bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical and neural contributions to hysteresis in the cardiac vagal limb of the arterial baroreflex
Authors: Studinger Péter , Goldstein Richard , Taylor J. Andrew
Published: July 2007

According to conventional wisdom, hysteresis in cardiac vagal baroreflex function exhibits a specific pattern: pressure falls are associated with longer heart periods and a smaller linear gain. A similar pattern occurs in the pressure–diameter relationship of barosensory vessels, and therefore it has been suggested that baroreflex hysteresis derives solely from vascular behaviour. However, we hypothesized that mechanical and neural baroreflex components contribute equally to baroreflex hysteresis. Blood pressure, carotid diameter and the electrocardiogram were recorded continuously during two trials of sequential bolus injections of nitroprusside and phenylephrine in 14 young healthy subjects. Baroreflex gain and its mechanical and neural components were estimated for falls and rises in pressure and diameter. The position or set point of the relations was quantified at the mean pressure and mean diameter. Gains were determined via piecewise linear regression. Set points and gains for fallsversusrises in pressure and diameter were compared with the Chow test. Hysteresis was observed in all individuals, but not in every trial. In most, but not all, trials pressure falls were associated with longer heart periods and smaller linear gain, as conventional wisdom would predict. However, the pattern of hysteresis derived from the interaction of both mechanical and neural components. The two components most often acted in opposition to determine differences in set point, but in conjunction to determine differences in baroreflex gain. Therefore, we conclude that hysteresis is not solely determined by barosensory vessel behaviour but by the complex interaction of mechanical and neural aspects of the arterial baroreflex.
Decrease in Thermal Contact Conductance and the Contact Pressure of Finned-Tube Heat Exchangers Assembled With Different Size Bullets
Authors: Madhusudana Chakravarti , Cheng Wui-wai
Published: July 2007

The thermal contact conductance (TCC) at the mechanically bonded tube/fin interface of a heat exchanger may be controlled by varying the amount of initial expansion of the tube. However, in this case, the TCC also varies with the temperature because of the differential expansion between the tube and the fin. The objectives of the present study are to determine the improvement in TCC resulting from higher degrees of the tube expansion, to determine the variation in TCC with the maximum temperature, and to estimate the change in contact pressure with the temperature. This paper presents the results of heat transfer experiments on mechanically expanded finned-tube specimens. Experiments were conducted in an atmosphere of nitrogen. The results showed that the TCC is enhanced by increasing the degree of initial expansion. There is a practical limit, however, to the maximum expansion that can be attempted. For the direction of heat flow prevailing in the experiments, the TCC and the contact pressure of every specimen decreased with increasing temperature.
River ice breakup processes: recent advances and future directions
Authors: Beltaos Spyros
Published: July 2007

The breakup of the winter ice cover is a brief but seminal event in the regime of northern rivers, and in the life cycle of river and basin ecosystems. Breakup ice jams can cause extreme flood events, with major impacts on riverside communities, aquatic life, infrastructure, navigation, and hydropower generation. Related concerns are underscored by the issue of climate change and the faster warming that is predicted for northern parts of the globe. Advances in knowledge of breakup processes and related topics, achieved over the past 15 years or so, are outlined. They pertain to breakup initiation and ice-jam formation, ice-jam properties and numerical modelling of ice jams, waves generated by ice-jam releases, forecasting and mitigation methods, sediment transport, ecological aspects, and climate-change impacts. Major knowledge gaps are associated with the dynamic interaction of moving ice with the flow and with the stationary ice cover. Increasing computing capacity and remote sensing sophistication are expected to provide effective means for bridging these gaps. Key words: climate, ecology, forecasting, ice jam, modelling, onset, sediment, wave.
Recent advances in basic and applied research in cohesive sediment transport in aquatic systems
Authors: Krishnappan Bommanna G
Published: July 2007

An overview of cohesive sediment transport processes is given in this paper, and a mass-balance equation that is commonly used to treat cohesive sediment transport is reviewed. The equation highlights transport parameters and processes that are important for modelling the transport of cohesive sediment. The flocculation mechanism that distinguishes cohesive sediment from its noncohesive counterpart is elaborated using a laboratory study that was carried out in a rotating circular flume using sediments from Hay River, Northwest Territories, Canada. A mathematical model of flocculation suitable for predicting flocculation of sediment in rotating circular flumes is reviewed. Other cohesive sediment transport processes such as erosion and deposition processes at the sediment-water interface, entrapment of fines in gravel beds, consolidation, fluid mud, and fluidization due to wave action are reviewed. Additional challenges and knowledge gaps that exist in the area of cohesive sediment transport are identified. Key words: cohesive sediment, flocculation, mathematical modelling of flocculation, rotating circular flume, erosion, deposition, fine sediment entrapment, fluid mud, consolidation, fluidization, waves.
Factors contributing to the failure of asbestos cement water mains
Authors: Hu Y , Hubble D W
Published: July 2007

