bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on the large subunit rRNA genes and their flanking regions of leuconostocs
Authors: Nour Mohamed
Published: April 2011

The 16S-23S (spacer-1) and 23S-5S (spacer-2) rRNA intergenic spacer regions of Leuconostoc lactis, Leuconostoc mesenteroides, Leuconostoc mesenteroides subsp. dextranicum, and Leuconostoc mesenteroides subsp. cremoris were amplified by polymerase chain reactions and sequenced. The 23S rRNA genes of Leuconostoc lactis, Leuconostoc mesenteroides, and Leuconostoc mesenteroides subsp. dextranicum were also sequenced. The RNase III-like and RNase E processing sites, as well as putative antitermination signals, were identified within the spacer regions. A single tRNAAla gene without the 3'-terminal CCA sequence was found in spacer-1 regions. Secondary structure models are proposed showing interactions between the two spacer regions of leuconostocs. For all strains studied, spacer-1 and spacer-2 were highly conserved and therefore could not be directly used for strain typing. Sequence information on 23S rRNA genes from Leuconostoc species allowed the determination of regions that can be used as targets for diagnostic probes and amplification primers. Secondary structures of variable helical elements of leuconostocs 23S rRNA were constructed and their primary structures were compared with those of several Gram-positive bacteria with low G+C contents. Comparative analysis revealed that restriction analysis of 23S rRNA variable regions appeared to be sufficient for the search for species-specific signatures. Our experimental observations revealed that one form of the rRNA operons was present in leuconostocs. We have also demonstrated the direct linkage between the three species of rRNA genes, which are organized as follows: 5'-16S rRNA - spacer-1 - tRNAAla - 23S rRNA - spacer-2 - 5S rRNA-3'.Key words: leuconostocs, rrn operons, rDNA, 23S, spacer regions, polymerase chain reaction.
The effects of differing concentrations of CO2 and O2 on the fermentative metabolism of the rumen fungi Neocallimastix patriciarum and Neocallimastix frontalis L2
Authors: Rees Elizabeth MR , Lloyd David , Williams Alan G
Published: April 2011

The effects of decreasing the concentration of CO2 and introducing up to 10% O2 into the headspace gases on the fermentative metabolism of the rumen fungi Neocallimastix patriciarum and Neocallimastix frontalis L2 were investigated. The relative proportion of metabolites produced by both fungi depended on the concentration of CO2 in the headspace. Under lowered CO2 levels, both fungi produced increased acetate, lactate, and H2, whereas the production of ethanol, formate, and (in the case of N. frontalis L2) succinate decreased. Lowered CO2 concentrations also decreased the rate of glucose utilization and cumulative gas production by both fungal isolates. In addition, decreased CO2 levels resulted in decreases in NAD(P)H ferredoxin oxidoreductase and hydrogenase activities, whereas malate dehydrogenase and pyruvate ferredoxin oxidoreductase activities were increased. Both N. patriciarum and N. frontalis L2 required at least 7% CO2 in the gas phase for growth. Both isolates also showed a degree of aerotolerance as they grew when exposed to 5% O2; they also grew in media lacking a reducing agent, providing that O2 was initially <1% of the total headspace concentration.Key words: rumen fungi, Neocallimastix, metabolism, carbon dioxide, oxygen.
The effect of growth conditions on in vitro adherence, invasion, and NAF expression by Proteus mirabilis 7570
Authors: Latta R K , Schur M J , Tolson D L , Altman E
Published: April 2011

Proteus mirabilis is a common cause of upper urinary tract infections. Fimbriae-mediated adherence of this organism to urinary tract epithelium and invasion of host cells are factors thought to be important in its pathogenesis. We have assessed the effect of growth in serum, blood, and urine on the ability of P. mirabilis 7570 to adhere to and invade in vitro the cell line EJ/28, derived from a human urinary tract tumour, and to express nonagglutinating fimbriae (NAF). Proteus mirabilis was capable of adhering to EJ/28 cells to varying degrees depending upon the growth conditions used. It was invasive under all conditions, except when grown in urine, and was found to be particularly so when serum or blood was present in the media. Expression of NAF occurred under all growth conditions examined and was limited only by a decrease in temperature.Key words: adhesion, invasion, nonagglutinating fimbriae, Proteus mirabilis.
Characterization of the expression and immunogenicity of the ns4b protein of human coronavirus 229E
Authors: Chagnon Fanny , Lamarre Alain , Lachance Claude , Krakowski Michelle , Owens Trevor , Laliberté Jean-François , Talbot Pierre J
Published: April 2011

Sequencing of complementary DNAs prepared from various coronaviruses has revealed open reading frames encoding putative proteins that are yet to be characterized and are so far only described as nonstructural (ns). As a first step in the elucidation of its function, we characterized the expression and immunogenicity of the ns4b gene product from strain 229E of human coronavirus (HCV-229E), a respiratory virus with a neurotropic potential. The gene was cloned and expressed in bacteria. A fusion protein of ns4b with maltose-binding protein was injected into rabbits to generate specific antibodies that were used to demonstrate the expression of ns4b in HCV-229E-infected cells using flow cytometry. Given a previously reported contiguous five amino acid shared region between ns4b and myelin basic protein, a purified recombinant histidine-tagged ns4b protein and (or) human myelin basic protein were injected into mice to evaluate whether myelin-viral protein cross-reactive antibody responses could be generated. Each immunogen induced specific but not cross-reactive antibodies. We conclude that ns4b is expressed in infected cells and is immunogenic, although this does not involve amino acids shared with a self protein, at least in the experimental conditions used.Key words: human coronavirus 229E, nonstructural protein, ns4b protein, expression, immunogenicity.
Monoclonal antibodies to 2,4-dichlorophenol hydroxylase as probes for the 2,4-D-degradative phenotype
Authors: Farhana Lulu , Fulthorpe Roberta R , Harbour Colin , New Peter B
Published: April 2011

