bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatial distribution of tetrasporophytes and gametophytes in four Maritime populations of Chondrus crispus
Authors: Craigie J. S. , Pringle J. D.
Published: May 2008

Four commercially important populations of Chondrus crispus Stackhouse were studied to assess the distribution of lambda-carrageenan (tetrasporophytes) and kappa-carrageenan (gametophytes) producing plants. Populations from Rustico, North Lake, and Miminegash, Prince Edward Island, were 22.2, 22.8, and 31.2%, respectively, in the percentage of tetrasporophytes. The population at Toney River, Nova Scotia, consisted of 51.4% tetrasporophytes, significantly (P < 0.01) higher than the other three populations. In each of the four populations significantly (P < 0.05 or P < 0.01) more tetrasporophytes were observed in the outermost portions of the beds. When the data from all populations were pooled, the inner beds had 23.0% tetrasporophytes while the outer beds had 40.4% and thus differed significantly (P < 0.01). The possible reasons for these distributions are discussed.
Erratum: A revision of Corniculariella
Authors: DiCosmo Frank
Published: May 2008

I am grateful to Dr. L. K. Weresub of the Biosystematics Research Institute, Ottawa, for bringing an error which appeared in the nomenclator of Corniculariella on page 1666 to my attention. The correct synonymy should read as follows.Corniculariella Karsten char. emend. DiCosmo.≡ Cornularia Sacc. [cited as "Karsten"], Sylloge Fung. Vol. 3. p. 598(1884).= Chondropodium Höhnel, Mitt. Sber. Akad. Wiss. Wein, 125: 19(1916).Chondropodium is considered a facultative synonym of Corniculariella and not an obligate synonym.
Etude cytologique de l'embryon du Pin d'Alep lors de la germination : influence d'un traitement stimulant par administration successive d'ions mercure et chlore
Authors: Pargney J. C. , Thalouarn P.
Published: May 2008

Since it is known that successive applications of Hg2+ and Cl− ions accelerates Apel pine seeds germination, a cytological study of the treated embryo was made during the first 6 days of imbibition. In comparison with control seeds germinating on filter paper imbibed with distilled water, treated seeds show precocious mitoses and an acceleration of lipolysis and proteolysis as well as synthesis of organelles. These phenomena are particularly evident in the radicle. Since water uptake occurs especially in the radicular pole of the seed, this result suggests a determining role of imbibition in the process of germination in the Alep pine. No abnormal ultrastructures are observed in treated seeds.not available
Electron microscopy of susceptible and resistant near-isogenic (sr6/Sr6) lines of wheat infected by Puccinia graminis tritici. I. The host–pathogen interface in the compatible (sr6/P6) interaction
Authors: Harder D. E. , Rohringer R. , Samborski D. J. , Kim W. K. , Chong J.
Published: May 2008

Membrane associations in the interfacial zone between host cytoplasm and haustoria of wheat stem rust are reported. The invaginated host plasmalemma (IPL) adhered tightly to the haustorial neck wall above an indistinct zone at the base of the neck. There was extensive proliferation of host endoplasmic reticulum (ER) near haustoria during the formative growth stages of the haustoria. Most of the proliferation occurred along the neck from the neck ring region to the area at the base of the haustorial body where the extrahaustorial sheath became evident. Closely spaced arrays of ER occurred along the neck and radiated into the host cytoplasm. The ER was closely associated with the IPL in the vicinity of the neck wall, and at points of contact or near contact, the ER was ribosome free and stained more densely. There was luminal continuity between ER cisternae and the extrahaustorial sheath matrix. In the host cytoplasm adjacent to haustoria, ER-derived membranous complexes were found. These complexes consisted of a lattice arrangement of large tubules and small tubules, the latter containing a thread of denser staining material at their centers. The large tubules were bounded by lightly stained membranes, whereas the membranes of the small tubules stained more densely. These complexes were interconnected by rough ER to form networks in host cytoplasm. The complexes formed part of the interface between host and pathogen through connections with the invaginated host plasmalemma.
A new species of Psilophyton from the Lower Devonian of northern New Brunswick, Canada
Authors: Doran Jeffrey B.
Published: May 2008

A new spiny trimerophyte is described from early to middle Emsian (Lower Devonian) strata of Atholville, New Brunswick, Canada, where the specimens occur in a secondarily silicified tuff. Psilophyton crenulatum sp.nov. is characterized by vegetative branches which are 2 mm to 8.3 cm long, twice to seven times dichotomous and terminated by slender recurved tips. Some vegetative divisions are two closely spaced dichotomies (double dichotomies) which appear as trifurcations. The central axis of the trifurcation varies from about 1 mm to 2.5 cm in length. Fertile units terminate a dichotomous axis, and are alternate and distichous or are helically arranged. They are five to seven times dichotomous in three dimensions and consistently pendulous after the second or third dichotomy. These units are covered with crenulations on the first few orders of branching and terminate in sporangia 3–5 mm long by 1–2 mm wide. Sporangia are consistently twisted around each other. In situ spores are 48–102 μm in diameter and are compared with the dispersed spore genus Apiculiretusispora. Stomata are reported but an epidermis is usually lacking in most specimens. Spines are terete in cross section, multicellular, up to 6 mm long, and undivided, bifurcate, or trifurcate. Crenulations are semicircular to oval and 100–200 μm in diameter. Vascular strands up to 1 mm in diameter are centrarch with metaxylem tracheids that have scalariform- to circular-bordered pits. Psilophyton crenulatum represents the oldest known bonafide species of Psilophyton. A reconstruction is included along with a discussion on the evolution of megaphyllous leaves, the origin of adventitious roots, and branching similarities between P. crenulatum and younger ferns.
Lipid changes during the germination of teliospores of the common bunt fungus, Tilletia caries
Authors: Weber D. J. , Trione E. J.
Published: May 2008