Asbestos cement (AC) water mains were installed extensively in North America, Europe, and Australia from the late 1920s to the early 1980s and still form a significant component of water distribution networks of many cities. These water mains are ageing and some water systems have experienced a high breakage rate in AC mains in recent years. It is essential that a clear understanding be developed of the factors contributing to their failure to ensure that municipalities and water authorities can manage their AC water-main assets. In this paper, the historical failure data of AC water mains from the City of Regina were collected and correlated with their corresponding environmental setting, including soil type, water quality, climate, and construction and maintenance practices. The predominant factors that influence the AC pipe breaks were identified. It was observed that pipe age, diameter, climate, clay soil, and construction and maintenance methods all influence the failure of AC water mains in the city, with climate and clay soil conditions being the two critical factors. Some chemical attack from the conveyed water and soil pore water may have occurred and detrimentally affected the structural integrity of the AC water mains. Key words: asbestos cement pipes, water mains, pipe failure, clay soil, climate.
Source characterization of ambient fine particles in the Los Angeles basin
Authors: Kim Eugene , Hopke Philip K
Published: July 2007

Integrated 24 h PM2.5 (particulate matter ≤2.5 µm in aerodynamic diameter) speciation data collected between 2001 and 2004 at three United States Environmental Protection Agency Speciation Trends Network monitoring sites in the Los Angeles (LA) basin (Simi Valley, downtown LA, and Rubidoux) were analyzed through the application of the positive matrix factorization and seven to nine sources were identified. Secondary particles provided the highest contributions to PM2.5 concentrations (29%–46% for secondary nitrate and 12%–23% for secondary sulfate). Rubidoux, which is located downwind of the LA metropolitan area, and animal feed lots had the highest secondary nitrate concentration, followed by downtown LA. Secondary sulfate concentrations were consistent among three sites. Gasoline vehicle and diesel emissions contributed 12%–22% and 7%–10%, respectively. In addition, other sources such as airborne soil, sea salt, aged sea salt, wood smoke, and incinerator emissions were identified. Key words: source apportionment, Los Angeles basin, speciation trends network, PM2.5.
Development and resistance of a biofilm in a planar fracture during biostimulation, starvation, and varying flow conditions
Authors: Ross Nathalie , Novakowski Kent S , Lesage Suzanne , Deschênes Louise , Samson Réjean
Published: July 2007

Investigations of biofilms in a planar fracture are required to develop a biobarrier concept in aquifers. A glass-fracture apparatus was designed to monitor a biofilm under three phases: biostimulation, starvation, and increased flow. Direct observations were performed using a light probe whereas indirect indications were obtained by enumerating planktonic bacteria, monitoring the oxidation–reduction potential (ORP), and interpreting tracer experiments using an analytical model for two-dimensional advection-dispersion. Biofilm clusters developed along the flow lines before extending to a fully-connected biofilm, covering 500 cm2 after 50 d. The starvation phase favoured bacterial attachment at first followed by detachment, which was accentuated by increases in groundwater velocity. The ORP declined over the three experimental phases and was significantly related to the distance from the biostimulation zone. The modeling suggested that an increase in transverse dispersion within the fracture only occurs during the biostimulation phase. Key words: fractured rock, groundwater flow, biofilms, biobarriers, advection–dispersion model, biostimulation, starvation, oxidation–reduction potential.
Nitrification by biomass immobilized in porous carriers
Authors: Zielinska Magdalena , Wojnowska-Baryla Irena
Published: July 2007

The possibility of using activated sludge immobilized in porous ceramic carriers in nitrification of ammonia present in municipal wastewater was investigated. Three different carriers made the stable filling of three column reactors with internal circulation. The properties of the carriers such as internal structure, size of active surface, and participation of hollow spaces in the carrier volume determined the effect of volumetric organic and nitrogenous loading on the loading of nitrogen oxidized. Key words: immobilized activated sludge, porous ceramic carriers, municipal wastewater, nitrification.
Modeling of water temperatures based on stochastic approaches: case study of the Deschutes River
Authors: Benyahya Loubna , St-Hilaire André , Quarda Taha B.M.J. , Bobée Bernard , Ahmadi-Nedushan Behrouz
Published: July 2007

Water temperature is an important physical variable in aquatic ecosystems. It can affect both chemical and biological processes such as dissolved oxygen concentration and both the metabolism and growth of aquatic organisms. For water resource management, stream water temperature models that can accurately reproduce the essential statistical characteristics of historical data can be very useful. The present study deals with the modeling in the Deschutes River of average weekly maximum temperature (AWMT) series using univariate stochastic approaches. Autoregressive (AR) and periodic autoregressive (PAR) models were used to model AWMT data. The AR model consisted of decomposing water temperature data into a long-term annual component and a residual component. The long-term annual component was modeled by fitting a sine function to the time series, while the residuals representing the departure from the long-term annual component were modeled using a Markov chain process. The PAR model was applied to the standardized data obtained by subtracting the AWMT series from interannual mean of each period. To test the performance of the above models, the leave-one-out (Jackknife) technique was used. The results indicated that both models have good predictive ability for a relatively large system such as the Dechutes River. On an annual basis from 1963 to 1980, the average root mean square error varied between 0.81 and 0.90 °C for AR(1) and PAR(1), respectively, and the mean bias remained near 0 °C. Averaged Nash-Sutcliffe coefficient of efficiency (NSC) values obtained by AR (0.94) and PAR (0.92) models were close and comparable. Of the two models, the PAR(1) model seemed the most promising based on its performance and ability to model periodicity in autocorrelations. Since no exogenous variables such as air temperatures and streamflow were incorporated, the use of the PAR model limits the managerial decisions in natural streams and rivers.Key words: average weekly maximum temperature, stochastic model, PAR, AR.
The Plastochron Index as Applied to Developmental Studies of Cottonwood
Authors: Larson Philip R. , Isebrands J. G.
Published: July 2007