Two different monoclonal antibodies (MAb) were raised against 2,4-dichlorophenol hydroxylase (DCP-hydroxylase) of Ralstonia eutropha JMP134 (pJP4), the second enzyme in the 2,4-D-degradative pathway of this bacterium. The utility of these antibodies in detecting and characterizing 2,4-D-degrading soil bacteria was investigated. One MAb (F6) reacted with DCP-hydroxylase from 27 out of 36 strains tested, while the other (MAb C3) reacted with only 17 isolates. When used with the colony blot technique, MAb F6 was useful for detecting cross-reacting strains on plates of pure cultures or of mixtures containing nondegraders even when 2,4-D degraders were outnumbered 60 to 1. 2,4-D-degrading strains could also be detected from plates spread with enrichment cultures but not from primary isolation plates spread from soil dilutions, presumably because the ratio of degraders to nondegraders was too low. Colonies of some strains that were very distantly related genetically, but produced functionally similar DCP-hydroxlase enzymes, were detected by MAb F6. This result suggests that MAbs could be useful for detecting functionally similar proteins expressed from tfdB analogs, even in the absence of detectable DNA homology between the genes encoding them.Key words: monoclonal antibody, 2,4-dichlorophenol hydroxylase, 2,4-dichlorophenoxyacetic acid, 2,4-D-degrading bacteria.
Localization of a phosphatidylglycerol/ phosphatidylinositol transfer protein in Aspergillus oryzae
Authors: Record Eric , Asther Michèle , Moukha Serge , Marion Didier , Burlat Vincent , Ruel Katia , Asther Marcel
Published: April 2011

The subcellular localization of the phosphatidylglycerol/phosphatidylinositol transfer protein (PG/PI-TP) of Aspergillus oryzae was investigated using Western blot analysis of the cell protein extracts, a cellular membrane fractionation technique, and transmission electron microscopy. The PG/PI-TP, as detected by Western blot analysis with a specific immune serum, was found to be mainly cytoplasmic and partly associated with intracellular membranes. A fractionation experiment was conducted after homogenization of the filamentous fungus mycelium. The endoplasmic reticulum, Golgi-like vesicles, and the plasma membrane were separated by isopycnic ultracentrifugation on a sucrose gradient, and our data revealed that the immunodetected PG/PI-TP was only associated with the Golgi-like apparatus. All these results were documented by electron microscopy and indicate here for the first time that there exists a specific phospholipid transfer protein in a filamentous fungus that is localized in the cytoplasm and associated with Golgi-like vesicles.Key words: phospholipid transfer protein, subcellular fractionation, ultrastructural localization, filamentous fungus, Aspergillus oryzae.
Evaluation of the oxolinic acid - esculin - azide medium for the isolation and enumeration of faecal streptococci in a routine monitoring programme for bathing waters
Authors: Figueras M J , Inza I , Polo F , Guarro J
Published: April 2011

m-Enterococcus agar (m-Ent) has been generally considered the reference medium for faecal streptococci in bathing waters. However, it shows several shortcomings, and therefore it is important to test newly developed media that can guarantee more precise results. In this sense, the recently described oxolinic acid - esculin - azide agar medium (OAA) and m-enterococccus agar (m-Ent) were comparatively evaluated for the detection of faecal streptococci from seawater and fresh water. The OAA medium showed a significantly higher relative recovery percentage and specificity for both types of water than m-Ent. A similar spectrum of species was recorded from both media, Enterococcus faecium being predominant in fresh water and Enterococcus faecalis, in seawater. The superior performance of the OAA medium in both types of bathing waters, added to the fact that it does not require the use of complementary confirmative tests, makes this medium an excellent candidate to be employed for monitoring programmes.Key words: faecal streptococci, water, monitoring, oxolinic acid - esculin - azide medium, m-enterococcus medium.
The growth-promoting effects of a bacterial endophyte on lodgepole pine are partially inhibited by the presence of other rhizobacteria
Authors: Bent Elizabeth , Chanway Christopher P
Published: April 2011