The lipids in teliospores of Tilletia caries were analyzed at 12 different sample periods during the germination process. The lipid analysis included the separation and identification of hydrocarbons, natural methyl esters of fatty acids, and free fatty acids. Dormant spores contained more free fatty acids than natural methyl esters of fatty acids. However, 12 h after imbibition of water, the free fatty acid content was a small percentage of the total fatty acid content and the natural methyl esters were then the major lipid fraction, and they remained the major lipid fraction throughout germination. Stable isotope [2H] exchange experiments indicated that the methylation of the fatty acids was not an artifact of the extraction process. The role of natural methyl esters of fatty acid in the germination process is not clear.
Comparative metabolism of L-tyrosine and L-phenylalanine in tobacco plants in relation to the biosynthesis of phenylacetic acids
Authors: Camirand Anne , Phipps Jenny , Wightman Frank
Published: May 2008

The biosynthesis of phenyl and p-hydroxyphenyl substances in tobacco plants (Nicotiana tabacum var. Mammoth) was investigated by feeding solutions of L-[U-14C]phenylalanine or L-[U-14C]tyrosine to excised shoots for 24 h. Radioactive metabolites were extracted into acetone, fractionated into acidic and basic ether fractions, and then analysed by gas–liquid chromatography or by TLC followed by liquid scintillation spectrometry and gas–liquid chromatography. Results show that the 14C label was incorporated into several p-hydroxyphenyl substances in shoots supplied with [14C]tyrosine and into both phenyl and p-hydroxyphenyl substances in shoots supplied with [14C]phenylalanine. The radioactive metabolites identified from each 14C-labelled amino acid are homologous to many of the indole substances postulated to be intermediates in the conversion of L-tryptophan to the growth hormone indole-3-acetic acid, in tobacco and other higher plants. The present data suggest that in tobacco plants similar metabolic pathways exist for the conversion of all three aromatic amino acids to their corresponding arylacetic acids.
Quantification of leaf shape with a microcomputer and Fourier transform
Authors: Kincaid Dwight T. , Schneider Robert B.
Published: May 2008

Using a microcomputer, digitizing surface, and a Fourier transform, we present an automated, precise, and repeatable method to trace, quantify, and reconstruct the shape of flat leaves and reduce the information to a few coefficients. These coefficients can be analyzed statistically to reconstruct average leaves, to access symmetry, to measure leaf complexity, to develop leaf shape signatures, and to allow shape analysis to proceed independently of surface area. We provide guidelines for determining if leaves have statistically significantly different shapes.
Gametophytes of Ophioglossum engelmannii
Authors: Whittier Dean P.
Published: May 2008

Gametophytes of Ophioglossum engelmannii Prantl grow in axenic culture on a nutrient medium containing inorganic nutrients and sucrose. The dark-grown prothalli are long, white, cylindrical structures without rhizoids. The gametophyte has a meristem with a single apical cell. Antheridia, which are partially sunken, and archegonia, which have short necks, are interspersed along the gametophyte. The prothalli are endophyte free. Since the gametophytes of O. engelmannii are undescribed from nature, no comparisons can be made between gametophytes from culture and those from nature. However, gametophytes grown in axenic culture have a morphology which is normal for the genus.
The life history and ecology of the snow alga Chloromonas polyptera comb. nov. (Chlorophyta, Volvocales)
Authors: Hoham Ronald W. , Mullet John E. , Roemer Stephen C.
Published: May 2008

Snow algae previously designated as Carteria nivale, Scotiella polyptera, S. polyptera var. polimantii, and S. polyptera var. magellanica were found to be developmental stages of the zygote of Chloromonas polyptera comb. nov. Five species of Scotiella from snow have now been identified as zygotes of different specis of Chloromonas. In this life cycle, biflagellate vegetative cells, zoospores, gametes, and sexual reproduction are reported for the first time. The different forms of the zygote have been reported previously in the literature from several parts of the world, but have been misinterpreted as several distinct taxa of snow algae. The stages in the life cycle of Chloromonas polyptera occur in old, rapidly melting snowbanks, usually less than 30 cm deep. In the same snowbanks, zygotes of C. polyptera germinate later than those reported for Chloromonas nivalis, Chloromonas brevispina, and Chloromonas pichinchae indicating the occurrence of algal succession. Higher light intensity and a more saturated snowbank appear necessary for germination of zygotes of C. polyptera when compared with other species of Chloromonas found in snow. Low levels of carbon dioxide in snow may be limiting for growth of C. polyptera and vegetative cells are sensitive to increasing temperature as observed through laboratory observation. Freezing does not appear to initiate meiosis in the zygotes of C. polyptera as reported for other Volvocalean algae found in snow.
Modifications to callus culture characteristics and plastid differentiation by the formation of an albino callus of Lotus corniculatus
Authors: Swanson E. B. , Tomes D. T. , Hopkins W. G.
Published: May 2008