Leaves of cottonwood (Populusdeltoides, Bartr.) plants grown under constant conditions are initiated at relatively uniform rates. Because of this uniformity, the plastochron index (PI), developed by Erickson and Michelini (1957), can be applied to quantitatively identify the developmental stage of the vegetative shoot. In a preliminary test, the PI was shown to be linearly related to time, with plastochron intervals ranging from 2.00 to 2.76 days. In a second test, leaf plastochron indexes (LPI) were calculated for a series of trees representing five size classes. Statistical models were developed for each size class, relating each of the dependent variables (leaf length, leaf area, leaf dry weight, number of vessels per internode, and number of vessels per petiole) to LPI. These models were used to demonstrate that the PI and LPI can serve two useful purposes when applied to developmental studies of woody plants: (1) to adjust plants of different developmental stages to a standardized morphological time scale, and (2) to predict developmental processes and events from simple, nondestructive measurements.
A Technique for Insect Control in Pollination Bags
Authors: Fowler D. P.
Published: July 2007

A slow release form of the insecticide 2,2-dichlorovinyldimethylphosphate was tested to determine if it would protect developing strobili and cones of Picea spp. enclosed in pollination bags. A single, small chip (1 × 1 × 0.5 cm) of polyvinylchloride impregnated with the insecticide was placed in each pollination bag when the strobili were isolated. Cone damage by the spruce budworm and spruce coneworm was reduced from 85% to less than 10% in bags containing the insecticide. No phytotoxic effects were observed.
The Use of Engelmann Spruce Latewood Density for Dendrochronological Purposes
Authors: Parker M. L. , Henoch W. E. S.
Published: July 2007

Two parameters of growth rings from Engelmann spruce (Piceaengelmannii Parry) near Peyto lake, Alberta were studied and compared. Indices of maximum density of the latewood were derived from densitometric plots of X-ray negatives. Indices of ring widths were also obtained from the same specimens. Latewood density proved to be more useful for dendrochronological studies than ring width. The indices of density were significantly correlated with mean maximum air temperature and monthly runoff during August for three rivers in the region near Peyto lake. Analysis of latewood density as well as ring width improves the potential for dating tree-ring materials, and for using them to estimate past environment, especially for trees, such as the Peyto lake Engelmann spruce, with rings that do not vary greatly in width from one year to the next.
Free Amino Acids as Affected by Light Intensity and the Relation of Responses to the Shade Tolerance of White Spruce and Shade Intolerance of Jack Pine
Authors: Durzan D. J.
Published: July 2007

Saplings of white spruce and jack pine, grown under field conditions, were exposed for 2 years to natural light, and shade at 45, 25, and 13% of the daily natural light intensity. Continuous shade affected the growth and shape of saplings and influenced metabolism by reducing levels of most nitrogenous compounds in all plant parts (leaves, stems and buds, and roots). Compared with the spruce, significant responses by amino acids to the range of shade treatment in the very intolerant jack pine were greater and covered a much greater proportion of the amino acid N. As saplings were entering winter dormancy, thresholds for significant responses by individual amino acids and intercalation of their metabolic paths with those not responsive reflected a metabolic basis for shade tolerance that represented not only past growth rates of sapling parts, particularly roots, but also the extent to which nitrogenous compounds accumulated and were compartmentalized amongst parts. The main effects of shade on nitrogen metabolism implicated the balance of four- and five-carbon α-keto acids (photosynthate) which evoked significant changes in levels of certain amino acids and the amides, glutamine, and asparagine. At low light intensities, and particularly in stems and buds of both species, soluble nitrogen was diverted into the storage compound arginine.
Variation in Decay in Aspen Stands as Affected by Their Clonal Growth Pattern
Authors: Wall R. E.
Published: July 2007

In two even-aged stands of trembling aspen (Populustremuloides Michx.), there were highly significant differences among clones in percent decay, volume of decay, gross volume, and net volume. Each clone had a unique pattern with respect to position of rot columns within the stem and the major types of rot present. Adjacent or intermingled clones on apparently the same site differed significantly in percent decay in several instances. Components of the same clone occupying two distinguishable sites did not differ significantly in percent decay in any of the clones harvested, but considerable differences in gross volume and decay volume were observed. Within some clones, decay volume tended to parallel gross volume but in others, a negative correlation between percent decay and gross volume was evident.
Effect and Characteristics of Pathogens on Foliage and Buds of Cold-Stored White Spruce and Lodgepole Pine Seedlings
Authors: Hocking D.
Published: July 2007

