bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental and theoretical basis of Lamb waves and their applications in material sciences
Authors: Sadler J , Maev R Gr
Published: July 2007

The subject of Lamb waves contains a vast field of literature comprising many individual topics, with the current focus being the effective creation and use of Lamb waves in the fields of material characterization and nondestructive evaluation (NDE). This review chooses to focus on the more recent literature dealing with Lamb waves, giving introductions to a variety of topics. Because of the large amount of literature dealing with Lamb waves, many of the sections of this paper could themselves be expanded into their own literature review. This review begins with a brief introduction of Lamb waves comparing them to the acoustic bulk wave, and Rayleigh wave, and outlines the physics of a guided wave. It discusses the advantages of using guided waves, and theoretical techniques to model Lamb waves. In addition, the review discusses some of the various methods for the detection and creation of Lamb waves; techniques to detect, identify, and extract the mode from the acoustic signal; the use of Lamb waves in material characterization; flaw detection and flaw measurement; and finally examines the scattering of Lamb waves at plate ends and joints. While much of this work is experimentally based in nature, this review has attempted to also include theoretical work when possible.

PACS Nos.: 43.90.+v, 81.70.Cv
Creep of compacted recycled asphalt pavement
Authors: Viyanant Chirayus , Rathje Ellen M , Rauch Alan F
Published: July 2007

Recycled asphalt pavement (RAP) can be beneficially used as fill in the construction of earth structures such as embankments and retaining structures. Experiments were conducted to evaluate the creep response of compacted RAP under sustained deviatoric stresses. Constant stress, consolidated-drained triaxial tests were performed on 100 mm diameter, compacted RAP specimens at multiple confining stresses and deviator stress levels. The test data displayed classic creep behavior, with clearly identifiable primary and secondary creep observed in all specimens. Tertiary creep and creep rupture were observed in specimens tested at larger deviator stress levels. The creep response of RAP was significant at confining pressures less than about 272 kPa, while the creep response was less severe at larger confining pressures. Upper yield stress levels, representing the deviator stress levels below which creep rupture does not occur, were identified and shown to be confining stress dependent. In general, the creep potential of RAP is significant and should be considered in design. The developed creep models can be used to predict the time-dependent deformation of earth structures utilizing RAP backfill.Key words: creep, recycled asphalt pavement, time-dependent behavior, rupture.
Radical-mediated cyclization reactions leading to spiro and [6,6]-fused heterocycles
Authors: Majumdar K C , Debnath P , Pal A K , Chattopadhyay S K , Biswas A
Published: July 2007

Regiochemical study of nBu3SnH–AIBN-mediated aryl-radical cyclization of different 3-(2-bromophenyl sul fenylmethyl)coumarins, 3-(2-bromophenylsulfonyl-methyl)coumarins, and 6-[(2-bromophenoxy)methyl]-4-methoxypyran-2-ones have been investigated with the formation of different [6,6]-fused and spirocylic heterocycles. The sulfides and ethers were prepared from 3-chloromethyl coumarin and 6-(bromomethyl)-4-methoxy pyran-2-one with different 2-bromothiophenol and 2-bromophenols under classical alkylation condition. The corresponding sulfones were prepared by oxidation of the sulfides with m-CPBA.Key words: aryl-radical cyclization, coumarin and pyrone derivatives, 5-exo-trig, 5-endo-trig, nBu3SnH, sulfur heterocycles.
Iodine-promoted Prins-cyclization of ketones — A facile synthesis of spirocyclic-4-iodo-tetrahydropyrans and 5,6-dihydro-2H-pyrans
Authors: Yadav J S , Subba Reddy B V , Krishna V Hari , Swamy T , Narayana Kumar GG KS
Published: July 2007

Homoallylic and homopropargylic alcohols undergo smooth coupling with ketones in the presence of molecular iodine at ambient temperature to produce spirocyclic-4-iodotetrahydropyrans and 5,6-dihydro-2H-pyrans, respectively, in high yields in a short reaction time with high selectivity. The use of molecular iodine makes this procedure quite simple, more convenient, and cost-effective.Key words: Prins-cyclization, iodine, homopropargylic alcohol, spirocyclic-4-iodopyrans.
A solvent-free protocol for facile condensation of indoles with carbonyl compounds using silica chloride as a new, highly efficient, and mild catalyst
Authors: Hasaninejad Alireza , Zare Abdolkarim , Sharghi Hashem , Shekouhy Mohsen , Khalifeh Reza , Beni Alireza Salimi , Zare Ahmad Reza Moosavi
Published: July 2007

A simple and efficient solvent-free procedure for the preparation of bis(indolyl)methanes via electrophilic substitution reactions of indoles with aldehydes and ketones is described. The reactions took place in the presence of a catalytic amount of silica chloride at room temperature. The advantages of this method are high yields, short reaction times, low cost, and compliance with green-chemistry protocols.Key words: silica chloride, indole, carbonyl compound, solvent-free, bis(indolyl)methane.
Nematodes as a source of total coliforms in a distribution system
Authors: Locas Annie , Barbeau Benoit , Gauthier Vincent
Published: July 2007

