bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on the systematics of ectomycorrhizal fungi in axenic culture. IV. The effect of some selected fungitoxic compounds upon linear growth
Authors: Hutchison Leonard J.
Published: February 2008

When cultures of ectomycorrhizal fungi were grown on potato dextrose agar supplemented with either benomyl (10 μg/mL), cycloheximide (2 μg/mL), rose bengal (10 μg/mL), malachite green (2 μg/mL), or sodium chloride (10 mg/mL), characteristic differences in linear growth rate reduction were exhibited. These fungitoxic compounds were able to differentiate ectomycorrhizal fungi into three growth-response categories, namely sensitive, semitolerant, and tolerant, which reflected taxonomic affinity. Linear growth of the Russulaceae and species of Hebeloma, for example, was inhibited by benomyl (10 μg/mL), whereas members of the Boletaceae and most species of Cortinarius were tolerant and species of Tricholoma were semitolerant at this concentration. Lactarius, Leccinum, and most Suillus species were sensitive to cycloheximide (2 μg/mL); Laccaria, Rhizopogon, and most Hebeloma species showed tolerance. Hygrophorus and most Lactarius species showed sensitivity to rose bengal (10 μg/mL), whereas Cortinarius, Laccaria, Suillus, and some Lactarius species (section Dapetes) exhibited tolerance. Malachite green (2 μg/mL) inhibited species of Lactarius, whereas species of Suillus and Tricholoma were tolerant. Xerocomus, Rhizopogon, Hygrophorus, and most Tricholoma species were sensitive to sodium chloride (10 mg/mL), whereas tolerance was exhibited by most species of Suillus, Laccaria, and Hebeloma. The results reveal that growth responses to these fungitoxic compounds have potential as taxonomic characters for the differentiation and identification of isolates of ectomycorrhizal fungi. Key words: ectomycorrhizal fungi, fungitoxic compounds, cultures, identification, systematics.
Pollen exine substructure In Fagus (Fagaceae): role of tufts in exine expansion
Authors: Claugher Don , Rowley John R.
Published: February 2008

We compare results obtained from mature pollen of Fagus sylvatica L. using high-resolution scanning electron microscopy with fransmission electron microscopy images from several stages, from the early free microspore through to mature pollen grains. Exine processes (tufts) on young and mature grains are rodlike, with cross striations 10–15 nm wide. The total diameter of the tufts is 70–100 nm on exines of young microspores and up to 200–250 nm on mature exines. Tufts about 70 nm wide on the young microspores contain about five stacks of loops about 30 nm in diameter, whereas larger tufts on more mature exines have many stacks of the 30 nm wide loops. At maturity there is a mixture of large (200–250 nm wide) and small (70–100 nm wide) tufts and some tapering down from over 200 nm in width to less than 100 nm. There is continuity and a similar range of widths between the tufts as they occur as bacules and components of the tectum. We conclude that either new large-sized tufts are inserted during growth or some of the small (original sized) tufts increase in diameter from their bases toward the outer tip, or that both of these processes occur.
Viability of Penicillium bilaji and Colletotrichum gloeosporioides conidia from liquid cultures
Authors: Cunningham J. E. , Kuiack C. , Komendant K. E.
Published: February 2008

The effect of water activity on Penicillium bilaji Chalabuda and Colletotrichum gloeosporioides f.sp. malvae conidia at 20 °C was examined. The optimal relative humidity for storage at 20 °C was found to be 12–34% for C. gloeosporioides spores and 100% for P. bilaji spores. Retention of viability by C. gloeosporioides spores was improved by drying the spores from a 20% sucrose solution. The data demonstrate the conditions required for adequate shelf stability for commercial, biological products for agricultural application, based on these two organisms. Key words: Penicillium bilaji, Collectotrichum gloeosporioides, water activity, germinability.
Soil–steel structure design by the Ontario Code: Part 2. Structural considerations
Authors: Abdel-Sayed G. , Bakht Baidar
Published: February 2008

The paper presents provisions of the Ontario Bridge Design Code for the structural design of the metallic shell of soil–steel structures, and also discusses the development background of these provisions. A simplified method of determining live load effects in the metallic shell is presented. The method is based on results of a well-tested plane strain finite element program. An empirical method for determining live load effects, which is based on tests of full-size structures, is also given. A worked example is given to illustrate the usage of the design provisions.
Courbes de remous sous les couverts de glace de la Grande Rivière
Authors: Michel B. , Drouin M.
Published: February 2008

The problem of backwater curve computations under ice covers is very complex. On top of the difficulties which are inherent to computation of backwater curves under open water flow conditions, the ice cover has to be taken into account; its thickness and roughness is time dependent because of variable flow and weather conditions. One of the major factors is the formation of hanging ice dams, especially in most northerly rivers.In this paper we present a complete method for the computation of backwater curves, based on mechanisms of ice formation: the law of equilibrium of the frontal edge, the accumulation of ice under this edge, thermal growth, and finally the equilibrium of hanging dams. The method is based upon measurements taken in the La Grande River.
The state of the art in analysis of cellular and voided slab bridges
Authors: Bakht Baidar , Jaeger Leslie G. , Cheung M. S. , Mufti Aftab A.
Published: February 2008