To test the hypothesis that rhizobacteria naturally present in soils may interfere with the extent of root colonization and plant growth promotion by plant growth-promoting rhizobacteria (PGPR), we studied two lodgepole pine PGPR (Bacillus polymyxa strains L6 and Pw-2) when inoculated singly and when coinoculated with a non-PGPR competitor (Curtobacterium flaccumfaciens PF322). Bacillus polymyxa Pw-2 and Curtobacterium flaccumfaciens PF322 were consistently found as endophytes, while Bacillus polymyxa L6 was never found within the root interior. Strains Pw-2 and L6 differed in the rate and type of growth promotion. Strain Pw-2 increased root growth (branching and elongation) and shoot biomass accumulation 6 and 9 weeks, respectively, after inoculation, while strain L6 increased primary root elongation and root biomass accumulation after 12 weeks. Seedlings coinoculated with Pw-2 and PF322 had decreased shoot biomass and primary root lengths when compared with seedlings inoculated only with Pw-2. This effect was not linked to a decrease in the population size of Pw-2 in the rhizosphere or in the root interior of coinoculated treatments. In contrast, strain L6-mediated growth promotion was not impaired by coinoculation with PF322. Strain L6 did interfere to some degree with the growth-promoting capability of strain Pw-2. These results indicate that endophytic PGPR may be less adapted to microbial competition than external root-colonizing PGPR, and that the efficacy of endophytic PGPR may be reduced by the presence of other bacteria on external or internal root tissues.Key words: PGPR, endophytes, colonization, coinoculation, competition.
Saccharomyces paradoxus and Saccharomyces cerevisiae are associated with exudates of North American oaks
Authors: Naumov Gennadi I , Naumova Elena S , Sniegowski Paul D
Published: April 2011

Genetic hybridization and karyotypic analyses revealed the biological species Saccharomyces paradoxus and Saccharomyces cerevisiae in exudates from North American oaks for the first time. In addition, two strains collected from elm flux and from Drosophila by Phaff in 1961 and 1952 were reidentified as S. paradoxus. Each strain studied showed a unique profile of chromosomal hybridization with a probe for the retrotransposable element Ty1. The wild distribution of natural Saccharomyces sensu stricto yeasts is discussed.Key words: genetical taxonomy, Saccharomyces paradoxus, oak exudates, Ty elements, electrophoretic karyotyping.
Analysis of bacteriophage inactivation and its attenuation by adsorption onto colloidal particles by batch agitation techniques
Authors: Rossi P , Aragno M
Published: April 2011

A batch agitation technique was designed to specify the different parameters that influence the inactivation and adsorption mechanisms of viruses in water. The advantage of this method over the classical procedures is that the kinetic reactions of the different subfractions of the virus population can be described simultaneously. A first set of experiments with phage T7 showed that this phage is rapidly inactivated in a constantly agitated liquid medium. This inactivation rate is highly influenced by temperature, but variation of the pH (from 5 to 9) and increase in salt concentration have no effect on it. The addition of colloidal clay particles (CCPs) of montmorillonite and attapulgite into the liquid medium considerably modifies this behavior, even at very low concentrations (0.025 mg/mL). The experiments show that the viruses react quickly with the particles and that bonding is not permanent. Viruses establish a dynamic equilibrium, which is strongly dependent on physicochemical parameters such as pH, ionic concentrations, and the presence of proteins or protein hydrolysates. A major environmental consequence is that the presence of CCPs seems to effectively protect the coliphage T7 from rapid inactivation.Key words: bacteriophage T7, viruses, inactivation and adsorption kinetics, colloidal particles, protective effect.
Evaluation of a microplate DNA - DNA hybridization method compared with the initial renaturation method
Authors: Goris Johan , Suzuki Ken-ichiro , Vos Paul De , Nakase Takashi , Kersters Karel
Published: April 2011

Previously reported hybridization data, obtained with the initial renaturation method (De Ley et al. 1970), were compared with data obtained with a microplate DNA - DNA hybridization method (Ezaki et al. 1989). The comparison was done for more than 82 hybridizations, within 4 sets of Bacillus/Virgibacillus, Myroides, Vibrio, and Xanthomonas/Stenotrophomonas strains, comprising DNA-base compositions ranging from 34 to 65%. Under the experimental conditions used, both methods were in very good correlation. With the microplate method, the variation between reciprocal hybridizations and repeated experiments was around 7%, while for the initial renaturation method, a 5% variation was calculated. It is concluded that the microplate method can be used as a reliable taxonomic tool.Key words: DNA, DNA hybridization, microplate method, initial renaturation method.
PKA from Saccharomyces cerevisiae can be activated by cyclic AMP and cyclic GMP
Authors: Cytrynska Malgorzata , Wojda Iwona , Frajnt Magdalena , Jakubowicz Teresa
Published: April 2011

Analysis of Saccharomyces cerevisiae genome revealed no sequence homologous to cyclic GMP (cGMP) dependent protein kinase from other organisms. Here we demonstrate that cyclic AMP (cAMP) dependent protein kinase purified from S. cerevisiae was almost equally activated by cAMP and cGMP at 3 × 10-6 M concentrations of either nucleotide in the presence of Mg2+ ions. Interestingly, if Mn2+ ions were used instead of Mg2+, cGMP was only 30% as effective as cAMP in the activation of cAMP-dependent protein kinase. Analogs of cAMP such as 8-chloro-cAMP and 3':5'-cyclic monophosphate of ribofuranosylbenzimidazole were as potent as cAMP in the enzyme activation, while N6,2'-O-dibutyryl-cAMP activated the enzyme to a lower extent. It was also found that yeast cAMP-dependent protein kinase can be activated by limited proteolytic digestion. The results presented were obtained with protamine and ribosomal protein S10 used as phosphorylation substrates.Key words: cAMP-dependent protein kinase, cAMP, cGMP, yeast, ribosomal protein S10.
Brewing spoilage lactobacilli detected using monoclonal antibodies to bacterial surface antigens
Authors: Whiting Michael S , Gares Sheryl L , Ingledew W M , Ziola Barry
Published: April 2011

