oriented soil chamber (HOSC), to measure stem and branch respiration easily and accurately. We extend the function of the LI-6400-09 soil CO2 flux chamber by attaching a custom-built polyvinyl chloride (PVC) collar to the stem surface. For small trees and branches we use pipe bushings to connect the chamber to stem surface. Using this technique we measured stem respiration in a young ponderosa pine (Pinus ponderosa Dougl. ex Laws.) plantation in the Sierra Nevada Mountains near Georgetown, Calif., from June to December 1998. The diurnal and seasonal variations in respiration rate correlate well with the corresponding stem temperature variation. The Q10 values varied from 1.9 to 2.8, which are within the range of Q10 values (1.3-3.3) reported in previous studies. The range of our stem respiration results (3.5-7.2 µmol·m-2·s-1) compares favorably with previous studies on young ponderosa pine trees. This technique provides an alternative to measure stem respiration, which employs widely used, commercially available, portable respiration measurement equipment and requires almost no additional equipment, especially for current owners of LI-6400 systems. Thus, the HOSC technique is appropriate for examining spatial variation of stem respiration.
Effects of forest harvesting on soil methane fluxes in Florida slash pine plantations
Authors: Castro Mark S , Gholz Henry L , Clark Ken L , Steudler Paul A
Published: April 2011

We examined the effects of forest harvesting on the net exchange of methane (CH4) between the atmosphere and sandy soils in two mature slash pine (Pinus elliottii Engelm. var. elliottii) plantations in northern Florida. Before each of the stem-only harvests, soils in these plantations were net sinks for CH4 (-0.03 to -2.6 mg CH4·m-2·d-1) on all but one sampling date. On this one pre-harvest sampling date, soils in one plantation were net sources of CH4. This emission coincided with an average soil moisture content of 83% water filled pore space (WFPS), which was significantly greater than the average soil moisture contents (25-66% WFPS) for all pre-harvest sampling dates. After harvesting, soils in both plantations became net sources of CH4. Average emission rates from harvested soils ranged from 3 to 11 mg CH4·m-2·d-1. Harvested soils were net sources of CH4 for at least 1 year after the harvest. However, the duration of the post-harvest CH4 emission period was reduced by bedding the plantation soils, a typical post-harvest site preparation treatment. Bedded soils in harvested stands were either relatively small net CH4 sources (0.2 mg CH4·m-2·d-1) or net CH4 sinks (-0.4 mg CH4·m-2·d-1). Soil CH4 fluxes were highly correlated with soil moisture contents (r2 = 0.66 and 0.71; significant at p < 0.05), which were strongly influenced by climate and forest management practices. For example, soil moisture contents for one of our sites, averaged over the pre-harvest, post-harvest, and post-harvest-plus-bedding periods were 46, 68, and 38% WFPS, respectively. Our results suggest that increased soil moisture in southern pine plantations induced by either precipitation events or forest management changes the direction of the soil CH4 flux from sink to source.
Improved AFLP analysis of tree species
Authors: Cervera M T , Remington D , Frigerio J -M , Storme V , Ivens B , Boerjan W , Plomion C
Published: April 2011

Amplified fragment length polymorphism (AFLP) is a high-throughput, molecular-marker technique that is used increasingly in a variety of genetic analyses. Here, the conditions for carrying out AFLP analysis have been established for different tree species, including both angiosperm and gymnosperm trees, with genome sizes ranging from 0.54 to 38 pg DNA/2C. Specific parameters have been determined to provide informative and reproducible AFLP fingerprints of peach (Prunus persica L.), eucalypt, oak, poplar, and loblolly pine (Pinus taeda L.). Typically, 80-130 amplified DNA fragments (i.e., loci analyzed per primer combination) were obtained. Subsequently, these AFLP conditions were evaluated for intra- and inter-specific genetic variability studies as well as for genome mapping purposes of woody species. This work demonstrates that AFLP is a powerful tool in forest tree genetics.
Effects of clear-cutting on decomposition rates of litter and forest floor in forests of British Columbia
Authors: Prescott C E , Blevins L L , Staley C L
Published: April 2011