Molding of cold-stored, spring-lifted seedlings of Piceaglanca (Moench) Voss var. albertiana (S. Brown) Sarg. reached an index of 71.7 and of Pinuscontorta Dougl. var. latifolia Engelm. an index of 35.6 during 10 weeks of storage. Mortality and reduced growth after planting out were directly related to the degree of molding. Of 37 fungus species isolated from moldy seedlings, 10 were considered significant and were further studied. All 10 grew at 5 °C and eight of them grew at 0 °C. All 10 were able to infect moist foliage at 2 °C, but only Epicoccumpurpurascens Ehrenb. ex Schlecht. could infect dry foliage, and then only at 95% r.h. Storage at 0 °C reduced molding to less than one-half that at 25 °C. Suitable seedling storage methods are discussed.
Observations on Spatial Distribution and the Relative Precision of Systematic Sampling
Authors: Payandeh Bijan , Ek Alan R.
Published: July 2007

In this paper, several observations are presented to point out the behavior of systematic sampling in forest inventory. A brief literature review and the results of empirical studies indicate that the relative precision of two-dimensional systematic sampling for a given forest stand varies with the variable of interest, spatial distribution of trees, plot size, and sampling intensity. More specifically, results of this study indicate that systematic sampling performs better than or as well as simple random procedures for clustered or near-randomly distributed forest populations for tree frequency estimation. For uniformly spaced populations such as plantations, however, simple random sampling should be most precise for tree frequency estimation. With basal area, results were less clear but considering this study plus others reported in the literature, systematic sampling should usually perform as well as or better than simple random procedures for most tree populations.
Studies of Moisture Status and Storage Conditions of Spring-Lifted, Mud-Packed Douglas-Fir Seedlings
Authors: Mellor G. E. , Keller R. A. , Tregunna E. B.
Published: July 2007

Two-year-old (2–0) Douglas-fir (Pseudotsugamenziesii) seedlings were lifted in the spring and mud-packed. These seedlings were tested (a) for moisture status during and after mud-packing or (b) for the effects of various storage conditions.Moisture status measurements indicated that the mud-packing process placed a reversible moisture stress on the seedlings. When the seedlings were planted, however, the mud-packed seedlings displayed a higher moisture stress than bare-root or unlifted seedlings. There was no difference in moisture stress between bare-root or unlifted seedlings.Mud-packed seedlings, stored in the field for 19 days and subsequently planted, had higher survival and root growth than those having other storage conditions. The other storage conditions included higher and lower temperatures than in the field and light versus dark. Treatment of the mud-packs with fertilizer and vermiculite had no effect on any of the parameters measured.
Protective Effect of an Ectomycorrhizal Fungus against the Root Pathogen Myceliumradicisatrovirens
Authors: Richard Claude , Fortin J.-André , Fortin Alain
Published: July 2007

The ectomycorrhizal fungus Suillusgranulatus prevented the phytopathogenic fungus Myceliumradicisatrovirens from adversely affecting the growth of aseptically grown seedlings of Piceamariana. Disease symptoms caused by M. radicisatrovirens are summarized for aseptically grown pine and spruce seedlings.
Reducing the Error in the Calculation of the Volume of Sectioned Logs
Authors: Goulding C. J.
Published: July 2007

The volume of a log sectioned into equal lengths can be calculated more accurately by Romberg's method than by Smalian's composite formula. The method is ideal for computer use and no additional field work is necessary. Some idea of the ideal number of measurements required can also be obtained.
Seedcoat Influences Dormancy of Loblolly Pine Seeds
Authors: Barnett James P.
Published: July 2007

The rate and percent of dark germination were low in untreated Pinustaeda L. seeds. Both increased with seedcoat clipping or removal, but not to the level of stratified seeds. Coats did not reduce the rate of initial water inhibition but did limit total uptake prior to germination, probably by restricting swelling of the megagametophyte and embryo. Respiration followed the pattern of water absorption in decoated seeds. However, it was at a common low level in stratified, clipped, and unstratified seeds until germination began, and there seemed to be no causal relation between respiration and coat permeability. Dormancy is likely to be the result of mechanical constraint by the seedcoat.
Distribution of Thermophilic and Thermotolerant Fungi in a Spruce-Pine Chip Pile
Authors: Smith Roger S. , Ofosu-Asiedu A.
Published: July 2007

A study into the distribution of thermophilic and thermotolerant fungi in a spruce-pine (Picea spp.—Pinus spp.) wood chip pile at Prince George, B.C., was carried out. Five treatments were examined: pine, spruce, spruce containing a core bag of fines, spruce containing a core bag of sterilized spruce chips and spruce containing a core bag of spruce chips inoculated with a Ptychogaster sp. [probably Chrysosporiumpruinosum (Gilman and Abbott) Carmichael]. Samples of wood chips buried at different locations in the chip pile were examined after 3, 6, and 12 month storage periods. From 100 randomly selected chips from each sample, the fungi were isolated on 2% malt, 2% agar, and 0.5% malic acid medium. Data on temperature during storage, pH of wood chips, moisture content, and weight loss at the time of sampling were calculated for the various sampling positions.Thermophilic fungi colonized the inner regions of the wood chip pile where higher wood substance losses occurred, while thermotolerant fungi inhabited the outer regions. Among the thermophilic fungi listed according to frequency of isolation were Byssochlamysemersonii Stolk-Apinis, Allescheriaterrestris Apinis, Sporotrichumthermophile Apinis, Thermoascusaurantiacus Miehe, and Humicolalanuginosa (Griffon and Maublanc) Bunce. The most common thermotolerant fungi were Aspergillusfumigatus Fresenius and C. pruinosum.Fungal distribution was generally related to position in the wood chip pile. Of the associated factors, temperature (17–60 °C) was most strongly related to fungal distribution, whereas treatment, pH of wood chips, and moisture content did not relate to fungal distribution.
Above-Ground Dry Matter Production in Three Stands of Trembling Aspen
Authors: Pollard D. F. W.
Published: July 2007

