bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of Fenvalerate on Enclosed Freshwater Planktonic Communities and on in situ Rates of Filtration of Zooplankton
Authors: Day Kristin E. , Kaushik N. K. , Solomon K. R.
Published: April 2008

The treatment of large-volume (~ 125 m3) in situ lake enclosures with fenvalerate at realistic field levels of agricultural contamination by drift or overspray (0.4–4.0 g fenvalerate∙ha−1) resulted in the disruption of the structure and function of the planktonic communities. The toxic effects ranged from short-term changes in the feeding behaviour of several species of zooplankton (Daphnia spp. and Ceriodaphnia lacustris) at 0.05 μg fenvalerate∙L−1 to a drastic reduction in the densities of most of the major groups of zooplankton at 0.1 μg fenvalerate∙L−1 for periods of up to 3 wk following treatment. In addition, indirect effects of toxicity were observed, e.g. populations of rotifers and phytoplankton increased in enclosures after the removal of the large-bodied cladocerans. This is thought to be the result of a reduction in competition and grazing, respectively. The emulsifying agents used in the emulsifiable concentrate formulation of fenvalerate were not found to be toxic to zooplankton at concentrations expected after agricultural use. The half-life of fenvalerate in an enclosure treated with a nominal concentration of 0.1 μg∙L−1 was estimated to be4.1 d by first-order reaction kinetics.
Coastal Upwelling and Oikopleura Occurrence ("Slub"): A Model and Potential Application to Inshore Fisheries
Authors: Taggart Christopher T. , Frank Kenneth T.
Published: April 2008

Variations in the occurrence of Oikopleura spp. were strongly linked to the wind field and ensuing water temperatures in an inshore region of eastern Newfoundland during June–August of 1979 and 1981–83. Oikopleura foul inshore fishing gear with their discarded houses ("slub") and fluctuate in abundance from day to day as a function of wind-driven upwelling. Densities of Oikopleura in cold upwelling water during four years ranged between 20 and 800/m3. Oikopleura densities < 1/m3 occurred when upwelling ceased and warmer water occupied the inshore region. A simple model incorporating a daily averaged wind vector, Julian day, and growing degree-day explained 62% of the daily variation in Oikopleura abundance in 1979. The model yielded density estimates that were significantly (p < 0.05) correlated with observed densities in each of the other three years. We provide evidence that net fouling by Oikopleura in the inshore and maximum Atlantic cod (Gadus morhua) catch is coincident and suggest that an annual hindcast index of slub intensity may help determine the impact of slub conditions on the inshore fishery.
Temperature Influences on Adult Size, Development, and Reproductive Potential of Aquatic Diptera
Authors: Rempel Robert S. , Carter John C. H.
Published: April 2008

Elevated temperature (2.5 and 4.0 °C) resulted in smaller body size of stream Diptera in outdoor experimental channels, and this trend applied to both predator and detritivore trophic groups. Comparison of cumulative emergence curves using the Kolmogorov–Smirnov test showed that most species developed more quickly in the heated channels; this led to greater overall survivorship. Reproductive potential, estimated from ovary area, did not change with body size for Conchapelopia aleta, Polypedilum aviceps, and Stempellinella brevis, and did so only weakly for Parametriocnemus lundbecki. In addition, females decreased in size more than males in the heated channels. Somatic growth appeared to be sacrificed to maintain reproductive potential, although loss of energy reserves could reduce the length of the reproductive stage. In balance, the aquatic Diptera demonstrated resistance to thermal elevation in the summer, even though ambient temperatures approached 30 °C. This may partially account for the group's ability to grow and develop throughout the year in extremely varied temperate environments.
Precision Micrometer Measurement of Mouth Gape of Larval Fish
Authors: Arts Michael T. , Evans D. O.
Published: April 2008

A precision micrometer device is described which standardizes measurement of mouth gape of larval fish and provides a greater degree of accuracy and speed than the conventional manual method. We compared gape measurements of larval lake whitefish (Coregonus clupeaformis) and lake herring (Coregonus artedii) using the gape micrometer versus the manual method. The micrometer measurements revealed a greater increase in gape with body length and resulted in a greater proportion of the variance in gape being explained, indicating that the gape micrometer is more sensitive and accurate than the manual method. Coefficient of variation of gape measurements on 238 larval yellow perch (Perca flavescens) decreased with body size from 0.5–4.0% at 0.8–1.2 cm standard length to 0.2–0.5% at 3.0 cm. The device has the added advantage that it could be adapted to connect to a microcomputer for direct data capture.
A Note on Variability of Marine Survival of Sockeye Salmon (Oncorhynchus nerka) and Effects of Flooding on Spawning Success
Authors: Thorne Richard E. , Ames James J.
Published: April 2008

Most of the annual variability in sockeye salmon (Oncorhynchus nerka) survival has been assumed to be associated with freshwater stages, while marine survival has been assumed to be very consistent from year to year. Data from Lake Washington sockeye salmon stock, including hydroacoustic surveys of presmolt populations, indicate that marine survival may vary on the order of 4–20%. However, the data also show that river flow conditions during spawning and gravel incubation have a major effect on production for this stock.
Simulation Model of English Sole (Parophrys vetulus) Population Dynamics in Washington and Oregon Coastal Waters
Authors: Peterman Randall M. , Bradford Michael J. , Kruse Gordon H.
Published: April 2008

