bluuebunny/crossref_metadata_2025 huggingface dataset:
Standard terms of reference to ensure satisfactory computer-based urban drainage design studies
Authors: James William , Robinson Mark A.
Published: February 2008

The main purposes of modelling are a reasonable understanding of the physical processes involved and a careful evaluation of reasonable alternative designs. The central concern is credibility.Inreasingly, government and municipal engineers involved in urban drainage design supervise studies in which sophisticated computer models are being used by specialists. Because of the large variety of programs available for modelling, the rapid evolution of the models, and because of their complex structures, the studies are becoming increasingly difficult to manage.In the initial study terms of reference, the following component study activities could be specified in detail when bids are requested: problem review, study objectives, performance criteria, requisite accuracy, review of available programs, available data and study resources, program selection criteria, model verification, model calibration, model validation, minimum level of discretization, sensitivity analysis, data preparation and output interpretation, documentation of the modifed program actually used, and preparation of machine readable input and output files for archiving. Many of these activities will be carried out by a reputable engineer in any case.By including these terms of reference, all consultants bidding will be assured that their costs will be met, and clients will be insuring their investment in design engineering with a modest premium. Each of these points is discussed using examples appropriate to stormwater management modelling studies. However, a number of the concepts can be applied generally to other disciplines using computer-based modelling.
Headed shear stud connectors in a stub-girder floor system: a preliminary study
Authors: Rezansoff T. , Hosain M. U.
Published: February 2008

The performance of headed shear stud connectors which attach the reinforced concrete slab to the supporting structural steel stubs in a stub-girder structural floor system was examined by testing 28 portions or subassemblages of a complete stub-girder. The major difference which affected the performance of the shear connectors in a stub-girder floor system as compared with conventional composite construction was the increasèd tension which must be carried by critically located shear connectors. One cause of the increase in tension was the secondary bending which resulted from the transverse (beam) shear acting on the concrete slab along the open panel of the stub-girder between interior structural steel stubs. This behavior is similar to the bending which takes place in the chords of a Vierendeel truss.A significant reduction in the shear strength of the connectors resulted from the induced tension. However, the shear strength could be predicted using current Canadian code strengths if allowance was made for the tension in the connectors. The analysis suggested that the resultant of the full applied shear force and 75% of the applied tension force was comparable with the shear connector strength given in the code.
Field monitoring and performance evaluation of the Whitehorse sewage lagoon
Authors: Whitley G. , Thirumurthi D.
Published: February 2008

The treated effluent from a four-cell (predominantly anaerobic) sewage lagoon in Whitehorse, the Yukon Territory, Canada, does not meet the quality guidelines of the Yukon Territory Water Board. The inflow rates and the biochemical oxygen demand (BOD5) and suspended solids (SS) on 24-h composite samples of municipal wastewater influent and effluent were monitored from August 1989 to September 1990 to assess the performance and to estimate the first-order BOD5 removal coefficient, K. This study in northern Canada included a measurement of solar energy (photosynthetically active radiation, PAR) using a quantum radiometer which recorded the duration as well as the magnitude of PAR, for 1 year. Moreover, pH, conductivity, and temperature of influent and effluent, coliforms and chlorophyll of effluent, as well as dissolved oxygen (DO), temperature, and SS of the lagoon contents at various depths were recorded. The value of K ranged from a low of 0.036/d in December (at 2.4 °C) to a high of 0.097/d in October (at 5.2 °C). The monthly average effluent BOD5 exceeded the Yukon Water Board's permissible limit of 45 mg/L during the months of January, February, March, June, and July. Key words: cold climate anaerobic lagoon, photosynthetically active radiation (PAR), lagoon short-circuiting, performance data, northern Canadian sewage lagoon, Yukon Territory, first-order BOD5 removal coefficient, chlorophyll.
Étude des assemblages boulonnés soumis à la flexion gauche
Authors: Loulou Rafi , Sibille Pierre , Houde Jules
Published: February 2008

In this article, the problem of bolted connections subjected to biaxial bending is considered. Such a problem has not, up to now, been treated theoretically. Indeed, structural steel construction manuals normally propose various checking procedures and generally present design methods for connections subjected to various loadings. However nothing is said about bolted connections subjected to biaxial bending. First, a complete theoretical formulation of the problem is presented. It is based on elastic analysis principles and the assembly is treated classically. The resulting system of three equations is reduced to a system of two equations that can be solved numerically through iterative processes included in an algorithm with calculations done on a microcomputer. Interaction curves for various load combination are supplied. These results are used to validate the derivation and solve typical applications. Key words: bolted connection, biaxial bending, axial force, elastic analysis, computing.
Disposal of hazardous wastes in Canada's Northwest Territories
Authors: Heeney P. L. , Heinke G. W.
Published: February 2008

