bluuebunny/crossref_metadata_2025 huggingface dataset:
Some further analogies between the Bak-Sneppen model for biological evolution and the spring-block earthquake model
Authors: Chimal-Eguía J C , Chavoya-Aceves O , Angulo-Brown F
Published: March 2003

In recent years, a great deal of attention has been devoted to so-called self-organized critical (SOC) systems, which are open, extended systems that organize themselves into steady metastable states without any temporal- or spatial-predominant scale (except those imposed by the finite size of the system). The SOC concept has been used to describe the statistical properties of several physical systems through numerical models based on cellular automaton. In particular, Bak and Sneppen proposed a SOC model for biological evolution at the level of entire species or faunas that exhibit punctuated equilibrium behavior. On the other hand, Olami, Feder and Christensen suggested that a two-dimensional spring-block earthquake model can explain some properties of real seismicity. In this paper, we show that there exist several further interesting analogies between these SOC models, besides those remarked on by other authors. Both of them exhibit punctuated equilibrium in the long term, which leads us to suggest an equivalent characterization of seismic and "evolutionary" provinces through the long-term slopes of the stair-shaped graphs of cumulative activity in the course of time.

PACS Nos.: 91.30P, 05.65, 87.23
The exact evolution of the time-dependent driven damped harmonic oscillator with time-dependent mass and frequency
Authors: Liang M , Yuan B , Zhong K
Published: March 2003

Under a new quantization scheme, the exact wave functions of the time-dependent driven damped harmonic oscillator with time-dependent mass and frequency are obtained. The wave functions are shape-unchanging wave packet with the center moving along the classical trajectory. The total phase of the wave function is explicitly expressed as the sum of the dynamical phase and the geometrical phase.

PACS Nos.: 03.65-w, 05.40-a
Analysis of pionnucleus interactions in the framework of a multistring model
Authors: Dhamija S , Kaur M , Dahiya S
Published: March 2003

A multistring model implemented through Monte Carlo code, modified-FRITIOF is used to analyse the data from π Em interactions at high energies. The model is based on the concept of classical strings, and using the method of longitudinal excitation as a means of string formation, the subsequent string fragmentation follows the Lund fragmentation scheme. The analysis gives interesting comparison between the data and the model predictions.

PACS No.: 25.70
Canonical perturbation theory for highly excited dynamics
Authors: Joyeux M , Sugny D
Published: March 2003

This article proposes an unified presentation of recent results dealing with canonical perturbation theory (also called the contact transformation method in the quantum mechanical context), which shows how the theory is best handled for investigating the highly excited dynamics of small molecules. The following systems are successively addressed: (i) semi-rigid molecules (one electronic surface, one minimum), (ii) floppy molecules (one electronic surface, several minima), and (iii) non-BornOppenheimer dynamics (several interacting electronic surfaces). The perturbative Hamiltonians obtained from the proposed procedures are checked against exact calculations performed on ab initio surfaces (HCP and HCN) and model Hamiltonians.

PACS No.: 31.15Md
Ar K X-ray production in slow, highly charged Ar q+(q = 818) + Ar collisions
Authors: Tawara H , Richard P
Published: March 2003

In the present work, mechanisms of Ar K X-ray production have been investigated under low-energy Arq+ + Ar collisions in a wide range of the ion-charge states. Ar K X-rays have been observed as a function of the collision energy over (0.753.75)q keV/u and of the charge state over q = 816 of projectile Arq+ ions. If the L-shell vacancies become available (q = 9), Ar K X-ray yields are found to be enhanced roughly three orders of magnitude, compared with Ar8+ ions with no L-shell vacancy; to show some threshold; and to tend to quickly saturate at higher collision energies. The present analysis, based on the energy correlation diagrams of the quasi-molecules, suggests that Ar K X-rays originate entirely from target Ar atoms through promotion via the rotational coupling between 2pσ 2pπ molecular orbitals. Furthermore, the observed cross sections are found to increase nonlinearly with the projectile Arq+ ion charge q (q = 9). This can be understood because of the combined effects of two contributions: (i) the increased number of the L-shell vacancies of projectile Arq+ ions and (ii) the enhanced fluorescence yields of target Ar atom. In addition, Ar K X-rays have been observed under 2.5q keV/u Ar17+ and Ar18+ + Ar collisions and found to originate from the decay of K-shell vacancies initially present in the projectile Ar ions through electron capture into their highly excited states, followed by cascade down to the ground states. For the first time, though very weak, the X-rays due to the two-electronone-photon transition, namely, K αα lines, have also been observed in bare Ar18+ ion collisions.