In a distribution system of a large North American city, recurring total coliforms and atypical coliforms were detected at the exit (distribution pumps) of a storage reservoir. The presence of total coliforms and atypical coliforms was noted when the pumps were in operation and the water temperature was higher than 18 °C. The total coliform and atypical coliform concentrations at the volute pump casings ranged from 0 to 93.5 colony forming units (cfu)/100 mL. Significant concentrations of nematodes were also detected at this sampling location, averaging 12.0 nematodes/L in 2001 and 17.4 nematodes/L in 2002. The hypothesis that coliforms were released from the nematodes during their transit through the high-pressure pump was tested by recovering nematodes by filtering large volumes of water and grinding the nematodes in the laboratory, using various techniques. Total coliform and heterotrophic bacteria concentrations ranged from 0 to 27 cfu/nematode and 0 to 643 cfu/nematode, respectively. The origin of the nematodes was traced back to the sand filters located at the two water treatment plants. The importance of invertebrates in the distribution system should not be dismissed and the associated health risks, if any, should be assessed.
Site-directed mutagenesis studies to probe the role of specific residues in the external loop (L3) of OmpF and OmpC porins in susceptibility ofSerratia marcescensto antibiotics
Authors: Begic Sanela , Worobec Elizabeth A.
Published: July 2007

Serratia marcescens is a nosocomial bacterium with natural resistance to a broad spectrum of antibiotics, making treatment challenging. One factor contributing to this natural antibiotic resistance is reduced outer membrane permeability, controlled in part by OmpF and OmpC porin proteins. To investigate the direct role of these porins in the diffusion of antibiotics across the outer membrane, we have created an ompF–ompC porin-deficient strain of S. marcescens. A considerable similarity between the S. marcescens porins and those from other members of Enterobacteriaceae was detected by sequence alignment, with the exception of a change in a conserved region of the third external loop (L3) of the S. marcescens OmpC protein. Serratia marcescens OmpC has aspartic acid instead of glycine in position 112, methionine instead of aspartic acid in position 114, and glutamine in position 124, while in S. marcescens OmpF this is a glycine at position 124. To investigate the role of amino acid positions 112, 114, and 124 and how the observed changes within OmpC porin may play a part in pore permeability, 2 OmpC sites were altered in the Enterobacteriaceae consensus (D112G and M114D) through site-directed mutagenesis. Also, Q124G in OmpC, G124Q in OmpF, and double mutants of these amino acid residues were constructed. Antibiotic accumulation assays and minimal inhibitory concentrations of the strains harboring the mutated porins were performed, while liposome swelling experiments were performed on purified porins. Our results demonstrate that the amino acid at position 114 is not responsible for either antibiotic size or ionic selection, the amino acid at position 112 is responsible for size selection only, and position 124 is involved in both size and ionic selection.
Replacing the general energy-coupling proteins of the phospho-enol-pyruvate:sugar phosphotransferase system ofSalmonella typhimuriumwith fructose-inducible counterparts results in the inability to utilize nonphosphotransferase system sugars
Authors: Sutrina Sarah L. , Inniss Patricia I. , Lazarus Leslie-Ann , Inglis Lizette , Maximilien Jacqueline
Published: July 2007

A Salmonella typhimurium mutant lacking Enzyme I and HPr, general proteins of the phosphoenolpyruvate:sugar phosphotransferase system (PTS), but producing homologues EIFructoseand FPr constitutively, did not grow in minimal medium supplemented with non-PTS sugars (melibiose, glycerol, and maltose) in the absence of any trace of Luria–Bertani broth; adding cyclic AMP allowed growth. On melibiose, rapid growth began only when melibiose permease activity had reached a threshold level. Wild-type cultures reached this level within about 2 h, but the mutant only after a 12–14 h lag period, and then only when cyclic AMP had been added to the medium. On a mixture of melibiose and a PTS sugar, permease was undetectable in either the wild type or mutant until the PTS sugar had been exhausted. Permease then appeared, increasing with time, but in the mutant it never reached the threshold allowing rapid growth on melibiose unless cyclic AMP had been added. On rich medium supplemented with melibiose or glycerol, the mutant produced lower (30%) levels of melibiose permease or glycerol kinase compared with the wild type. We propose that poor phosphorylation of the regulatory protein Enzyme IIAGlucose, leading to constitutive inducer exclusion and catabolite repression in this strain, accounts for these results.
Occurrence of antibiotic-resistant bacteria and endotoxin associated with the land application of biosolids
Authors: Brooks J.P. , Maxwell S.L. , Rensing C. , Gerba C.P. , Pepper I.L.
Published: July 2007

The purpose of this study was to determine the prevalence of antibiotic-resistant bacteria and endotoxin in soil after land application of biosolids. Soil was collected over a 15 month period following land application of biosolids, and antibiotic resistance was ascertained using clinically relevant antibiotic concentrations. Ampicillin, cephalothin, ciprofloxacin, and tetracycline resistance were all monitored separately for any changes throughout the 15 month period. Endotoxin soil concentrations were monitored using commercially available endotoxin analysis reagents. Overall, land application of biosolids did not increase the percentage of antibiotic-resistant culturable bacteria above background soil levels. Likewise, land application of biosolids did not significantly increase the concentration of endotoxin in soil. This study determined and established a baseline understanding of the overall effect that land application of biosolids had on the land-applied field with respect to antibiotic-resistant bacterial and endotoxin soil densities.
Phosphate removal under denitrifying conditions byBrachymonassp. strain P12 andParacoccus denitrificansPP15
Authors: Shi Hoi-Ping , Lee Chi-Mei
Published: July 2007

