bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Harvest Policies for a Mixed-Stock Fishery: Fraser River Sockeye Salmon, Oncorhynchus nerka
Authors: Collie Jeremy S. , Peterman Randall M. , Walters Carl J.
Published: July 2008

We investigated harvest strategies aimed at rebuilding the less abundant stocks of Fraser River sockeye salmon, Oncorhynchus nerka. Monte Carlo simulations were run to estimate catch under four different harvest policy designs and three alternative parameterizations of the Ricker model. A pooled regression model was fit to 34 yr of spawner–recruit data from the 10 major stocks of Fraser sockeye. Compared with estimating separate parameters for each stock, the pooled regression model resulted in a more precise estimate of the Ricker a parameter (productivity at low stock sizes). Exploitation rate for maximum sustainable yield depends only on the a parameter and is thus well defined by the pooled regression even though the corresponding optimal escapement levels remain uncertain. A reduction in harvest rates to 70% from the current average 80% increased the simulated 40-yr catch by 31%. More extreme harvest-rate reductions, involving 50% exploitation rates on some stocks for four generations, allowed faster rebuilding and further increases in catch. Extreme harvest-rate reductions were necessary to obtain a 0.5 or greater probability of correctly detecting increased escapements, should the less-abundant runs increase as expected.
A Catch-at-Length Analysis that Incorporates a Stochastic Model of Growth
Authors: Sullivan Patrick J. , Lai Han-Lin , Gallucci Vincent F.
Published: July 2008

A length-structured population model, which incorporates von Bertalanffy growth, is used to describe changes in population abundance over time. The model is incorporated into a catch-at-length algorithm that uses a nonlinear least squares approach to estimate relative abundance, fishing mortality, selectivity, and the von Bertalanffy growth parameters L∞ and k. The algorithm is applied to a simulated data set for Pacific cod (Gadus macrocephalus) and to catch data on Pseudotolithus typus and Decapterus russellii. The parameter estimates of Pacific cod obtained from this algorithm were comparable with the values that were originally used to simulate the data. Although the catch data of P. typus did not exhibit the full range of sizes present in the population due to differential vulnerability of the population to the fishery, the estimates of L∞ and k reflect the growth over the entire size range of the population. Other population estimates for P. typus were in agreement with observed biological information. The estimated growth parameters L∞ and k of D. russellii showed some discrepancy with the information available on mature individuals present in this fishery but appeared to adequately represent year 1 growth. The estimated population and exploitation parameters fit the observed catch-at-length. Estimates made with the catch-at-length approach can be improved by using auxiliary information that may be available on abundance, fishing effort, recruitment, and growth.
Thermal Niche of Larval Sea Lamprey,Petromyzon marinus
Authors: Holmes John A. , Lin Ping
Published: July 2008

We used behavioral and physiological responses of larval sea lamprey, Petromyzon marinus, to temperature to describe the thermal niche and define optimal thermal habitat. Acclimation temperature had a weak direct positive effect on acute preferred temperatures in summer but no effect on acute preferred temperatures in winter tests. Swimming speed, mass, and acclimation temperature accounted for 66% of the variation in the active metabolic rate of larval sea lamprey. When larvae are swimming at their maximum prolonged rate, the relationship between temperature and metabolic rate is a unimodal curve, as has been found for more active fish species. The final preferred temperature in summer, 20.8 °C, is similar to the temperature at which maximum scope for activity occurs, approximately 19 °C. We propose the "fundamental thermal niche" of larval sea lamprey to be the range of temperatures between 17.8 and 21.8 °C. Some practical applications for the thermal niche are sketched with respect to the integrated management of sea lamprey in the Great Lakes.
Assessment of the Estuarine Hermaphroditic Fish Rivulus marmoratus as a Useful Euryhaline Species for Acute Toxicity Tests as Shown Using Cadmium
Authors: Park E.-H. , Chang H.-H. , Joo W. N. , Chung H.-S. , Kwak H.-S.
Published: July 2008

The estuarine hermaphroditic teleost Rivulus marmoratus was sensitive to toxic effects of cadmium showing low 96-h LC50 values of 0.8–32.8 mg Cd/L for different life stages at 10‰ salinity, 25 °C, and pH 7.0. Toxicity was greater at higher temperatures, at higher pH, and at lower salinity. Tolerance to cadmium increased after pretreatment with a low dose of cadmium, but the effect decreased when intervals between pretreatment and challenge treatment were longer than 4 d. The gill lamellae and kidney tubules were the primary target organs for acute toxic effects of cadmium in adult fish. These results suggest that R. marmoratus, which is small, physiologically tolerant, hardy, and easy to breed, may prove to be a useful euryhaline model for estuarine metal toxicity studies.
Effects of Rearing Density on the Growth Response of Juvenile Fathead Minnow (Pimephales promelas) under Toxicant-Induced Stress
Authors: Arthur A. D. , Dixon D. G.
Published: July 2008