Above-ground biomass, annual production, and leaf area index (LAI) were estimated for several years in aspen stands aged 6, 15, and 52 years old in 1968. Based on regressions of dry weight on stem diameter, biomass (stems and branches) estimates for 1968 were 21 500 kg ha−1 in the juvenile stand, 51 200 kg ha−1 in the intermediate stand, and 91 800 kg ha−1 in the mature stand. Net annual above-ground production (stems and branches) for these stands in 1968 was 6900, 7000, and 1340 kg ha−1 respectively. In 1969, foliage amounted to 2600, 2600, and 1500 kg ha−1, providing LAI of 2.4, 2.9, and 1.6 for the stands. Net assimilation rates were roughly 20, 17, and 9 g m−2 week−1.Aspen stands regenerated as suckers may attain maximum annual production within a few years, coincident with the development of maximum LAI.
Use of Logarithmic Regression in the Estimation of Plant Biomass
Authors: Baskerville G. L.
Published: July 2007

The basic assumptions of regression analysis are recalled with special reference to the use of a logarithmic transformation. The limitations imposed on inference-making by failure to comply with these assumptions are discussed and ways to avoid the limitations indicated. A systematic bias of the order of 10 to 20% which is inherent in most, if not all, prior uses of the logarithmic equation to estimate plant biomass is noted as is the correction for the bias.
Distribution of Area Increment Over the Bole of Fertilized Douglas-Fir
Authors: Mitchell K. J. , Kellogg R. M.
Published: July 2007

Consideration is given to the distribution of growth increment at 6 points up the stem of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) 5 years after fertilization. The fully stocked stand, near Port Alberni, B.C., was 49 years old with heights and diameters reaching 100 ft and 20 in. respectively when fertilized with 220 and 440 lb/acre of urea. No change of consequence occurred in tree form in the codominant and intermediate crown classes as a result of the volume response which was still evident, although greatly diminished, after 5 years. In dominant trees, however, cross-sectional area growth in the central third of the stem was less than the controls even though other parts of the bole showed a positive response which lasted until the 4th year. The net volume response was negligible. The estimation of volume response to fertilization in dominant trees from breast-height measurements should possibly be approached with caution.
The Relation Between Leaf Production and Wood Weight in First-Year Root Sprouts of Two Populus Clones
Authors: Larson Philip R. , Isebrands J. G.
Published: July 2007

The relationship between leaf production and wood production in two clones of Populus grown for 1 year under intensive culture was investigated. Wood weight at any one stem position was highly correlated with the cumulative leaf area above that position. About one-half the total stem weight was bark, but the bark/wood ratio decreased with increasing leaf area. Wood specific gravity in creased from stem top to stem base, with mid-stem values of about 0.35. Leaf surface area and leaf dry weight were highly correlated with leaf lamina length; the latter therefore provides an easily measured, non-destructive estimate of photosynthesizing leaf surface. Marked clonal differences existed in all parameters measured.
Root Grafts and their Silvicultural Implications
Authors: Eis S.
Published: July 2007

Many trees in stands of Douglas fir, western hemlock and western red cedar on Vancouver Island were joined by functional grafts. In a partially cut stand, 45% of the stumps showed evidence of continued growth and half of these (23%) were still growing vigorously more than 22 years after logging. On experimentally detopped trees, growth extended several meters up the bole. Dominant trees usually supported the growth of the root system and lower boles of grafted suppressed trees.Translocation through grafts may partially explain the frequent stagnation and slow recovery of stands after thinning from above, and may be involved in the usually rapid increase of growth after thinning from below. It is probably a contributing factor in establishing dominance and determining mortality in overtopped trees. In species that graft freely, the use of silvicides in spacing and thinning treatments should be restricted to young stands before grafts are established.
Persistence, Size, and Weight of Needles on Douglas-fir and Western Hemlock Branches
Authors: Smith J. Harry G.
Published: July 2007

Branches of young trees were sampled to determine length, width, thickness, and volume of 6-needle samples, both fresh and dry weights of 100-needle samples, and persistence of needles. Significant differences in needle size and weight were associated with position in crown, tree, year of formation, and species. Therefore special studies are required to document these differences and to determine, for example, influences of fertilizers on needles. Although average needle weights and their proportions of oven-dry weights can be estimated adequately for some studies of biomass and for simulation of forest fuels, sub-sampling for tree-to-tree differences should improve results obtained.
Relationship Between the Degree of Resistance to a Pulsed Electric Current and Wood in Progressive Stages of Discoloration and Decay in Living Trees
Authors: Tattar Terry A. , Shigo Alex L. , Chase Thomas
Published: July 2007