In this study, we used the denitrifying phosphorus-removing bacterium Brachymonas sp. strain P12 to investigate the enhanced biologic phosphorus-removal (EBPR) mechanism involved with polyhydroxybutyrate (PHB), glycogen, and phosphorus uptake in the presence of acetate under anoxic or aerobic conditions. The results showed that excess acetate concentration and aerobic cultivation can enhance PHB formation efficiency and that PHB formation might be stimulated by glycogenolysis of the cellular glycogen. The efficiency of the uptake of anoxic phosphorus was greater when PHB production was lower. The EBPR mechanism of Brachymonas sp. strain P12 for PHB, phosphorus, and glycogen was similar to the conventional anaerobic–aerobic (or anaerobic–anoxic) EBPR models, but these models were developed under anoxic or aerobic conditions only, without an anaerobic stage. The anoxic or aerobic log phase of growth is divided into two main phases: the early log phase, in which acetate and glycogen are consumed to supply enough energy and reducing power for PHB formation and cell growth (phosphorus assimilation), and the late log phase, which ends the simultaneous degradation of PHB and remaining acetate for polyphosphate accumulation. Glycogenolysis plays a significant role in the alternate responses between PHB formation and phosphorus uptake under anoxic or aerobic conditions. After the application of the denitrifying phosphorus-removing bacterium Brachymonas sp. strain P12, aerobic cultivation increases the level of PHB production, and anoxic cultivation further increases phosphorus uptake.
Biology and taxonomy ofBacillus cereus,Bacillus anthracis, andBacillus thuringiensis
Authors: Vilas-Bôas G.T. , Peruca A.P.S. , Arantes O.M.N.
Published: July 2007

Three species of the Bacillus cereus group (Bacillus cereus, Bacillus anthracis , and Bacillus thuringiensis ) have a marked impact on human activity. Bacillus cereus and B. anthracis are important pathogens of mammals, including humans, and B. thuringiensis is extensively used in the biological control of insects. The microbiological, biochemical, and genetic characteristics of these three species are reviewed, together with a discussion of several genomic studies conducted on strains of B. cereus group. Using bacterial systematic concepts, we speculate that to understand the taxonomic relationship within this group of bacteria, special attention should be devoted also to the ecology and the population genetics of these species.
Cold-stress-altered phosphorylation of EF-Tu in the cyanobacterium Anabaena sp. strain PCC 7120
Authors: El-Fahmawi Bassam , Owttrim George W.
Published: July 2007

Growth of prokaryotes at reduced temperature results in the formation of a cold-adapted ribosome through association with de novo synthesized polypeptides. In vitro and in vivo phosphorylation studies combined with affinity purification and mass spectrometry identified that the phosphorylation status of translation elongation factor EF-Tu was altered in response to cold stress in the photosynthetic, Gram-negative cyanobacterium Anabaena sp. strain PCC 7120. In response to a temperature downshift from 30 to 20 °C, EF-Tu was rapidly and transiently hyperphosphorylated during the acclimation phase followed by a reduction in phosphorylation below background levels in response to prolonged exposure. EF-Tu was identified as a phosphothreonine protein. Unexpectedly, ribosomal protein S2 was also observed to be a phosphoprotein continuously phosphorylated during cold stress. The phosphorylation status of EF-Tu has previously been associated with translational regulation in other systems, with a reduction in translation elongation occurring in response to phosphorylation. These results provide evidence for a novel mechanism by which translation is initially downregulated in response to cold stress in Anabaena.
Virus occurrence in municipal groundwater sources in Quebec, Canada
Authors: Locas Annie , Barthe Christine , Barbeau Benoit , Carrière Annie , Payment Pierre
Published: July 2007

A 1 year study was undertaken on groundwater that was a source of drinking water in the province of Quebec, Canada. Twelve municipal wells (raw water) were sampled monthly during a 1 year period, for a total of 160 samples. Using historic data, the 12 sites were categorized into 3 groups: group A (no known contamination), group B (sporadically contaminated by total coliforms), and group C (historic and continuous contamination by total coliforms and (or) fecal coliforms). Bacterial indicators (total coliform, Escherichia coli , enteroccoci), viral indicators (somatic and male-specific coliphages), total culturable human enteric viruses, and noroviruses were analyzed at every sampling site. Total coliforms were the best indicator of microbial degradation, and coliform bacteria were always present at the same time as human enteric viruses. Two samples contained human enteric viruses but no fecal pollution indicators (E. coli, enterococci, or coliphages), suggesting the limited value of these microorganisms in predicting the presence of human enteric viruses in groundwater. Our results underline the value of historic data in assessing the vulnerability of a well on the basis of raw water quality and in detecting degradation of the source. This project allowed us to characterize the microbiologic and virologic quality of groundwater used as municipal drinking water sources in Quebec.
Development of 2 types of competitive enzyme-linked immunosorbent assay for detecting antibodies to the rinderpest virus using a monoclonal antibody for a specific region of the hemagglutinin protein
Authors: Khamehchian S. , Madani R. , Rasaee M.J. , Golchinfar F. , Kargar R.
Published: July 2007