The effects of rearing density on the apparent toxicity of pentachlorophenol and 2,4,5-trichlorophenol were investigated using 28-d growth and survival tests with larval fathead minnow (Pimephales promelas). The fish were held at rearing densities of 1, 5, or 10 fish per 1-L cage. Among individual fish, those held at the lowest density showed three times less variability in wet weight at 28 d than those at the highest density. Two-way analysis of variance of the growth data showed a significant interaction between concentration and density for both toxicants, suggesting that density affected the nature of the relationship between exposure concentration and response. The change in the concentration–response relationship was most dramatic for 2,4,5-trichlorophenol; a quadratic function for fish reared at low and medium densities changed to a linear function at the highest density. The estimated thresholds of toxicant impact on growth were twofold lower for low- versus high-density fish for both chemicals. Testwater volumes and replenishment were high enough in these experiments that decreased toxicant loading at higher densities did not appear to be a factor contributing to these results.
Maturity and Molt Status of Crustacea: Determining Classification without Prior Criteria
Authors: Warren William G.
Published: July 2008

Existing methodology for estimation is reviewed for the situation where, a priori, the existence of two or more groups can be postulated but, in contrast with discriminant analysis, there is no sample in which the correct categories are known. Such mixture models are applied to two data sets related to the maturity and molt status of snow crab, Chionoecetes opilio, namely (1) the classification of crab as morphometrically mature or immature on the basis of the chela height – carapace width relationship and (2) the determination of the number of molts of crab, during a known period at liberty, from the relationship of size at release and size at recapture of tagged animals, in the latter example, a theoretical constraint is imposed that links the relationships at the different stages. The solution is obtained by "nesting" an iterative procedure within an EM algorithm. The method permits hypotheses concerning the number of groups to be tested, including the hypothesis that the data come from a single homogenous group, and each individual is assigned a probability of belonging to a group.
Concentrations of Heavy Metals and Selenium in Tissues and Some Foods of Walrus (Odobenus rosmarus rosmarus) from the Eastern Canadian Arctic and Sub-Arctic, and Associations between Metals, Age, and Gender
Authors: Wagemann R. , Stewart R. E. A.
Published: July 2008

Atlantic walrus (Odobenus rosmarus rosmarus) harvested at Igloolik and Hall Beach (Foxe Basin) and Inukjuak and Akulivik (eastern coast of Hudson Bay) and clams (Mya truncata) and cockles (Serripes groenlandicus) collected at Igloolik were analyzed for heavy metals and Se. Pb was high in walrus from both Hudson Bay and Foxe Basin compared with other marine mammals, but levels were higher in animals from Hudson Bay than Foxe Basin, showing a geographic trend of increasing concentration from north to south. In some tissues of clams, Pb was also high, up to 3 μg/g (wet weight). Hg levels in walrus were low compared with those in other Arctic marine mammals; in liver, Hg showed a geographic trend similar to Pb. Cd in liver and particularly in kidney of walrus was high compared with other Arctic marine mammals and was higher in those from Foxe Basin than Hudson Bay. Associations among metals and between metals and age were found in walrus that were also reported for other marine mammals, namely between Hg and Se in liver, Hg and Cd in liver, Hg and Cd with age in kidney, Cd with Zn in liver and kidney, and Hg and Se in liver with gender.
Diel Feeding and Positioning Periodicity of a Grazing Mayfly in a Trout Stream and a Fishless Stream
Authors: Cowan Cathy A. , Peckarsky Barbara L.
Published: July 2008

We studied the feeding and positioning periodicity on natural substrates of the overwintering and fast-growing summer generations of a grazing mayfly, Baetis bicaudatus, in a third-order trout stream and a fishless, first-order tributary in western Colorado. At 4-h intervals over 24-h, we recorded the number of Baetis on stone tops in flow-through enclosures in situ and in streamside circular flow-through chambers. We determined the feeding periodicity of Baetis using abundance of plant pigments as an index of gut fullness. Baetis were nocturnal in the trout stream; more animals were found on stone tops and guts were fuller at night, suggesting that individuals came to stone tops to feed during darkness. However, Baetis from the fishless stream were either aperiodic or weakly nocturnal. We tested the hypothesis that nocturnal feeding by Baetis is a response to the presence of visually feeding trout by conducting transplant experiments in the circular streams. After 24 h, Baetis transferred from the trout stream to fishless water remained strongly nocturnal, while Baetis transferred from the fishless stream to trout water became significantly more nocturnal, suggesting that the risk of fish predation outweighs the benefits of relaxing nocturnal periodicity to feed continuously.
Return of Pacific Sardine (Sardinops sagax) to the British Columbia Coast in 1992
Authors: Hargreaves N. B. , Ware D. M. , McFarlane G. A.
Published: July 2008

The Pacific sardine (pilchard) (Sardinops sagax) supported an important commercial fishery in British Columbia for more than 20 yr before it suddenly collapsed in the mid-1940s. We report here the first confirmed catches of Pacific sardine in British Columbia since the 1950s and discuss the most likely explanation and possible future significance to British Columbia fisheries of the return of this species.
Fossil Pigment Records of Phytoplankton in Trout-stocked Alpine Lakes
Authors: Leavitt P. R. , Schindler D. E. , Paul A. J. , Hardie A. K. , Schindler D. W.
Published: July 2008