We constructed an empirically based simulation model of population dynamics for English sole (Parophrys vetulus) occupying waters off the Washington and Oregon coast. While the original purpose for developing this model was to provide a tool for analysis of management questions, we also found it useful in evaluating hypotheses about biological processes in the early life history of sole. By comparing the ability of alternative sets of model hypotheses to reflect historical variation in abundance of age 4 recruits, we found some combinations of hypothesized mechanisms to be better than others. Approximately 61% of the interannual variation in recruitment was accounted for by a model which included (1) the effect of ocean temperatures on spawning timing, egg hatching, and fish growth, (2) density-dependent larval mortality, (3) age-dependent mortality of fish younger than age 4 yr, and (4) density-dependent growth of age 1 fish. This model explained more variation in recruitment than previous models of this population and emphasized the importance of timing of spawning on the subsequent abundance of the cohort.
Statistical Power of Trends in Fish Abundance
Authors: Peterman Randall M. , Bradford Michael J.
Published: April 2008

Estimation errors inherent in stock assessment methods may make it difficult to estimate time trends in fish abundances correctly. Our objective was to quantify the probability that trends in abundance of recruits will be successfully identified. For this analysis, we used an empirically based simulation model of English sole (Parophrys vetulus) off the west coast of North America. The unique wealth of data and past analyses of this population permitted us to include deterministic and stochastic components of growth, mortality, and reproduction in a realistic manner. Errors were also included in two simulated stock assessment methods: a trawl survey and cohort analysis. Under various conditions, we calculated the probability (analogous to statistical power) that these methods will meet three management objectives concerning time trends in recruitment. Monte Carlo simulations showed that although power depends on the objective, under most realistic conditions the probability of correctly detecting recruitment time trends may be unacceptably low. These results suggest new management guidelines for fisheries.
Fish Catches and Long-Term Tidal Cycles in Northwest Atlantic Fisheries: A Nonlinear Regression Approach
Authors: Cabilio Paul , DeWolfe David L. , Daborn Graham R.
Published: April 2008

Selected long-term fisheries catch data from the New England – Fundy area and the Grand Banks were examined for concordance between changes in fish catches and the 18.6-yr nodal cycle of the tides using a nonlinear regression model. Significant positive correlations were found for Atlantic cod (Gadus morhua), haddock (Melanogrammus aeglefinus), alewife (Alosa pseudoharengus), Atlantic herring (Clupea harengus harengus), and scallop (Placopecten magellanicus), with lag times that are biologically appropriate for the time from hatching to recruitment into the fishery. A significant negative correlation with the nodal cycle was evident for Atlantic menhaden (Brevoortia tyrannus), for which this area constitutes the most northerly part of its range. Cod catches on the Grand Banks showed no correlation with the nodal cycle. It is suggested that the correlations between the nodal cycle and the changes in fish catches are caused by correlated changes either in sea surface temperature or in productivity resulting from changes in the degree of vertical mixing.
Otolith Microstructore of Larval Herring (Clupea harengus): Image or Reality?
Authors: Campana Steven E. , Gagné Jacques A. , Munro Jean
Published: April 2008

When assessed with light microscopy, daily increment formation did not appear to occur in the otoliths of known-age larval herring (Clupea harengus). Increment counts underestimated age in all larvae. The age-increment discrepancy increased curvilinearly with age and appeared to stabilize after 50–60 d. Both the magnitude and rate of increase of the discrepancy were consistent with a hypothesis of resolution-limited increment visibility; models of daily otolith growth indicated that discrete daily growth increments would not be resolvable with a light microscope for the first 15–20 d after hatch. The hypothesis was also consistent with the observed effects of otolith polishing, a systematic difference in increment counts between different-sized sagittae in the same larvae, and other published reports of apparent nondaily increment formation in slow-growing pelagic larvae. Previous reports of growth rate limited increment formation appear to provide an empirical description of the same phenomenon. Otolith-based age, growth and mortality estimates can be expected to be biased if resolution effects are ignored. However, various procedures are available for the identification of potentially sensitive species and samples.
Effects of Mammalian and Salmon Gonadotropin-Releaslng Hormones and Analogues on Plasma Gonadotropin Levels and Ovulation in Coho Salmon (Oncorhynchus kisutch)
Authors: Kraak G. Van Der , Donaldson E. M. , Dye H. M. , Hunter G. A. , Rivier J. E. , Vale W. W.
Published: April 2008

The effects of intraperitoneal injections of mammalian gonadotropin-releasing hormone (mGnRH) and salmon gonadotropin-releasing hormone (sGnRH; [Trp7, Leu8]-mGnRH) as well as analogues of each peptide on plasma gonadotropin levels and ovulation in coho salmon (Oncorhynchus kisutch) were investigated. The native peptides had similar potencies in terms of the magnitude and duration of the gonadotropin release response. Analogues including the D-Ala6 and (imbz1) D-His6 derivatives of [Pro9-NEt]-mGnRH and the D-Arg6 and D-Ala6 derivatives of [Pro9-NEt]-sGnRH stimulate a more prolonged increase in plasma gonadotropin levels than native forms of these peptides. Each of the analogue peptides at a dosage of 0.2 mg/kg body wt induced a high rate of ovulation; the native salmon peptide at the same dosage was also effective although the time of ovulation was delayed compared with the response to analogue peptides. A higher dosage of the native salmon peptide (1.0 mg/kg body wt) was less effective in stimulating gonadotropin release and failed to induce a high rate of ovulation. Our studies demonstrate that several analogues of mGnRH and sGnRH have superactive agonist activity in coho salmon and are effective in inducing ovulation in this species.
Ammonium Transformations in Springwater within the Riparian Zone of a Small Woodland Stream
Authors: Hill A. R. , Warwick J.
Published: April 2008