An achlorophyllous mutant callus (Leo 5u) arose spontaneously from a green callus genotype (Leo 5) of Lotus corniculatus L. (cv. Leo). The Leo 5u callus had no detectable plastid ribosomal RNA (rRNA) and ultrastructural analysis revealed no 70s ribosomes, and few thylakoids or plastoglobuli. The white callus growth was completely inhibited by adding exogenous cytokinins to the medium and any subsequent growth was from isolated green revertant islands in the white callus. Green plants were regenerated from these islands and produced fertile plants; however, subsequent regenerants have failed to flower. Reculturing of callus from Leo 5u plants produed a callus (Leo 5u(r)) similar in regeneration and growth rate to the original Leo 5. While the fresh weight growth rate of Leo 5u callus was faster than Leo 5 or Leo 5u(r), no difference in dry weights was observed. Amyloplasts have been maintained in the Leo 5u callus for over 3 years and have maintained their ability to form chloroplasts. It is hypothesized that the plastid genome is required solely for the differentiation of the plastid while the cell nucleus is responsible for initiating the division and compartmental maintenance of the plastid.
Restricted taxonomic value of leaf sections in Canadian narrow-leaved Festuca (Poaceae)
Authors: Aiken S. G. , Darbyshire S. J. , Lefkovitch L. P.
Published: May 2008

Diverse anatomical patterns observed in 18 narrow-leaved Festuca taxa are illustrated by composite block diagrams formed from a synthesis of at least 10 leaf cross sections from five plants chosen across the geographical range of each taxon; the terms used are described; and cross sections are illustrated using semithin leaf sections and block diagrams. Measurements on seven variables and notes on sclerenchyma patterns from the cross sections are presented in anatomical descriptions for 18 taxa (16 species and 2 infraspecies). Results of analyses of variance and deviance show that five of the seven variables have significant differences in mean values that coincide with the taxonomy. However, the range of values observed for each taxon was found to overlap with that of others so much that measuring these variables for an unknown plant would not always give a reliable identification to species, although it would reduce the possibilities.
Temporal variation of litter decomposition in relation to simulated soil climate. Long-term decomposition in a Scots pine forest. V
Authors: Jansson P.-E. , Berg B.
Published: May 2008

Decomposition of Scots pine needle litter was studied in a Scots pine forest in central Sweden. A 6-year series with annual incubations of needle litter was used to analyse the climatic influence on the process. The original litter was of similar chemical properties between years and each year new litter was incubated, in the same way, in the autumn. Sampling took place at time intervals ranging from 1 month to 1 year. Soil climate variables such as temperature and water contents and tensions were calculated with a soil water and heat model from standard meteorological data. Decomposition rates from periods longer than 145 days were correlated with different soil climatic factors. The responses for the 1st and 2nd incubation years were not significantly different, but higher coefficients of determination (r2) were found for the 2nd year. Estimated actual evapotranspiration or soil temperature explained temporal variation of decomposition to about 70%; soil water content only or soil water tension only explained 90%. When moisture and temperature were combined, 95 and 99% of the variation could be explained for the 1st and 2nd year, respectively. When time periods down to 1 month were included, very poor fits were found with the same climate response functions. However, the relationships were improved by an inertia function which indicated a time lag of 2–3 months between soil climate and the response in decomposition rate.
Changes in the weight and nutrient composition of litter fall in three forest ecosystem types on coastal British Columbia
Authors: deCatanzaro J. B. , Kimmins J. P.
Published: May 2008

Changes in weight and nutrient concentrations (N, P, K, Ca, Mg) of foliage and twig litter fall were measured over an 18-month period at three positions along a topographic sequence of ecosystem types. Conifer foliage confined in litter bags was found to lose weight at the same rate on all three sites: about 35% after 12 and 40% after 18 months. Confined broadleaf foliage decomposed at about the same rates on all sites, but unconfined samples decomposed significantly faster on the lower, hygric sites, probably as a result of greater fragmentation losses. Twig weight loss of conifers was extremely variable, ranging from 10 to 28% after 12 months. The total mass of K, Mg, and Ca decreased over the study period in all foliage litter, while N increased and P was variable. K tended to be more mobile on the hygric sites. Ca was found to be the most rapidly lost element in almost all cases. It was concluded that the observed similarity in weight loss of conifer foliage on all sites is partially due to a confinement effect and partially to a substrate chemistry effect. The nutrient data suggest that there may be some differences in decomposition processes on the lower, hygric sites compared with other ecosystem types. This agrees with the observation that the humus form in the hygric site is different (duff mull) from that on the other two sites (felty mor).
Anthocyanin pigmentation in seedlings of selected species of Phaseolus and Vigna (Fabaceae)
Authors: Nozzolillo Constance , McNeill John
Published: May 2008