Paleolimnology, bioenergetics modelling, and mesocosm experiments were used to quantify changes in phytoplankton following introduction of trout into fishless alpine lakes in the Canadian Rocky Mountains. During the 1960s, Snowflake and Pipit lakes were stocked with brook (Salvelinus fontinalis), cutthroat (Oncorhynchus clarkii) and rainbow trout (O. mykiss) either singly or in combination. Stocked trout eliminated large invertebrates (Daphnia spp., Hesperodiaptomus arcticus, Gamrnarus lacustris), but the fish died within 15 yr. High performance liquid chromatographic analysis of carotenoids and chlorophylls in sediments inferred that algal abundance increased 4- to 10-fold shortly after fish stocking. In contrast, phytoplankton composition and biomass were constant in nearby, unstocked Harrison Lake, as inferred from fossils. Pigment analysis of mesocosms showed that phytoplankton were sensitive to moderate fertilization: 11 μg P∙L−1resulted in four- to six-fold increases in algal biomass. Bioenergetics modelling was used to estimate phosphorus (P) excretion from trout. The flux of excreted P was highly correlated (r2 = 0.76, p < 0.0001, N = 12) to changes in algal biomass, as estimated from fossil pheophytin b. Consequently, we infer that nutrient recycling by stocked trout was one of several mechanisms that contributed to increased algal biomass.
Estimating the Number of Fish Landed from Their Total Weight c and a Sample Average Weight
Authors: Sampson David B.
Published: July 2008

Assessing the status of a commercially exploited fish stock usually involves fitting a model for the stock's dynamics to observations of the number of fish landed. Typically, the number of fish landed is estimated from the ratio of the total landed weight, which is known exactly, over the sample average weight of a fish. This paper examines how errors in the sample average weight are transformed asymmetrically into errors in the estimate of the numbers landed when samples consist of fixed numbers of fish. Two alternative estimators are developed and are shown, using Monte Carlo simulations, to be less biased than the standard estimator.
Diel Patterns of Drift by Five Species of Mayfly at Different Levels of Fish Predation
Authors: Forrester Graham E.
Published: July 2008

Stream insects that drift downstream in the water column are at risk from fishes that feed visually in mid-water, and the restriction of drifting to nighttime is hypothesized to have evolved as an avoidance response to this type of predator. I tested the hypothesis that low daytime drifting is a proximate response to the presence of drift-feeding fishes by manipulating fish density (brook trout, Salvelinus fontinalis) in two field experiments. Daytime drift activity of five prey taxa (all mayflies: Ephemeroptera) was low in both experiments and did not change following fish removal. By night, however, nighttime drift activity of two mayflies, Baetis and Paraleptophlehia, was increased in areas containing fish. The other three mayflies, Ephemerella, Stenonema, and Eurylophella, which showed less drift activity overall, displayed no consistent responses to fish presence. The original hypothesis predicts that risk from drift-feeding fishes should result in reduced daytime drifting. The increases in nighttime drifting away from patches dense with trout were not predicted by the original hypothesis, but may be an additional avoidance response to reduce long-term predation risk in streams where trout are distributed patchily in space.
Application and Future Potential of Statolith Increment Analysis in Squids and Sepioids
Authors: Jackson George D.
Published: July 2008

Periodic increments within the squid statolith microstructure are now routinely used to obtain individual age estimates. Validation and culture studies have shown that statolith increments (similar to increments in larval fish otoliths) are produced daily in a number of squid species and in one sepioid. However, sample sizes for validation studies are small and there is need for further, more comprehensive validation experiments. Statolith age analysis has revealed that temperate squids can complete their life cycle in less than 2 yr while tropical species live for less than 8 mo. Obtaining individual age estimates has also facilitated the identification of cohorts by analysing hatch date distributions. Size-at-age analysis has been used for some preliminiary growth modelling, and there is a continued need for more accurate age-based squid growth models. There is now potential to use image analysis systems for increment counts and for width analysis of increments. Future studies should be aimed at obtaining age information from a wider number of species, considering how other features within the statolith microstructure, such as zones, might reflect past habitats, and determining how statolith length or weight measurements might be related to past growth histories.
QTL mapping of seed-quality traits in sunflower recombinant inbred lines under different water regimes
Authors: Ebrahimi A. , Maury P. , Berger M. , Poormohammad Kiani S. , Nabipour A. , Shariati F. , Grieu P. , Sarrafi A.
Published: July 2008

The objectives of the present research were to determine the effects of water stress on seed-quality traits and to map QTLs controlling the studied traits under two different water treatments in a population of sunflower recombinant inbred lines (RILs). Two experiments were conducted in greenhouse and field conditions, each with well-watered and water-stressed treatments. The experiments consisted of a split-plot design (water treatment and RIL) with three blocks. Analyses of variance showed significant variation among genotypes, and a water treatment × genotype interaction was also observed for most of the traits. Two to 15 QTLs were found, depending on trait and growth conditions, and the percentage of phenotypic variance explained by the QTLs ranged from 5% to 31%. Several QTLs for oil content overlapped with QTLs for palmitic and stearic acid contents in all four conditions. An overlapping region on linkage group 3 (QTLs 2.OC.3.1 and 4.SA.3.1) was linked to an SSR marker (ORS657). A principal component analysis was performed on four fatty acid traits. Two principal components, P1 and P2, were used for QTL analysis. This method improved the ability to identify chromosomal regions affecting the fatty acids. We also detected the principal-component QTLs that did not overlap with the fatty acid QTLs. The results highlight genomic regions of interest in marker-based breeding programmes for increasing oil content in sunflower.
Fluorescent in situ hybridization and characterization of the SalI family of satellite repeats in the Haliotis L. species (abalone) of the Northeast Pacific
Authors: Hernández-Ibarra Norma Karina , Leitch Andrew R. , Cruz Pedro , Ibarra Ana M.
Published: July 2008