PACS Nos.: 34.70+e, 32.80Rm
Integral-equation analysis of the kinetic-ballooning modes in tokamaks
Authors: Hirose A , Elia M
Published: March 2003

The existence of kinetic-ballooning modes in the regime that is stable against the ideal MHD (magnetohydrodynamic) mode has been confirmed by nonlocal analysis based on integral-equation formalism. In contrast to the previous results based on differential-shooting codes, the kinetic-ballooning mode in the second stability regime does not require a finite ion-temperature gradient.

PACS Nos.: 52.35Kt, 52.55Fa
Dielectronic recombination-rate coefficients to excited states of Be-like oxygen and dielectronic satellite lines
Authors: Murakami I , Safronova U I , Kato T
Published: March 2003

We calculate energy levels, radiative transition probabilities, and autoionization rates for Be-like oxygen (O4+) including 1s2 2lnl' (n = 28, l [Formula: see text] n  1) and 1s23l' nl (n = 36, l [Formula: see text] n  1) states by the multiconfigurational HartreeFock method (Cowan code) and the perturbation theory Z-expansion method (MZ code). The state selective dielectronic recombination-rate coefficients to excited states of Be-like oxygen are obtained, which are useful for modeling O V spectral lines in a recombining plasma. Configuration mixing plays an important role for the principal quantum number, n, distribution of the dielectronic recombination-rate coefficients for 2snl (n [Formula: see text] 5) levels at low electron temperature. The orbital angular momentum quantum number, l, distribution of the rate coefficients shows a peak at l = 4. The total dielectronic recombination-rate coefficient is derived as a function of electron temperature. The dielectronic satellite lines are also obtained.

PACS Nos.: 34.80Lx, 32.80Dz, 32.30Jc, 31.10+z
Visible spectrum of highly charged ions: The forbidden optical lines of Kr, Xe, and Ba ions in the Ar I to Kr I isoelectronic sequence
Authors: López-Urrutia J.R. Crespo , Beiersdorfer P , Widmann K , Decaux V
Published: March 2003

We present experimental data on visible transitions in highly charged ions observed in the Lawrence Livermore National Laboratory (LLNL) electron beam ion traps, including results from lines within the ground-state configuration and the first excited configuration. Measurements of lines produced by Kr (q = 11+ to 22+), Xe (q = 18+ to 35+), and Ba (q = 28+ to 36+) ions, corresponding mainly to 3sl 3pm 3dn configurations, were carried out. The ionization stages were determined experimentally by sweeping the electron beam energy over the ionization threshold of each species. We propose possible identifications for the lines with the help of simple atomic structure calculations. However, most observed lines remained unidentified, demonstrating that the understanding of visible spectra from highly charged ions, even if obtained under nearly "ideal" experimental conditions, is still in its infancy. These spectral data may be useful for the diagnostics of magnetically confined plasmas and may set the stage for future measurements of radiative lifetimes. In our experiments, we used the emission from visible lines to image the intersection of the electron beam with a beam of neutral atoms injected into the trap at a right angle as well as the ion cloud in the trap. Under some conditions, the diameter of the ion cloud may be an order of magnitude larger than that of the electron beam.

PACS Nos.: 32.30Jc, 39.30+w, 52.59Rz
Laser-frequency stabilization using a lock-in amplifier
Authors: Weel M , Kumarakrishnan A
Published: March 2003

We describe how a lock-in amplifier can be used in a feedback loop to lock the frequency of a laser to an atomic transition in 85Rb. A simple physical explanation is presented to describe the shape of the feedback signal generated by the "lock in" and the dependence of this signal on the phase of the reference signal. We also present a mathematical model of the feedback signal. Using the output of the lock in as feedback, we show that the laser frequency can be stabilized to a few MHz. The experiment is relatively simple to set up and could easily be adapted as an undergraduate laboratory experiment.