Load distribution characteristics of cellular structures are greatly influenced by transverse cell distortion and because of this these structures require a somewhat different analysis than those used for other common types of bridges.This paper summarizes the results of an extensive literature search and initial review of the current methods of analyzing cellular and voided slab bridges. The various methods of calculating the equivalent plate parameters, which are necessary for two-dimensional analysis, are also reviewed.
Dynamic response of bridges to multiple truck loading
Authors: Hawk Hugh , Ghali Amin
Published: February 2008

An analytical procedure called the iterative dynamic substructuring method (IDSM) is described for determining the response of a beam–slab bridge system traversed by multi-axle trucks. The trucks are idealized as systems of beams mounted on springs and the bridge as a grid. The IDSM applies mode superposition analysis to the bridge and truck as separate structures connected only at the time-dependent contact points. The bridge is subjected to forces equal to the time-dependent forces on the truck springs, while the truck is subjected to “ground” motion displacements. Since the forces in the spring and the ground motion are interdependent, an iterative procedure is necessary to achieve compatibility of forces and displacements at the contact points.The IDSM is employed to study the response to multiple vehicle loading of the Conestogo River bridge which was field tested by the Ontario Ministry of Transportation and Communications. The purpose of the analysis is to compare single with multiple vehicle loadings under various conditions of truck speeds and positions. The results are used to assess the validity of the reduction in impact factors applied to multiple vehicle loading in the Ontario Bridge Code.
An experimental study of jet dilution in crossflows
Authors: Hodgson John E. , Rajaratnam N.
Published: February 2008

This paper presents the results of an experimental study on the dilution produced in jets discharged into crossflows. A general correlation has been developed to predict the centreline dilution. This relation has been found to agree reasonably well with field observations. It has also been possible to predict the growth of the width and the thickness of the deflected jet. This paper would be useful in the design of submerged outfalls in rivers. Key words: jets, crossflows, dilution, open channel flow, environmental hydraulics.
Distortional buckling of steel beams in cantilever-suspended span construction
Authors: Albert Charles , Essa Hesham S. , Kennedy D. J. Laurie
Published: February 2008

The behaviour of cantilever-suspended span systems is influenced by the type of loading and the presence of flange restraint. An experimental program consisting of 33 full-scale tests was undertaken to examine the stability of beams in a single overhang configuration. The results indicate that torsional flange restraint significantly enhances the buckling resistance and is particularly effective when combined with a web stiffener. Lateral bracing of the bottom flange at column supports is of considerable importance in maintaining stability. Simulating the proper boundary conditions is essential, since test specimens are very sensitive to unwanted restraints and can buckle in a higher energy mode.A finite element model was developed that takes into account inelastic material behaviour, residual stresses and cross-sectional distortions. The predicted buckling capacities are in good agreement with experimental results. Key words: cantilever-suspended span, steel beams, distortional buckling, flange restraint, inelastic behaviour.
Characterization and treatment of lime sludge dewatering effluents
Authors: Zhou H. , Smith D. W. , Stanley S. J.
Published: February 2008

With ever increasing regulatory constraints on the disposal of residuals produced during water treatment, the cost of handling, treatment, transport, and disposal of these residuals has become a significant portion of overall water treatment costs. In plants practicing lime softening, a major source of residuals is lime sludge. Of the many options proposed for the management of lime sludges most include sludge dewatering. The dewatering process produces effluents that also must be disposed of. This paper presents the results of the characterization of dewatering effluents from a large water treatment plant. Also presented are treatment and management options which were evaluated through designed bench-scale experiements.The quality and quantity of supernatant effluents from the thickener and centrate from the centrifuge were determined. It was found that the supernatant is composed predominantly of calcium ions and caustic alkalinity which can be treated through pH adjustment. The centrate was found to be of much poorer quality with poor settling and filterability properties. These qualities were found to be mostly attributed to the high organic content of the centrate. Bench-scale tests found that polymer pretreatment could substantially improve both the settleability and filterability of the centrate. Key words: water treatment, sludge dewatering, softening, polymers, sludge conditioning.
Construction methods for minimizing vibration levels in floors with lumber joists
Authors: Smith Ian , Chui Ying Hei
Published: February 2008

The National Building Code of Canada 1990 specifies the allowable spans for lumber floor joists that are expected to lead to satisfactory vibrational behaviour. This paper discusses construction methods that improve the floor behaviour once the flooring and joists appropriate to a particular building occupancy have been selected. Laboratory tests on full-size floors demonstrate that adding between-joists bridging and supporting all four floor edges significantly improves the overall vibrational performance of wood floors. Bridging consisting of solid blocking glued to the underside of the flooring and a mild steel strap nailed to the underside of blocking and joists is more effective than several alternative details. Incorporating pads of damping material between flooring and joists, or at bearings, can have a detrimental effect on floor performance. The use of elastomeric adhesive, in lieu of nailed flooring-to-joist connections, does not significantly enhance the mechanical performance of floors with lumber joists. Key words: lumber, vibration, serviceability, floors, design detailing.
Bend ice jams: laboratory observations
Authors: Urroz Gilberto E. , Ettema Robert
Published: February 2008