The SalI satellite repeat previously identified in Haliotis L. (abalone) was thought to be present in H. rufescens and absent in H. fulgens . However, we show here that SalI is also found in H. fulgens and is not useful for screening hybrid individuals bred in aquaculture or occurring naturally in the wild. SalI is a family of predominantly subtelomeric tandemly repeated sequences, and sequenced clones revealed clustering to species and little intraspecific variation. Analysis of SalI sequence divergence between Haliotis species of the Northeast Pacific revealed that evolutionary distances correlate well with bathymetric and latitudinal species distributions. Analysis of the structure of the tandem repeats revealed two regions of high sequence conservation that may contain conserved transcription factor binding sites, a surprise for an apparently “non-coding” tandem repeat. We speculate that these regions might be involved in heterochromatin silencing, perhaps mediated via transcriptional activity and RNA interference. The repeats show substantial differences in their chromosomal distributions, even between individuals of the same species, indicating a dynamic organization of repeats, perhaps mediated via sequence homogenization.
Inheritance studies of apple scab resistance and identification ofRvi14, a new major gene that acts together with other broad-spectrum QTL
Authors: Soufflet-Freslon V. , Gianfranceschi L. , Patocchi A. , Durel C.-E.
Published: July 2008

Scab, caused by the fungal pathogen Venturia inaequalis , is the most common disease of cultivated apple (Malus ×domestica). The fungal races 6 and 7 have now overcome the major resistance gene Vf, which is widely used in apple breeding programmes. New breeding strategies to achieve durable resistance are thus necessary. The aim of this study was to determine the genetic basis of quantitative resistance of the apple cultivar ‘Dülmener Rosenapfel’, known to be scab resistant under different environmental conditions. An F1progeny derived from the cross between the susceptible cultivar ‘Gala’ and ‘Dülmener Rosenapfel’ was tested in a greenhouse with a multi-isolate inoculum of V. inaequalis. Rvi14, a new major gene that conditions a chlorotic-type reaction, was mapped on linkage group (LG) 6 in a genomic region not known to be involved in disease resistance. A further three quantitative trait loci (QTL) for resistance were identified. One co-localized with Rvi14 on LG6, whereas the remaining two were detected on LG11 and LG17, in genomic regions already reported to carry broad-spectrum QTL in other genetic backgrounds. Since a selective genotyping approach was used to detect QTL, an expectation-maximization (EM) computation was used to estimate the corrected QTL contributions to phenotypic variation and was validated by entire progeny genotyping.
Performance of an anchored sheet pile wall on the CN Rail line, Boston Bar, British Columbia
Authors: Gaffran P. , Sego D. C. , Peterson A. E.
Published: July 2008

The performance of a 6 m high anchored steel sheet pile retaining wall, constructed to allow CN Rail to twin its main-line track, is presented. The instruments installed gave measurement of the load and its variation along the tieback anchors; the distribution of the strain along the height of the wall which allowed an earth-pressure distribution to be postulated; and the lateral deflection of the wall. The earth-pressure distributions, inferred from the field measurements, were adequately predicted using the Terzaghi and Peck recommendation coupled with the Boussinesq procedure to account for the train loads. The best-fit lateral pressure distributions were in turn used to calculate displacement profiles by modelling the wall as a beam. The results matched the measured profiles reasonably well, thus endorsing a simplified technique for predicting displacements of an anchored wall. Key words : retaining wall, tieback, earth-pressure distribution, wall deflection, railway.
An evaluation of simplified techniques for estimating three-dimensional undrained ground movements due to tunnelling in soft soils
Authors: Rowe R. K. , Lee K. M.
Published: July 2008

A number of simplified approaches have been used by various researchers to estimate the three-dimensional stress changes and ground deformations due to shallow tunnels in soft soils. The effectiveness of these simplified analyses, such as (i) axisymmetric analysis, (ii) longitudinal plane strain analysis, and (iii) empirical cumulative probability distribution approach, has been examined by comparison of results with those from a full three-dimensional elastoplastic finite-element analysis. For tunnels located at shallow depths, axisymmetric analyses are generally found to be unable to predict the correct magnitude of displacement around a tunnel heading. However, the trend of the three-dimensional deformation behaviour near the tunnel heading can be reasonably approximated by the average of the normalized displacement curves predicted by the two axisymmetric assumptions as described in this paper. The three-dimensional distribution of the displacement near the ground surface, on the other hand, can be approximately predicted by the cumulative probability approach, provided that the three empirical parameters required by the equations are reasonably estimated. In this paper, these parameters were estimated from the result of a two-dimensional plane strain cross-sectional analysis. Finally, it was found that modelling of three-dimensional deformations by a longitudinal plane strain analysis did not give good results for the cases examined. Key words : tunnelling, soft ground, analysis.
Rock slope stability and distributed joint systems
Authors: Carter Bruce J. , Lajtai Emery Z.
Published: July 2008