Seedlings of 31 taxa of Phaseolus and Vigna were grown in light (cool-white fluorescent, 600 lx) at 20 °C under a 16-h photoperiod. Anthocyanin pigmentation was present in all 9 taxa (6 species) of Phaseolus and in 22 taxa (12 species) of Vigna. Pigmentation appeared in less than 1 week and was usually intense in Phaseolus seedlings. Most Vigna seedlings required a longer period to develop a paler color. Malvidin was the major aglycone in five of the species of Phaseolus examined, whereas delphinidin and cyanidin were major aglycones in three species of Vigna. Anthocyanins were located in the subepidermal layer of the stem and hypocotyl of all taxa except two, P. vulgaris cv. Royalty and P. coccineus, both of which had pigment in the epidermal layer instead. Three Vigna species, V. longifolia (subgenus Lasiopron) and V. adenantha and V. caracalla (subgenus Sigmoidotropis), also had pigment in cortical cells. Anthocyanoplasts were evident only in members of the subgenus Ceratotropis. Numerical analysis of the anthocyanin data placed Vigna longifolia in association with members of Vigna subgenus Vigna, but the two species of Vigna subgenus Sigmoidotropis associated closely with members of the genus Phaseolus. It is concluded that several aspects of seedling anthocyanin pigmentation, when present, can provide additional data useful to the taxonomy of the Phaseolus–Vigna complex. Characters of interest include speed of the photoresponse, tissue site of pigmentation, chemical nature of the pigments, and presence or absence of anthocyanoplasts.
Effect of aqueous leachates from polyvinyl chloride on seed germination and growth of various crop species
Authors: Sharma M. P.
Published: May 2008

Aqueous leachates obtained from soaking 0.5-cm2 pieces of flexible polyvinyl chloride (PVC) sheets in water for 1, 4, or 24 weeks and applied to various crops in sand culture exhibited no effect on seed germination but severely inhibited the growth, measured as fresh and dry weights of foliage, of all the crop species tested. In general, growth inhibition of various crops by PVC leachates of 4- and 24-week duration was significantly greater than that caused by the leachates of 1-week duration. There was, however, no significant difference in growth inhibition by PVC leachates of 4- and 24-week duration. Growth of broadleaved species, cucumber (Cucumis sativus L.), faba bean (Vicia faba L.), pea (Pisum sativum L.), sugar beet (Beta vulgaris L.), and tomato (Lycopersicum esculentum Mill.), was inhibited more than in the monocot species, com (Zea mays L.). Residues from PVC leachates persisted in sand and caused severe growth inhibition of all crop species tested for two subsequent plantings.
Field survival of sclerotia of Typhula incarnata and of T. ishikariensis biotype A
Authors: Matsumoto N. , Tajimi A.
Published: May 2008

Survivorship patterns of sclerotia of Typhula incarnata Lasch:Fr. and of T. ishikariensis S. Imai biotype A were compared under field conditions from May to November, using plastic containers with 10- or 250-μm mesh. Minute arthropods always existed in the 250 μm mesh containers, but the difference in mesh size did not affect the viability of sclerotia. Percent viable sclerotia of T. incarnata decreased from 86.0 to 24.2 for those placed on the soil surface, to 5.0% for those buried in soil 81 days after treatment, and then remained the same until the end of the experiment. Most of the T. ishikariensis biotype A sclerotia survived; however, in some containers buried in the soil, half to all of the sclerotia were dead. Several mycoparasites were isolated from both types of sclerotia. The possibility of biological control by reducing the number of sclerotia is discussed in relation to the difference in epidemiology of Typhula incarnata and T. ishikariensis biotype A.
Mitosis in the rice blast fungus and its possible implications for pathogenic variability
Authors: Row K. V. S. R. Kameswar , Aist J. R. , Crill J. P.
Published: May 2008

Mitosis in Pyricularia oryzae was reexamined, using both living and stained specimens. During prophase, the spindle pole body becomes quiescent and separates into two parts. The nucleolus disperses as chromosomes become visible. At metaphase, the spindle pole bodies are situated at the ends of the intranuclear spindle to which the chromosomes are attached at different points along its length. Anaphase A disjunction of chromatids is asynchronous; consequently, lagging chromosomes are typical. Anaphase B involves a marked elongation of the central spindle as first one incipient daughter nucleus and then the other migrates out of the original, intact nuclear envelope. During telophase, the central spindle and remainder of the nuclear envelope disappear, the chromatin returns to the dispersed state, and the nucleolus reappears. Contrary to earlier reports, mitosis in P. oryzae is virtually identical with that now known to be typical for other Ascomycetes, such as Ceratocystis and Nectria. The high frequency of pathogenic variability in P. oryzae could result from aneuploidy, and several mechanisms by which aneuploidy could arise are postulated.
Determination of urea and ammonia in leaf extracts: application to ureide metabolism
Authors: Shelp Barry J. , Sieciechowicz Konrad , Ireland Robert J. , Joy Kenneth W.
Published: May 2008