A panel of thirteen monoclonal antibodies (Mabs) was assembled that reacts with surface antigens on eight of eleven Lactobacillus brewing spoilage organisms, including one or more of L. brevis, L. buchneri, L. casei-alactosus, L. plantarum, or unspeciated isolate(s). Immunoblotting was done to identify the antigens involved in Mab binding. Antigen stability in situ was tested by protease treatment and by surface antigen extraction of washed bacteria. Protease susceptibility of extracted surface antigens was also examined. In most cases, Lactobacillus surface antigens detected by the Mabs appear to be noncovalently bound proteins readily altered or removed from the bacterium by various environmental conditions. This research identifies brewing conditions that need to be tested to ascertain whether bacterial surface antigen-reactive Mabs can be used for the rapid, sensitive, and specific detection of Lactobacillus brewing spoilage organisms.Key words: brewing spoilage organism, immunoassay, Lactobacillus, monoclonal antibodies, surface antigens.
Sinuous stem growth in a Douglas-fir (Pseudotsuga menziesii) plantation: growth patterns and wood-quality effects
Authors: Spicer R , Gartner B L , Darbyshire R L
Published: April 2011

Stem sinuosity is thought to negatively impact wood quality, but no studies have characterized its vertical and radial effects on wood properties. Here we study wood quality along the entire stem in 25-year-old plantation-grown Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirb.) Franco) trees (32 trees total) that had been scored for sinuosity at age 12. We also study compression wood formation in the radial direction for one internode that had been scored for sinuosity at age 12 and subsequently produced 13 more annual rings. Trees with highly sinuous leaders at age 12 were more likely to be sinuous in other years, and developed more slope of grain defect (approximately 15% log volume) than less sinuous trees, but did not differ in the size of the pith-containing core. Leaders originally scored as highly sinuous developed more compression wood than control trees but only near the pith. Internode length did not differ among sinuosity classes. The size of the pith deviations (radial distance from centreline) remained constant up the stem despite a decline in internode length. However, the frequency of pith deviations was highest at 10-15 years, when internode length reached a peak. The relationship between temporal patterns of growth rate, sinuosity, and tree biomechanics deserves further attention.
Soil processes dominate the long-term response of forest net primary productivity to increased temperature and atmospheric CO2 concentration
Authors: Medlyn Belinda E , McMurtrie Ross E , Dewar Roderick C , Jeffreys Mark P
Published: April 2011

Predicting the responses of forest growth to elevated temperature (T) and atmospheric CO2 concentration ([CO2]) on decadal time scales presents a formidable challenge because of the many interacting processes involved. A key uncertainty concerns the relative importance of plant and soil processes to the overall long-term response. In this study, the plant-soil model G'DAY was used to simulate forest growth responses to T and [CO2] on different time scales for forests in cool and warm climates. An equilibrium-based graphical analysis was used to distinguish the roles played by plant and soil processes in determining the response. Doubled [CO2] caused a large initial increase (~20%) in net primary productivity (NPP), but this did not persist in the long term. By contrast, a 2°C increase in T caused a persistent long-term increase in NPP of approximately 10-15%. These responses were similar at cool and warm sites. The equilibrium analysis indicated that soil processes dominated the long-term responses predicted by the model. In particular, the predicted long-term increase in NPP under elevated T reflected an increase in predicted N mineralization and plant N uptake, assuming that a constant fraction of mineralized N is taken up by plants. The analysis highlights key uncertainties for future research.
Seed production of Pinus sylvestris after release cutting
Authors: Karlsson Christer
Published: April 2011

The effects of release cutting on cone, seed production, and seed quality were investigated in 1995-1996 among Scots pine (Pinus sylvestris L.) seed trees in central Sweden. The effects of diameter, height, crown length, and age of trees on cone production were also examined. Cone and seed production were about five times higher in seed trees that had been released for 4 or 5 years, compared with control trees in the unreleased forest. Seed trees released for less than 3 years had about the same level of cone production as the controls. After release, the number of cones increased more in the lower part of the tree crowns than in the uppermost 2 m. The mean 1000-seed weight, seed viability, and number of viable seeds per cone were not significantly different between released and unreleased trees. In 1996, there were about eight times more cones than in 1995, probably because summer temperatures were higher in 1994 than in 1993, the years when the respective flower buds were initiated. Within the investigated range of diameters, 250-430 mm at breast height, a 10-mm increase in diameter was correlated with a 10% increase in mean cone production. However, the variation in cone production between individual trees was considerable. Tree height, length of green crown, and tree age showed no significant correlations with cone production.
Reduction in branch sapwood hydraulic permeability as a factor limiting survival of lower branches of lodgepole pine
Authors: Protz Clark G , Silins Uldis , Lieffers Victor J
Published: April 2011