In the past decade, many jurisdictions have attempted to estimate the quantities and types of hazardous wastes generated within their boundaries. Similar studies done in the Northwest Territories (N.W.T.), Canada, are out-of-date, incomplete, or specific to only one type of wastes or geographic location. In 1990, an industry, business, and community survey was conducted to determine the types and quantities of hazardous wastes generated in the N.W.T. and the currently used disposal methods for these wastes. It revealed that 2500 tonnes of hazardous wastes were generated each year, including waste oil and petroleum products, fuel tank sludges, acid batteries, spent solvents, antifreeze, and waste paint.In many regions, disposal of these wastes may be routine, but waste disposal in arctic and subarctic regions presents unique difficulties. Severe climate, expense of transportation, isolation, and small quantities of wastes generated can make standard solutions expensive, difficult, or impossible to apply. Unique solutions are needed for northern waste disposal. The aim of this paper is to give an overview of low-cost, on-site or local hazardous waste disposal options that can be applied in the N.W.T. and also in other arctic, remote, or less-developed regions. Key words: hazardous wastes, Northwest Territories, cold climate regions, waste disposal.
Breach of a naturally embanked dam on Yalong River
Authors: Chen Y. J. , Zhou F. , Feng Y. , Xia Y. C.
Published: February 2008

A huge slide involving 68 × 106 m3 of soils occurred along the right bank of Yalong River in Sichuan Province, China. The sliding materials blocked the river and formed a dam-like structure having a height of 175 m and creating a reservoir with a capacity of approximately 680 × 106 m3. The dam breach which was caused by overtopping lasted 13 h and resulted in an estimated maximum flood discharge of 53 000 m3/s. Based on the hydrograph created by measuring the flows downstream of the dam, the process of dam breach was roughly estimated. Key words: landslide dam, cohesionless material, overtopping, breach, flood, hydrograph, failure process.
Model tests of dynamic ice loading on the Chinese JZ-20-2 jacket platform
Authors: Timco G. W. , Irani M. B. , Tseng J. , Liu L. K. , Zheng C. B.
Published: February 2008

A model test program has been performed to study the dynamic ice loads on a jacket platform used in Bohai Bay, China. The tests were performed at a geometric scale factor of 1:26. The prototype structure/foundation compliance was modelled and the structure was subjected to scaled ice sheets corresponding to the ice conditions in the Bohai Bay. The loads, moments, displacements, and accelerations of the structure were measured. The test variables include the ice thickness, ice speed, elevation of ice cover, and structure orientation with respect to the ice motion. An analysis of the data shows good agreement with measured full-scale information. Key words: ice, loads, dynamic, vibration, jacket structure, foundation, China.
Modeling spills on grass and impermeable surfaces
Authors: McBean Edward A. , Belore Randy , Capka Joseph
Published: February 2008

A general, two-dimensional spill model for the spread of liquids on land is developed. Evaporative and infiltrative fluxes are estimated as losses of fluid, in combination with the surface affinity depth and position-computing methods to develop time-varying spill profiles. Laboratory experimental results are used to demonstrate the validity of the computer model using water and carboxy-methyl cellulose doped-water to reflect different viscosities. Key words: surface spills, position-computing, numerical modeling, hazardous spills.
Use of foliage sulphate concentrations to predict response to urea application by Douglas-fir
Authors: Turner John , Lambert Marcia J. , Gessel Stanley P.
Published: February 2008

The foliage from 11 Douglas-fir fertilizer installations in the American Pacific Northwest were chemically analyzed to find a possible parameter to predict response to nitrogen application. It was found that the trees with high foliar sulphate sulphur reserves had a high response to nitrogen fertilizer while those with low foliar sulphate sulphur reserves had a low response. The basis for the assessment was the known biochemical relationship between nitrogen and sulphur in protein and the necessity for adequate foliar sulphur concentrations for nitrogen to be utilized by the plant. Foliar sulphate sulphur concentration was found to be a better single parameter for determining fertilizer nitrogen requirements than foliar nitrogen concentration.
Statistical distributions for fitting diameter and height data in even-aged stands
Authors: Hafley W. L. , Schreuder H. T.
Published: February 2008

The beta, Johnson's SB, Weibull, lognormal, gamma, and normal distributions are discussed in terms of their flexibility in the skewness squared (β1) − kurtosis (β2) plane. The SB and the beta are clearly the most flexible distributions since they represent surfaces in the plane, whereas the Weibull, lognormal, and gamma are represented by lines, and the normal is represented by a single point.The six distributions are fit to 21 data sets for which both diameters and heights are available. The log likelihood criterion is used to rank the six distributions in regard to their fit to each data set. Overall, Johnson's SB distribution gave the best performance in terms of quality of fit to the variety of sample distributions.
Patterns of development in Abiesbalsamea crowns and effects of megastrobilus production on shoots and buds
Authors: Powell G. R.
Published: February 2008

Measurements and detailed mapping of buds, shoots, and branches of megasporangiate zones of mature Abiesbalsamea (L.) Mill. trees during a period of several years showed that first-order nodal branches were consistently more vigorous than first-order internodal branches of the same age and that lengths of first-order shoots of any 1 year decreased down the crown on nodal branches and, on average, down successive internodes and also down each internode. Similar gradients in bud lengths occurred. Patterns of a similar nature occurred down each branch. Relationships were found between bud lengths and lengths of shoots developed by those buds and between shoot lengths and lengths of terminal buds developed on those shoots. The numbers of buds produced in terminal-bud units showed a curvilinear relationship and numbers of lateral buds produced showed a straight-line relationship with the length of the shoots on which they were initiated. When megastrobili were borne, shoot lengths decreased, hence, numbers of buds produced also decreased, and many more shoots than in non-strobilus-bearing years failed to produce any lateral buds.The nature of the patterns of development which maintain the excurrent crown shape and the periods of development when apical control appears to be operative are discussed.
Photosynthesis in a half-sib family experiment in pitch pine
Authors: Ledig F. Thomas , Clark Joseph G.
Published: February 2008