A competitive enzyme-linked immunosorbent assay (C-ELISA) has been developed and standardized for the detection of antibodies to the rinderpest virus (RPV) in sera from cattle, sheep, and goats. The test is specific for rinderpest because it does not detect antibodies to peste-des-petits-ruminants virus (PPRV). The test depends on the ability of the monoclonal antibody (MAb) directed against the hemagglutinin (H) protein of RPV to compete with the binding of RPV antibodies in the positive serum to the H protein of this virus. This MAb recognized a region from amino acids 575 to 583 on the H protein of RPV that is unique to the RPV H protein and is not present on the hemagglutinin-neuraminidase protein of PPRV. Another C-ELISA (peptide C-ELISA) was set up using this specific region as an antigen. A threshold value of 64.4% inhibition was established for the RPV C-ELISA, with 90 known RPV-negative and 30 RPV-positive serum samples. Using common serum samples, a cutoff value of 43.0% inhibition for the peptide C-ELISA was established. Based on statistical analysis, the overall sensitivity and specificity of the RPV C-ELISA, relative to those of a commercial kit, were found to be 90.00% and 103.33%, respectively. However, the sensitivity and specificity of the peptide C-ELISA were found to be 180.00% and 73.33%, respectively. Although a common MAb in 2 new C-ELISA systems was used, variation in their percent inhibition, due to the use of different antigens, was observed. Taking into consideration the difference in percent inhibition of the 2 described assays and the commercial kit (50%), it was found that the RPV C-ELISA and the peptide C-ELISA are more specific and sensitive tools than the commercial kit for assessing herd immune status and for epidemiologic surveillance.
The effect of flavones and flavonols on colonization of tomato plants by arbuscular mycorrhizal fungi of the genera Gigaspora and Glomus
Authors: Scervino Jose M. , Ponce María A. , Erra-Bassells Rosa , Bompadre Josefina , Vierheilig Horst , Ocampo Juan A. , Godeas Alicia
Published: July 2007

No clear data are available on how flavonoids from different chemical groups affect root colonization by arbuscular mycorrhizal fungi (AMF) and whether flavonoids affecting the presymbiotic growth of AMF also affect root colonization by AMF. In the present work, we compared the effect of flavones (chrysin and luteolin) and flavonols (kaempferol, morin, isorhamnetin, and rutin) on root colonization (number of entry points and degree of root colonization) of tomato plants ( Lycopersicum esculentum L.) with the effect of these flavonoids on the presymbiotic growth of these AMF, which has been reported in a recent study. With all tested AMF ( Gigaspora rosea , Gigaspora margarita , Glomus mosseae, and Glomus intraradices) a correlation between the number of entry points and the percentage of root colonization was found. When the number of entry points was high, root colonization was also enhanced. Application of the flavones chrysin and luteolin and of the flavonol morin increased the number of entry points and the degree of colonization,whereas the flavonols kaempferol, isorhamnetin, and rutin showed no effect. These results show that in contrast to their effect on the presymbiotic growth of the AMF on the level of root colonization, the tested flavonoids do not exhibit a genus- and species-specificity. Moreover, comparison of our data with the data obtained by J.M. Scervino, M.A. Ponce, R. Erra-Bassells, H. Vierheilig, J.A. Ocampo, and A. Godeas. (2005a. J. Plant Interact. 15: 22–30) indicates that a positive effect on the hyphal growth of AMF does not necessarily result in an enhanced AM root colonization, further indicating that the mode of action of flavonoids at the level of root colonization is more complex.
Current and future uses of real-time polymerase chain reaction and microarrays in the study of intestinal microbiota, and probiotic use and effectiveness
Authors: Carey Christine M. , Kirk Jennifer L. , Ojha Shivani , Kostrzynska Magdalena
Published: July 2007

Probiotics are defined as live microorganisms that confer a health benefit to the host when administered in adequate amounts. In addition to human health benefits, probiotics can improve various aspects of growth and performance in livestock and poultry, as well as control undesirable microorganisms in food animals. Studies indicate that probiotics can prevent or treat certain conditions, including atopic disease in infants, food allergy, infection after surgery, acute diarrhea, and symptoms associated with irritable bowel syndrome. Understanding the complete mechanism, effectiveness, and potential use of probiotics is limited by the availability and sensitivity of current methods (i.e., culturing techniques). In recent years, real-time polymerase chain reaction (PCR) and microarrays have become prominent and promising methods to examine quantitative changes of specific members of the microbial community and the influence of probiotics on the structure and function of human and animal intestinal ecosystems. Culture-independent studies have established that only a fraction of organisms present in feces are cultivable, therefore, results obtained by cultivation are limited. Conversely, in-depth knowledge of microbial genomes has enabled real-time PCR and microarrays to be more sensitive and has resulted in precise methods for comprehensive analysis of the complex gut microbiota. Additionally, these technologies can assess the influence of intestinal microorganisms on host metabolism, nutrient status, and disease. This paper reviews method technologies and applications of real-time PCR and microarray assays as they relate to the effect and use of probiotics on the intestinal microbiota and gastrointestinal disease.
Cellular functions and transcriptional regulation of a third thioredoxin from Schizosaccharomyces pombe
Authors: Kim Su-Jung , Jung Eui-Man , Jung Hyun-Joo , Song Yun Seon , Park Eun-Hee , Lim Chang-Jin
Published: July 2007