Branch sapwood hydraulic permeability, tracheid size, and earlywood to latewood ratio of annual rings were examined in lower and upper branches of closed-canopy and open-grown lodgepole pine (Pinus contorta Dougl. ex Loud.) trees. Hydraulic permeability, expressed on either a leaf area or sapwood area basis, was lower in lower branches (0.16 × 10-5 and 5.82 × 10-5 m2, respectively) than upper branches (0.26 × 10-5 and 10.47 × 10-5 m2, respectively) and was related to narrower tracheids in the sapwood of lower branches. Earlywood/latewood ratio declined in the lower branches of shaded trees. The hydraulic conductivity of upper and lower branches in closed canopy trees was reduced by drilling small holes radially through the stem. Stomatal conductance was lower, and after a growing season there was greater foliage mortality in drilled lower crown branches than in similarly treated upper branches, suggesting that the hydraulic conductivity of lower branches was closer to the lower limit required to maintain foliage than in upper branches. These data suggest that high foliage mortality and eventual death of lower branches does not occur solely because of low light but also from reduced stomatal conductance and photosynthesis resulting from shade-initiated reductions in earlywood, tracheid diameter, and branch hydraulic conductivity.
Partitioning of current photosynthate to different chemical fractions in leaves, stems, and roots of northern red oak seedlings during episodic growth
Authors: Dickson Richard E , Tomlinson Patricia T , Isebrands J G
Published: April 2011

The episodic or flushing growth habit of northern red oak (Quercus rubra L.) has a significant influence on carbon fixation, carbon transport from source leaves, and carbon allocation within the plant; however, the impact of episodic growth on carbon partitioning among chemical fractions is unknown. Median-flush leaves of the first and second flush were photosynthetically labeled with 14CO2, and partitioning of 14C into lipids and pigments, sugars, amino acids, organic acids, protein, starch, and structural carbohydrates of source leaves, stem, and roots was determined. In addition, four chemical fractions (sugars, starch, amino acids, and total structural carbohydrates) were quantitatively analyzed in leaves, stems, and roots. Chemical changes in source leaves reflected leaf maturation, changing sink demand during a growth cycle, and leaf senescence. Starch and sugar storage in leaves, stems, and roots during lag and bud growth stages indicate a feedback response of these tissues to decreasing sink strength and temporary storage of both starch and sugar in these plant tissues. Northern red oak, with episodic shoot growth patterns, provides an experimental system in which large changes in sink strength occur naturally and require no plant manipulation. Metabolic changes in leaf, stem, and root tissue of red oak have broad application for other oak species and for both temperate and tropical tree species with cyclic growth habits.
Effects of ontogeny and soil nutrient supply on production, allocation, and leaf area efficiency in loblolly and slash pine stands
Authors: Jokela Eric J , Martin Timothy A
Published: April 2011

The effects of ontogeny and soil nutrient supply on aboveground biomass accumulation, allocation, and stemwood growth efficiency of loblolly (Pinus taeda L.) and slash pine (Pinus elliottii Engelm. var. elliottii) were investigated in north-central Florida over 16 years using a 2 × 2 × 2 factorial experiment (species, fertilization, weed control). Aboveground biomass growth responses to the combined fertilizer and weed control treatments (FW) averaged ~2- and 2.8-fold for slash and loblolly pine, respectively. In the same treatment, annual needlefall (NF) production for slash pine approached a "steady state" of 6 Mg·ha-1 at ages 8-14 years, while loblolly pine NF production peaked at 7 Mg·ha-1 at age 10 years, and then declined 17% following curtailment of the fertilizer treatment. Periodic stemwood biomass increment (PAI) for the FW treatment for both species culminated at about 15 Mg·ha-1·year-1 at age 8 years and then declined rapidly (~275%) to <4 Mg·ha-1·year-1 at 15 years; reductions for the untreated control were considerably slower. The progressive decline in PAI following peak leaf area development was closely associated with a decrease in stemwood production per unit leaf area (growth efficiency). A unit increase in leaf area index in the 7- to 9-year-old stands produced about 3.0 and 3.1 times more stemwood biomass per year than in the 14- to 16-year-old stands for loblolly and slash pine, respectively.
Black spruce and vegetation response to chemical and mechanical site preparation on a boreal mixedwood site
Authors: Sutherland Brad , Foreman Fred F
Published: April 2011

The growth and development of outplanted black spruce (Picea mariana (Mill.) BSP) and competing vegetation five growing seasons after mechanical and chemical site preparation treatments are presented. The largest stem volume increase for black spruce coupled with the lowest vegetation indices for competing trees and shrubs were recorded on the treatment consisting of chemical site preparation with liquid hexazinone applied at 3.1 kg active ingredient (a.i.)·ha-1 followed by chemical tending in the second and fourth growing season with glyphosate applied at 1.78 kg a.i.·ha-1. Black spruce stem volume growth was second highest and the vegetation indices for competing trees and shrubs the highest, on plots treated with hexazinone site preparation. Among mechanical treatments, black spruce stem volume was highest on plots treated with mixed-mound site preparation. No other mechanical site-preparation treatment improved the growth of black spruce over boot-screef site preparation alone. The vegetation index of trembling aspen (Populus tremuloides Michx.) was reduced on mixed-mound and area-mixed site preparation treatments. The vegetation index of red raspberry (Rubus idaeus L.) was reduced on area-mix and area- and strip-screef treatments. By the fifth growing season, site-preparation treatment had little effect on the comparative growth of grasses and forbs. High-speed strip-mixing with 80 cm wide strips spaced at 2-m centres, on deep, fertile, silty loams of Site Region 3W-Lake Nipigon, does not appear feasible as an alternative to chemical site preparation or conventional manual and mechanical site preparation.
Forest ecotone response to climate change: sensitivity to temperature response functional forms
Authors: Loehle Craig
Published: April 2011