Intraprovenance variation in the rate of photosynthetic CO2 exchange was determined for 20 half-sib families of pitch pine. During early seedling development, rates of CO2 uptake were comparable with those for highly productive crop plants and the highest yet reported for conifers. Differences among families were small but statistically significant. Genotype-environment interactions were relatively unimportant, i.e., patterns of photosynthetic response to temperature and light were the same for all families within the limits of error.
Allelopathic inhibition of black cherry. II. Inhibition by woodland grass, ferns, and club moss
Authors: Horsley Stephen B.
Published: February 2008

A comparison of paired field plots on poorly drained Allegheny hardwood sites demonstrated that the presence of hay-scented fern (Dennstaedtiapunctilobula Michx.), New York fern (Thelypterisnoveboracensis L.), short husk grass (Brachyelytrumerectum Schreb.), and club moss (Lycopodiumobscurum L.) was correlated with reduced numbers of black cherry (Prunusserotina Ehrh.) seedlings; numbers of red maple (Acerrubrum L.) seedlings were fewer where associated with the ferns and grass but not with club moss; numbers of sugar maple (Acersaccharum Marsh.) seedlings were fewer with the ferns but not grass or club moss. Height of the 10 tallest black cherry seedlings on each plot was less with the ferns and grass but not with club moss. In a greenhouse study, foliage extracts of all four ground covers inhibited growth of black cherry seedlings that had exhausted cotyledonary reserves. Allelopathic interference by herbaceous ground cover species apparently played a strong role in inhibiting establishment and growth of black cherry seedlings on poorly drained Allegheny Plateau sites.
Influence of artificial shade on water stress of containerized ponderosa pine seedlings
Authors: Buchanan Bruce A. , Davault Michael F. , Fisher James T.
Published: February 2008

Artificially shaded and unshaded containerized Pinusponderosa Laws, seedlings were planted in the Sacramento Mountains of southern New Mexico on July 29, 1975. Xylem pressure potential (Pstem) and relative water content (RWC) were measured four times per day from August 1 to 16, 1975. Shading had little effect on RWC but significantly increased Pstem; midafternoon (1530 hours, MDST) increase averaged 2 bars (1 bar = 105 Pa). During the study RWC ranged from 86 to 94% and Pstem ranged from −4 to −10 bars. At the end of September no mortality had occurred in either treatment.
Biomass and nitrogen distribution in four 13-year-old loblolly pine plantations in the Hilly Coastal Plain of Alabama: discussion
Authors: Burkhart Harold E.
Published: February 2008

not available
Kraft pulping of jack pine killed by the Swaine sawfly
Authors: Hunt K. , Benoit P.
Published: February 2008

Kraft pulping studies were done on jack pine (Pinusbanksiana Lamb.) defoliated by Swaine jack pine sawfly (Neodiprionswainei Midd.). Trees dead as long as 7 years, dead and living trees sprayed with Lindane insecticide, and dead trees wrapped in cotton to prevent secondary insect attacks were tested. There was a statistically significant decrease in unscreened pulp yield (adjusted to screened pulp permanganate No. 20) with length of time since death, e.g., 44.6% (1 year) to 43.4% (7 years); but sufficient variation exists between the trees in any category such that, from a practical viewpoint, all trees tested could be used for pulp manufacture. There were no apparent differences in pulp yield between treated and untreated trees dead for the same length of time. Pulp strength decreased approximately linearly with length of time since death. A decrease in the chip thickness range of −6 mm to +2 mm (total laboratory accepts) and an increase in the −2 mm (pan) thickness range with length of time since death were observed.
Fire history and recent fire rotation periods in the Nova Scotia Acadian Forest
Authors: Wein Ross W. , Moore Janice M.
Published: February 2008

Descriptive records of wildfires since the earliest writings and quantitative provincial fire records since 1915 have been used to produce a synthesis of fire history for the Province of Nova Scotia, Canada. Large annual burns were common up to the mid-1930's. Annual burns totalling over 15 000 ha occurred in each of the years 1918, 1920, 1921, 1930, 1934, 1944, and 1947, and annual burns totalling over 30 000 ha occurred in each of the years 1920 and 1921. Lightning has accounted for 1% of the number of fires (three per year). Thirty percent of the fires have occurred in the month of May; however, fires have been recorded for all months. Fire rotation periods for the province as a whole were 1000 or 2500 years, using the mean annual burn or median annual burn, respectively, for all burns in the years 1915 to 1975. In contrast, calculations of burned areas on maps produced at the turn of the century gave presuppression fire rotation periods of just over 200 years. Vegetation types have had widely varying fire rotation periods. The vegetation of Cape Breton Island has been subjected to almost no fires over 20 ha, whereas the vegetation type with the shortest fire rotation period (in the interior of western Nova Scotia) has been subjected to fire rotation periods as low as 65 years at the turn of the century, to about 2000 years for the years 1958 to 1975. A summary of fire rotation periods for the Boreal, Great Lakes – St. Lawrence, and Acadian Forest Regions found in the literature is presented for comparison with the Nova Scotia data, and more detailed comparisons are made between the fire rotation periods of the similar vegetation types in New Brunswick and Nova Scotia.
Selection of conifer seeds by deer mice and red-backed voles
Authors: Martell Arthur M.
Published: February 2008