Methods are described for the routine determination of urea and ammonia in plant tissues. Ureido compounds such as allantoin and allantoate interfere with the urea assay but can be conveniently removed by ion-exchange chromatography prior to the color reaction with α-isonitrosopropiophenone. This assay was used to examine the effect of the urease inhibitor acetohydroxamate on leaf urea levels. A survey of methods for ammonia determination showed that for plant extracts and assay mixtures containing amides, microdiffusion followed by nesslerization provided a convenient and reliable technique. This procedure was used to determine asparaginase and glutaminase activities as well as ammonia levels in leaf tissue. In a study of detached soybean leaves, 5 mM acetohydroxamate, supplied via the transpiration stream, inhibited the production of ammonia normally observed in the presence of methionine sulfoximine (a glutamine synthetase inhibitor) and caused an accumulation of urea. The data were interpreted as evidence that leaf ammonia can arise from urea metabolism and supported a role for urea, probably derived from ureide breakdown, in the provision of nitrogen for amino acid and protein synthesis.
Sir Charles Edward Saunders, Dominion Cerealist
Authors: Morrison Malcolm J.
Published: May 2008

Charles Edward Saunders was born in London, Ontario, in 1867. His father, Sir William Saunders, was the first director of the Dominion Experimental Farms (1886–1911). Charles received his B.A. with honours in science from the University of Toronto in 1888 and his Ph.D. in chemistry from Johns Hopkins University in Baltimore, Maryland, in 1891. He attempted a career in music, his first love, from 1893 to 1902. With his father, Charles attended the 1902 International Conference on Plant Breeding and Hybridization in New York, where he learned of Mendel’s theories of inheritance and their applicability to plant breeding. When he began work in 1903 in the Division of Cereal Breeding and Experimentation at the Central Experimental Farm in Ottawa, he used the knowledge he had gained at that conference. It was Charles’s goal to achieve “fixity” in the varieties that had been bred and released using phenotypic mass selection, prior to his tenure as Cerealist. He selected four heads from the wheat variety Markham and in the winter of 1904 he performed a “chewing test” to select for gluten elasticity and colour. Seeds from two heads were chosen, and seeds from one went on to produce the variety Marquis after extensive yield trials on the Prairies. Marquis was 7 to 10 days earlier than Red Fife, the standard bread wheat of the Prairies. The earliness and tremendous yield of Marquis wheat resulted in the rapid and successful settlement of the Great Plains and countless billions of dollars in revenue to Canada. By 1923, 90% of the spring wheat in Canada and 70% in the USA was Marquis. Charles continued as Dominion Cerealist until his retirement in 1922. He was knighted in 1934, and died in 1937.
Operating speed models for two-lane rural roads in Pakistan
Authors: Memon Rizwan A. , Khaskheli G. B. , Qureshi A. Sami
Published: May 2008

One of the suitable techniques used to improve safety on roads is to check the consistency of geometric design. The concept of design consistency has emerged worldwide, but no research has been found to date on design consistency in Pakistan. The most common parameter for the evaluation of design consistency is operating speed. Several models have been developed to predict operating speed on two-lane rural roads. However, these models were based on spot speed data collected through traditional speed measuring devices. This study uses continuous speed profile data collected using a vehicle equipped with a VBox (a global positioning system based device). Eleven test sections were selected in two provinces of Pakistan (i.e., Sindh and Balochistan). Driver behavior is also studied in the present research. Models were developed for prediction of operating speed on horizontal curves and on tangents. Validation of the developed models shows compatibility with the experimental data; hence, the developed speed prediction models can be used to evaluate the geometric design consistency of two-lane rural roads in Pakistan.
Initial assessment of bridge backwater using an artificial neural network approach
Authors: Cobaner Murat , Seckin Galip , Kisi Ozgur
Published: May 2008

The assessment of backwater resulting from extra energy losses on flood flows caused by bridge constrictions is of vital interest in hydraulic engineering due to its importance in the design of waterways and management of flooding. Although many detailed methods for estimating bridge backwater have been developed, an initial estimate of the magnitude of bridge backwater using a practical model, such as the multiple linear regression (MLR) technique, has a crucial importance for rapid evaluation of flood damages upstream of the bridge structure. In the current study, first, two artificial neural network (ANN) models using the same amount of input data as that of an MLR approach were developed, and then the ability of these ANN models versus the MLR models was investigated for the initial assessment of bridge backwater, both models having been based on the comprehensive laboratory data of the Hydraulic Research Wallingford in UK. The comparison of the results by the MLR and the ANN approaches revealed that the ANN model gave better predictions than those of the MLR model when applied to these laboratory data. United States Geological Survey (USGS) field data were also used for the validation and comparison of these methods. The results showed that ANN approaches yielded more accurate results than those of the MLR models when applied to these field data including actual flood profiles through many bridges.
Effect of styrene–butadiene–styrene content on the adhesion properties of bitumen before and after heat aging
Authors: Zieliński Krzysztof
Published: May 2008

This article describes the effect of heat aging and styrene–butadiene–styrene (SBS) content in bitumen on the adhesion properties of mastics (bitumen-filler mix) to concrete and steel substrates. Test results showed that the adhesion strength of bituminous mastics to concrete and steel substrates decreased as the SBS content increased. Bitumen types modified with 9%–12% of SBS, commonly used in waterproofing materials, showed an approximately three times weaker bond with concrete and steel substrates than the nonmodified equivalents. Results also showed that after heat aging, the adhesion strength of the nonmodified bitumen was always higher than that of the unheated bitumen modified with 9%–12% of SBS.
Short-term effects of soil compaction on growth of Pinuscontorta seedlings
Authors: Conlin T.S.S. , Driessche R. van den
Published: May 2008