The degree of resistance to a pulsed electric current of wood in progressive stages of discoloration and decay in living trees was correlated primarily with the moisture and mineral contents of the wood. Below the fiber saturation point, the degree of resistance was correlated primarily with the amount of moisture while above the fiber saturation point resistance was correlated primarily with the concentration of mobile potassium and calcium ions. The apparatus used to produce the current and to measure the resistance to it was accurate in detecting and in indicating the stage of deterioration of discolored and decayed wood. The apparatus was tested and found to be reliable electrically within the range of resistances encountered in the trees studied.
Photo-electric Measurement of Douglas Fir Needle Area
Authors: Balderston M. B.
Published: July 2007

A photo-electric device suitable for determining projected area of up to 60 Douglas fir needles at a time is described. Arrangement of the light source, lens, and selenium cell, and the method of operation, were designed to take into account seven points considered important for satisfactory measurements.
A Height–Density Concept and Measure
Authors: Honer T. G.
Published: July 2007

A concept of density based on the crown width/height relationship is proposed. For a tree of specified height, the point density measure is defined as the ratio of the area required by a tree growing free of aerial competition, to the area available when growing under competitive conditions. Using this definition, the derivation of an area–density measure is described and its relationship to the 'height–stocking concept' of Wilson, and Krajicek's 'crown competition factor' is discussed.
Nitrogen Fertilization and Water Effects on Photosynthesis and Earlywood–Latewood Production in Douglas-fir
Authors: Brix H.
Published: July 2007

Single tree plots in a 23-year-old stand of Douglas-fir were: (1) fertilized at a rate of 448 kg nitrogen (N) per ha with NH4NO3 in April; (2) irrigated in the summer of the same year and in the following year with 25 mm of water per week; (3) given the combined fertilizer and irrigation treatment, or (4) left untreated. Diameter growth at breast height (1.37 m) increased in the first year by 16, 15 and 59%, respectively, above that of the control. Similar effects were obtained at breast height in the second year and also at the one-half tree height position. Only earlywood production was affected significantly; this resulted from an increase in rate and length of time of earlywood production. Treatment effect on nitrogen, phosphorus (P) and potassium (K) concentration of leaves, leaf growth and water stress of soil and trees, was studied. Rate of photosynthesis was reduced similarly by water stress for fertilized and unfertilized trees; an increase in CO2 diffusion resistance appeared to cause the reduction in rate. Tree water stress had a more adverse effect on stem diameter growth than on rate of photosynthesis. The interaction between irrigation and fertilization indicates that nitrogen fertilization will have the most effect on stem diameter growth in years and on sites with favorable soil-water conditions.
Cone Production of Douglas-fir and Grand Fir and its Climatic Requirements
Authors: Eis S.
Published: July 2007

Thirty-six-year records of Douglas-fir and grand fir cone counts were analyzed with eight climatic variables to find which combinations of climatic factors were related to the induction of reproductive buds and the successful development of the strobili. Cool, cloudy weather during June, July, and August, 26–24 months before cone maturation, was the first prerequisite for abundant reproductive bud initiation. The second was cold, sunny weather during December, January, and February, 20–18 months before cone maturation. A wet April, 16 months before cone maturation, resulted in a higher proportion of megasporangiate strobili being differentiated, while a warm, dry, sunny June, 14 months before cone maturation, favored successful bud development. Since the prerequisites for a good cone crop include an alternation of cool, moist summers (2 years prior) and warm, dry summers (1 year prior), good cone crops in two consecutive years can not be expected. And since additional environmental prerequisites must be fulfilled, a lapse of several years between good cone crops is probable.
Succession in Unburned Subarctic Woodlands
Authors: Strang R. M.
Published: July 2007

A preliminary comparison of burned and unburned tracts in the northern boreal forest of the lower Mackenzie River valley indicates that, without periodic fires, trees will be eliminated and the climax vegetation will be a moss/lichen association. The implications for land management are adumbrated.
Black Spruce Fuel Weights and Biomass in Two Interior Alaska Stands
Authors: Barney Richard J. , Cleve Keith Van
Published: July 2007

This study reports the fuel weight and biomass distribution in a 51-year-old lowland and a 55-year-old upland black spruce (Piceamariana [Mill.] B.S.P.) stand in interior Alaska. Biomass distribution is shown for overstory, standing and down dead tree components, herbaceous understory, and the moss layer. The lowland stand contained over 11000 stems/acre (27170 stems/ha) and 82 ft2 of basal area per acre (18.8 m2 of basal area per hectare), and the upland stand contained 6000 stems/acre (14820 stems/ha) and 96 ft2 of basal area per acre (22.0 m2 of basal area per hectare). Moss layers contributed 54.6 and 45.5 t/acre (120.1 and 100.1 metric t/ha) to biomass totals in the lowland and upland sites, respectively. Total biomass was 64.7 t/acre (142.3 metric t/ha) in the lowland site and 58.0 t/acre (127.6 metric t/ha) in the upland site.
Invitro Study of Carbon and Nitrogen Metabolism of Principal Fungi Associated with Fomesconnatus in Sugar Maple Acersaccharum
Authors: Tattar Terry A. , Rich A. E.
Published: July 2007