Detection and removal of seeds of white pine (Pinusstrobus), jack pine (Pinusbanksiana), and black spruce (Piceamariana) by deer mice (Peromyscusmaniculatus) and southern red-backed voles (Clethrionomysgapperi) were tested in the laboratory. Both deer-mice and red-backed voles showed a strong preference for seeds of white pine over those of either black spruce or jack pine. Deer mice apparently found jack pine seeds more palatable than did red-backed voles. Detection and removal rates for black spruce seeds varied among experiments. In general, changes in detection rate of black spruce seeds were accompanied by similar changes in detection rate of control dishes and in removal rate of black spruce seeds. Prior conditioning of deer mice to eat jack pine seeds did not produce an increase in either detection or removal of those seeds.
The response of bud morphogenesis in black spruce and white spruce provenances to environmental variables
Authors: Pollard D. F. W. , Logan K. T.
Published: February 2008

Complements of needle primordia were assessed on terminal buds of 1-year spruce (Picea) seedlings formed during experimental treatments of temperature, light intensity, soil moisture potential, and nutrient supply. Several provenances of widely scattered locations were examined in each experiment. While there were strong provenance and treatment effects in most experiments, in no instance was provenance × treatment interaction detected. The results are discussed in relation to genotype × environment interactions reported in field trials.
Seed dormancy in striped maple
Authors: Wilson B. F. , Hibbs D. E. , Fischer B. C.
Published: February 2008

Striped maple (Acerpensylvanicum L.) seeds showed delayed germination unless they were buried. With no pericarp but with intact, papery testae, seeds germinated at 5 °C after 3–6 months cold, moist stratification. They did not germinate at 23 °C even after stratification. With testae removed from the root tip germination was 20–30% at 23 °C and 100%: after 3 months stratification. Germination with testae removed (but not with testae intact) was accelerated by benzyladenine. Gibberellic acid had no effect. Testa-imposed dormancy did not seem to be related to inhibitors or restriction of water uptake but may have been due to mechanical restriction of radicle elongation.
The occurrence of bisexual strobiles on black spruce (Piceamariana (Mill.) B.S.P.) in the forest–tundra ecotone: Keewatin, Northwest Territories
Authors: Elliott Deborah L.
Published: February 2008

During fieldwork in the summer of 1977 in the vicinity of Ennadai Lake (District of Keewatin, N.W.T., Canada), a stand of upland black spruce (Piceamariana (Mill.) B.S.P.) possessing bisexual strobiles was encountered within the forest–tundra ecotone. This is the first reported occurrence of bisexual strobiles for this species. It is hypothesized that the occurrence of male and female reproductive tissue in the same reproductive structure is an indicator of stress in this arboreally marginal environment.
Estimation of butt rot in a white spruce plantation
Authors: Lachance D.
Published: February 2008

Presence or absence of decay in trees in a 46-year-old white spruce (Piceaglauca) plantation was predicted from ocular observations and from one increment boring in each tree at 15–20 cm from the ground. Amount of decay was estimated from increment cores and compared with measurements taken after tree felling and dissection. Ocular and boring predictions of tree condition were 63.5 and 86.8% correct respectively. This accuracy was increased to 76.1 and 98.0% respectively when 2 dm3 of decay in a tree was considered negligible. There was a linear correlation (r = 0.67) between the estimated area of decay (in square decimetres) from the increment core and the total volume of decay (cubic decimetres) in the tree. A regression equation applicable on a stand basis is given.
Introduction and overview of a multidisciplinary research project: the structure and function of a black spruce (Piceamariana) forest in relation to other fire-affected taiga ecosystems
Authors: Cleve Keith Van , Dyrness C. T.
Published: February 2008

not available
Environmental and successional relationships of the forest communities of the Porcupine River drainage, interior Alaska
Authors: Yarie J.
Published: February 2008

The structure and function of taiga ecosystems over a 3 600 000 ha area of northeastern interior Alaska was shown to be consistent with a hypothesis relating vegetative structure and dynamics to site nutrient status and soil temperature. Ordination of modal community descriptions and correlation of the ordination values with environmental parameters indicated that controls of vegetative structure and function found for the Fairbanks area, where the hypothesis was developed, can be applied to the interior Alaska taiga. High productivity sites were associated with warmer soil temperatures, smaller accumulation of soil organic layers, and lower C:N ratios. Lower productivity sites were associated with the opposite trends. Black spruce (Piceamariana (Mill.) B.S.P.) generally dominated the less productive sites, while white spruce (Piceaglauca (Moench) Voss) and hardwoods occupied the more productive sites. The successional trends described for other areas of interior Alaska appear to be valid for this remote study area.
Summer shortwave radiation at a subarctic forest site
Authors: Slaughter C. W.
Published: February 2008