Field enrichments with ammonium were conducted for periods of 4–4.5 h on two springs in the riparian zone of a small woodland stream near Toronto, Ontario. Springwater lost much of the injected ammonium as it flowed over organic and sandy riparian substrates before entering the stream. Negligible nitrate release occurred during the ammonium enrichments. Laboratory experiments revealed that riparian substrates rapidly removed ammonium from enriched springwater. Sediments covered with aerated ammonium-enriched water showed a small nitrate-N increase of 9–12 μg∙L−1 after 5 h. An absence of ammonium depletion in sterilized organic substrates and very small losses in low-temperature (1 °C) incubations suggested that microbial activity rather than adsorption was responsible for ammonium uptake. The rapid loss of ammonium from springwater overlying acetylene-treated substrates, despite the complete inhibition of nitrification, indicated that microbial immobilization was mainly responsible for ammonium depletion. We suggest that ammonium transformations in spring-fed areas of overland flow within the riparian zone may contribute significantly to the regulation of nitrogen inputs to small woodland streams.
A Time-Saving Filtration System For Nutrient Analysis
Authors: Bowman G. T. , Schuknecht B. A. , Wilken J. E. , Sonzogni W. C.
Published: April 2008

Conventional membrane filtration to separate particulate material from water samples, such as in the analysis of dissolved nitrogen and phosphorus, is time consuming and subject to contamination. To minimize this problem, a device is presented that allows filtration of up to 80 samples per hour without introducing contamination or affecting the sample integrity. The device requires only partial dismantling and minimal cleaning with dilute hydrochloric acid between samples. Validation tests show that the device does not alter dissolved constituents in filtered samples. Unlike conventional membrane filtering apparatus, a cumbersome vacuum flask is not required. The system is compact and easily adapted to mobile and shipboard laboratories.
A Synoptic View of the Golf Stream Front with 70-kHz Sonar: Taking Advantage of a Closer Look
Authors: Nash Richard D. M. , Magnuson John J. , Clay Clarence S. , Stanton Timothy K.
Published: April 2008

Acoustical scattering across the near-surface frontal zone of the Gulf Stream off Cape Natteras was greatest in the thermal front. Little biological scattering was evident in the colder Slope water, but in the Gulf Stream, scatterers formed five horizontal bands. Interpretation and new applications of acoustical information in biological oceanography are discussed.
Overview of Studies on the Nutrient Status of Lake Ontario
Authors: Lean D. R. S.
Published: April 2008

Balancing human demands on the environment with the overall welfare of the biosphere is one of the greatest challenges facing society today. In lakes, the limits of use and abuse are set by biogeochemical processes. This issue integrates measurements of take physics and nutrient availability with the response of the microbial community in Lake Ontario. Such information is vital to the understanding of factors affecting the base of the food chain and relates to the phosphorus abatement programs of the past 15 yr.
Stratification, Currents, and Upwelling in Lake Ontario, Summer 1982
Authors: Simons T. J. , Schertzer W. M.
Published: April 2008

A description is presented of physical measurements carried out on Lake Ontario during the summer of 1982. Seasonal variations of stratification and circulation are illustrated by monthly averages of temperature and current distributions in a north–south cross section of the lake. Day-to-day variations of temperature and currents are presented for three periods coinciding with biochemical investigations along the same transect of the lake. A wind-induced upwelling event followed by alongshore propagation of a warmwater wave is described and the dynamics involved are discussed.
Subcellular Phosphorus Kinetics for Lake Ontario Plankton
Authors: Lean D. R. S. , Cuhel R. L.
Published: April 2008

The subcellular distribution of recently incorporated 32PO4 was used to demonstrate that plankton in the surface waters of Lake Ontario were phosphorus deficient to some extent throughout the entire study period from April to October 1982. Most (~80%) of the initial uptake of carrier-free radioactive PO4 was in the low molecular weight (LMW) fraction. Ribonucleic acid (RNA) was the other major fraction. Although uptake was often complete within 1 h, changes in the subcellular distribution continued for 6–20 h with about half the LMW32P being transferred to RNA. Both a phospholipid fraction and a fraction extracted with hot trichloroacetic acid (HTCA) containing DNA and high molecular weight polyphosphate increased to 4–15% of the total isotope incorporated. In contrast with these experiments where net P uptake was zero, with added PO4 the net influx continued for periods in excess of 30 h but the subcellular distribution was constant within 2–4 h. About 80% of the initial uptake was as LMW32P and a rapid net synthesis of LMW polyphosphate was observed. These patterns were common for both small and large plankton size classes.
Influence of Light Intensity, Light Quality, Temperature, and Daylength on Uptake and Assimilation of Carbon Dioxide and Sulfate by Lake Plankton
Authors: Cuhel Russell L. , Lean David R. S.
Published: April 2008