Isolates of Phialophoramelinii and Acrostaphylus sp. from discolored tissue, Trichodermaviride and Mortierella sp. from decayed tissue, and Fomesconnatus from a narrow band of discolored tissue at the border of decayed and discolored tissue, of sugar maple (Acersaccharum) were grown in liquid culture media containing sources of carbon and nitrogen found in tissue of sugar maple. These compounds included the carbohydrates of wood and their component monosaccharides and translocation compounds from xylem sap. Growth was measured as oven-dried weight of mycelium. All fungi utilized the carbohydrate and nitrogen sources, except Mortierella sp. which did not utilize cellulose or xylose. Only P. melinii utilized substantially gallic acid. The degradation of cell walls in living trees may occur both in discolored and decayed tissue and may be caused by nonhyme-nomycetous and hymenomycetous fungi. Selective utilization of host components by some of these may enable successful colonization of wounds and initiation of the processes of discoloration and decay.
Interaction of Cottonwood Clones with Site and Planting Year
Authors: Mohn C. A. , Randall W. K.
Published: July 2007

Height and diameter growth to age three and the number of first year branches were analyzed for 25 cottonwood clones grown in six plantations in central Mississippi. Plantations were on two contrasting sites and planted in three consecutive years. Results showed small clone × planting year interactions and large clone × site interactions for all parameters. In the lower Mississippi Valley, therefore, emphasis should be placed on testing over a range of sites rather than replicating over time.
Accumulation and Utilization of Carbohydrate Reserves in Shoot Growth of Pinusresinosa
Authors: Olofinboba M. O. , Kozlowski T. T.
Published: July 2007

Evidence is presented which emphasizes the importance of food reserves and conditions controlling late-season photosynthesis (e.g. during bud development) to subsequent-year shoot growth ofPinusresinosa. By the end of August, after shoot elongation ceased, current 14C-photosynthate was mobilized by roots, stems, and twigs. Much of the currently produced photosynthate accumulated as reserves in roots, stems, and twigs. When phloem blocks were applied in March behind the prior-year internode of defoliated shoots, thereby preventing phloem translocation of currently produced photosynthate from old needles to the buds, considerable shoot expansion still occurred, indicating utilization of reserve photosynthates of the prior-year internode.
Analyses of a Forest Drainage Experiment in Northern Ontario. I: Growth Analysis
Authors: Payandeh Bijan
Published: July 2007

This paper presents a growth analysis of a forest drainage experiment carried out over 40 years in northern Ontario. It is based on remeasurement data obtained in 1969 from 38 growth plots established following drainage in 1929 and from increment cores and sectioned trees.Results indicate that both annual tree diameter and height growth increased significantly after draining; that tree growth before draining was related to site quality only, while after draining it was related also to tree vigor and distance of water flow from the nearest ditch; that both stand diameter and height growth were related to site index, stand age, and initial stocking; and that stand basal area and volume growth were, in addition, related to a product sine function of distance of water flow from the ditch, peat moisture, decomposition, and depth.Both individual tree and stand growth responded well to draining, with younger and more vigorous trees that were growing on better-quality sites showing the greatest response. For a given site, growth response was not greatest for trees and stands nearest the ditch, but for those some distance away.
Simultaneous Linear Prediction and Construction of Volume Tables
Authors: Bélanger J. , Cléroux R.
Published: July 2007

In this paper a technique is proposed which finds a unique linear predictor which is used to construct volume tables for different tree species, when it is multiplied by proper scaling factors. This technique uses the fact that one species can give information about some other. This information can be used in future studies where data are not available on all the species considered.
A New Index Representing Individual Tree Competitive Status
Authors: Moore James A. , Budelsky Carl A. , Schlesinger Richard C.
Published: July 2007

A new competition index, modified Area Potentially Available (APA), was tested in a complex unevenaged stand composed of 19 different hardwood species. APA considers tree size, spatial distribution, and distance relationships in quantifying intertree competition and exhibits a strong correlation with individual tree basal area growth. The most important characteristic of APA is its potential for evaluating silvicultural practices.
The Distribution and Composition of Extractives in Jack Pine Trees
Authors: Sinclair G. D. , Dymond D. K.
Published: July 2007

The distribution of acetone-soluble extractives in jack pine trees of different diameters, and at different locations within a single tree was studied. The amount of extractives varied from 3% in a 10 cm diameter tree to 9.6% in a 50 cm diameter tree. Within a single tree the top had the least amount of extract, 2.7%, while the needle bearing twigs had the greatest amount, 4.6%. Gas–liquid chromatographic analysis of the extracts showed that the composition was relatively similar for all sizes of trees and within one tree except in the top and the branches. The heartwood of the tree had a much higher extractive content than the sapwood and contained a higher concentration of resin acids, pinocembrin, and pinobanksin.
Effects of Stratification on Western Hemlock Germination
Authors: Edwards D. G. W.
Published: July 2007

In a laboratory study stratification had little or no effect on the germination capacity, but it significantly increased the rate of germination in western hemlock seedlots. The greatest increase occurred after 1–2 weeks of chilling on moist filter paper. Naked stratification in plastic bags produced nearly the same response. For stratification longer than 2 weeks, increments in germination rate became progressively smaller. Excellent germinability was indicated by germination values over 30, poor germination by germination values below 13.
Salts of Methyl-2-benzimidazole Carbamate (MBC) and Assessment of Their Potential in Dutch Elm Disease Control
Authors: Kondo E. S. , Roy D. N. , Jorgensen E.
Published: July 2007