A deterministic (GEOSLIDE) and a probabilistic (PROSLIDE) microcomputer code are introduced to aid in performing rock wedge analyses based on the limit equilibrium method. The deterministic code evaluates the stability of a single rock wedge formed by discontinuities in rock through three-dimensional vector algebra, GEOSLIDE undertakes a full kinematic analysis (daylighting and obstruction), analyzes both wedge and plane sliding, and provides for anchor designs and sensitivity analyses (cohesion, friction, and water forces). Through multiple stability analyses, PROSLIDE evaluates the probability of failure for a rock slope by examining the distribution of the factors of safety from all the potential sliding wedges formed by the discontinuities of the rock mass. The probability of failure is expressed as the ratio of kinematically free wedges that have a factor of safety less than unity to the total number of wedges, PROSLIDE can form and analyze as many as 2000 different pairs of discontinuities in less than 30 min using a 25 MHz 486 IBM-compatible computer. In a worked example, the probability of failure for a fixed slope strike and loading condition is shown to vary with the slope angle, following the characteristic 'S' shape of a cumulative distribution function. The effect of an anchor force is to spread the distribution over a wider range of the factor of safety (SF), pushing many wedges into a potential upslide situation and splitting the distribution about the failure zone of the stability diagram (−1 < SF < 1). Key words : rock slope, rock wedge, stability analysis, factor of safety, probability of failure, Monte Carlo simulation.
Supernormal fluid pressures in sedimentary rocks of southern Ontario – western New York State
Authors: Raven K. G. , Novakowski K. S. , Yager R. M. , Heystee R. J.
Published: July 2008

Fluid pressures up to 1.7 times greater than hydrostatic have been measured in argillaceous Paleozoic rocks of low permeability in southern Ontario and western New York State. These supernormal formation fluid pressures were measured at depths of 50–310 m using submersible pressure transducers with straddle packers and multiple-packer casings isolating the test intervals. Measurements were obtained over periods of 7–46 months following casing installations. The pressure measurements from 11 monitoring wells are compiled and supporting hydrogeologic data for 5 selected wells are used as examples to illustrate the occurrence of supernormal fluid pressures in the Ordovician, Silurian, and Devonian sedimentary sequence of southern Ontario and western New York State. Possible explanations for the occurrence of supernormal fluid pressures in sedimentary rock are evaluated considering the available geologic and hydrogeologic information obtained from the monitoring wells. Based on this review, it is hypothesized that gas migration and accumulation from deeper distant sources via permeable vertical pathways is the most plausible explanation for the observed fluid pressures, although secondary contributions from local neotectonic activity are also possible. The implications of such supernormal fluid pressures on regional groundwater flow in sedimentary rocks and related activities such as waste disposal in sedimentary rock are briefly discussed. Key words : supernormal fluid pressure, sedimentary rocks, gas migration.
Simulation of risk of progressive slope failure
Authors: Chowdhury R. N.
Published: July 2008

Understanding of progressive failure of slopes is of immense interest to geotechnical engineers and others concerned with the occurrence of landslides. One important aspect of research is the development of relevant analytical and numerical techniques. Both deterministic and probabilistic approaches can be used to study the development of progressive failure, provided valid geomechanics models form the basis of such studies. In this paper the risk of failure is simulated within a probabilistic framework. Of particular interest is the increase in the probability of failure, as overstress (and consequent localized failure) is considered to have actually occurred over an increasing proportion of a slip surface within the slope. The perception or interpretation of local failure is often based on observational data from surface measurements and subsurface instrumentation. Knowledge of spatial progression of failure may similarly be based on indirect and direct evidence. In the proposed simulation process the peak and residual shear strength of the slope material are regarded as one-dimensional random fields, and therefore spatial variability of each parameter is taken into consideration. Key words : analysis, clays, failure, shear strength, slopes, stability, landslides, probabilistic analysis, reliability analysis, progressive failure, slip surfaces, risk simulation, statistical analysis.
Modeling relative error in stem basal area estimates
Authors: Gregoire T. G. , Zedaker S. M. , Nicholas N. S.
Published: July 2008

The computed estimate of basal area was the focus of this investigation into the accuracy of tree diameter measurements. Diameter at breast height was measured on 101 trees, the breast height disc was removed from the stem, and each disc outline was then digitized to determine its actual area. Actual areas were compared with the basal areas computed with the field measurements of diameter by expressing the deviations as a proportion of the actual areas. These relative errors averaged 3.1% when basal area was computed with a taped diameter at breast height, and they averaged −2.5% when the mean of two calipered, perpendicular diameter at breast height measurements were used. Noncircularity accounted for about 2.6% of the bias, on average, in basal areas from taped diameters. Root mean square error of relative basal area errors ranged from 7.3 to 7.9% among these methods. The difference between basal areas computed with a taped diameter at breast height and with calipered diameter at breast height was computed and expressed as a proportion of the actual basal area. On average, a difference of 5% was observed. Interval estimates for these differences are presented.
Spatial and temporal patterns of sulfur and nitrogen in wood of trees across the north central United States
Authors: Ohmann L. F. , Grigal D. F.
Published: July 2008