A growth chamber experiment was conducted with Pinuscontorta Dougl. ex Loud. var. latifolia Engelm. seedlings grown in soil compacted at 0.1, 2.0, 4.0, 6.0, and 8.0 MPa pressure. Three moisture regimes were applied factorially to compaction levels by watering from above or by maintaining 2- or 10-cm water tables at the base of the 40-cm soil columns. All treatments were grown at either 22:14 °C or 26:18 °C (light:dark) for 13 weeks. Soil compaction increased bulk density, penetrometer resistance, and soil CO2 and ethylene. The presence of water tables resulted in elevated soil gravimetric water content, which rose with increased compaction and resulted in reduced penetrometer resistance and soil O2. Increased compaction was associated with decreased needle lengths, root dry weights, and net photosynthesis and increased rates of shoot respiration. Compaction had a small effect on height growth, with the tallest seedlings occurring at the greatest compaction rate. Shoot concentrations of mineral nutrients also decreased as soil compaction increased. Within the water table treatments, increased gravimetric soil water content was generally paralleled by a rise in the negative effects of compaction on growth, root/shoot dry weight ratios, and shoot mineral nutrient concentrations.
A simultaneous density-integral system for estimating stem profile arid biomass: slash pine and willow oak
Authors: Parresol Bernard R. , Thomas Charles E.
Published: May 2008

In the wood utilization industry, both stem profile and biomass are important quantities. The two have traditionally been estimated separately. The introduction of a density-integral method allows for coincident estimation of stem profile and biomass, based on the calculus of mass theory, and provides an alternative to weight-ratio methodology. In the initial development of the technique, sectional bole weight was predicted from a density integral formed from two equations that were fitted independently using ordinary least squares: (1) a stem-profile, or taper, function and (2) a specific gravity function. A test for contemporaneous correlations using slash pine (Pinuselliottii Engelm. var. elliottii) and willow oak (Quercusphellos L.) data showed highly significant correlations between the density integral and the stem-profile equation as well as the specific gravity equation. However, there was little or no correlation between the stem-profile and specific gravity equations. Because contemporaneous correlations exist between some of the equations, more efficient parameter estimation can be achieved through joint-generalized least squares, better known as seemingly unrelated regressions. However, the improvement in efficiency across parameters varies markedly based on the pattern of contemporaneous correlations. A simultaneous system of three equations was derived for slash pine and willow oak with nonlinear constraints across equations. Parameter estimates from seemingly unrelated regressions estimation had smaller standard errors in all cases than those from ordinary least squares estimation. For slash pine, standard errors were reduced by 11 to 29% and for willow oak, by 5 to 20%.
Seedbed and canopy cover effects on balsam fir seedling establishment in Isle Royale National Park
Authors: McLaren Brian E. , Janke Robert A.
Published: May 2008

While balsam fir (Abiesbalsamea (L.) Mill.) dominated forests are vanishing from the southwest end of Isle Royale National Park, Michigan, renewal of fir stands is occurring on the northeast end. We speculate that the difference is related both to severe browsing by moose (Alcesalces L.), and to the frequency of disturbances like fire and windthrow. A survey of 24 stands and in situ experimentation on Isle Royale show that balsam fir seedling survival is optimal under 40–79% canopy cover. Late-season and overwinter mortality in 1-year-old seedlings is highest under >80% canopy cover, while germination is lowest under <40% cover. We also rank germination substrates by "preference ratios," and by comparing the overwinter survival of young fir seedlings on five natural media. We find best performance on hypnaceous moss, variable survival success on rotten wood, and highest mortality on broadleaf litter. However, ample seedling densities occur on the southwest end of the island, and the failure of fir to reach the overstory in this area is apparently not related to poor seedling establishment.
The impacts of NAFTA on U.S. and Canadian forest product exports to Mexico
Authors: Prestemon Jeffrey P. , Buongiorno Joseph
Published: May 2008

The North American Free Trade Agreement (NAFTA) will lower barriers to trade and investment across the continent. This paper presents predictions of the effects of NAFTA on Mexico's imports of intermediate wood products, scrap and waste paper, pulp, and newsprint from the United States and Canada. Predictions were made with a partial equilibrium model. Model development involved estimating (i) elasticities of Mexico's import demand with respect to price and demand shifters and (ii) elasticities of prices with respect to their determinants, and then predicting, with these elasticities, the impacts of NAFTA on imports and prices. The effects of NAFTA on the exogenous variables affecting import demand and prices were summarized for three scenarios, based on the predictions of broader studies of the agreement. The results suggest that the full long-term impact of the NAFTA would be to increase the value of all Mexican imports from the United States and Canada by 21 to 85%. The effect would vary greatly by product and country of origin. Mexican imports of particleboard, hardwood veneer, scrap and waste paper, and wood pulp would be the least affected, mainly because of their smaller tariffs and inelastic price responses. Imports of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) lumber, hardwood lumber, softwood plywood, and newsprint from the United States would increase the most under NAFTA.
Wood volume increment in thinned, 50- to 55-year-old, mixed-species Allegheny hardwoods
Authors: Nowak Christopher A.
Published: May 2008