Presented herein are the results of laboratory experiments aimed at obtaining preliminary insights into characteristic features of ice jams in river bends. The experiments, which focused on jams comprising a continuum of ice pieces small compared to river width, were carried out using a curved flume and polypropylene beads to simulate ice pieces. They revealed that jam thickness was greatest along the inner bank, and especially in the lee, of a bend. In many respects, jam-thickness distribution was found to be analogous to alluvial bed topography. Additionally, flow in the jam-covered bend flume was found to develop a double helicoidal flow pattern which resembled mirror-image combinations of flow field associated with open water flow in alluvial bends. Key words: ice jams, river ice, river bends.
Flexural behaviour of bolted joints of corrugated steel plates
Authors: Mikhailovsky Leonid , Kennedy D. J. Laurie , Lee Raymond W. S.
Published: February 2008

Even though the design of corrugated steel plate culverts is based on compression ring theory, soil-steel structure interaction will likely lead to the development of bending moments in the steel plates. Successful application of these structures requires that these moments be accommodated without distress, while the plate carries axial thrust. This requires ductile flexural behaviour.The results of 13 flexural tests, with two-point loading, on lap joints of 3, 5, and 7 mm thick corrugated steel plates, as well as one test on plain 5 mm thick corrugated steel plate, are reported. Bolt configurations consisting of 2, 3, and 4 bolts per complete corrugation were tested to investigate the postulate that lap joints subject to bending moments can be made in a correct or incorrect manner. Correct lap joints are those that do have a bolt near the edge of the lap on the tension side where prying tends to occur, that is, where the gap between the lapped plates tends to open up when the joint is subject to moment. Incorrect laps do have a bolt at this location. Laps with 2 bolts are either correct for both positive and negative bending moments or incorrect for both. Statistically, laps with 3 bolts will be incorrect 75% of the time and laps with 4 bolts all the time.The tests confirm the postulate and show that, in the incorrect laps, tearing of the corrugated plates, starting at the edges of the bolt holes in the critical location where there is prying, occurs shortly after the maximum moment is reached. The tearing leads to a reduction in the moment resistance and reduced ductility even though the maximum moment for incorrect laps may be comparable to that for correct laps. Correct laps exhibit tremendous ductility, achieving joint rotations of 0.4 radians or more. Laps with 4 bolts per corrugation are weaker flexurally than laps with 2 bolts per corrugation because the critical net area on the tension side is less. Shaped washers placed under the bolt heads at the critical location do not improve the behaviour. Inadequate torquing in the bolts leads to increased flexibility, and reduced strength of the lap joints and increased opening of the gap between the plates. Key words: bolted, corrugated, culvert, ductility, flexure, joints, lap, moment resistance, plate, steel, tearing.
Engineering properties of rubberized concrete
Authors: Eldin Neil N. , Senouci Ahmed B.
Published: February 2008

Growing piles of discarded tires are potential sources of fire and health hazards. The current disposal methods are wasteful and costly. As a possible solution to the problem of scrap-tire disposal, an experimental study was conducted to examine the potential use of rubber aggregate (tire chips and crumb rubber) as mineral aggregate substitute in Portland cement concrete mixes. The research focused on determining the strength characteristics of rubberized concrete and examined the relationship between the size, percentage, and shape of rubber aggregate and the strength measured.Rubberized concrete was found to possess good esthetics, acceptable workability, and a smaller unit weight than plain concrete. However, it exhibited low compressive and tensile strengths and lower resistance to repeated freezing and thawing cycles than that of plain concrete. A statistical analysis of the experimental data suggested that only the percentage by volume of rubber in the mix has a significant effect on strength. The size and shape was found insignificant. Unlike plain concrete, rubberized concrete did not demonstrate the typical brittle failure. It exhibited a ductile, plastic failure, and showed the ability to absorb a large amount of plastic energy under compressive and tensile loads. Key words: rubberized concrete, concrete properties, compression, durability, failure, modulus of elasticity, slump, tension, toughness, workability.
Evidence for genetic control of response to sulfur dioxide and ozone in Populustremuloides
Authors: Karnosky David F.
Published: February 2008

This study was designed to estimate the degree of genetic control of the response to sulfur dioxide (SO2) and ozone (O3), alone and in combination, in trembling aspen (Populustremuloides Michx.). Rooted cuttings from 11 randomly selected trees in central Wisconsin were used in the study. Significant interclonal variation was found in the response of the 11 clones to 3-h exposures to 0.50 ppm SO2, 0.20 ppm O3, and 0.35 ppm SO, plus 0.05 ppm O3. Clonal repeatability estimates of 0.464 for SO2 plus O3, 0.620 for O3, and 0.642 for SO2 suggest that much of this variation between clones can be attributed to genetic differences in response to SO2 and O3.
Growth response of young balsam fir fertilized with nitrogen, phosphorus, potassium, and lime
Authors: Timmer V. R. , Stone E. L. , Embree D. G.
Published: February 2008