The structural gene encoding a third thioredoxin (Trx) homologue, TRX3, of the fission yeast Schizosaccharomyces pombe was characterized and its regulation was studied. The determined DNA sequence encoded a putative 290 amino acid sequence of Trx with a molecular mass of 31 889 Da. The TRX3 mRNA level was increased in S. pombe cells harboring plasmid pTRX3, suggesting that the cloned TRX3 gene was functional. Yeast cultures harbouring plasmid pTRX3 exhibited shorter generation times and higher survival on solid minimal media plates incorporating mercury chloride (0.01 mmol/L) or hydrogen peroxide (1 mmol/L) compared with control cultures. Yeast cells containing extra copies of TRX3, but not TRX1 and TRX2, gave rise to lower reactive oxygen species levels than control cells. Oxidative stress owing to hydrogen peroxide and menadione enhanced the synthesis of β-galactosidase from the TRX3–lacZ fusion gene in Pap1-positive cells but not in Pap1-negative cells. The TRX3 mRNA level was increased by oxidative stress only in Pap1-positive cells. Basal expression of the TRX3 gene also depended on Pap1. We concluded that S. pombe TRX3 is linked with yeast growth and oxidative stress response, with its expression being regulated by oxidative stress in a Pap1-dependent manner.
3-Hydroxy fatty acids found in capsules of Cryptococcus neoformans
Authors: Sebolai Olihile M. , Pohl Carolina H. , Botes Piet J. , Strauss Catharina J. , van Wyk Pieter W.J. , Botha Alfred , Kock Johan L.F.
Published: July 2007

Using immunofluorescence confocal laser scanning microscopy, immunogold transmission electron microscopy and gas chromatography – mass spectrometry, we demonstrated the presence of 3-hydroxy fatty acids in Cryptococcus neoformans . Our results suggest that these oxylipins accumulate in capsules where they are released as hydrophobic droplets through tubular protuberances into the surrounding medium.
Isolation of bacterial endophytes from germinated maize kernels
Authors: Rijavec Tomaž , Lapanje Aleš , Dermastia Marina , Rupnik Maja
Published: July 2007

The germination of surface-sterilized maize kernels under aseptic conditions proved to be a suitable method for isolation of kernel-associated bacterial endophytes. Bacterial strains identified by partial 16S rRNA gene sequencing as Pantoea sp., Microbacterium sp., Frigoribacterium sp., Bacillus sp., Paenibacillus sp., and Sphingomonas sp. were isolated from kernels of 4 different maize cultivars. Genus Pantoea was associated with a specific maize cultivar. The kernels of this cultivar were often overgrown with the fungus Lecanicillium aphanocladii ; however, those exhibiting Pantoea growth were never colonized with it. Furthermore, the isolated bacterium strain inhibited fungal growth in vitro.
Complementary use of voting methods and interactive utility analysis in participatory strategic forest planning: experiences gained from western Finland
Authors: Pykäläinen Jouni , Hiltunen Veikko , Leskinen Pekka
Published: July 2007

This paper introduces the concept of complementary use of voting methods and interactive utility analysis (IUA) in strategic natural resource planning in western Finland as organized by Metsähallitus. The voting and IUA methods were used by three working groups, the aim in using these methods being to support the working groups in formulating their decision proposals for Metsähallitus. Ordinal preference information was collected by using the voting methods, whereas the IUA method defined the participants’ preferences by using the interval scale. In all the three working groups, four out of seven alternatives shared the first place in ranking when applying the voting methods, and one alternative was priorized over the other alternatives when using the IUA method. The stakeholders’ feedback indicated that the methods used were not too difficult to use and understand. The IUA method was especially efficient in promoting the participants’ learning process, which as a consequence made formulation of the decision proposal easier for them. It was also noticed that the standard versions of the voting methods do not necessarily fulfill the needs of decision support in strategic natural resource planning as such. Instead, complementary use with more profound methods (e.g., IUA) may be needed.
Genetic variation of growth rhythm traits in the limits of a latitudinal cline in Scots pine
Authors: Notivol E. , García-Gil M. R. , Alía R. , Savolainen O.
Published: July 2007

Scots pine ( Pinus sylvestris L.) has the widest distribution of pine species and the populations are locally adapted to very different environmental conditions. Adaptive traits such as those related to growth are optimal for understanding adaptation of populations to local conditions in widely distributed forest species. A study of the timing of growth during the first growing period of families in four populations from the latitudinal limits of the distribution range was conducted. Individual growth curves were fitted, and a set of variables related to growth rhythm and timing of budset was obtained for genetic analyses. Pooled heritabilities across populations were very high for most of the traits (0.43–1.09), and population differentiation for growth variables showed high values as well (QST= 0.19–0.71). Phenotypic correlations were higher than genetic ones, and most of them were positives. Even no general patterns of additive variances were found, the high additive genetic variance obtained (14% ± 8%, mean ± SE) suggests that additive genetic variance is not the limiting factor for adaptation to a new optimum within much of the range for these traits. Changes in means, additive genetic variances, and additive genetic coefficient of variation by population are also discussed.
The reduction of organic-layer depth by wildfire in the North American boreal forest and its effect on tree recruitment by seed
Authors: Greene David F. , Macdonald S. Ellen , Haeussler Sybille , Domenicano Susy , Noël Josée , Jayen Karelle , Charron Isabelle , Gauthier Sylvie , Hunt Simon , Gielau E. Trent , Bergeron Yves , Swift Lynn
Published: July 2007