PACS No.: 42.60Mi
The rotating-saddle trap: a mechanical analogy to RF-electric-quadrupole ion trapping?
Authors: Thompson R I , Harmon T J , Ball M G
Published: March 2003

The rotating-saddle potential ball-bearing trap has long been used as a mechanical analogue to explain the operating principles of the Paul-type RF-electric-quadrupole ion trap. This paper outlines the shortcomings of this analogy, as well as explaining how and why this system remains an excellent tool for explaining ion-trap operation. The basic theory of the operating principles of the rotating-saddle trap is provided, which, unlike the Paul Trap is analytically solvable in the friction-free regime. In addition, some extensions to this theory are presented to examine such effects as friction. These results are compared with the equivalent results for Paul-Trap theory, as well as to experimental results measured with a rotating-saddle trap constructed at the University of Calgary. The technical details of this trap, an excellent tool for either lecture demonstrations or teaching laboratory experiments, are also presented, as well as some comments on building such a trap.

PACS Nos.: 45.50-j, 01.50Pa, 32.80Pj
Measurement of radiative lifetimes in Sm II
Authors: Scholl T J , Holt R A , Masterman D , Rivest R C , Rosner S D , Sharikova A
Published: March 2003

We have measured the radiative lifetimes of 82 levels of Sm II using the beam-laser method. The levels studied had term energies up to ~29 600 cm1 and lifetimes in the range 9190 ns. Experimental uncertainty was less than 7%, with a typical value of 1.6%. We have used these lifetimes to update transition probabilities for 35 transitions in the wavelength range 363771 nm, which are useful for stellar abundance determinations.

PACS Nos.: 32.70Cs, 95.30Ky
Precise atomic lifetime measurements with stored ion beams and ion traps
Authors: Träbert E
Published: March 2003

For many years, atomic lifetime measurements on multiply-charged ions have been done almost exclusively by beam-foil spectroscopy. For low ion charges, however, spin-changing "intercombination" transitions have a rate that renders them too slow for traditional fast-beam techniques. Here ion traps and fast-ion beams have been combined in the concept of heavy-ion storage rings. These devices have permitted not only an extension of intercombination lifetime measurements down to singly charged ions, but they also facilitated similar measurements on electric-dipole forbidden transitions. The electron-beam ion trap (EBIT) complements the storage-ring work for work on highly charged ions. Achievements, technical issues, and prospects are outlined.

PACS Nos.: 32.70Cs, 32.30Jc, 34.50Fa
Electron-beam ion-trap spectra of tungsten in the EUV
Authors: Utter S B , Beiersdorfer P , Träbert E
Published: March 2003

At the Livermore electron-beam ion-trap facility, extreme-ultraviolet spectra of tungsten have been recorded in the wavelength range 4085 Å. The electron-beam energy was varied systematically to identify the individual spectra of Rb-like W37+ to Cu-like W45+. About 60 spectral features have been identified.

PACS Nos.: 32.30Rj, 39.30+w, 31.50+w
Hot model of muonium formation in liquids
Authors: Walker David C , Karolczak Stefan , Gillis Hugh A , Porter Gerald B
Published: March 2003

The mechanism of formation of muonium atoms from positive muons was studied here through measurements of the yield of diamagnetic muon states in dipolar aprotic solvents and for scavenger solutions in hexane and methanol. The results are compared with published data on common solvents covering a full range of the physicochemical properties of liquids that affect an ionic formation mechanism, namely their static dielectric constants, electron mobilities, and radiolysis yields of electrons. It is concluded that muonium is not formed by a thermal charge-neutralization reaction in these chemically-active media, though that mechanism does contribute to muonium formation in inert media like liquefied noble gases. It is clear that muonium materializes on a much shorter timescale than the recently proposed "delayed" mechanism (microseconds) and the earlier "spur" model (nanoseconds). In contrast, the data referring to all these liquids are consistent with the intra-track "hot" model. This is the only Mu-formation model proposed so far in which the immediate precursors of Mu (Mu(hot)) are neither scavengable nor ionic.Key words: muonium atoms, formation mechanism, hot model, spur model, delayed-muonium-formation model, diamagnetic yields.
One-pot synthesis of terpyridines and macrocyclization to C3-symmetric cyclosexipyridines
Authors: Masciello Lucie , Potvin Pierre G
Published: March 2003