The biochemical composition of newly produced phytoplankton biomass in Lake Ontario varied systematically with respect to experimentally manipulated incident light intensity and environmentally imposed water temperature and daylength, but was insensitive to light quality. Total uptake of 14C-labeled bicarbonate was light dependent (Popt:dark = 60–200), while 35SO42− uptake was light stimulated (Popt:dark < 5). Subcellular allocation of 14C for relative protein, carbohydrate, and lipid polymer synthesis responded sensitively to subsaturating light. Pathways of 35S assimilation were unaffected by light intensity. Night protein synthesis and attendant respiration of polymeric carbohydrates was a function of prior light history: with daytime illumination at Popt, day and night rates of 35SO4-S incorporation into protein were often indistinguishable. Using April–November data from Popt only, allocation of carbon to carbohydrate polymer storage for night growth was strictly proportional to nightlength. The proportion of carbon contained in protein was strongly correlated with in situ water temperature. The lack of cross-correlation suggests that temperature and daylength exert independent constraints on the biochemical composition of lake microplankton.
Nitrogen Transformations in Lake Ontario
Authors: Lean D. R. S. , Knowles R.
Published: April 2008

Concentrations of ammonium plus nitrite in Lake Ontario were highly correlated with ammonium regeneration from zooplankton excretion (r = 0.966), inferring that elevated nitrite concentrations result from nitrification. Nitrapyrin-sensitive dark 14C-labeled bicarbonate assays confirmed high rates of nitrification by chemoautotrophic bacteria. 15N-labeled nitrate experiments showed that nitrate, not ammonium, was the principal form of N used for total microbial protein synthesis. Size fractionation experiments also suggested that small cells were responsible for most of the ammonium uptake, while large cells used mostly nitrate. Nitrate depletion in the surface waters during summer stratification resulted from movement to particulate N, nitrite, and ammonium as well as losses in particulate N due to sedimentation. At least one third, however, was unaccounted for (i.e. 30 mg N∙m−2∙d−1) and may have been converted to protein which would move up the food chain to larger organisms (e.g. fish) not sampled during conventional water chemistry. Nitrous oxide profiles showed that nitrate losses through denitrification are unlikely to occur. Consequently, unless nitrate loading to Lake Ontario is reduced, nitrate concentrations should be expected to continue to increase.
Picoplankton and Nanoplankton Biomass in Lake Ontario: Relative Contribution of Phototrophic and Heterotrophic Communities
Authors: Pick F. R. , Caron D. A.
Published: April 2008

The seasonal and vertical abundance of phototrophic and heterotrophic nanoplankton (2–20 μm) and picoplankton (0.2–2 μm) was estimated in Lake Ontario during 1982 by epifluorescence microscopy. Phototrophic and heterotrophic nanoplankton abundance differed by less than an order of magnitude and was typically present at densities of 103 cells∙mL−1. Heterotrophic nanoplankton was, on average, only half as abundant as phototrophic nanoplankton, but on several dates was more abundant than the latter. Both populations peaked in late June to early July. Phototrophic picoplankton, primarily chroococcoid cyanobacteria, increased rapidly during midsummer, reaching a maximum epilimnetic concentration of 4 × 105 cells∙mL−1 in late August. Heterotrophic picoplankton (bacteria) showed a similar seasonal pattern, reaching maximum abundance in September (6 × 106) cells∙mL−1). The concentrations of both picoplankton populations were significantly correlated with temperature. By late summer, picoplankton biomass represented 74% and pico-cyanobacteria alone 50% of the total weight biomass of microorganisms < 20 μm; these populations are generally missed by inverted microscope techniques.
Seasonal and Vertical Distribution of Ciliophora in Lake Ontario
Authors: Taylor William D. , Heynen Miriam L.
Published: April 2008

Ciliated protozoa were sampled at discrete depths from April through October 1982 at a nearshore (38 m depth) and an offshore (178 m depth) station in Lake Ontario. Nearshore, ciliates increased from less than 1 g∙m−2 in early spring to a maximum of about 5 g∙m−2 (wet weight) inside the thermal bar in late May and early June. Summer values varied around 2 g∙m−2 and declined even further in October. Offshore ciliate biomass was relatively constant; the observed range was only 2.8–6.5 g∙m−2. Early spring biomass was much higher than nearshore, suggesting that a significant population persists through the winter, but the spring biomass increase was later. Although biomass concentration was greater in the epilimnion, on an areal basis most of the population resided in the hypolimnion. The hypolimnetic population declined during the summer period of thermal stratification. The observed number of taxa ranged from 15 to 30 per sample. Most had distinct seasonal and vertical distributions. The majority appear to be algivores, but the role of ciliates in the food web of Lake Ontario remains largely unknown. Their biomass is comparable with that of metazoan zooplankton, and with their higher metabolic rates, they probably perform much more of the total grazing.
Spatial Heterogeneity of Nutrients and Organic Matter in Lake Ontario
Authors: Neilson M. A. , Stevens R. J. J.
Published: April 2008

During spring, Lake Ontario was vertically homogeneous except for the bottom 2 m where soluble reactive silica (SRS) and temperature (TEMP) were significantly (p < 0.05) elevated and dissolved oxygen was depleted. With stratification, soluble reactive phosphorus (SRP) and total filtered phosphorus, SRS, and nitrate-plus-nitrite were depleted in the epilimnion due to phytoplankton uptake. Total unfiltered phosphorus (TP) and ammonia (NH3) exhibited higher epilimnetic concentrations, the former being attributed to tributary inputs which were maintained throughout the stratified period, even though inputs from Niagara River served to dilute the epilimnion. Increased levels of TP, SRP, and SRS were also evident within the nepheloid layer. Horizontal distributions of TP and NH3 were governed by point-source inputs throughout the study period. Distributions of the soluble nutrients were governed by phytoplankton uptake in the spring, point/nonpoint inputs and upwelling in the summer, and differential breakdown of stratification in the fall. Spring distribution of particulate organic matter (POM) was strongly related to nutrient availability and water column stability, while phytoplankton species composition determined fall POM distribution. Significantly higher (p < 0.05) POM levels, detrital content, and productivity were observed nearshore of the thermal bar.
Phosphate Ion Interactions at the Sediment–Water Interface in Lake Ontario: Relationship to Sediment Adsorption Capacities
Authors: Manning P. C.
Published: April 2008