A thinning study in 50- to 55-year-old, even-aged, mixed species Allegheny hardwoods produced highly variable merchantable stemwood volume increment responses. Regression equations relating parameters of stand growth (ingrowth, mortality, survivor growth, net growth, and gross growth) to relative stand density had R2 values ranging from 0.07 to 0.48. When study plots with similar pretreatment species composition were assigned to four groups using cluster analysis, R2 values were increased to 0.94–0.99. There were significant differences in the relationships between relative stand density and growth response variables among all plot groups. At all densities, plots with a high percentage of black cherry (Prunusserotina Ehrh.) had the highest volume increment. Plots with a high percentage of black cherry and a low percentage of sugar maple (Acersaccharum Marsh.) showed a decrease in volume increment, relatively high ingrowth, and relatively low mortality with a decrease in relative stand density. Plots with a high percentage of sugar maple and low percentage of black cherry showed an increase in volume increment, relatively low ingrowth, and relatively high mortality with decreases in relative stand density. Guidelines for thinning Allegheny hardwoods recommend a residual relative stand density of 60%. These guidelines may need to be revised to incorporate considerations of species composition. Stands of pole-size to small sawtimber-size trees dominated by black cherry may require a residual density higher than 60% to maximize the volume increment of merchantable stemwood. The volume increment in similarly structured stands dominated by sugar maple might be maximized at densities lower than 60%.
Sapwood taper models and implied sapwood volume and foliage profiles for coastal Douglas-fir
Authors: Maguire Douglas A. , Batista João L.F.
Published: May 2008

Sapwood dimensions lend insight into the functional and ecophysiological structure of trees and can therefore be profitably applied in various types of growth analyses and simulation models. Ten taper models were fitted to sapwood data from the stems of 134 Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) trees and were compared by various fit statistics, residual behavior, and validation performance on 21 additional trees. The recommended model was a variable exponent model with six parameters and three basic tree-level predictors: diameter, height, and height to crown base. The resulting equation can be applied for estimating sapwood area at crown base, leaf area, sapwood volume, and vertical foliage distribution on standing trees. Ten sample plots are examined to demonstrate that sapwood taper models allow more explicit portrayal of stand structure in dimensions that have a direct functional link to various growth and developmental processes.
Process versus empirical models: which approach for forest ecosystem management?
Authors: Korzukhin Michael D. , Ter-Mikaelian Michael T. , Wagner Robert G.
Published: May 2008

The emergence of forest ecosystem management presents new information challenges for forest managers. Shifting views of the forest from primarily one as a production system for wood fibre to an ecosystem with spatially and temporally complex interrelationships is changing the demand for information about the forest. These new information needs are characterized by greater complexity, limited availability of mechanistic hypotheses, and a paucity of data. Empirical and process modelling approaches have evolved in forest management to solve different problems, and debate about the two approaches has existed for some time. Which approach to forest modelling will best be able to meet the challenges of ecosystem management? Empirical models seek principally to describe the statistical relationships among data with limited regard to an object's internal structure, rules, or behaviour. In contrast, process models seek primarily to describe data using key mechanisms or processes that determine an object's internal structure, rules, and behaviour. In addition, mechanisms included in process models are general enough that they can maintain some degree of relevance for new objects or conditions (mechanism constancy), while empirical models tend not to be tied to any specific mechanism, so that derived model parameters must remain constant (parameter constancy) for new objects or conditions. Based on these differences, we argue that process models offer significant advantages over empirical models for increasing our understanding of and predicting forest (a tree, a stand, a landscape) behaviour. Process models are, therefore, more likely to meet the information challenges presented by ecosystem management.
Evidence of genetic drift in chestnut populations
Authors: Machon N. , Burel L. , Lefranc M. , Frascaria-Lacoste N.
Published: May 2008

The genetic diversity and differentiation of six French populations of chestnut, Castaneasativa Mill., were analysed with isozyme markers. This work extends previous studies on Italian and Turkish populations. Results suggest that human interference has dramatically reduced the number of alleles per locus. This reduction is probably due to the process of genetic drift, as successively smaller numbers of genotypes were sampled in the course of reforestation and subsequent propagation of this species.
L'accroissement annuel réel dans les modèles de simulation de peuplements forestiers
Authors: Boudoux Michel
Published: May 2008

The use of 'real' annual increment rather than current annual increment is suggested for forest simulation models. A method of calculation of real annual diameter increment is described as a function of age and present tree diameter. This method is based on a convergent recursive algorithm using current annual growth rate as an initial value. The possibility of calculating an unbiased real annual increment based on increment core data is demonstrated. The second part of the article consists of an application of the method to a data bank involving more than 1000 black spruce (Piceamariana Mill. B.S.P.) for which a matrix of current and real annual increments was calculated. Subsequently, the development of an average stem was simulated by different methods for purposes of comparison.
Importance de la coupe forestière sur l'habitat hivernal de l'orignal dans le sud-ouest du Québec
Authors: Crête Michel
Published: May 2008