Past simulation studies using a variety of models have generally agreed that climatic warming could have adverse effects on forests, including large-scale diebacks in some regions and drastic range shrinkages of many species. These effects should be most evident at biome transition zones. Other studies have pointed out, however, that past models have used a parabolic temperature response function that is based on geographic range limits rather than functional responses or data and that this parabolic model could exaggerate dieback effects. A new model is proposed for growing degree-days temperature response, which is asymptotic rather than parabolic. In this new model, tree height growth rate increases and then levels off with increasing growing degree-days. Species from more southern regions have a higher asymptote. It is shown that this model can be derived from the integration of a parabolic growth response to temperature over a year-long sinusoidal temperature regime. The SORTIE forest simulation model was modified to incorporate this response function. An ecotonal region was simulated under a warming scenario. The traditional parabolic temperature response model produced a wide zone of dieback following warming. In contrast, the new asymptotic response function produced no dieback and a stable ecotone that migrated north at <100 m/100 years.
Soil pH-induced changes in root colonization, diversity, and reproduction of symbiotic arbuscular mycorrhizal fungi from healthy and declining maple forests
Authors: Coughlan Andrew P , Dalpé Yolande , Lapointe Line , Piché Yves
Published: April 2011

Acer saccharum Marsh. (sugar maple) is one of only few arbuscular mycorrhizal trees to form extensive stands in northern temperate biomes. Recent maple decline could result from altered intensity and quality of root colonization by associated mycobionts or possible shifts in symbiotic fungal community composition following environmental stresses. In this study the effects on arbuscular mycorrhizal fungi of soil acidification, one of several proposed causal stresses underlying forest decline, and remedial liming were investigated under glasshouse conditions. Acer saccharum seedlings were grown in unsterilized, pH altered, forest soils from healthy and declining maple stands. Over a range of treatment pHs normally tolerated by A. saccharum, fungal populations and responses to pH changes differed between the two soils. The declining site with more acidic soil had an initially larger spore population but lower taxonomic diversity than the healthy site. However, liming stimulated sporulation of several taxa initially apparently absent from the declining site spore population. The quantity of colonization generally increased with pH for both sites. Five Glomus taxa and Scutellospora calospora (Nicol. & Gerd.) Walker & Sanders are added to the list of fungi known to form arbuscular mycorrhizas with A. saccharum, and the known range of Acaulospora cavernata Blaszkowski is extended from Poland to eastern North America.
Geographic variation in growth, carbon isotope discrimination, and monoterpene composition in Pinus pinaster Ait. provenances
Authors: Tognetti Roberto , Michelozzi Marco , Lauteri Marco , Brugnoli Enrico , Giannini Raffaello
Published: April 2011

The geographic variation in monoterpene composition, growth, and carbon isotope discrimination (Δ) was assessed for trees of maritime pine, Pinus pinaster Ait., from five provenances (one Portuguese, Corsican, and Tuscan and two Sardinian: Telti and Limbara) grown on four different field sites in Sardinia island, Italy. Analysis of monoterpenes as biochemical markers revealed differentiation among the provenances and suggest four groupings, corresponding to the pooled Sardinian provenances (Telti and Limbara) and the other individually separated provenances. The five provenances exhibited statistically significant variation for height and diameter. Significant variation for growth parameters were also observed among the locations studied. The five provenances showed weak variations for Δ (range 17.1-17.5), while highly significant differences were observed amongst the four sites. A strong negative correlation was observed between mean tree height and mean Δ for the five provenances only at one site (the coolest and highest); the relationship was weak for the five seed sources at the other three locations. The Portuguese provenance that showed the highest potential for growth amongst the seed sources studied had a distinct terpene pattern and a tendency for lower Δ (higher WUE) than the other populations.
Variance and efficiency of the combined estimator in incomplete block designs of use in forest genetics: a numerical study
Authors: Villanueva Beatriz , Moro Javier
Published: April 2011

The efficiency of combined interblock-intrablock and intrablock analysis for the estimation of treatment contrasts in alpha designs is compared using Monte-Carlo simulation. The combined estimator considers treatments and replications as fixed effects and blocks as random effects, whereas the intrablock estimator considers treatments, replications, and blocks as fixed effects. The variances of the estimators are used as the criterion for comparison. The combined estimator yields more accurate estimates than the intrablock estimator when the ratio of the block to the error variance is small, especially for designs with the fewest degrees of freedom. The accuracy of both estimators is similar when the ratio of variances is large. The variance of the combined estimator is very close to that of the best linear unbiased estimator except for designs with small number of replicates and families or provenances. Approximations commonly used for the variance of the combined estimator when variances of the random effects are unknown are studied. The downward or negative bias in the estimates of the variance given by the standard approximation used in statistical packages is largest under the conditions in which the combined estimator is more efficient than the intrablock estimator. Estimates of the relative efficiency of combined estimators have an upward bias that can exceed 10% of the true value in small- and middle-sized designs with two or three replicates. In designs with four or more replicates, often used in forest genetics, the bias is negligible.
Cadmium variability in leaves of a Salix fragilis: simulation and implications for leaf sampling
Authors: Luyssaert S , Meirvenne M Van , Lust N
Published: April 2011