Growth responses of a young, naturally regenerated Abiesbalsamea stand managed for Christmas trees in Nova Scotia were measured over the 2 years after application of dolomitic limestone and factorial combinations of four levels of N, two levels of P, and two levels of K. In the first season, nitrogen-treated trees were darker green and had heavier terminal buds. Other significant responses owing to nitrogen were greater numbers of apical and lateral buds in the second season and greater length of leaders, lateral shoots, and needles in both seasons. The only significant main effect of P was on bud development. Neither K nor lime had any significant influence, and no significant interactions among any nutrients were detected. Growth responses did not differ significantly among three rates of N application over the 2-year period indicating.that for short-term cultural purposes the higher rates are inefficient on this site.
Comparing and predicting forest stand susceptibility to gypsy moth
Authors: Houston David R. , Valentine Harry T.
Published: February 2008

One hundred and sixty-eight forest stands in the northeastern United States with different histories of defoliation and responses to defoliation by the gypsy moth were compared by principal-components analysis (PCA) ordinations. The ordinations were based on tree structure-feature variables. PCA ordinations separated stands into meaningful groups that historically have been either susceptible or resistant to prolonged gypsy moth infestation. The best separation of resistant and susceptible stands occurred when the structure-feature variables were measured separately for tree species in different gypsy moth food-preference classes. Tree mortality after defoliation often was greater in the resistant wet bottom and mesic slope and ridge stands than in the susceptible dry ridge and sand stands. Our ordinations suggest that some stands, as a consequence of high oak mortality, may now be more resistant than before.
The relationship between electrical resistance and severity of decline symptoms in Acersaccharum
Authors: Newbanks Dennis , Tattar Terry A.
Published: February 2008

Electrical resistance (ER) measurements of the xylem–cambium area were affected by time of year, air temperature, tree diameter, species, bark blemishes, callus tissue, decay, and measurement techniques. Our results indicate that in urban sugar maples there was no statistically significant correlation between ER and tree response to physiologic stress, as measured by visual crown classification (based on the severity of decline symptoms) and by increment core data. Trees in a non-urban, campus setting showed a significant correlation between electrical resistance and visual crown symptoms (r = 0.61). Trees with intermediate crown-condition ratings had the highest average ER, and on the basis of ER, individual trees could not be placed into stress-response categories because of large variations in ER within each crown-condition class. No significant correlation was found between ER and applied physiologic stresses in nursery-grown sugar maples.
Physical properties of the oleoresin system of the four major southern pines
Authors: Hodges John D. , Elam William W. , Watson William F.
Published: February 2008

Oleoresin viscosity, flow (rate, duration, and total amount), and rate of crystallization were determined for Pinuselliottii Engelm., Pinuspalustris Mill., Pinustaeda L., and Pinusechinata Mill, in central Louisiana, U.S.A. Physical properties of the oleoresin and tree morphological characteristics (diameter at breast height, growth rate, height, crown ratio, and age) were not strongly related in either of the four species. Pinuselliottii oleoresin was extremenly viscous, crystallized very slowly, and flowed at a slow rate over a long period, and total yield was moderate. Pinuspalustris oleoresin was of moderately high viscosity and very high yield and had a high rate of flow. Pinustaeda and Pinusechinata oleoresin had, on the average, low viscosity, a moderate to low total yield, a short duration of flow, and rapid rate of crystallization. A discriminant function analysis revealed that 19% of the Pinustaeda and 6% of the Pinusechinata trees had oleoresin properties more similar to Pinuspalustris and Pinuselliottii than to the means for their own species. This information is being used to assess tree susceptibility to attack by Dendroctonusfrontalis Zimm.
Growth and development of sugar maple as revealed by stem analysis
Authors: Fayle D. C. F. , MacDonald G. B.
Published: February 2008

Patterns of annual height and radial growth over a 50- to 60-year period are discussed for three 16- to 18-m-tall sugar maple (Acersaccharum Marsh.) of intermediate crown position growing in tolerant hardwood forest in central Ontario. Two of the trees had been released when they were about 6 m tall. Changes in the growth layer profile as the trees developed showed similarities to those reported for conifers but were modified by light conditions and crown characteristics. A repetitive pattern of changes in height and radial increment in response to changing environmental conditions occurred. Overall changes in the pattern of ring width at breast height appeared to be a good indicator of growth performance as they were close to those for specific volume increment.
Response of crop trees of sugar maple, white ash, and black cherry to release and fertilization
Authors: Ellis Robert C.
Published: February 2008

In Grey County, southern Ontario, a crop-tree release and fertilization experiment was carried out in 35- to 85-year-old hardwood stands of variable composition. The objective of the treatments was to improve the growth rate of selected high-quality trees. A method is described for the selection and allocation of crop trees to treatments according to a competition index (CI). Release involved thinning to reduce a tree's CI by nominal levels 0, 50, and 75%. Fertilizer was applied within a circular plot equal to 1.5 times the crown radii at rates of N = 295 and 590 kg/ha (ureaform); P = 227 and 454 kg/ha (triple superphosphate). Fertilization resulted in increased foliar concentrations of N and P in sugar maple (Acersaccharum Marsh.), white ash (Fraxinusamericana L.), and black cherry (Prunusserotina Ehrh), but only black cherry responded to N fertilizer with an increase in diameter growth; none responded to P fertilizer. The diameter growth of sugar maple showed a response that was linearly related to the degree of release. Black cherry and white ash showed only small responses to release. It was concluded that P was not limiting to any species on these soils, and N may be limiting only to black cherry. Crop-tree release was an effective treatment for stimulating the growth of sugar maple, but it appeared to be relatively ineffective for white ash or black cherry at this age.
Hormonal enhancement of cone production in Douglas-fir grafts and seedlings
Authors: Puritch George S. , McMullan Eleanor E. , Meagher Michael D. , Simmons Clarence S.
Published: February 2008