We compared prefire and postfire organic-layer depths in boreal forest types (14 fires) across Canada, and examined tree recruitment as a function of depth. There was extensive within-stand variation in depth, much of it due to clustering of thinner organic layers around boles. There were no significant differences in postfire organic-layer depth among sites with different prefire forest species composition, but sites in the eastern boreal region had thicker postfire organic layers than those in the western boreal region. Mean organic-layer depth was much greater in intact stands than after fires; overall, fire reduced organic-layer depth by 60%, largely because of increases in the area of thin (<3 cm) organic layers (1% in intact stands vs. 40% in postfire stands). There was more variation in organic-layer depth within postfire than within prefire stands; notably, some areas in postfire stands were deeply combusted, while adjacent parts were only lightly combusted. We speculate that the diminished role of energy loss to latent heat around tree boles increased organic-layer consumption around tree boles. Seedlings were clustered around burned tree bases, where organic layers were thinner, and the dependence of a species on thin organic layers was an inverse function of seed size.
Effects of logging in the southern boreal peatlands of Manitoba, Canada
Authors: Locky David A. , Bayley Suzanne E.
Published: July 2007

To evaluate changes in surface water chemistry, peat, and the plant community in logged peatlands, we compared plots in 1–4 year old (class I) and 9–12 year old (class II) clearcuts with plots in wooded controls. Indicator species were significantly different between wooded and clear-cut plots but not between clear-cut plot age classes. Surface waters in class I clearcuts had significantly higher temperature and nutrients compared with controls, and this was attributed to warming of the soil, which resulted in faster decomposition and greater nutrient availability. Hummocks, important peatland plant microhabitats, were reduced in height in all clearcuts because of compaction and abrasion. These abiotic changes caused a shift in the plant community. Total plant diversity was approximately 30% higher on clearcuts and consisted primarily of herbs, particularly grasses. However, bryophyte and lichen diversity and cover was greatest in wooded controls. Picea mariana (Mill.) BSP regeneration was not compromised by clear-cutting and was greater in class II clearcuts. Greater diversity and cover of Salix species in class II clearcuts suggests stable shrub community formation, which may be persistent and may slow succession. The use of appropriate equipment to minimize site disturbances while the ground is frozen may reduce long-term shifts in the plant community.
Dendrochronological reconstruction of spruce budworm outbreaks in northern Maine, USA
Authors: Fraver Shawn , Seymour Robert S. , Speer James H. , White Alan S.
Published: July 2007

Using dendrochronological analyses, we reconstructed a 300 year history of eastern spruce budworm ( Choristoneura fumiferana (Clem.)) outbreaks in northern interior Maine. By analyzing radial growth patterns from the budworm host, red spruce ( Picea rubens Sarg.), and nonhost, northern white cedar ( Thuja occidentalis L.), we identified five outbreaks beginning ca. 1709, 1762, 1808, 1914, and 1976, all of which have been documented from eastern Canada. However, little or no evidence was found in our study for the 1830s, 1870s, or 1940s outbreaks also documented there. The mean outbreak return interval in our study (67 years) was roughly twice that postulated for eastern Canada. Differences in forest types, and associated stand dynamics, between the regions may explain the longer return intervals, and consequently the absence of these three outbreaks in Maine. Results also indicate that small, slow-growing trees exhibit a budworm signal very similar to that of overstory trees, once tree-ring series have been properly standardized.
Seed banks of an Arizona Pinus ponderosa landscape: responses to environmental gradients and fire cues
Authors: Abella Scott R. , Springer Judith D. , Covington W. Wallace
Published: July 2007

We measured soil seed banks in 102 plots within a 110 000 ha Arizona Pinus ponderosa landscape, determined seed-bank responses to fire cues and tree canopy types (open or densely treed patches), compared seed-bank composition among ecosystem types, and assessed the utility of seed banks for ecological restoration. Liquid smoke was associated with increased community-level emergence from seed banks in greenhouse experiments, whereas heating to 100 °C had minimal effect and charred P. ponderosa wood decreased emergence. We detected 103 species in seed-bank samples and 280 species in aboveground vegetation. Erigeron divergens was the commonest seed-bank species; with the exception of Gnaphalium exilifolium , species detected in seed banks also occurred above ground. Although a dry, sandy-textured black-cinder ecosystem exhibited the greatest seed density, seed-bank composition was more ecosystem-specific than was seed density. Native graminoids (e.g., Carex geophila and Muhlenbergia montana ) were common in seed banks, whereas perennial forbs were sparse, particularly under dense tree canopies. Our results suggest that (i) smoke may increase emergence from seed banks in these forests, (ii) seed banks can assist establishment of major graminoids but not forbs during ecological restoration, and (iii) seed-bank composition is partly ecosystem-specific across the landscape.
Integrated carbon analysis of forest management practices and wood substitution
Authors: Eriksson Erik , Gillespie Andrew R. , Gustavsson Leif , Langvall Ola , Olsson Mats , Sathre Roger , Stendahl Johan
Published: July 2007