The utilization of habitat by moose on a winterlong basis was studied in Mont-Tremblant Provincial Park and in part of Pontiac County (Québec). The comparison of plant composition from the feeding and cover strata showed significant differences for most of the seven forest types compared. However, the most important tree and shrub species were the same for both study areas. The abundance of browsable stems was the most important habitat component which influenced the use of the forest stands by moose. Stands containing shade-tolerant hardwoods (Acersaccharum Marsh., Betulaalleghaniensis Britton, etc.) which had been harvested were used more intensively than uncut stands in both study areas. The increased density of stems in the feeding stratum caused by the opening of the forest canopy explains the greater use of the harvested areas. The more intensive logging of the forest types with shade-tolerant hardwoods caused a higher use of harvested stands in Mont-Tremblant Park than in Pontiac County. Stands containing shade-intolerant hardwoods (Betulapapyrifera Marsh., Populustremuloides Michx., etc.) which had been logged were used more frequently than uncut stands in Pontiac County while the opposite trend was observed in Mont-Tremblant Park. The apparently slower and less abundant regeneration of the feeding stratum and the greater snowfall in Mont-Tremblant Park could explain the lesser frequentation of harvested stands of this area as compared with the other. According to these results, logging regulations are suggested for major forest types of southwestern Québec.
EDTA-promoted exudation of 14C-labeled compounds from detached cottonwood and bean leaves as related to translocation
Authors: Dickson Richard E.
Published: May 2008

Mature and developing cottonwood (Populusdeltoides Bartr.) and bean (Phaseolusvulgaris L.) leaves were photosynthetically labeled for 30 min with 14CO2. Radioactive compounds in exudate obtained by placing the cut petioles in 20 mM Na2EDTA for 6 h were compared with those found in chloroform–methanol–water extracts of leaf lamina and petiole. Of the total activity lost in 6 h, 54% was recovered in the exudate from mature bean leaves compared with 3% recovered from cottonwood leaves. Smaller amounts were recovered in exudate from developing leaves compared with mature leaves of both species. Thus EDTA was not very effective for maintaining translocation rates in excised cottonwood leaves. Most of the radioactivity in the exudate was in sugars, indicating relatively pure sieve tube contents. However, radioactive amino acids and organic acids were always present, particularly in exudate from developing leaves. These amino and organic acids could either be derived from metabolism outside of the phloem with subsequent leakage into the EDTA solution, or be a component of the normal translocation stream. Of the total activity in exudates from developing cottonwood leaves, 17% was found in the amino acid and 33% was found in the organic acid fraction compared with 7% and 5% in these fractions, respectively, from developing bean leaves. The distribution of activity in the sugar, amino acid, and organic acid fractions of cottonwood petiole extract was similar to that found in the exudate. In contrast, proportionally less sugar and more amino acids and organic acids were labeled in bean petiole extract compared with the exudate, indicating lateral movement and metabolism in the bean petiole.
Physiology of gibberellins in conifers
Authors: Pharis R. P. , Kuo C. G.
Published: May 2008

The literature on endogenous gibberellins (GAs) of conifers, and on processes correlated with changes in GA-like substances, or processes affected by exogenous application of GAs is reviewed. It is now apparent that GAs mediate or influence many different growth and development processes in conifers, although just how they evoke the observed responses remains obscure.Practically, the use of certain GAs on conifers should allow advances to be made in the areas of tree breeding (i.e. the promotion of early flowering) and enhancement and regularization of seed production. The possible use of GAs to enhance early vegetative growth is feasible for many species. The use of endogenous GA levels, rate of synthesis, or metabolism as screening techniques in progeny testing, while still speculative, appears attractive.
Estimating juvenile tree volumes for provenance and progeny testing
Authors: Kovats M.
Published: May 2008

The development of a tree volume-estimating method for juvenile trees ranging from 1 to 10 m in height is described and application is suggested. Volume equations are given for coastal Douglas fir (Pseudotsugamenziesii (Mirb.) Franco), lodgepole pine (Pinusconiorta Dougl.), and two spruce species (Piceaengelmannii Parry and Piceaglauca (Moench) Voss) of British Columbia. The method features flexible diameter reference height and a height limit, beyond which the conventional diameter at breast height and volume estimating methods apply.
Genetic diversity in red pine: evidence for low genic heterozygosity
Authors: Fowler D. P. , Morris R. W.
Published: May 2008

Starch gel electrophoresis was used to survey for genetically determined enzyme mobility differences among 297 megagametophytes of red pine (Pinusresinosa Ait.) from five widely separated geographical sources. Consistent and reproducible enzyme banding patterns were observed with five of the seven isozyme systems assayed. No variation in band mobility was observed in any of these systems. This result stands in contrast with those reported from surveys of allozyme variation in other coniferous species but is consistent with the low degree of genetic variation observed in red pine for higher levels of genetic organization. It is concluded that red pine is genetically depauperate.Possible explanations for restricted genetic diversity are discussed. The most plausible explanation suggests that red pine was at sometime, possibly during the Pleistocene, reduced to a small refugial population and has yet to reestablish equilibrium heterozygosity.