Incoming shortwave solar radiation in a black spruce (Piceamariana (Mill.) B.S.P.) taiga forest at 65°45′ N was measured during four summers, in a clearing and beneath the forest canopy. The ratio of radiation received beneath the canopy to radiation received in the clearing varied from 0.33 to 0.60. Prediction of shortwave radiation in the clearing based on continuous measurements at a permanent site 35 km distant was feasible; however, on-site measurement of shortwave incoming radiation remains necessary for specific daily values.
Productivity and nutrient cycling in taiga forest ecosystems
Authors: Cleve Keith Van , Oliver Lola , Schlentner Robert , Viereck Leslie A. , Dyrness C. T.
Published: February 2008

This paper considers the productivity and nutrient cycling in examples of the major forest types in interior Alaska. These ecosystem properties are examined from the standpoint of the control exerted over them by soil temperature and forest-floor chemistry. We conclude that black spruce Piceamariana (Mill.) B.S.P. occupies the coldest, wettest sites which support tree growth in interior Alaska. Average seasonal heat sums (1132 ± 32 degree days (DD)) for all other forest types were significantly higher than those encountered for black spruce (640 ± 40 DD). In addition, black spruce ecosystems display the highest average seasonal forest-floor and mineral-soil moisture contents. Forest-floor chemistry interacts with soil temperature in black spruce to produce the most decay-resistant organic matter. In black spruce the material is characterized by the highest lignin content and widest C/N (44) and C/P (404) ratios. Across the range of forest types examined in this study, soil temperature is strongly related to net annual aboveground tree production and the annual tree requirement for N, P, K, Ca, and Mg. Forest floor C/N and C/P ratios are strongly related to annual tree N and P requirement and the C/N ratio to annual tree production. In all cases these controls act to produce, in black spruce, the smallest accumulation of tree biomass, standing crop of elements, annual production, and element requirement in aboveground tree components.
Site-to-site variations in nitrogenase activity in a subarctic black spruce forest
Authors: Billington Margaret M. , Alexander Vera
Published: February 2008

An estimate of nitrogen fixation in terms of acetylene reduction was made at two sites in a subarctic black spruce (Piceamariana (Mill.) B.S.P.) forest to determine site-to-site variations. The work was initially done to provide base-line comparative data for the primary intensive site, and for a site preparatory to an experimental burn. The principal conclusions were that, in contrast with the Alaskan arctic coastal tundra, microtopographic variations were not associated with big differences in acetylene reduction. Lichens with nitrogen-fixing phycobionts were an important influence on the activity; however, a high overall proportion of the activity was attributable to the moss cover, at least in part because of associated cyanobacteria. Daily rates for June and July averaged 74, 119 and 109 μg C2H4•m−2•day−1, respectively, for the 3 years. In common with other high-latitude sites, moisture was the major factor controlling nitrogenase activity.
Relationships between cellulose decomposition, Jenny's k, forest-floor nitrogen, and soil temperature in Alaskan taiga forests
Authors: Fox John F. , Cleve Keith Van
Published: February 2008

Forest-floor decomposition is compared among 16 Alaskan taiga forest stands. These include black spruce (Piceamariana (Mill.) B.S.P.), white spruce (Piceaglauca (Moench) Voss), and birch (Betulapapyrifera Marsh.), aspen {Populustremuloides Michx.), and balsam poplar (Populusbalsamifera L.) types, spanning a wide range in decomposition rates, forest-floor microclimates, and litter quality. Jenny's index of decomposition rate, k, is reasonably well correlated with annual cellulose (filter-paper) decomposition differences among stands. Both estimates of decomposition rate are correlated with forest-floor heat sum and forest-floor nitrogen concentration. These between-site correlations support inferences based upon experimental work claiming that temperature and forest-floor chemical quality have a major influence upon the level of decomposition in a particular stand. Inferences about the factors regulating decomposition rate around an average level within one stand cannot legitimately be made from the same correlations. Moisture has not been considered in this analysis, but could also be important to between-stand differences in decomposition rate.
Habitat and leaf habit as determinants of growth, nutrient absorption, and nutrient use by Alaskan taiga forest species
Authors: Chapin III F. Stuart , Tryon Peter R.
Published: February 2008

Four evergreen and four deciduous trees and shrubs were sampled from habitats with differing soil temperature regimes in interior Alaskan forests to examine the relative importance of habitat and leaf habit in determining seasonal patterns of shoot growth, tissue nutrient concentration, respiration rate, and phosphate absorption rate. Leaf habit was the primary determinant of shoot growth, with deciduous species producing leaf area and leaf biomass earlier in the season than evergreens. Deciduous trees produced more biomass per shoot and per unit ground area than did evergreens. The seasonal pattern of leaf nitrogen and phosphorus concentration was correlated closely with patterns of leaf growth, declining through the growing season in deciduous species first as nutrient concentrations were diluted by increasing leaf biomass and later as nutrients were retranslocated from senescing leaves. In evergreens the seasonal decline in nutrient concentration was entirely due to dilution by increasing leaf biomass, and there was no evidence of autumn retranslocation from 1st-year leaves. In contrast to seasonal pattern, the magnitude of leaf phosphorus and root nitrogen and phosphorus concentrations was correlated more closely with habitat than with leaf habit, generally being lower in cold sites. Leaf respiration was highly correlated with leaf nitrogen concentration, so that the seasonal pattern of leaf respiration was determined primarily by leaf habit, whereas the magnitude of respiration was more closely correlated with habitat. Root respiration showed no consistent correlation with either habitat or leaf habit but was lower than leaf respiration, as would be expected from low root nitrogen concentration. Phosphate absorption rate was determined more strongly by habitat than by leaf habit, being lower in cold sites characterized by slow plant growth and consequently low annual nutrient requirement. Evergreen species were more effective at absorbing phosphate at low solution concentrations than were deciduous species. Phosphate absorption was less temperature sensitive than root respiration, so that roots of all species absorbed more phosphorus per unit of carbon respired at low root temperature.
The photosynthetic capacity, nutrient content, and nutrient use efficiency of different needle age-classes of black spruce (Piceamariana) found in interior Alaska
Authors: Hom J. L. , Oechel W. C.
Published: February 2008