Four examples of 2,6-dicinnamoylpyridines were obtained in 6065% yields in condensations of commercially available 2,6-diacetylpyridine and benzaldehydes in 1:2 stoichiometry. At 2:1 ratios, four related 6,6''-diacetylated-4'-arylterpyridines were isolated in 7073% yields in one-pot condensations in the presence of NH3. 4,4'-Azo benzaldehyde, prepared from nitrobenzaldehyde in three steps and 40% overall yield was similarly converted to a novel azo-linked bis(terpyridine) in 50% yield in a reaction that assembles seven molecules in one step. The 6,6''-diacetylated-4'-arylterpyridines and the correspondingly substituted 2,6-dicinnamoylpyridines were condensed in 1:1 ratio together with NH3 to form 4,4'',4IV-triarylcyclosexipyridines in 2226% yields. These were obtained as mixed Na+ and K+ complexes and were insoluble amorphous solids, except for one example bearing 4-neopentoxyphenyl substituents. 1H NMR showed that the 4,4'',4IV-tri(4-neopentoxyphenyl)cyclosexipyridine complexes form aggregates in solution and at low concentrations show twofold symmetry arising from a loss of planarity.Key words: terpyridines, 4'-aryl-6,6''-diacetylterpyridines, azo-bisterpyridine, cyclosexipyridines, macrocyclization.
Nitroarene reduction using Raney nickel alloy with ammonium chloride in water
Authors: Bhaumik Kankan , Akamanchi K G
Published: March 2003

Aromatic nitroarenes are reduced in high yields using a user-friendly combination of Raney nickel alloy and ammonium chloride in water at 8090°C.Key words: Raney nickel alloy, nitroarenes reduction, ammonium chloride, water.
Kinetics of oxidation of α,β-unsaturated aldehydes by quinolinium dichromate
Authors: Chaubey Girija S , Das Simi , Mahanti Mahendra K
Published: March 2003

A series of α,β-unsaturated aldehydes (crotonaldehyde, cinnamaldehyde, acrylaldehyde, and methacrylaldehyde) were oxidized by quinolinium dichromate in sulfuric acid to the corresponding acids in 50% (v/v) acetic acid  water medium. The kinetic data have been discussed with reference to the aldehyde hydration equilibria. The kinetic results support a mechanistic pathway proceeding via a rate-determining oxidative decomposition of the chromate ester of the aldehyde hydrate.Key words: kinetics, oxidation, unsaturated aldehydes, quinolinium dichromate.
Medium-sized cyclophanes. Part 62:1 Formylation of anti-[n.2]metacyclophanes  Through-space electronic interactions between two benzene rings
Authors: Yamato Takehiko , Furukawa Tsuyoshi , Tanaka Kan , Ishi-i Tsutomu , Tashiro Masashi
Published: March 2003