The rate of mass loss of three standard substrates (pine needle litter, aspen leaf litter, and forest floor material) was measured in forests and adjacent clearcuts at 21 sites throughout British Columbia, to test the hypotheses that (i) rates of mass loss are greater in clearcuts than in forests and (ii) clear-cutting would stimulate decomposition most in colder zones. Mass loss ranged from 53 to 75% after four years in pine needles, 49 to 70% after 3 years in aspen leaves, and 11 to 20% after 4 years in forest floor material. Mass loss from pine needles was significantly slower in clearcuts throughout the 4-year incubation. Aspen leaf litter and forest floor material lost mass at similar rates in forests and clearcuts. The effect of clear-cutting did not vary between relatively cold and warm sites. The effect of clear-cutting was not related to the size of the clearcuts, which ranged from 1 to 97 ha.
Estimation de la hauteur des peuplements forestiers par diffusiomètre radar
Authors: Martinez J M , Beaudoin A , Durand P , Toan T Le , Stach N
Published: April 2011

This paper presents the results of an analysis of radar airborne scatterometer data obtained over an Austrian black pine (Pinus nigra Arnold ssp. nigricans Host.) forest in Lozère, France. This system provides vertical sounding inside canopy from which can be derived tree height estimations. The objective of this paper is to analyse the validity of these measurements and, then, to study the interest of this kind of sensors for better forest management. The mean and top height estimations give very good results with a relative error of about 6%. The radar measures the back scatter coefficient of the vegetation from which can be estimated other parameters such as stem volume or basal area. The radar backscatter coefficient is found to be sensitive to the biomass in a low to intermediate range of values (0-200 m3/ha), particularly when the canopy backscattering is separated from the ground echo. The estimation of stem volume using a regression with both tree height estimations and backscatter measurements gives satisfying results. Finally, we discuss the interest of this kind of sensor data for an improved and detailed forest management giving an example of application on the evaluation of the variability of the local site index within a stand.
Susceptibility of Betula pendula clones to Phytobia betulae, a dipteran miner of birch stems
Authors: Ylioja Tiina , Roininen Heikki , Heinonen Jaakko , Rousi Matti
Published: April 2011

Larvae of Phytobia betulae Kangas (Diptera: Agromyzidae) mine within the differentiating xylem tissue of birch trees from canopy to stem base, resulting in permanent brown tunnels in the wood. In birch products the tunnels are considered to be an aesthetic defect. The aim of the study was to determine whether European white birch (Betula pendula Roth) clones differed in their susceptibility to Phytobia and to ascertain the relationship between the size of the trees and their susceptibility. We counted the number of pith flecks (larval tunnels) in eight or nine micropropagated clones of B. pendula in three 4- to 6-year-old field trials. After adjusting for the positive effect of tree size on Phytobia there were significant two- and three-fold differences between clones in Phytobia resistance. A significant genotype × environment interaction in susceptibility of birch to Phytobia was observed. A slow-growing clone was the least susceptible to Phytobia.
Evaluation of digital and film hemispherical photography and spherical densiometry for measuring forest light environments
Authors: Englund Sylvia R , O'Brien Joseph J , Clark David B
Published: April 2011

This study presents the results of a comparison of digital and film hemispherical photography as means of characterizing forest light environments and canopy openness. We also compared hemispherical photography to spherical densiometry. Our results showed that differences in digital image quality due to the loss of resolution that occurred when images were processed for computer analysis did not affect estimates of unweighted openness. Weighted openness and total site factor estimates were significantly higher in digital images compared with film photos. The differences between the two techniques might be a result of underexposure of the film images or differences in lens optical quality and field of view. We found densiometer measurements significantly increased in consistency with user practice and were correlated with total site factor and weighted-openness estimates derived from hemispherical photography. Digital photography was effective and more convenient and inexpensive than film cameras, but until the differences we observed are better explained, we recommend caution when comparisons are made between the two techniques. We also concluded that spherical densiometers effectively characterize forest light environments.