The complex fluxes between standing and harvested carbon stocks, and the linkage between harvested biomass and fossil fuel substitution, call for a holistic, system-wide analysis in a life-cycle perspective to evaluate the impacts of forest management and forest product use on carbon balances. We have analysed the net carbon emission under alternative forest management strategies and product uses, considering the carbon fluxes and stocks associated with tree biomass, soils, and forest products. Simulations were made using three Norway spruce ( Picea abies (L.) Karst.) forest management regimes (traditional, intensive management, and intensive fertilization), three slash management practices (no removal, removal, and removal with stumps), two forest product uses (construction material and biofuel), and two reference fossil fuels (coal and natural gas). The greatest reduction of net carbon emission occurred when the forest was fertilized, slash and stumps were harvested, wood was used as construction material, and the reference fossil fuel was coal. The lowest reduction occurred with a traditional forest management, forest residues retained on site, and harvested biomass was used as biofuel to replace natural gas. Product use had the greatest impact on net carbon emission, whereas forest management regime, reference fossil fuel, and forest residue usage as biofuel were less significant.
Population and biomass dynamics of trees in a northern hardwood forest at Hubbard Brook
Authors: Siccama Thomas G. , Fahey Timothy J. , Johnson Chris E. , Sherry Thomas W. , Denny Ellen G. , Girdler E. Binney , Likens Gene E. , Schwarz Paul A.
Published: July 2007

We quantified the dynamics of the tree stratum at Hubbard Brook Experimental Forest (HBEF), New Hampshire, to examine why live biomass reached a plateau in about 1980. Total aboveground biomass increased from 209 Mg·ha–1 in 1981 to 216 Mg·ha–1 in 2001. From 1991 to 2001, in-growth of ≥10 cm diameter at breast height (DBH) trees averaged 4.7 trees·ha–1·year –1 with a corresponding in-growth biomass of 0.29 Mg·ha–1·year–1. Mortality of trees ≥10 cm DBH averaged 5.3 trees·ha–1·year–1 (1.12% of trees·year–1). Dying trees represented 2.24 Mg·ha–1·year–1 of aboveground biomass from 1991 to 2001. The biomass pools of standing dead, snags, and coarse woody debris in this forest currently are near steady state with residence times of 7.5, 15, and 6.2 years, respectively. The plateau in live biomass was mostly associated with lower wood production. Aboveground net primary productivity was estimated at 6.53 Mg·ha–1·year–1 (3.28 Mg·ha–1·year–1 for aboveground woody tissues and 3.25 Mg·ha–1·year–1 for leaf production), considerably lower than published estimates for the 1956–1965 period at the HBEF. Net ecosystem productivity in this young, second-growth forest is near zero, indicating that it may not be a sink for carbon.
La restauration passive des sapinières mixtes de seconde venue : une alternative pour la conservation des sapinières mixtes anciennes
Authors: Tremblay Junior A. , Bélanger Louis , Desponts Mireille , Brunet Geneviève
Published: July 2007

Les méthodes actuelles d’exploitation forestière tendent à diminuer la proportion de forêts anciennes et à fragmenter le paysage forestier, ce qui peut causer des inconvénients à certains groupes d’espèces associés à ces habitats. Pour pallier ce problème de conservation dans un paysage qui comporte peu de forêts anciennes, certains types de peuplements qui ont un bon potentiel de restauration écologique pourraient être considérés dans les stratégies de conservation. Dans cette étude, la structure et la biodiversité de sapinières mixtes de seconde venue qui ont subi une épidémie de tordeuse des bourgeons de l’épinette ( Choristoneura fumiferana (Clem.)), de 1974 à 1986, ont été analysées quant à leur ressemblance à celles de sapinières mixtes anciennes. Trois critères structuraux ont été analysés et deux groupes reconnus pour contenir des espèces indicatrices de forêts anciennes ont été retenus, soit les plantes invasculaires et champignons saprophytes et les oiseaux forestiers. Les sapinières mixtes de seconde venue présentent des caractéristiques structurales qui s’apparentent à celles des sapinières mixtes anciennes et comportent des espèces appartenant à des groupes indicateurs de forêts anciennes. Ainsi, les sapinières mixtes de seconde venue étudiées démontrent une résilience et possèdent un potentiel de restauration de forêts anciennes.
Concentrations of Ca and Mg in early stages of sapwood decay in red spruce, eastern hemlock, red maple, and paper birch
Authors: Smith Kevin T. , Shortle Walter C. , Jellison Jody , Connolly Jon , Schilling Jonathan
Published: July 2007

The decay of coarse woody debris is a key component in the formation of forest soil and in the biogeochemical cycles of Ca and Mg. We tracked changes in density and concentration of Ca and Mg in sapwood of red maple ( Acer rubrum L.), red spruce ( Picea rubens Sarg.), paper birch ( Betula papyrifera Marsh.), and eastern hemlock ( Tsuga canadensis (L.) Carr.) in Maine and New Hampshire. We repeatedly sampled 10 logs of each combination of tree species and location at the time of felling and at 2-year intervals for 6 years (birch and hemlock) or 8 years (spruce and maple). We found that density loss was essentially linear for the time period investigated, with birch and maple sapwood decaying at faster rates than spruce and hemlock. Repeated-measures analysis and regression modeling of log-transformed concentrations indicated a significant accumulation of Ca for sapwood of all tree species at both locations (30%–90% increase after 6–8 years of ground contact). Regression estimates of Mg concentration in spruce and maple declined about 20% during the 8 years of ground contact. There was no significant trend for Mg concentration in birch and hemlock. Variation in decay rates and trends in Ca and Mg concentration may be due to differences in sapwood quality, the community of wood decay fungi and associated organisms, or to abiotic conditions.
Comparing effective dispersal in expanding population ofPinus sylvestrisandPinus nigrain calcareous grassland
Authors: Debain Sandrine , Chadœuf Joël , Curt Thomas , Kunstler Georges , Lepart Jacques
Published: July 2007