Formylation of anti-[n.2]metacyclophanes (1) (n = 2, 3, 4) with dichloromethyl methyl ether in the presence of TiCl4 occurred selectively at para-position to the internal methyl substituents of anti-[n.2]metacyclophanes. Similar reaction of anti-5,13-di-tert-butyl-8,16-dimethyl[2.2]metacyclophane (6a) with dichloromethyl methyl ether in the presence of TiCl4 led to ipso-formylation at the tert-butyl group to give anti-5-tert-butyl-13-formyl-8,16-dimethyl[2.2]-meta cyclophane (7a) as well as the corresponding 2,7-di-tert-butyl-trans-10b,10c-dimethyl-10b,10c-dihydropyrene (10), anti-5-tert-butyl-8,16-dimethyl-13-(3-methyl-1-butene-2-yl)[2.2]metacyclophane (8), and anti-5,13-di-tert-butyl-exo-1-hydroxy-8,16-dimethyl[2.2]metacyclophane (9) depending on the reaction conditions. The higher yield of ipso-formylated product is obtained in the presence of AlCl3 MeNO2 in 80% yield along with anti-5-tert-butyl-8,16-dimethyl-13-(3-methyl-1-butene-2-yl)[2.2]metacyclophane (13). Thus, the yield of ipso-formylation at the tert-butyl group of 6a was strongly affected by the activity of the formylation catalyst. Interestingly, in the formylation of anti-6,14-di-tert-butyl-9,17-dimethyl[3.2]metacyclophane (6b) under the same reaction conditions, syn-6,14-di-tert-butyl-7-formyl-9,17-dimethyl[3.2]metacyclophane (14b) was obtained in 40% yield arising from the anti-syn-ring inversion of the formylation intermediate along with ipso-formylation product 7b in 42% yield. In the formylation of anti-[4.2] meta cyclophane (6c) only the mono-ipso-formylated product 7c was obtained in 92% yield. The formation of a two-fold ipso-formation product, i.e., anti-5,13-diformyl-8,16-dimethyl[2.2]metacyclophane (3a), was not observed under the reaction conditions used. The mechanism of the ipso-formation as well as the formation of the present novel reaction products 8 and 9 is also discussed. Key words: cyclophanes, strained molecules, electrophilic aromatic substitution, ipso-formylation, σ-complex intermediates, through-space electronic interactions.
Aqueous-gas phase partitioning and hydrolysis of organic iodides
Authors: Glowa G A , Wren J C
Published: March 2003

The volatility and decomposition of organic iodides in a reactor containment building are important parameters to consider when assessing the potential consequences of a nuclear reactor accident. However, there are few experimental data available for the volatilities (often reported as partition coefficients) or few rate constants regarding the decomposition (via hydrolysis) of organic iodides. The partition coefficients and hydrolysis rate constants of eight organic iodides, having a range of molecular structures, have been measured in the current studies. This data, and data accumulated in the literature, have been reviewed and discussed to provide guidelines for appropriate organization of organic iodides for the purpose of modelling iodine behaviour under postulated nuclear reactor accident conditions. After assessment of the partition coefficients and their temperature dependences of many classes of organic compounds, it was found that organic iodides could be divided into two categories based upon their volatility relative to molecular iodine. Similarly, hydrolysis rates and their temperature dependences are assigned to the two categories of organic iodides.Key words: organic iodide, hydrolysis, partition coefficient, iodine behaviour model, nuclear reactor safety.
A pentanortriterpenoid with a novel carbon skeleton and a new pregnane from Trichilia connaroides
Authors: Zhang Hua-Ping , Wu Shao-Hua , Shen Yue-Mao , Ma Yun-Bao , Wu Da-Gang , Qi Shu-Hua , Luo Xiao-Dong
Published: March 2003

A new rearranged pentanortriterpenoid (trijugin C) and a new pregnane (3β,4α-dihydroxypregnan-16-one) were isolated from the EtOH extract of Trichilia connaroides (Meliaceae). Trijugin C has been shown to be a derivative of methyl angolensate with a novel carbon skeleton. The structures were elucidated on the basis of spectral analysis including 1H-1H COSY, HMQC, HMBC, and NOESY experiments. The possible biogenetic pathway of trijugin C is discussed.Key words: Trichilia connaroides, Meliaceae, pentanortriterpenoid, trijugin C, pregnane.
Photobehavior of aqueous uranyl ion and photo-oxygenation of isobutane using light from the visible region
Authors: Bergfeldt Trevor M , Waltz William L , Xu Xiangrong , Sedlák Petr , Dreyer Uwe , Möckel Hermann , Lilie Jochen , Stephenson John W
Published: March 2003