Tree wood tissue was sampled in 169 forest stands, which represented five forest types, across the states of Minnesota, Wisconsin, and Michigan. The molar ratio of elemental sulfur to nitrogen for 3 decades of wood growth (1956 to 1985) was related to (i) location, as defined by five sampling zones, (ii) the molar ratio of elemental sulfur to nitrogen in soils, and (iii) wet sulfate deposition. There were also differences in molar ratios of sulfur to nitrogen among tree species and no significant interactions between species and zone. The sulfur to nitrogen ratios of both soil and wood increased from west to east across the sulfate deposition gradient. This trend is consistent with growing evidence that sulfate and other sulfur ions deposited through air pollution are accumulating in various compartments of forest ecosystems in the north central United States. These results also support studies that indicate that more sulfur is being taken up by trees than needed for nutrition.
Repeated measures analysis of variance: application to tree research
Authors: Moser E. B. , Saxton A. M. , Pezeshki S. R.
Published: July 2008

Repeated measures data occur in a wide variety of experimental situations and are often analyzed without full consideration of the statistical issues involved. In this paper, a discussion of model construction, univariate versus multivariate solutions, and statistical assumptions is motivated by examples from a tree physiology experiment. In addition, several examples from the forestry literature are reviewed. It is hoped that this discussion will help scientists with little statistical training to become aware of the different analyses available and perhaps to recognize the associated models in their own research. The examples range from a simple repeated measures design with one within-subject factor and no between-subjects factors to a more complex design involving multiple within-subject and between-subjects factors. The modelling approach used here permits a straightforward comparison between the univariate and multivariate solutions. Although no single approach is consistently best, the multivariate approach is always appropriate and provides the same interpretations as the univariate approach. However, when appropriate assumptions such as sphericity are met, power considerations tend to favor the more traditional univariate analysis.
An analysis of forest property tax burdens under a land and reforestation tax system: a western Washington case study
Authors: Bare B. Bruce
Published: July 2008

A per acre property tax model is proposed for taxing plantation-grown timber in western Washington State. The taxable assets consist of the bare land value plus the reforestation investment necessary to establish the timber stand. Under this system, an annual ad valorem property tax, or a harvest yield tax that substitutes for all, or part, of the annual ad valorem tax is levied on the full value of the tax base. Thus, unlike the traditional case where an annual property tax is levied on modified bare land and timber values to reduce the deferred yield bias associated with long-lived timber crops, the tax base under the proposed system requires no comparable modification. A variety of input scenarios are used to compare the numerical consequences of applying the proposed tax system with those of a land only, a land plus timber, and a harvest yield tax system; all levied at full value. Further comparisons with Washington's existing forest tax system, which is composed of an annual ad valorem property tax on a legislatively mandated statutory bare land value and a 5% harvest yield tax imposed in lieu of an annual ad valorem property tax on maturing timber, demonstrates how highly modified Washington's current system has become to accommodate forest owners and temper the deferred yield bias the property tax theoretically fosters.
Effects of root competition and flooding on growth of Chinese tallow tree seedlings
Authors: Jones Robert H. , Sharitz Rebecca R.
Published: July 2008

In separate experiments, tolerance of root competition and of flooding were assessed for seedlings of Chinese tallow tree (Sapiumsebiferum (L.) Roxb.), an invasive species in some North American floodplains. In the root competition experiment, pots containing seedlings of Chinese tallow tree and a native North American floodplain species (green ash, Fraxinuspennsylvanica Marsh.) were buried in the soil of a closed-canopied floodplain forest in South Carolina. Approximately half of the pots were invaded by roots of surrounding vegetation. In both species, total seedling mass in invaded pots was 70% of that in uninvaded pots. In the flood tolerance experiment, potted seedlings of tallow tree and a highly flood-tolerant species (water tupelo, Nyssaaquatica L.) were subjected to flooded and well-drained treatments in two light regimes: 20 and 100% of full sunlight. Mortality of flooded tallow trees was lower than of flooded tupelos (0 vs. 7.5%). Growth reductions under flooding were similar for both species in 20% light, but greater for tallow tree than for tupelo in 100% light. Flooded tallow trees produced hypertrophied lenticels and adventitious roots. Sensitivity to root competition and high flood tolerance may explain why seedlings of Chinese tallow tree are concentrated in low wet areas of floodplain forests.
Nuclear magnetic resonance imaging: a noninvasive analysis of moisture distributions in white oak lumber
Authors: Olson James R. , Chang Sun Joseph , Wang Paul C.
Published: July 2008