Plant analysis is a valuable tool to evaluate the pollution level. However, leaf sampling is complicated because of the high variability within the crown. To investigate the variability of cadmium (Cd) in the leaves of a tree, we sampled one Salix fragilis L. at 292 locations, each with a volume of 0.3 × 0.3 × 0.3 m. The Cd concentration was found to be normally distributed within a range from 2.4 to 10.6 mg·kg1 dry mass (DM), with an average of 6.3 mg·kg1 DM. A trend was found with high values in the lower parts of the crown and low Cd concentrations at the top. After removal of this trend the residuals showed a clear spatial structure modelled by a variogram. The Cd distribution in the leaves of the entire tree was predicted by sequential indicator simulation. These results were used to evaluate the current sampling strategy for tree leaves, i.e., sampling sun leaves of the upper third of the tree crown. The latter procedure was found to yield biased estimates of the average Cd concentration as well as the risk of exceeding a contamination threshold. An alternative sampling procedure is proposed. This procedure investigates whether a trend is present. Once the height where sampling will result in a correct statement of the tree's pollution is located, the rest of the stand could be sampled at this height.
A generalized logistic model of individual tree mortality for aspen, white spruce, and lodgepole pine in Alberta mixedwood forests
Authors: Yao Xiaohong , Titus Stephen J , MacDonald S Ellen
Published: April 2011

A generalized logistic model of individual tree mortality was developed for trembling aspen (Populus tremuloides Michx.), white spruce (Picea glauca (Moench) Voss), and lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) in Alberta boreal mixedwood forests based on an empirical data base of permanent sample plots. The model is suitable for observations from unequal remeasurement intervals. The maximum likelihood estimation was used to fit the model, the likelihood ratio test was combined with our understanding of mortality process to select the important variables, and the Hosmer-Lemeshow goodness-of-fit test was conducted to evaluate the fit. The fitted model predicts the survival probability of an individual tree based on the tree diameter at breast height, annual diameter increment, stand basal area, species composition, and site productivity.
Dendroclimatology of high-elevation Nothofagus pumilio forests at their northern distribution limit in the central Andes of Chile
Authors: Lara Antonio , Aravena Juan Carlos , Villalba Ricardo , Wolodarsky-Franke Alexia , Luckman Brian , Wilson Rob
Published: April 2011

Nothofagus pumilio (Poepp et Endl.) Krasser, is a deciduous tree species that grows in Chile and adjacent Argentina between 36 and 56°S, often forming the Andean tree line. This paper presents the first eight tree-ring chronologies from N. pumilio at its northern range limit in the central Andes of Chile (3639°S) and the first precipitation reconstruction for this region. Samples were taken from upper tree-line stands (15001700 m elevation) in three study areas: Vilches, Laguna del Laja, and Conguillío. Results indicate that, at the northern sites (Vilches and Laguna del Laja), the tree-ring growth of N. pumilio is positively correlated with late-spring and early summer precipitation and that higher temperatures reduce radial growth, probably because of an increase in evapotranspiration and decrease in water availability. At the southern Conguillío study area, radial growth was negatively correlated with late-spring and early summer precipitation. The presence of volcanic activity in this latter study area, which might have masked the climate signal, did not seem to have a significant influence on radial growth. A reconstruction of NovemberDecember (summer) precipitation for the period 18371996 from N. pumilio tree-ring chronologies accounted for 37% of instrumentally recorded precipitation variance. This is the first precipitation reconstruction from N. pumilio chronologies. Only temperature and snow cover have previously been reconstructed using this species. The reconstruction indicates that the driest and wettest 25-year periods within the past 160 years are 18901914 and 19171941, respectively.
Light attenuation by early successional plants of the boreal forest
Authors: Shropshire Christy , Wagner Robert G , Bell F Wayne , Swanton Clarence J
Published: April 2011

The influence of eight early successional plant species from the boreal forest on photosynthetically active radiation (PAR) were compared using a controlled plant competition study. Four woody (green alder, Alnus crispa (Ait.) Pursh; upland willow, Salix humilis Marsh.; white birch, Betula papyrifera Marsh.; wild red raspberry, Rubus idaeus L.) and four herbaceous (eastern bracken fern, Pteridium aquilinum L.; bluejoint grass, Calamagrostis canadensis Michx.; large-leaved aster, Aster macrophyllus L.; fireweed, Epilobium angustifolium L.) plant species were studied using an additive density experiment with jack pine (Pinus banksiana Lamb.) seedlings. The transmission of PAR through the plant canopies was measured using a line quantum sensor under six plant density treatments at the time of maximum canopy development each year. Four measures of plant abundance (planting density, actual density, projected leaf area index, and crown cover) were evaluated for their ability to predict PAR transmission through the plant canopies. Visual estimates of crown cover provided the best models each year. Vertical profiles of PAR transmission were used to compare the canopy structure among plant species and were used to refine the models. During the second growing season, increasing crown cover of bluejoint grass and large-leaved aster had the largest influence on PAR. In the third season, green alder, upland willow, and white birch (along with bluejoint grass and fireweed at the jack pine crown level) had the greatest influence on PAR. PAR measurements taken from a nearby forest for several of the plant species indicate that the models developed from our controlled experiment are reasonably applicable to naturally occurring plant populations.
Balsam fir (Abies balsamea) establishment dynamics during a spruce budworm (Choristoneura fumiferana) outbreak: an evaluation of the impact of aging techniques
Authors: Parent Sylvain , Morin Hubert , Messier Christian
Published: April 2011