The chemical forms of iron and phosphorus in surficial sediments of the Niagara Basin of Lake Ontario were determined by Mossbauer spectral and chemical extraction methods. The core locations lie on a transect across a boundary separating sediments displaying a crusty iron- and phosphorus-rich red layer a few centimetres beneath the sediment–water interface from sediments displaying no such layer. Concentrations of nonapatite inorganic phosphorus are relatively low at the surfaces of the layered cores whereas the iron forms are quantitatively similar. It is proposed that the red layers prevent upward diffusion of pore-water ferrous and phosphate ions to the surface. The degree of phosphorus recycling within the top few centimetres of sediment can then be estimated. Approximately 0.035% nonapatite inorganic phosphorus is carried into the anoxic zone. The data, combined with loadings of fine-grained sediment, indicate that Lake Ontario sediments have a net annual binding capacity of ~3500 metric tons of phosphorus, which compares with current loadings of ~8900 metric tons. This binding capacity supports current recommended phosphorus loadings to Lake Ontario.
Highly similar noncoding genomic DNA sequences: ultraconserved, or merely widespread?
Authors: Hickey Donal A.
Published: April 2008

In this note, I propose an explanation for the seeming contradiction between bioinformatics-based predictions of an essential function for ultraconserved DNA sequences, and the lack of an experimental demonstration of such function.
Antioxidants cannot suppress the lethal phenotype of a Drosophila melanogaster model of Huntington’s disease
Authors: Bahadorani Sepehr , Hilliker Arthur J.
Published: April 2008

Substantial evidence suggests that antioxidants may play a major role in delaying the progress of Huntington’s disease (HD). Here we investigated the effects of superoxide dismutase (cytoplasmic Cu/ZnSOD and mitochondrial MnSOD) and supplementation with dietary antioxidants (α-tocopherol and coenzyme Q10) on survival to adulthood in a Drosophila melanogaster model of HD. Our results illustrate that neither overexpression of superoxide dismutase nor supplementation of dietary antioxidants can rescue the lethal phenotype of HD flies. We discuss these results in conjunction with other evidence that antioxidants may only avert the oxidative stress induced progression of HD.
Cereal cyst nematode resistance conferred by theCre7 gene fromAegilops triuncialisand its relationship withCregenes from Australian wheat cultivars
Authors: Montes M. J. , Andrés M. F. , Sin E. , López-Braña I. , Martín-Sánchez J. A. , Romero M.D. , Delibes A.
Published: April 2008

Cereal cyst nematode (CCN; Heterodera avenae Woll.) is a root pathogen of cereal crops that can cause severe yield losses in wheat ( Triticum aestivum ). Differential host–nematode interactions occur in wheat cultivars carrying different CCN resistance (Cre) genes. The objective of this study was to determine the CCN resistance conferred by the Cre7 gene from Aegilops triuncialis in a 42-chromosome introgression line and to assess the effects of the Cre1, Cre3, Cre4, and Cre8 genes present in Australian wheat lines on Spanish pathotype Ha71. Inhibition of nematode reproduction was rank-ordered as Cre1 ≥ Cre4 ≥ Cre7 >> Cre8 > Cre3. Lines carrying Cre1, Cre4, or Cre7 exhibited a significantly higher level of resistance than those carrying Cre8 or Cre3. Allelism tests indicated that Cre7 segregated independently of Cre1 on chromosome 2BL and Cre4 on chromosome 2DL, and these genes could consistently be combined in the same genotype, inducing a more durable resistance. Tests to determine the chromosomal location of Cre7 using addition lines were inconclusive.
Molecular and cytological characterization of 5S rDNA inOryzaspecies: genomic organization and phylogenetic implications
Authors: Zhu Xiao-Yan , Cai De-Tian , Ding Yi
Published: April 2008

We investigated the molecular characteristics and chromosomal organization of 5S rDNA in the genus Oryza , including diploid and tetraploid species. A phylogenetic tree of Oryza species was constructed based on the non-transcribed spacer sequences of 5S rDNA, and some novel relationships were discovered. Specifically, comparative sequence analysis of 5S rDNA in several wild rice species showed unique characteristics inconsistent with the model of concerted evolution: (1) multiple distinct 5S rDNA types were detected within a species, leading to intraspecific divergence of 5S rDNA; (2) multiple identical 5S rDNA types were shared among species, resulting in interspecies clustering of 5S rDNA types; and (3) intraspecific nucleotide diversity was detected within a 5S rDNA class. Our results obtained by fluorescence in situ hybridization revealed that each rice species studied contained only one 5S rDNA locus with two hybridization sites, which were located on either chromosome 7 or chromosome 11. These results suggest that different 5S rDNA classes within the rice genome were arranged together and that one pair of 5S rDNA loci from a diploid progenitor of the tetraploid species might have been lost during evolution. Taken together, our data show that 5S rDNA in rice species is more informative at the gene level than at the chromosome level.
Comparative mapping among subsectionAustrales(genusPinus, family Pinaceae)
Authors: Shepherd Mervyn , Williams Claire G.
Published: April 2008