Methyl-2-benzimidazole carbamate (MBC) was solubilized by formation of salts (MBC-phosphate, -nitrate, -hydrochloride, -sulfate, and -sodio derivative). All the salts of MBC exhibited greater fungitoxicity towards Ceratocystisulmi than the parent compound and lower phytotoxicity towards elms. MBC-phosphate was root injected into 12 healthy, mature, field-grown white elms (Ulmusamericana L.) and one with severe symptoms of Dutch elm disease. Controls consisted of seven elms injected with distilled water alone. To date, bioassays of trees treated with MBC-phosphate using the root-injection method have demonstrated extremely good distribution throughout the tree at a concentration which, on the basis of laboratory tests, is sufficient to arrest development of C. ulmi. Treated elms could not be successfully inoculated with C. ulmi conidia, whereas control trees could. Recovery of C. ulmi from the diseased elm was greatly reduced after root injection with MBC-phosphate.
Variation in the Susceptibility of Lodgepole Pine Provenances to Sirococcus Shoot Blight
Authors: Illingworth K.
Published: July 2007

Sirococcusstrobilinus Preuss. was identified as the cause of a shoot blight of lodgepole pine (Pinuscontorta Dougl. ex Loud.) seedlings grown in a nursery in central British Columbia. Marked variation in susceptibility to this fungus was noted among the 153 provenances representing the entire range of lodgepole pine. Genetic variation in host susceptibility is inferred.
The pollination mechanism and the optimal time of pollination in Douglas-fir (Pseudotsugamenziesii)
Authors: Owens John N. , Simpson Sheila J. , Molder Marje
Published: July 2007

The development of the pollination mechanism and the engulfment of pollen by the stigmatic tip is described for Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) based on scanning electron microscopy. This information is used to determine and explain the optimal time of pollination and amount of pollen needed for maximum seed set. After dormancy the integument tip of the ovule developed into an unequally two-lobed stigmatic tip covered with long unicellular hairs. Most ovules had fully developed stigmatic tips when the seed cone emerged from the bud scales in early April. The conelets remained open and the stigmatic tip was most receptive for at least 4 days. Pollen freely sifted down between the bracts and ovuliferous scales and adhered to the stigmatic hairs. Six days after the conelets became receptive, stigmatic hairs around the micropyle began to collapse and were ungulfed with the entangled pollen into the micropyle. Also, ovuliferous scales began to thicken, restricting movement of pollen to the stigmatic tips. By 8–10 days after conelets became receptive, the stigmatic tips were completely engulfed, the ovuliferous scales had thickened enough to close the conelet, and the conelet had begun to bend down.Maximum seed set occurred when (1) cones were pollinated within 4 days after seed-cone buds had emerged half of the way out of their bud scales; (2) a minimum of 0.2 g of pollen was used per pollination bag; (3) a minimum of 11 pollen grains adhered to each stigmatic tip; and (4) at least 3 pollen grains were taken into each micropylar canal. The engulfing process occurred at the same rate and in the same manner regardless of whether living or heat-killed pollen was present or absent on the stigmatic surface. Poor seed set as it related to the pollination mechanism is discussed.
Cleaning yellow birch seedling stands to increase survival, growth, and crown development
Authors: Erdmann Gayne G. , Peterson Jr. Ralph M. , Godman Richard M.
Published: July 2007

Nine year diameter growth, height growth, survival, change in crown position, and quality responses of 7-year-old dominant and codominant (Betulaalleghaniensis Britton) seedlings to five intensities of cleaning near Marquette, Michigan are reported. The best compromise between survival, growth rate, and quality development without corrective pruning is to clean within a 2.4-m radius of selected crop trees. If corrective pruning is feasible, the 3.7-m cleaning radius treatment would be best because diameter growth is 30% greater.
Promotion of cone and seed production in rooted ramets and seedlings of western hemlock by gibberellins and adjunct cultural treatments
Authors: Ross Stephen D. , Piesch Richard F. , Portlock Franklin T.
Published: July 2007

Over 100-fold increases in numbers of seed cones and 6- to 24-fold increases in pollen cones were achieved for 7- and 8-year-old rooted ramets of sexually mature western hemlock (Tsugaheterophylla (Raf.) Sarg.) from stem injections of gibberellin A4/7 (GA4/7) mixtures and calcium nitrate fertilization. Female, but not male, flowering was also promoted significantly in nitrate-fertilized 6-year-old seedlings, both by stem injections (47% flowering) and foliar sprays (40% flowering) of GA4/7. Flower induction in 3-year-old potted seedlings required water stress in addition to GA4/7 foliar sprays (30% initiated seed cones and 7% pollen cones). The cones produced developed normally and set sound seeds. For mature ramets, flower promotion was roughly proportional to the logarithm of GA4/7 + GA9 concentration from 25 to 400 mg•L−1; calcium nitrate fertilization, though ineffective when used alone, significantly enhanced this response. Treatments of 6- and 12-week durations, beginning 24 May, were equally effective in promoting both male and female flowering. However, production of seed cones was only slightly enhanced and that of pollen cones not at all when treatment was delayed until 7 July (6 weeks), indicating the need to start GA applications before cone-bud differentiation has been completed (late June for pollen cones and mid-July for seed cones).