Gibberellic acid (GA) and naphthaleneacetic acid (NAA) were applied alone and in combination to both girdled and nongirdled branches of Douglas-fir in four seed orchards (two containing seedlings and two containing grafts). GA significantly increased seed-cone buds and cones and caused a nonsignificant increase in pollen-cone buds. Cone production was not significantly affected by girdling or the application of NAA. Trees treated with the combination of GA + NAA responded similarly to those treated with GA alone. Cone production response to GA varied according to the orchard locations, with better response in the normally more productive orchards. The percentage of trees flowering was increased by GA. Hormone treatments had no effect on seeds per cone but they significantly reduced filled seed per cone. Owing to increased cone number, however, the GA treatments greatly increased the yield of viable seed. NAA increased the percentage of seed germinating and the rate of seed germination, while GA had no effect.
Performance and comparison of stand growth models based on individual tree and diameter-class growth
Authors: Ek Alan R. , Monserud Robert A.
Published: February 2008

A distance-dependent individual tree based growth model (FOREST) was compared with a diameter-class growth model (SHAF) for describing changes in stand density and structure. Projections of Lake States' northern hardwood stand development were made by each model for 5–26 years over a range of stand conditions and harvest treatments. Results from numerous performance tests and comparisons of actual and predicted diameter distributions, basal areas, and numbers of trees, indicate the individual tree model was considerably more sensitive to harvest treatments and reproduction response than the diameter-class model. Conversely, the latter was much less expensive to operate. Prediction of species and individual tree growth with the individual tree model appeared to provide sensitivity nearly equal to that observed for predictions of the stand as a whole. Long-term projections (120 years) for reserve (no cut) and clear-cut stand conditions further suggest the potential and limitations of the models for management analyses.
The Canadian softwood lumber industry: discussion
Authors: Muller R. A.
Published: February 2008

An econometric model of the Canadian softwood lumber industry described by Glenn H. Manning is discussed. Problems are caused by the inclusion of production of lumber for export to the United States in the demand equations for Canada and the rest of the world and by the interpretation of productivity in the Canadian supply equation. Some improvements are suggested.
Vegetation, soils, and forest productivity in selected forest types in interior Alaska
Authors: Viereck Leslie A. , Dyrness C. T. , Cleve Keith Van , Foote M. Joan
Published: February 2008

Vegetation, forest productivity, and soils of 23 forest stands in the taiga of interior Alaska are described. The stands are arranged on an environmental gradient from an aspen (Populustremuloides Michx.) stand on a dry, steep south-facing bluff, to open black spruce (Piceamariana (Mill.) B.S.P.) stands underlain by permafrost on north-facing slopes. The coldest site is a mixed white spruce (Piceaglauca (Moench) Voss) and black spruce woodland at the treeline. Mesic upland sites are represented by successional stands of paper birch (Betulapapyrifera Marsh.) and aspen, and highly productive stands of white spruce. Several floodplain stands represent the successional sequence from productive balsam poplar (Populusbalsamifera L.) and white spruce to black spruce stands underlain by permafrost on the older terraces. The environmental gradient is described by using two soil factors: soil moisture and annual accumulated soil degree days (SDD), which range from 2217 SDD for the warmest aspen stand to 480 SDD for the coldest permafrost-dominated black spruce site. Soils vary from Alfie Cryochrepts on most of the mesic sites to Histic Pergelic Cryochrepts on the colder sites underlain by permafrost. A typical soil profile is described for each major forest type. A black spruce stand on permafrost has the lowest tree standing crop (15806 g•m−2) and annual productivity (56 g•m−2•year−1) whereas a mature white spruce stand has the largest tree standing crop (24 577 g•m−2) and an annual productivity of 540 g•m−2•year−1, but the successional balsam poplar stand on flood plain alluvium has the highest annual tree increment (952 g•m−2•year−1). The study supports the hypothesis that black spruce is a nutrient poor, unproductive forest type and that its low productivity is primarily the result of low soil temperature and high soil moisture.
Biomass and productivity of white spruce stands in interior Alaska
Authors: Yarie J. , Cleve K. Van
Published: February 2008

A total of 58 trees was sampled from eight stands across a large area of interior Alaska. Regression equations were developed to estimate standing aboveground biomass for 22 white spruce (Piceaglauca (Moench) Voss) stands. Aboveground standing biomass of white spruce in mature stands ranged from 0.92 to 23.28 kg/m2 and current annual production ranged from 89 to 2853 g•m−2•year−1.
Nitrogen and phosphorus nutrition and nutrient cycling by evergreen and deciduous understory shrubs in an Alaskan black spruce forest
Authors: Chapin III F. Stuart
Published: February 2008