Accurate predictions about plant invasions require estimation of demographic and dispersal parameters in low-density, expanding populations. We used inverse modelling on the spatial distribution of seedlings to estimate the effective reproductive rate and dispersal parameters in expanding populations of native Pinus sylvestris L. and non-native Pinus nigra Arnold in the Causse Méjean, southern France. The objective was to compare the ability of these two species to colonize these calcareous grasslands. Four empirical models of dispersal were compared. The mixed discrete dispersal kernels had the best fit (lower Aikake information criterion), whereas other candidate models underestimated the tail of the dispersal curve. However, the alternative functions performed quite similarly. The models showed clear differences between P. sylvestris and P. nigra, with the latter species having a higher net reproductive rate and higher effective dispersal. Our results based on the effective dispersal of seedlings over 4 years of age predict a faster spread rate for the non-native P. nigra compared with native P. sylvestris. Our results suggest that P. nigra may expand rapidly into the Causse Méjean grasslands in the forthcoming decades.
A shift in the gap dynamics of Betula alleghaniensis in response to single-tree selection
Authors: Webster Christopher R. , Jensen Nicholas R.
Published: July 2007

We investigated yellow birch ( Betula alleghaniensis Britt.) growth patterns and disturbance frequency before and after the advent of selection harvesting at the Ford Forestry Center in the Upper Peninsula of Michigan, USA, through the use of tree-ring analysis. Based on the boundary-line release detection procedure, 88% of the trees in our sample (n = 67) displayed evidence of at least one moderate or major release. Prior to active forest management, releases were infrequent, and trees that originated during that period had growth histories consistent with establishment after large-scale disturbances (i.e., large canopy gaps, >200 m2). Conversely, tree cohorts that recruited to the canopy more recently displayed a growth pattern suggestive of periodic small gap expansion. Given the declining representation of yellow birch in these forests, the latter strategy, although probably sufficient to prevent extirpation, is unlikely to ensure a sustainable and harvestable population of this and other midtolerants in managed uneven-aged forests. Our results highlight the importance of considering the cumulative influence of infrequent disturbances and chance events on the maintenance of tree species diversity.
Refining volume estimates of down woody debris
Authors: Fraver Shawn , Ringvall Anna , Jonsson Bengt Gunnar
Published: July 2007

Down woody debris (DWD) plays a vital role in forest ecosystem structure and function. Although volume is likely the most common metric used to characterize DWD, an evaluation of the formulae used for volume estimation on individual DWD pieces has received little attention. We determined actual volume of 155 diverse DWD pieces (types, species, lengths, and diameters) by detailed field measurements. By comparing the actual and calculated volumes from six commonly used formulae, we assessed their bias, precision, and accuracy. Based on observed DWD forms, we developed a new formula, namely the “conic−paraboloid”, which was included in the assessment. Among the formulae that require length and two end diameter measurements, the conic−paraboloid had the lowest bias, highest precision, and hence greatest accuracy. Newton’s and the centroid formulae had higher accuracy yet require more field measurements. Smalian’s, conical frustum, and average-of-ends formulae had poor performance relative to the others. Accuracy of all formulae decreased with increasing piece length. Thus, partitioning pieces into two, three, and four sections for additional measurement improved accuracy. As decay advances, pieces become progressively more elliptical in cross section. Using the cross-sectional area derived from only the long axis of the ellipse leads to substantial volume overestimates for well-decayed DWD.
Dead wood dynamics in declining balsam fir and spruce stands in New Brunswick, Canada
Authors: Taylor Sarah L. , MacLean David A.
Published: July 2007

Forest management prescriptions increasingly incorporate snag and downed dead wood (DDW) guidelines. This study utilizes permanent inventory plots to determine dead wood dynamics in 33 balsam fir ( Abies balsamea (L.) Mill.) – spruce ( Picea spp.) (BFSP) and 17 spruce – balsam fir (SPBF) stands in New Brunswick, Canada. Stands were declining, unmanaged, and had a history of recurrent spruce budworm ( Choristoneura fumiferana (Clem.)) outbreaks and aerial insecticide spraying. Fixed-area sampling matched remnants of 1165 dead trees and 864 corresponding pieces of DDW to plot trees that died over the last 15–18 years with known year and cause of death. Declining BFSP stands had the highest accumulation of dead wood (196 m3/ha) compared with SPBF and nondeclining BFSP (122 m3/ha and 77 m3/ha, respectively). Dead wood dynamics were influenced by cause of death, as a function of differences in tree height at death affecting snag decay, fragmentation, and fall. One-half of all dead trees never made a significant contribution to the snag population (25% uprooted and 25% stem breakage), and attrition resulted in only 50% of snags standing with a mean height of 6 m 15–20 years after death. This study will be of direct value to those managing or modeling dead wood dynamics in similar forests.