Comparative mapping in conifers has not yet been used to test for small-scale genomic disruptions such as inversions, duplications, and deletions occurring between closely related taxa. Using comparative mapping to probe this smaller scale of inquiry may provide clues about speciation in a phylogenetically problematic taxon, the diploxylon pine subsection Australes (genus Pinus , family Pinaceae). Genetic maps were constructed for two allopatric species of Australes, P. elliottii var. elliottii and P. caribaea var. hondurensis , using microsatellites and an F1hybrid. A third map was generated directly from the meiotic products of an adult F1hybrid, eliminating the need for an F2generation. Numerous small-scale disruptions were detected in addition to synteny and collinearity, and these included (1) map shrinkage, (2) a paracentric inversion, (3) transmission ratio distortion, and (4) mild selection against a parental haplotype. Such cryptic signatures of genomic divergence between closely related interfertile species are useful in elucidating this problematic evolutionary history.
Isolation of wheat–rye 1RS recombinants that break the linkage between the stem rust resistance gene SrR and secalin
Authors: Anugrahwati D. Ratna , Shepherd Kenneth W. , Verlin Dawn C. , Zhang Peng , Ghader Mirzaghaderi  , Walker Esther , Francki Michael G. , Dundas Ian S.
Published: April 2008

Chromosome 1R of rye is a useful source of genes for disease resistance and enhanced agronomic performance in wheat. One of the most prevalent genes transferred to wheat from rye is the stem rust resistance gene Sr31. The recent emergence and spread of a stem rust pathotype virulent to this gene has refocused efforts to find and utilize alternative sources of resistance. There has been considerable effort to transfer a stem rust resistance gene, SrR, from Imperial rye, believed to be allelic to Sr31, into commercial wheat cultivars. However, the simultaneous transfer of genes at the Sec-1 locus encoding secalin seed storage proteins and their association with quality defects preclude the deployment of SrR in some commercial wheat breeding programs. Previous attempts to induce homoeologous recombination between wheat and rye chromosomes to break the linkage between SrR and Sec-1 whilst retaining the tightly linked major loci for wheat seed storage proteins, Gli-D1 and Glu-D3, and recover good dough quality characteristics, have been unsuccessful. We produced novel tertiary wheat–rye recombinant lines carrying different lengths of rye chromosome arm 1RS by inducing homoeologous recombination between the wheat 1D chromosome and a previously described secondary wheat–rye recombinant, DRA-1. Tertiary recombinant T6-1 (SrR+ Sec-1–) carries the target gene for stem rust resistance from rye and retains Gli-D1 but lacks the secalin locus. The tertiary recombinant T49-7 (SrR– Sec-1+) contains the secalin locus but lacks the stem rust resistance gene. T6-1 is expected to contribute to wheat breeding programs in Australia, whereas T49-7 provides opportunities to investigate whether the presence of secalins is responsible for the previously documented dough quality defects.
Transcript expression profile of water-limited roots of hexaploid wheat (Triticum aestivum‘Opata’)
Authors: Mohammadi Mohsen , Kav Nat N.V. , Deyholos Michael K.
Published: April 2008

Triticum aestivum ‘Opata’ is an elite hard red spring wheat that has been used as a parent of the ITMI (International Triticeae Mapping Inititative) mapping population and also in the production of synthetically derived hexaploid wheats, some of which (following selection) show increased drought tolerance relative to Opata. Here, we describe the response of Opata roots to water withholding, using physiological variables and oligonucleotide microarrays. We identified 394 distinct transcripts whose abundance differed (p ≤ 0.05) at least 1.5-fold between water-limited and control roots of Opata, of which 190 transcripts increased and 204 decreased following water limitation. In addition to previously characterized markers of abiotic stress and many genes of unknown function, we identified multiple putative glucanases and class III peroxidases as being particularly responsive to stress. We also compared these data to previously described microarray analyses of Opata’s more drought-tolerant, synthetic-derived progeny, and found a relatively high correlation (r = 0.7) between responsive transcripts in the two genotypes, despite differing physiological responses. Some of the transcripts that we confirmed by qRT-PCR as being differentially expressed between Opata and the more tolerant synthetic-derived genotype under stress include a class III peroxidase, an AP2-family transcription factor, and several transcripts of unknown function.
Assessment of molecular diversity at QTLs for preharvest sprouting resistance in wheat using microsatellite markers
Authors: Fofana Bourlaye , Humphreys Gavin , Rasul Golam , Cloutier Sylvie , Daryl Somers
Published: April 2008

Breeding for preharvest sprouting (PHS) resistance is of great interest in wheat-growing areas where high rainfall occurs during grain ripening and harvest. We have characterized 32 wheat accessions using 33 microsatellite markers flanking PHS quantitative trait loci (QTLs) previously identified on group 3, 4, 5, and 6 chromosomes of hexaploid wheat. A total of 229 alleles, with an average of 6.94 alleles per marker, were observed among the 32 wheat lines. The polymorphic information content (PIC) was estimated and ranged between 0.25 and 0.90, with an average of 0.67. A cluster analysis revealed 3 main clusters and 3 singlet wheat lines, which is in agreement with pedigree-based relationships, seed coat colour, and origin. Canadian wheat accessions were subdivided into 4 sub-clusters based on pedigree and wheat classes. Grouping of preharvest sprouting germplasm into clusters was consistent with cluster-specific allele diversity observed in the PHS-resistant lines AUS1408, Red-RL4137, White-RL4137, and Kenya321. The implications of these findings in white wheat breeding for PHS tolerance are discussed.
Incorporating crown ratio into prediction equations for Douglas-fir stem volume
Authors: Hann David W. , Walters David K. , Scrivani John A.
Published: April 2008