The photosynthetic capacity of different needle age-classes of black spruce (Piceamariana (Mill) B.S.P.) was studied using 14C labelling on whole branches at a site near Fairbanks, Alaska. Black spruce had highest photosynthetic rates in the 1-year-old tissue with the four most current age-classes showing similar high rates before declining with age. Older needles were found to maintain 40% of maximum photosynthetic rates after 13 seasons. Highest level of nitrogen was found in current needles with the first eight age-classes maintaining high levels before declining to 70% of maximum values in the oldest needles. Phosphorus levels were much higher in current tissue with a gradual decline after the 1-year-old tissue to a value of 55% of maximum values in the oldest tissue. Nutrient use efficiency was found to be highest in the 1-year-old tissue and declined with needle age. The loss of nutrient use efficiency may be due to the use of older tissue as aboveground nutrient stores, a decline in the efficiency of the photosynthetic apparatus of the needles, or an increase in the leaf specific weight. Black spruce has adapted to the low nutrient availability with low photosynthetic rates and low nutrient contents. Greater longevity of the needles would maximize the photosynthetic return per unit nitrogen invested in the needles.
Effects of soil temperature on the carbon exchange of taiga seedlings.: I. Root respiration
Authors: Lawrence William T. , Oechel Walter C.
Published: February 2008

Seedlings of Alnuscrispa (Ait.) Pursh, Populusbalsamifera L., Populustremuloides Michx., and Betulapapyrifera Marsh., hardwood species of the taiga of interior Alaska, were grown in sand in a controlled environment room at day–night temperatures of 25 and 20 °C, respectively, with a 20-h day length. After establishment, pots containing each species were placed under soil-temperature treatments of 5, 15, and 25 °C while maintaining extant air-temperature and light regimes. Both total and maintenance respiration of the roots were measured under these temperature treatments by monitoring the efflux of CO2 from the potted soil mass. An estimate of root-growth respiration was calculated as the difference between total and maintenance respiration. Total root respiration increased from three- to five-fold as soil temperature increased over the 20 °C experimental range. Growth-respiration response was species specific, occurring only at 5 °C soil temperature in A. crispa, at both 15 and 25 °C in P. balsamifera, and at all three soil temperatures in P. tremuloides. Growth respiration of the roots was a nearly constant fraction of total root respiration within a species, averaging 0.17 mg CO2•h−1•g root dry weight−1 in A. crispa and P. balsamifera, but nearly twice that, 0.33 mg CO2•h−1•g root dry weight−1, in P. tremuloides. Growth respiration was not determined for B. papyrifera.
Effects of soil temperature on the carbon exchange of taiga seedlings.: II. Photosynthesis, respiration, and conductance
Authors: Lawrence William T. , Oechel Walter C.
Published: February 2008

Potted seedlings of Poputustremutoides Michx., Populusbalsamifera L., Alnuscrispa (Ait.) Pursh., and Betulapapyrifera Marsh., hardwoods of the taiga of interior Alaska, were placed under soil-temperature treatments of 5, 15, and 25 °C with plant tops under a growth-room regime of 20-h day length and day–night air temperatures of 25 and 20 °C, respectively. Photosynthesis showed a differential soil-temperature effect among the species. Maximum photosynthetic rates of 9.5 mg CO2•h−1•dm−2 were observed for P. tremuloides at 25 °C soil and 25 °C air temperature; 9.3 mg CO2•h−1•dm−2 for P. balsamifera at the same temperature combination; and 7.8 mg CO2•h−1•dm−2 for A. crispa at 25 °C air temperature and the lowest soil-temperature treatment, 5 °C. The maximum photosynthetic rate observed for B. papyrifera was 4.9 mg CO2•h−1•dm−2 at 25 °C soil temperature and 20 °C air temperature; low values being due to nonsaturating light conditions. Both leaf dark respiration and conductance were reduced by the 5 °C soil-temperature treatment at one or more air temperatures in all species except A. crispa which was unaffected by cold soils. A cold-soil reduction of conductance was most pronounced at air temperatures above 20 °C.
Moss leaf water content and solar radiation at the moss surface in a mature black spruce forest in central Alaska
Authors: Skre O. , Oechel W. C. , Miller P. M.
Published: February 2008