Seasonal patterns of biomass, nitrogen (N), and phosphorus (P) were determined for major plant parts of the deciduous shrub Vacciniumuliginosum L. and the evergreen shrub Ledumgroenlandicum Oeder. in a black spruce (Piceamariana (Mill.) B.S.P.) forest in interior Alaska. New growth comprised 52 ± 7% of aboveground biomass in Vaccinium compared with the evergreen Ledum for which a maximum of 38 ± 3% of aboveground biomass was new growth. In Vaccinium the spring decline in leaf N and P concentration was due to dilution by increasing leaf biomass, whereas the autumn decline in N and P concentration was due to retranslocation, at which time 68–72% of leaf N and P was retranslocated from leaves. In contrast, the entire decline in N and P concentration of new growth in Ledum was due to dilution by increasing leaf biomass. Uptake contributed 60–68% of the maximum N and P requirement for aboveground growth of Vaccinium, with the remainder coming from stored reserves. Ledum supported 71–79% of its aboveground nutrient requirement by direct uptake from soil and may have been less dependent upon stored nutrient reserves. Vaccinium and Ledum together comprised only 0.8–2.8% of the standing crop of aboveground vascular biomass and N and P pools at Washington Creek but contributed 16% of vascular aboveground production and 19–24% of the N and P cycled annually by vascular plants. The importance of understory shrubs is due to their small support structure and rapid turnover of biomass and nutrients (34–43% of aboveground pools annually) relative to that of the trees (2–5% annually). Understory shrubs at Washington Creek and in other evergreen forests are much more important in nutrient cycling than their small biomass would suggest.
Temperature control over root growth and root biomass in taiga forest trees
Authors: Tryon Peter R. , Chapin III F. Stuart
Published: February 2008

Root elongation of greenhouse-grown Alaskan taiga tree seedlings increased with increasing root temperature in all six species examined and was most temperature sensitive in warm-adapted aspen (Populustremuloides Michx.). Root elongation was slower in fine than large roots and in black spruce (Piceamariana (Mill.) B.S.P.) was less temperature sensitive in fine than in large roots. Root elongation in the laboratory was slowest in black spruce, which has an inherently slow growth rate, and most rapid in poplar (Populusbalsamifera L.) and aspen, which grow more rapidly. In contrast, field root elongation rates tended to be highest in black spruce from cold wet sites, suggesting that site factors other than soil temperature (e.g., moisture) predominated over genetic differences among species in determining field root elongation rates. The seasonal pattern of root elongation was closely correlated with soil temperature and reached maximum rates in July for all tree species (except aspen medium-sized roots). Most roots of each species were in the top 20 cm of soil. However, root growth penetrated to greater depth in warm compared with cold sites. Root biomass in a 130-year black spruce forest (1230 g/m2) comprised only 15% of total tree biomass. Root biomass of 25-year aspen and 60-year poplar sites (517 and 5385 g/m2, respectively) comprised a greater proportion (57% in poplar) of total tree biomass than in spruce.
Effects of forest-floor disturbance on soil-solution nutrient composition in a black spruce ecosystem
Authors: Cleve K. Van , Dyrness C. T.
Published: February 2008

This study summarizes the effects of forest-floor disturbance on soil-solution chemistry. For comparative purposes chemical analyses are also presented of soil solution collected beneath undisturbed black spruce (Piceamariana (Mill.) B.S.P.) stands, stream water, and precipitation in the same area. The disturbance treatments were superimposed on the forest floor following removal of the black spruce overstory. These included burning of the forest floor, and mechanical removal of one-half and all of the forest floor. Conductivity, pH, and the concentrations of [Formula: see text], [Formula: see text], phosphates, K, Ca, and Mg were determined in the various water samples. Only in the case of the most severe treatments, one-half and all of the forest floor removed, was there substantial changes in conductivity, pH, and the concentrations of Ca and Mg. Potassium and P showed no consistent treatment effects. Lack of significant change in solution N concentration may reflect increased microbial activity and N immobilization in the forest floor in response to disturbance.
Conclusions and directions for future research in taiga forest ecosystems
Authors: Cleve K. Van , Dyrness C. T.
Published: February 2008

not available
Energy status and cytochromes in isolated endophytic vesicle clusters of red alder root nodules
Authors: Ching Te May , Monaco Philip A. , Ching Kim K.
Published: February 2008

Anaerobically isolated endophytic vesicle clusters from root nodules of Alnusrubra Bong. were low in cellular energy charge (0.4 to 0.5), total adenylate pool (0.4 to 0.9 nmolùmg protein−1), and nitrogenase activity (0.1 to 0.3 nmolùmg protein−1). Upon addition of substrate (glucose, sucrose, isocitrate + isocitrate dehydrogenase + NADP), energy charge decreased by 2 to 20%, total adenylate pool increased by 3- to 11-fold, and nitrogenase activity increased by 50 to 500%. Only ATP and dithionite supported substantial nitrogenase activity and greatly elevated energy status. Treating vesicle clusters with macerase and cellulase to remove the host capsule facilitated substrate and oxygen uptake, resulting in a 240% increase in total adenylate pool, a 60% increase in energy charge, and a 730% increase in nitrogenase activity. Isolated vesicle clusters contained about 320 nmol cytochromes•g protein−1, with an average molar distribution of 17% cytochrome a-a3, 39% b, 22% c, and 21% o. No cytochrome P 450 was observed in vesicle clusters. The presence of cytochromes a-a3 and o may be a mechanism of oxygen tolerance whereby the nitrogenase in Frankia spp. can operate in an environment without the protection of leghaemoglobin.
Chemical characteristics of precipitation and hydrogen input in throughfall and stemflow under some eastern Canadian forest stands
Authors: Mahendrappa M. K.
Published: February 2008