Crown ratio was incorporated into four Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) total-stem cubic volume equations as a nonlinear multiplier. Two of the equations are traditional linear equations, one is nonlinear, and one is a new component approach that divides stem volume into that above and that below breast height. These equations, with and without crown ratio terms, were fitted to a modeling data set, and the statistical significance of the crown ratio terms was examined. All equations were then applied to a validation data set for comparison of their predictive abilities. The crown ratio term proved to be highly significant in the component approach, and component equations that included crown ratio had the smallest bias and the greatest prediction precision of all equations examined. That form was therefore selected as the most accurate characterization of Douglas-fir stem volume.
Cultivation and weed control for aspen seedling establishment in the southern Rocky Mountains
Authors: Fisher James T. , Neumann Robert W.
Published: April 2008

Containerized aspen (Populustremuloides Michx.) seedlings were planted at high-elevation sites in southern (May 1982) and northern (July 1983) New Mexico. Each plantation compared fall cultivation (20 cm depth), prior to planting the following spring or summer, with cultivation at the time of planting. Subtreatments of the tests included applications of the postemergent herbicide dalapon and the preemergents linuron, trifluralin, or simazine applied 2 to 3 weeks before planting. First season survival exceeded 75% for the best treatment at each site. Cultivation, in general, effectively reduced weed cover and improved seedling success. Fall cultivation, in particular, improved seedling survival and growth only at the relatively dry southern site. Except for spring-cultivated plots in the south, some herbicide applications improved weed control and seedling performance over cultivation alone. The combination of fall cultivation plus trifluralin is considered the best site preparatory treatment tested.
Pathogenicity of Bursaphelenchusxylophilus on three species of pine
Authors: Bedker P. J. , Wingfield M. J. , Blanchette R. A.
Published: April 2008

Three species of 11-year-old pine trees were inoculated with Bursaphelenchusxylophilus in the field. Four branches in single whorls on red, Scots, and jack pine trees were wounded and inoculated with 10 000 nematodes each or with water extracts from Botrytiscinerea cultures. Prior to field inoculations, the pathogenicity of the nematode isolate was confirmed on seedlings in the greenhouse. Fourteen weeks after inoculation, 27 of 80 and 13 of 52 branches were dead or dying on Scots and jack pine trees, respectively. No symptoms were observed on red pine trees inoculated with B. xylophilus or on any controls. Branch death was attributed to the formation of girdling cankers resulting from inoculation. An average of 9.14, 10.39, and 0.02 nematodes were extracted per gram of wood from branch samples collected from Scots, jack, and red pine trees at 14 weeks, respectively, and at 58 weeks an average of 13.82, 1.01, and 0.05 nematodes per gram of wood sampled were recovered. Proportions of branch samples with nematodes declined from 14 to 58 weeks after inoculation. Although limited mortality of branches occurred, the pine wood nematode was not found to cause tree death following inoculation.
Fire behavior in immature jack pine
Authors: Stocks B.J.
Published: April 2008

A series of experimental fires, each 0.4 ha in size, was conducted between 1975 and 1981 in an unthinned stand of immature jack pine (1948 origin) in central Ontario to gather quantitative fire behavior data for forest fire management purposes. Twelve fires were conducted over a broad range of burning conditions. Fire behavior and impact characteristics (i.e., rate of spread, fuel consumption, and frontal fire intensity) were found to be strongly correlated with fire weather severity as expressed through various component codes and indices of the Canadian Forest Fire Weather Index (FWI) System. This type of experimental fire information, along with wildfire data, is being used in the development of guidelines for quantitative prediction of fire behavior in major Canadian forest fuel types.
Evaluating growth responses to fertilization: Reply
Authors: Auchmoody L. R.
Published: April 2008

not available
Distance methods and density estimators
Authors: Payandeh Bijan , Ek Alan R.
Published: April 2008

not available
Effects of drainage on substrate temperature and phenology of some trees and shrubs in an Alberta peatland
Authors: Lieffers V. J. , Rothwell R. L.
Published: April 2008

A 50-ha portion of an intermediate fen in north central Alberta was drained in 1984. Study sites were established in the drained area and in an adjacent undrained area. In each site, seasonal water table depth and substrate and air temperatures were monitored. The drainage lowered the water table from 20 to 50 cm compared with the adjacent undrained site. Substrate of the drained area warmed above 0 °C slightly later than the undrained area but maximum summer temperatures were higher in the drained site. Temperatures in 1985 at the 10-cm depth of the drained site peaked in early August at 15–16 °C, 3–4 °C higher than the undrained site. Forty-five black spruce (Piceamariana (Mill.) B.S.P.), 45 tamarack (Larixlaricina (Du Roi) K. Koch), and 25 dwarf birch (Betulapumila L.) were tagged and examined twice weekly. For tamarack and dwarf birch, flowering and bud flush were significantly earlier by 2–6 days in the drained site. For black spruce, flowering was earlier in the drained site; bud flush, however, was earlier in the undrained site in 1985 but there were no differences between sites in 1986. For both black spruce and tamarack, the mean date at which individual trees reached 50% of total leader elongation was earlier in the drained site in both 1984 and 1985.
3-p sampling and design versus model-based estimates
Authors: Van Deusen Paul C.
Published: April 2008