In a mature black spruce (Piceamariana (Mill.) B.S.P.) forest near the University of Alaska, Fairbanks, AK, samples of four common moss species, Polytrichumcommune Hedw., Hylocomiumsplendens (Hedw.) B.S.G., Pleuroziumschreberi (Brid.) Mitt., and Sphagnumsubsecundum Nees. were collected at intervals during the 1976 season to determine the diurnal variation in leaf water content and daily water loss as functions of temperature, moisture, radiation, and wind speed. The field measurements were followed by laboratory experiments on intact cores in an open system and on excised shoots in closed cuvettes. In these experiments, water loss rates varied by species and were affected by vapor pressure deficits and wind speed; where vapor pressure deficit is more constant than these other factors, variations in light intensities had less effect on water loss rates. Polytrichumcommune, which translocates water from the soil, avoided moisture stress to a greater extent than the other moss species which were more dependent on water absorption through the leaves. Hylocomiumsplendens was below the water content for compensation for almost 50% of the July measurement period. Observed patterns of the rates of water loss and of the moisture required to reach field capacity are correlated with the moisture status of the mosses in the field. Field measurements of photosynthetically active radiation (PAR) at the moss surface and above the forest canopy showed that the transmission of diffuse radiation through the forest canopy increased with increasing cloudiness. PAR at the moss surface was above the compensation level for photosynthesis with sunny and cloudy conditions. Sunflecks (short periods of direct sunlight), which had an intensity of about 76% of the radiation incident on the forest canopy, occurred on up to 35% of the ground surface and provided a major source of the radiation received. Species varied in their pattern of attenuation of light through the moss canopy. A mixed stand of P. commune and P. schreberi and stands of H. splendens transmit light deeply. Sphagnumsubsecundum, on the other hand, shows rapid attenuation of light high in the canopy. The observed pattern of light attenuation helps explain the vertical position of the green–brown interface and the death of green material in the moss canopy.
Patterns of translocation of carbon in four common moss species in a black spruce (Piceamariana) dominated forest in interior Alaska
Authors: Skre O. , Oechel W. C. , Miller P. M.
Published: February 2008

The patterns of translocation of carbon in different-age tissues of four common moss species in a black spruce (Piceamariana (Mill.) B.S.P.) dominated forest near Fairbanks, Alaska, were studied by 14C labelling and carbohydrate analysis. A simple, in-vial combustion technique was developed for combustion of small (< 10 mg) radioactively labelled samples of plant tissue. The method was used to measure specific activity of 14C in moss tissue 2 h and 5, 15, and 25 days after labelling with 14CO2 gas in sealed chambers. The procedure was repeated three times during the summer. Patterns of 14C translocation varied by species; Polytrichumcommune Hedw. retained the most label after 2 h and Sphagnumsubsecundum Nees. the least. Polytrichumcommune had the second-highest fraction of 14C in brown tissue after 35 days and S. subsecundum the highest. Hylocomiumsplendens (Hedw.) B.S.G. and Pleuroziumschreberi (Brid.) Mitt, did not show consistent patterns of translocation 2 h or 35 days after labelling. 14C was found to accumulate in the growing shoot tips and in the brown tissue of all four species. Loss of 14C because of respiration was high in all four species during the first labelling period indicating high rates of photosynthesis and growth during the peak summer season. The carbohydrate analysis indicated that the increase in 14C activity in brown tissue by the end of the season was due to translocation for storage. In all species there was a strong increase in the storage polysaccharide content by the end of the season after the growth was finished, especially in brown tissue.
The effects of experimental fires on black spruce forest floors in interior Alaska
Authors: Dyrness C. T. , Norum Rodney A.
Published: February 2008

Seven units (about 2 ha each) of black spruce – feather moss forest were experimentally burned over a range of fuel moisture conditions during the summer of 1978. Surface woody fuels were sparse and the principal carrier fuel was the forest floor (largely mosses and their decomposition products). Forest floors after burning comprised a small-scale mosaic of unburned, scorched, lightly burned, moderately burned, and heavily burned (organic materials entirely consumed) conditions. Percentage of the unit area in the moderately and heavily burned condition ranged from 11.2 to 77.2% and percent decrease in forest-floor thickness varied from 27.4 to 63.1% in the seven units. Forest-floor consumption was most closely correlated with the moisture content of lower moss (01 horizon) and lower duff layers (022 horizon) at the time of burning. For the first 3 years after fire, biomass production was greater on heavily burned than on lightly burned sites (58 vs. 37 g/m2 on an annual basis). Heavily burned sites were completely dominated by the invading species Epilobiumangustifolium L., Ceratodonpurpureus (Hedw.) Brid., and Marchantiapolymorpha L., whereas lightly burned plots were occupied by sprouting species such as Calamagrostiscanadensis (Michx.) Beauv., Vacciniumuliginosum L., and Ledumgroenlandicum Oeder. Soil pH and amounts of total P and available P in the forest floor increased significantly as a result of burning; and in all cases, increases reached a maximum in moderately and heavily burned areas. Total N in the forest floor increased significantly in moderately burned, but decreased slightly in heavily burned areas. Total N and total P showed smaller increases in the surface mineral soil as a result of burning. Supplies of available P in the mineral soil increased almost 4-fold in moderately burned and over 16-fold in heavily burned areas.
Artificial regeneration of trees and tall shrubs in experimentally burned upland black spruce/feather moss stands in Alaska
Authors: Zasada John C. , Norum Rodney A. , Veldhuizen Robert M. Van , Teutsch Christian E.
Published: February 2008