At the Acadia Forest Experiment Station (AFES) in central New Brunswick chemical characteristics of rain samples collected at five different locations were determined during the 1977–1981 period. Throughfall and stemflow samples from six softwood and three hardwood stands were collected and chemically characterized starting from the early 70's. In 1976 two of four plots in each of the stands were treated with urea at a rate of 225 kg N•ha−1. Both the quantities of rain and their pH values varied considerably between collections, months, and years. The weighted mean pH of summer (May–October) rain collected intensively during the 1977–1981 period ranged from 4.5 to 5.1, with an overall weighted average value of 4.75 for the 5 years. Sulfur and nitrate N measured during May–October 1982 amounted to 6.18 and 1.52 kg•ha−1, respectively, for the 6-month period. The concentration of hydrogen ion in the throughfall was less than that in the rain. Hardwood throughfall had lower hydrogen levels (higher pH) than the softwood throughfall. The pH of the stemflow from softwoods was lower than that of rain in most cases. Although not significantly, the hydrogen ion concentration of both throughfall and stemflow on the fertilized plots was lower than on the untreated plots. The hydrogen load of rain was reduced by all tree species, but there was considerable variation between species in their abilities to decrease total hydrogen reaching the soil.
Growth patterns in a young western hemlock plantation infested with dwarf mistletoe
Authors: Thomson A. J. , Smith R. B.
Published: February 2008

Relative height and diameter values of 22-year-old western hemlock trees (Tsugaheterophylla (Raf.) Sarg.) were normally distributed, with a constant standard deviation from year to year. Ranking of individual trees in the distribution changed with time, presumably because the root systems encountered successively more favourable or unfavourable microsites. Competition effects were detectable on height and diameter at breast height (dbh), although these effects were considerably masked by the microsite effect. Dwarf mistletoe (Arceuthobiumtsugense (Rosendahl) G. N. Jones) effects were detectable on height growth, but not dbh growth. Height increment in a particular year varied in a pattern similar to February precipitation, while diameter increment varied in a pattern similar to March–May precipitation. This may account for the observation that the degree of correlation of height and diameter increments in a particular year varied from low to high.
The timber supply function under regulatory constraints
Authors: Johansson Per Olov , Löfgren Karl Gustaf
Published: February 2008

In this paper the properties of the supply function of a present value maximizing forest farmer are analyzed. In particular, we consider how its properties are changed by the presence of binding constraints on cutting behaviour. This is done by comparing the properties of the supply function under rationing with the corresponding properties under a free market. One result from this exercise being that the effect of a relaxation of the constraint will increase (decrease) the cuts in periods whose cuts are complements (substitutes) to the cut of the constrained period. Another result being that the supply function in one particular period will be less price elastic under rationing than under a free market. This latter result is supported with some preliminary empirical evidence from the Swedish roundwood market.
Forest community types of west-central Alberta in relation to selected environmental factors
Authors: Corns I. G. W.
Published: February 2008

The forests of the Wapiti map area, Alberta, were studied to ascertain relationships among forest growth, plant community distribution, and environmental factors within the western boreal and subalpine forests. Quantitative data on tree productivity, vegetation, and soils were collected from 137 plots. The 16 described forest community types (CTs) of predominantly fire origin were dominated by lodgepole pine (Pinuscontorta Dougl. var. latifolia Engelm.), white spruce (Piceaglauca (Moench) Voss), black spruce (Piceamariana (Mill.)B.S.P.), or aspen (Populustremuloides Michx.), were floristically simple (111 vascular plants), had tree productivity ranging from 0.4 m3 ha−1 year−1 in the Piceamariana/Ledumgroenlandicum/Rubuschamaemorus type to 5.0 m3 ha−1 year−1 in the Populusbalsamifera/Rosaacicularis/Thalictrumvenulosum type, and occurred on soils representing Luvisolic, Brunisolic, Gleysolic, Regosolic, Podzolic, and Organic orders. Two major successional trends are apparent in the upland boreal forest: lodgepole pine and aspen to the Piceaglauca/Rubuspubescens – Maianthemumcanadense type on moist sites at low elevations and lodgepole pine and black spruce forest to the Picea spp. – Abieslasiocarpa/Hylocomiumsplendens type on moist to well-drained sites at higher elevations. The Pinuscontorta/Menziesiaglabella/Rubuspedatus CT succeeds to the Piceaengelmanii – Abieslasiocarpa/Menziesiaglabella CT in closed canopy subalpine forests.
Stem growth and respiration of young balsam fir trees in thinned and unthinned stands
Authors: Lavigne M. B.
Published: February 2008