The unadjusted and adjusted 3-p estimators suggested by L. R. Grosenbaugh (Soc. Am. For. Proc. 1963: 36–42. 1964) are examined as examples of design versus model-based estimators. This paper shows that the 3-p adjusted estimator has near optimal properties under a regression superpopulation model and is a member of the class of generalized regression estimators having desirable robustness properties. The variance estimators suggested by L. R. Grosenbaugh (1964, and For. Sci. 22(2): 173–176. 1976) also have bias-robust properties. The understanding that the model-based view lends will enable practitioners to consider alternative estimators and to have greater confidence in 3-p sampling as a practical tool.
Response of the mountain pine beetle, Dendroctonusponderosae Hopkins (Coleoptera: Scolytidae), to five semiochemicals in British Columbia lodgepole pine forests
Authors: Borden J. H. , Ryker L. C. , Chong L. J. , Pierce Jr. H. D. , Johnston B. D. , Oehlschlager A. C.
Published: April 2008

Five principal semiochemicals were field tested in multiple funnel traps for behavioral activity against Dendroctonusponderosae infesting lodgepole pine, Pinuscontorta var. latifolia Engelmann, in British Columbia. The basic experimental design was to test each compound by adding it in varying concentration or enantiomeric composition to a blend of other semiochemicals. (−)-trans-Verbenol was attractive to both sexes. (±)-exo-Brevicomin and (±)-frontalin (in one of two experiments) were attractive with other semiochemicals to females at a release rate of 0.05 mg/24 h. At higher release rates (±)-exo-brevicomin was inhibitory to males, and frontalin was inhibitory to both sexes. Thus both serve as multifunctional pheromones. For neither exo-brevicomin nor frontalin were the separate enantiomers attractive at the low release rate, suggesting that they had an additive effect. However, at the high release rate both enantiomers mimicked the inhibitory effect of the racemates. Verbenone acted as an antiaggregation pheromone for both sexes. Increasing the release rate of myrcene from 18 to 150 mg/24 h to approximate the release rate from a newly attacked tree had the effect of doubling the catch of responding beetles. A conceptual model is proposed for the sequential interaction of these semiochemicals in the mass attack of a tree. Pioneer females release trans-verbenol, which acts in combination with myrcene from the host tree to attract mainly males. The responding males release exo-brevicomin and later frontalin, which in combination with trans-verbenol and myrcene attract mainly females. Meanwhile autoxidation of α-pinene in the host resin results first in the production of predominately trans-verbenol, which supplements that produced by the beetles. Later, autoxidation of α-pinene and microbial conversion of cis- and trans-verbenol result in the production of the antiaggregation pheromone verbenone. This compound, in combination with large amounts of exo-brevicomin and frontalin as the tree becomes fully occupied, results in the close-range redirection of responding beetles toward nearby trees.
Age structure of red pine (Pinusresinosa Ait.) at its northern limit in Quebec
Authors: Bergeron Yves , Gagnon Daniel
Published: April 2008

At the northern limit of red pine (Pinusresinosa Ait.) fire may be of critical importance in determining the persistence of red pine and its restriction to islands and shores of lakes. The objectives of the study were to document the distribution pattern of red pine populations of the Lake Duparquet area in northwestern Quebec and to analyze the age structure and fire history of the populations. The combined age structure of 22 red pine populations is balanced and uneven aged, with two periods of increased recruitment from 1805 to 1864 and from 1925 to 1974. The analysis of individual populations indicates that they can be separated into three groups associated with specific site conditions: (i) uneven-aged populations with constant recruitment occurring on xeric sites, (ii) even-aged populations without regeneration occurring on mesic sites, and (iii) uneven-aged populations, showing both a constant recruitment and peak periods of regeneration, occurring on sites with xeric and mesic portions. Although all fires registered, lethal and nonlethal, are generally asynchronous between sites, the fires of 1825 and 1944 seem to have affected large areas of the lake. Two mechanisms for the maintenance of red pine were detected: self-regeneration of populations resistant to fires on xeric sites, and the transitory colonization of mesic sites by populations susceptible to lethal fires and established by seed from distant seed sources. Red pine may be restricted to lake landscapes because of the abundance of sites protected from lethal fires.
Dynamics of large woody debris in streams in old-growth Douglas-fir forests
Authors: Lienkaemper G. W. , Swanson F. J.
Published: April 2008

Transfer of large woody debris (>10 cm diameter) from old-growth Douglas-fir (Pseudotsugamenziesii (Mirbel) Franco) forests into five first-to fifth-order stream reaches (drainage areas of 0.1 to 60.5 km2) has ranged from 2.0 to 8.8 Mg•ha−1•year−1 in 7- to 9-year study periods. Amounts of large debris in these streams range from 230 to 750 Mg•ha−1 with generally lower values in larger channels. The addition of woody debris is widely scattered in time and space and comes mainly from single trees rooted away from the streambank. We infer that wind is a major agent for entry of wood into these streams. Downstream movement of debris is strongly related to length of individual pieces; most pieces that moved were shorter than bankfull width.