Nuclear magnetic resonance (NMR) imaging is a valuable diagnostic tool that detects the presence of hydrogen protons or water in material studied. Recently the technique was successfully used to observe the occurrence of defects within logs. The present study examined the feasibility of using NMR imaging for analyzing moisture distributions within white oak (Quercusalba L.) lumber. At selected days during drying, three thicknesses of lumber were imaged to detect free water, using a clinical 0.5-T whole body NMR scanner. NMR was shown to provide a noninvasive image of the internal structure of lumber. Images revealed that growth ring orientation and rays may play an important role in the drying process. Moisture distributions (shell and core) were qualitatively observed. For a quantitative interpretation, images were measured with an optical densitometer. The average moisture content of the board was correlated successfully to the weighted average optical density for the shell and core regions combined.
Clonal differences in the structure of a mixed stand of Salixviminalis in response to Melampsora and frost
Authors: Verwijst Theo
Published: July 2008

This study presents results from a stand structure analysis of an energy forest plantation of Salixviminalis L., clone 77-683. The stand, which was expected to contain only one clone, was shown to be composed of at least one male and one female clone. The male clone was susceptible to Melampsoraepitea Thüm. and displayed a larger proportion of frost damage after infection and lower mean size and weight than the uninfected clone. Regression analysis showed that the infected and uninfected shoots differed significantly in their size-weight relationships. Relative differences in size and damage between infected and uninfected stools were larger within the stand than along the border rows. The results illustrate how genetic differences in response to a pathogen can result in unevenly structured stands.
Canopy gaps and light penetration into a wind-exposed tropical lower montane rain forest
Authors: Lawton Robert O.
Published: July 2008

Penetration of light into the understory of tropical lower montane rain forests at Monteverde, Costa Rica, depends largely on the nature of canopy disruption by limb fall and tree fall. Midday photosynthetic photon flux densities (PPFD) above the forest canopy are low because of cloud cover (modal values are 400–500 μmol•m−2•s−1; daily integrations are 19 mol•m−2). The proportion of above-canopy PPFD that penetrates to the understory is greater in the elfin forests on wind-exposed ridge crests than in taller cloud forests in protected ravines (39 and 54% of understory locations receive <2% PPFD, respectively). PPFD is higher, and its vertical gradients steeper, in elfin forest gaps than in gaps of the same area in the taller forest. Gaps may or may not influence PPFD in adjacent forest understory, depending on vegetation structure on the gap periphery. In the taller cloud forest, understory PPFD is not correlated with distance to the nearest gap, but in the elfin forest it is (r = −0.467). This variation in the light environment is an integral part of disturbance and regrowth in these forests and seems to have played a major role in the evolution of tree growth strategies.
The influence of feeding on aerial and aquatic oxygen consumption, nitrogenous waste excretion, and metabolic fuel usage in the African lungfish, Protopterus annectens
Authors: Iftikar F. I. , Patel M. , Ip Y. K. , Wood C. M.
Published: July 2008

We studied the utilization of air versus water as a respiratory medium for O2consumption (Mo2) in the bimodally breathing African lungfish, Protopterus annectens (Owen, 1839), (151.2 ± 3.7 g) at 26–28 °C. We also investigated the impact of a single meal on this respiratory allocation and nitrogenous waste excretion in lungfish entrained to a 48 h feeding cycle. Correction for the “microbial blank” was found to be critically important in assessing the aquatic component of Mo2. After correction, total Mo2was low (~1000 μmol·kg–1·h–1), and lungfish took about 40% of Mo2from water and 60% from air. Following a meal of chironomid larvae (3.3% of body mass), Mo2values from both air and water increased in proportion over the first 3 h and continued to increase to a peak at 5–8 h postfeeding, at which point total Mo2(still 40% from water) was approximately 2.5-fold greater than the prefeeding level. When the same fish, entrained to the same 48 h feeding regime, were fasted, Mo2declined then later increased prior to the next anticipated feeding. In fed fish, the elevation in Mo2relative to fasted values was approximately 3-fold at 0–3 h and 9-fold at 5–8 h. This specific dynamic action (SDA) effect lasted until 23–26 h and amounted to only 9.5% of the oxycalorific content of the ingested meal. N-waste efflux was only slightly elevated after feeding, where there was a tendency for greater urea–N excretion (significant at 42–48 h); however, the lungfish remained ammoniotelic overall during the 48 h postfeeding period.
Role of predation and hunting on eastern cottontail mortality at Cape Cod National Seashore, Massachusetts
Authors: Boland Kelly M. , Litvaitis John A.
Published: July 2008

The degree that hunting may influence game populations depends on whether hunting mortality is additional to (additive) or replaces (compensatory) natural-caused mortalities. In response to limited information on the effects of exploitation on eastern cottontail ( Sylvilagus floridanus (J.A. Allen, 1890)) populations within Cape Cod National Seashore (CCNS), we initiated an investigation of cause-specific mortality using transmitter-equipped cottontails in hunted and nonhunted areas as a way to examine the additive versus compensatory aspect of hunting. Predation caused >70% of all deaths, whereas hunting caused 10% of deaths in the areas sampled. Survival rate was substantially lower among hunted sites (0.05) than at nonhunted sites (0.19) during the winter–spring of year 1, but there was no difference between hunted (0.33) and nonhunted (0.40) sites during year 2. Lower survival in year 1 was likely due to deep and persistent snow that increased vulnerability to predation and probably reduced the prospect for hunting mortalities to be compensated by reductions among other mortality factors. However, at least partial compensation apparently occurred during year 2 when winter weather was less severe. Cottontails at CCNS are near the northern edge of their geographic range and therefore may be ultimately limited by severe weather conditions. Compared with predation, we do not believe that the current levels and distributions of hunting influence cottontail populations at CCNS.
Timing of breeding and environmental factors as determinants of reproductive performance of tree swallows
Authors: Dawson Russell D.
Published: July 2008