The effects of recurrent spruce budworm (Choristoneura fumiferana (Clem.)) outbreaks on balsam fir (Abies balsamea (L.) Mill.) mortality have been extensively studied in Canada. Most studies report substantial seedling recruitment of balsam fir during outbreaks when reproductive trees are dying. According to previous research, this contradiction could be due to inaccuracies in the conventional aging method. Counting the maximum number of growth rings found at the tree base would significantly underestimate tree age. Counting terminal bud scars found on the entire trunk, including buried stem, would give a more accurate tree age. In this study, we compare recruitment dynamics obtained for aging seedlings in two balsam fir populations (about 500 km apart) using (i) the conventional method and (ii) bud scar counts. For both populations, the conventional method shows substantial recruitment during adult mortality, while the second aging technique reveals reduced recruitment during the epidemic phase of the spruce budworm outbreak.
Growth responses following nitrogen and NPKMg additions to previously N-fertilized Scots pine and Norway spruce stands on mineral soils in Sweden
Authors: Jacobson Staffan , Pettersson Folke
Published: April 2011

To study growth responses to refertilization, 12 Scots pine (Pinus sylvestris L.) and 6 Norway spruce (Picea abies (L.) Karst.) stands used in long-term nitrogen (N) fertilization experiments were refertilized with N, either alone or with various combinations and doses of phosphorus (P), potassium (K), and magnesium (Mg). Many of the experimental plots had previously been subjected to heavy N fertilization regimes over a period of 2030 years. On average, for all the experiments, the latest N addition resulted in a significant growth increase, corresponding to 57% of the mean annual volume increment and comparable with the response to the initial fertilization. Differences in growth response between fertilization with N alone or in combination with PKMg were in most cases insignificant for both tree species. Overall, the joint addition of PKMg resulted in a nonsignificant additional growth increase of 0.2 m3·ha1·year1, corresponding to 6% of the N fertilization effect. Repeated additions of N alone had no effect on the P, K, and Mg concentrations in current-year needles. It was concluded that the repeated N fertilizations did not cause any serious nutrient deficiencies.
Effect of decision variable definition and data aggregation on a search process applied to a single-tree simulator
Authors: Wikström Peder
Published: April 2011

This paper focuses on how computer execution times and net present value (NPV) are affected by different groupings of tree-selection harvest controls, different procedures to determine harvest timing, and tree data aggregation. The problems related to stand management are viewed as a hierarchy, where the main problem is determining harvest periods and the subordinate problem is determining what trees to cut in a given set of harvest periods. The solution technique is a derivative-free search process, and the objective is to maximize the NPV of harvest revenues for a stand over a given planning horizon. The tree-selection harvest controls are based on diameter and species groupings. The procedure to determine harvest timing is based on Tabu search and fixed cutting cycles, respectively. Sensitivity analysis is performed for a selection of stands in southern Sweden, where each stand is represented by a set of inventoried plots. Both even-aged and uneven-aged management are considered. Solutions improved with the number of decision variables. The Tabu search procedure proved very efficient at determining harvest periods for the even-aged problems. For the uneven-aged problems, fixed cutting cycles approximated the harvest timing problem, but at considerably shorter execution times. It is suggested that aggregated data be used for determining harvest timing, after which, using the original nonaggregated data, the tree-selection problem for a given set of harvest periods can be resolved.
Are forest floors in mid-rotation stands of loblolly pine (Pinus taeda) a sink for nitrogen and phosphorus?
Authors: Piatek Kathryn B , Allen H Lee
Published: April 2011

We examined decomposition and nutrient dynamics in fresh litter and net N mineralization in old litter to determine (i) if forest floor is a source of available nutrients in mid-rotation loblolly pine (Pinus taeda L.) stands and (ii) the effect of site preparation and vegetation control on forest floor nutrient dynamics. Four types of fresh litter were decomposed in situ in mesh bags: two containing only pine (differing by history of stand management) and two pinehardwood mixes (ratios 1:5 and 5:1). Litter bags were recovered every May and October for 26 months. Litter type, in particular the presence and amount of leaves, affected decomposition and nutrient dynamics in fresh litter. After 26 months, all fresh litters lost 55% of mass; decay rate constants were 0.43 (needles) to 0.60 year1 (leaves). Pine (1) and pine (2) and needles in mix 1:5 immobilized N. Almost all fresh litters also immobilized P. After 26 months of decay, N and P pools suggested an accumulation in the needles of 0.72.7 kg N·ha1 and 0.20.5 kg P·ha1 and mineralization of 1.13.7 kg N·ha1 in mix 5:1 needles and mix 1:5 leaves. All fresh litters mineralized K, Ca, and Mg. Old litter was incubated in situ in capped polyvinyl chloride containers from May to November. Monthly rates of net N mineralization in old litter were determined in KCl extracts of NH4+ and NO3. Net N mineralization in old litter was 0.751.5 kg N·ha1 per 6 months and was attributed to mineralization in mineral soil. We conclude that forest floors in these stands are not a source of available N or P. Instead, forest floors appear to be sinks for N and probably P.