Fall seed-dispersing species, birch (Betulapapyrifera Marsh.), alder (Alnuscrispa (Ait.) Pursh), and black spruce Piceamariana (Mill.) B.S.P.), and summer-seeding species, aspen (Populustremuloides Michx.), balsam poplar (P. balsamifera L.), feltleaf willow (Salixalaxensis (Anderss.) Cov.), Scouler willow (Salixscouleriana Barratt), and Bebb willow (Salixbebbiana Sarg.), were artificially sown on seedbeds created by experimental burning in the upland black spruce/feather moss forest types in interior Alaska. At least 40% of the seeds dispersed in the fall had germinated before dispersal of summer seeds began. Germination occurred on moderately and severely burned seedbeds but not on scorched and lightly burned surfaces. Seedling survival occurred almost exclusively on severely burned surfaces. After 3 years, 82% of the plots containing some severely burned surfaces and sown with seeds from species seeded in the fall were stocked whereas 32% of the plots sown with species seeded in the spring and with the same seedbed condition were stocked.
Effect of shortened auxin treatments on the rooting of girdled slash pine shoots
Authors: Cunningham Michael W. , Buijtenen J. P. Van
Published: February 2008

Slash pine (Pinuselliottii Engl.) shoots collected from 30 ortets, approximately 8 years from seed, were girdled for different lengths of time and treated at the time they were girdled with one of five rooting powders varying in indolebutyric acid concentration. Girdling 2, 4, or 6 weeks prior to placement in the rooting bench significantly promoted rooting, but girdling times did not significantly differ from one another. Treatment with 1 or 2% IBA also promoted rooting, with 2-weeks' girdling plus 1 or 2% indolebutyric acid yielding the best results (70 and 73%, respectively). Shoots treated with 2% IBA produced significantly more primary roots than the other auxin treatments.
Postglacial paleoecology and successional relationships of a bog woodland near Prince Rupert, British Columbia
Authors: Banner A. , Pojar J. , Rouse G. E.
Published: February 2008

The historical development of a bog woodland on the north coast of British Columbia is reconstructed using pollen analysis, peat stratigraphy, and 14C dating. The succession spans 8700 ± 210 years in the following sequence: Pinuscontorta Dougl. – Alnusrubra Bong. – ferns/pioneer alluvial forest; Piceasitchensis (Bong.) Carr. – Alnus – Tsugaheterophylla (Raf.) Sarg. – (Thujaplicata) Donn. – Lysichitonamericanum Hulten & St. John – ferns/moist productive alluvial forest on regosols; Thuja – Chamaecyparisnootkatensis (D. Don) Spach – Tsuga – Pinus/scrub forest on peaty mineral soils; Pinus – Chamaecyparis – ericaceous shrubs – Sphagnum L. spp./bog woodland on organic soils. This ecosystem sequence is correlated with changes in paleoclimate reported for southwestern British Columbia and may also be associated with edaphic factors such as changing drainage patterns, the formation of cemented soil horizons, and the accumulation of thick organic surface horizons. The succession from forest to muskeg is contrasted with other evidence for succession from muskeg to forest in north-coastal British Columbia and southeast Alaska. We interpret the regional vegetation and soils as a dynamic complex of ecosystems linked successionally through climatically sensitive pathways. Local site factors such as topography, landform, drainage, and nutrient regime are important secondary factors controlling the direction of succession.
Tree-crown defoliation measurement from digitized photographs
Authors: Lee Y. Jim , Alfaro Rene I. , Sickle G. A. Van
Published: February 2008

Sequential color slides of a Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) tree were taken over several years to record the progression of crown defoliation by Douglas-fir tussock moth (Orgyiapseudotsugata McDunnough) and foliage recovery. The slides were digitized using a microdensitometer and analysed with a GEMS-300 image analysis system in an effort to detect changes in the amount of crown foliage. Digital images were successfully registered (overlaid) to standardize comparisons of the tree-crown profile in the various photographs. Image analysis algorithms developed for airborne or satellite multispectral scanner data were used to detect changes in crown profiles. The decrease in the amount of defoliation over time after the initial severe insect attack, estimated by a variable threshold technique, was similar to ocular ground-based estimates by well-trained observers. The supervised maximum-likelihood classification technique was found not suitable in this study.
Enhancement of shoot elongation in Douglas-fir by gibberellin A4/7 and its relation to the hormonal promotion of flowering
Authors: Ross Stephen D.
Published: February 2008

The enhanced stem elongation that frequently accompanies the gibberellin A4/7 (GA4/7) promotion of flowering in Pinaceae species was investigated for Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) vegetative propagules in relation to their physiological age, GA4/7 concentration, and treatment timing. Maximum growth enhancement, but marginal promotion of flowering (males and females), occurred when GA4/7 was applied in early spring before vegetative buds had begun to swell. In contrast, shoot elongation was only slightly enhanced when GA4/7 treatment was timed (vegetative bud burst ±4.5 weeks) to bracket the critical period for effecting differentiation of axillary primordia into cone buds. Also, the GA4/7 concentration optimal for flowering was supraoptimal for shoot elongation, and the growth response to GA4/7 decreased, whereas the flowering response increased, with increasing physiological age of the propagules (scions 4–45 years old). These findings are consistent with a hypothesis that exogenous GA4/7 is first utilized for vegetative growth processes, increased flowering occurring only after a threshold concentration is reached.