Decreased reproductive success among birds breeding later in the season is a common pattern in temperate environments, although the underlying mechanisms remain unresolved. The quality hypothesis suggests that high-quality individuals can begin breeding earlier in the season than poorer quality parents, and are also able to invest more in reproduction. Alternatively, the date hypothesis suggests that reduced success among late birds is due to some correlate of date, such as decreased food abundance or offspring value. To test these hypotheses, I manipulated the date that tree swallows, Tachycineta bicolor (Vieillot, 1808), raised offspring by swapping clutches among nests so that birds were raising young either earlier or later than intended, and compared reproductive performance with control nests. My results showed that fledging success was related to the date hypothesis, with later birds being less successful in raising offspring than early breeding birds. Size and mass of offspring were not explained by either hypothesis, but rather by weather conditions experienced prior to measurements being taken. My results highlight the importance of events such as periods of inclement weather that can have significant impacts on offspring quality independently of both date of breeding and parental quality.
ON THE EFFECTS OF GEOGRAPHICAL CONSTRAINTS ON TASK EXECUTION IN COMPLEX NETWORKS
Authors: de ANGELIS ANDRÉ FRANCESCHI , TRAVIESO GONZALO , RUGGIERO CARLOS ANTÔNIO , da FONTOURA COSTA LUCIANO
Published: July 2008

In the present work, the effects of spatial constraints on the efficiency of task execution in systems underlain by geographical complex networks are investigated, where the probability of connection decreases with the distance between the nodes. The investigation considers several configurations of the parameters defining the network connectivity, and the Barabási–Albert network model is also considered for comparisons. The results show that the effect of connectivity is significant only for shorter tasks, the locality of connections implied by the spatial constraints reduces efficiency, and the addition of edges can improve the efficiency of the execution, although with increasing locality of the connections the improvement is small.
MULTI-RELAXATION TIME LATTICE BOLTZMANN MODEL FOR MULTIPHASE FLOWS
Authors: KUZMIN A. , MOHAMAD A. A. , SUCCI S.
Published: July 2008

Multi-relaxation time (MRT) for Lattice Boltzmann method is gaining renewed attention among researchers in the field. The advantage of such formulation over the widely popular single-time relaxation version, is twofold: better numerical stability and wider span of physical applications, extending to non-isotropic flows. In this work, the numerical advantages of the MRT model versus single-relaxation time (BGK) operator are quantitatively assessed through direct numerical simulations of droplet formation and capillary wave propagation on interphase boundaries. The results show that by proper tuning of the collision operator, and particularly of the higher-order kinetic modes (ghosts), appreciable improvements in stability limits, of the order of 20%, and viscosity limits, of the order of 80%, can be achieved. Moreover, a theoretical analysis accounting for the reasons behind such stability improvement, is also presented.
MODELING EVACUATION OF EMERGENCY VEHICLES BY CELLULAR AUTOMATA MODELS
Authors: MOUSSA NAJEM
Published: July 2008

An evacuation of the emergency vehicle (EV) from an origin point (e.g., accident location) to a destination point (e.g., hospital) in lower and higher congestions is simulated using city cellular automata models. We find that the mean speed of the EV and its arrival time all depend enormously on the cars density, the route length of the EV and the turn capability of the cars. Dangerous situations that occurred during the evacuation of the EV are also investigated. By allowing high turning capabilities to cars, considerable improvements are obtained. Indeed, the EV mean speed is enhanced and its arrival time is optimized. Moreover, at relatively high density, a significant reduction of the risk of accident is expected.
FINITE TEMPERATURE PHASE TRANSITION OF A SCALAR FIELD ON A FUZZY SPHERE
Authors: DAS C. R. , DIGAL S. , GOVINDARAJAN T. R.
Published: July 2008

We study finite temperature phase transition of neutral scalar field on a fuzzy sphere using Monte Carlo simulations. We work with the zero mode in the temporal directions, while the effects of the higher modes are taken care by the temperature dependence of r. In the numerical calculations we use "pseudo-heatbath" method which reduces the auto-correlation considerably. Our results agree with the conventional calculations. We report some new results which show the presence of meta-stable states, first order symmetry breaking transition and existence of multiple triple points in the phase diagram..
PARTICLE CREATION AND UIRs OF DE SITTER GROUP
Authors: MORADI SHAHPOOR
Published: July 2008

In this paper using the first Casimir operator of de Sitter group we obtain the field equations for spin-0 and spin-1/2 fields. After finding the exact solutions, we calculate the Bogoliubov coefficients and the particle creation rate for scalar and Dirac particles. Three series of inequivalent representations are distinguished for de Sitter group: the principal, complementary and discrete series. It is shown that only for principal series massive particles are produced. The thermal particle creation rate is compared with the previous results and it is shown that the results are the same.