Average respiration rate per square decimetre of stem surface area was greater in a thinned stand of balsam fir (Abiesbalsamea (L.) Mill.) than in an unthinned stand. While respiration rates of internodes were highly correlated to their rates of stem growth, the differences in respiration among internodes and stands could not be explained by the unequal use of respiration products to support synthesis alone. Maintenance respiration rates were greater for internodes with higher rates of stem growth, and consequently the efficiency of using photosynthates for growth was reduced in the thinned stand. In addition, breast-height internodes respired at higher rates than upper stem internodes with equal growth rates. It is argued that lower stem internodes expended more respiration products for translocation than upper stem internodes. The rate of stem growth per unit of foliar weight was less in the thinned than in the unthinned stand, indicating that the higher rate of respiration per unit of stem surface area counteracted the beneficial effects of thinning on the rate of photosynthesis per unit of foliar weight.
Control of height growth components in seedlings of California red and white fir by seed source and water stress
Authors: Hallgren Stephen W. , Helms John A.
Published: February 2008

Terminal bud growth in 2nd-year seedlings and subsequent elongation of the overwintering bud in the 3rd year were studied in California red fir (Abiesmagnifica A. Murr.) and two elevational sources of white fir (A. concolor (Gord. and Glend.) Lindl.). During each growing season the seedlings were either watered or left unwatered to provide 2nd and 3rd year treatments of wet–wet, dry–wet, wet–dry, and dry–dry seasons. Harvests were done biweekly during the second growing season and once at the end of the third growing season. Rate and duration of primordium production were negatively related and there were no differences among seed sources for the number of primordia produced in the 2nd year. Watering more than doubled the number of primordia, mainly through increasing the rate of production. Internode number and length were negatively related on a genetic and environmental basis. Changes in internode length tended to compensate for environmentally induced changes in internode number which resulted in a year to year stability in height growth. Height growth was more buffered against changes in internode number in red fir than in white fir. Watering induced a summer shoot in 80% of low-elevation white fir seedlings and 40% of red fir and high-elevation white fir seedlings. Summer shoots doubled the height increment for the current season and increased the number of needle primordia in the winter bud by 26%. The larger buds were the result of a prolonged period of primordium production.
Variation in host foliage nutrient concentrations in relation to western spruce budworm herbivory
Authors: Clancy Karen M. , Wagner Michael R. , Tinus Richard W.
Published: February 2008

The western spruce budworm, Choristoneuraoccidentalis Freeman, prefers to feed on early season, new foliage; phenological age of host foliage has profound influences on larval growth and development. Budworm growth, survival, and reproduction also differ with host plant species. Seasonal and interspecific variation in foliar nutrients suggests that they may be key nutritional factors affecting budworm performance. Foliar concentrations and balances of N and eight mineral elements (P, K, Ca, Mg, Mn, Cu, Fe, Zn, P/N, Cu/Zn, Mn/Fe, and Ca/Mg) in current-year needles varied with season and tree species (Pseudotsugamenziesii (Mirb.) Franco, Abiesconcolor (Gord. & Glend.), and Piceaengelmannii Parry ex Engelm.). Seasonal trends occurring in all host species as the new needles matured were (i) declines in N, P, K, and Zn; (ii) increases in Ca, Mn, P/N, Mn/Fe, and Ca/Mg; and (iii) an increase followed by a decrease in Fe. Nutrients showing distinct differences among host species included N, P, K, Ca, Fe, and Zn, plus the Cu/Zn ratio. Mg and Cu were different among some but not all host species or sampling times.
A soft optimization approach to forest land management planning
Authors: Bare B. Bruce , Mendoza Guillermo A.
Published: February 2008

Forest land management planning provides a rich environment for the use of optimization techniques that incorporate multiple criteria and operate within a soft optimization decision environment. Using de novo programming, several approaches for examining planning problems are described where the objective is not simply to optimize a given system, but to design an optimal system. Both single and multiple objective linear programming models are used to illustrate this new approach and several illustrative examples are discussed.
Forest health surveys: problems in assessing observer objectivity
Authors: Innes John L.
Published: February 2008

The quality of data collected in surveys of forest health depends on a subjective interpretation of tree condition. Many factors influence classification, including the observer's experience, the observer's bias, the weather at the time of the classification, and the appearance of the tree. The effects of some of these factors can be quantified and attempts made to reduce their impact. It may be possible to account for others during the analysis and interpretation stages of the inventory process.
Response of red and jack pines to inoculation with microbial associates of the pine engraver, Ipspini (Coleoptera: Scolytidae)
Authors: Raffa Kenneth F. , Smalley Eugene B.
Published: February 2008

The invasion of Pinusresinosa and Pinusbanksiana by the pine engraver, Ipspini, was simulated by inoculating mature trees with the beetle's fungal symbionts, Ceratocystisips and Ceratocystisnigrocarpa. Trees responded to inoculation by forming necrotic lesions in advance of the fungi and contained the attack. Ceratocystisips induced more extensive lesion formation than did C. nigrocarpa, demonstrating differences in host responses to and (or) virulence of these potential pathogens. Host responses were more extensive to live fungi than to mechanical wounds or killed inoculum, although there were also significant differences between the latter two treatments. Pinusbanksiana responded by forming more extensive lesions than P. resinosa to all treatments.