The photochemical and photophysical behavior of the aqueous uranyl ion [UO2(H2O)5]2+ has been studied under the influence of visible light and with added perchloric acid over the range of 0.014 M. In the presence of 2-methylpropane (isobutane), photo-oxygenation of isobutane occurs to yield, as the major product, 2-methyl-2-propanol (tert-butyl alcohol) along with lesser amounts of 2-methyl-2-propene (isobutene) and other C1C8 products. The quantum yield for formation of tert-butyl alcohol is independent of light intensity at the irradiation wavelength of 415 nm and of uranyl concentration, but it increases from 0.016 ± 0.001 at 0.01 M HClO4 (pH 2) to 0.13 ± 0.01 at 4 M HClO4. The emission spectrum from the electronically excited uranyl ion and the associated quantum yields have been measured in the presence and absence of isobutane, as a function of added perchloric acid. While in both cases the shape of the spectrum remains invariant, the quantum yields increase with increasing perchloric acid concentration. The strong dependence on added perchloric acid is interpreted within the context of the presence and interconversion of two electronically excited species, an acid form, *[UO2(H2O)5]2+, and a base form, *[UO2(H2O)n(OH)]+. It is proposed that both forms react with isobutane to give a tert-butyl radical, and that oxidation of coordinated aqua ligands occur, the latter generating a hydroxyl radical whose reaction with isobutane rapidly leads also to a tert-butyl radical. The reaction of this alkyl radical with ground-state [UO2(H2O)5]2+ then gives rise to the stable tert-butyl alcohol product and reduced forms of uranyl ion. Based upon the values of the quantum yields and of excited-state lifetime measurements reported in the literature, a comprehensive mechanism has been developed in a quantitative manner to provide calculated values of the rate constants for the individual mechanistic steps. The calculated rate constants provide a basis to calculate the values of quantum yields for emission and chemical reaction, as well as for lifetimes, that agree very satisfactorily with the experimental values over a 400-fold concentration change in added perchloric acid.Key words: photo-oxidation, photo-oxygenation, uranyl ion, isobutane, tert-butyl alcohol, lifetime, quantum yield, acidbase dissociation.
Considerations about phenol electrohydrogenation on electrodes made with reticulated vitreous carbon cathode
Authors: Laplante François , Brossard Louis , Ménard Hugues
Published: March 2003

The electrocatalytic hydrogenation (ECH) of phenol was carried out in aqueous media with catalytic powders. The catalytic powders were composed of palladium nanoaggregates deposited on various substrates such as Al2O3, BaSO4, and BaCO3. Composite powders are trapped (upon stirring) into a reticulated vitreous carbon (RVC) matrix, allowing a rapid in situ build-up of the electrode and alleviating the use of a binder, since the latter may have a detrimental effect on the ECH. For a given amount of noble metal (5% palladium by weight), it is observed that the ECH of phenol to cyclohexanol increases in the following order: Pd/BaCO3< Pd/BaSO4< Pd/Al2O3. It is deduced that the ECH rate is largely dependent on the adsorption of organic molecules on the nonmetallic substrate, and a model is considered to explain such a behavior. The ECH of phenol is also feasible at a reasonable rate with composite Pd/Al2O3(0.25% Pd by weight) powders fabricated by physical vapor deposition because the peripheral distribution of Pd nanoaggregates is favorable towards the ECH.Key words: electrocatalytic hydrogenation (ECH) of phenol, reticulated vitreous carbon (RVC), alumina-based catalyst, agglomeration process, adlineation point, adsorption.
Regeneration of Cryptomeria japonica on a sloping topography in a cool-temperate mixed forest in the snowy region of Japan
Authors: Hirayama Kimiko , Sakimoto Michinori
Published: March 2003

Cryptomeria japonica D. Don shows a limited distribution on and around ridges in its native habitat. To clarify the regeneration process of this species, we analysed spatial patterns among five size classes on a slope extending from a ridge to a valley bottom, and growth patterns of understorey trees related to their slope position, in a cool-temperate old-growth mixed forest in Japan. Although the largest size-class trees ([Formula: see text]20 cm diameter at breast height (DBH)) were confined to the upper part of the slope, understorey size-class trees ([Formula: see text]50 cm stem length and <10 cm DBH) extended their range below the upper regions by layering. The annual growth of understorey size class stems increased towards the lower slope in relation to the understorey light conditions. However, snow pressure injured understorey trees and killed many regenerating medium-sized trees on the steeply inclined expanding site. These results indicate that increased snow pressure, influenced by slope topography, may inhibit the clonal expansion of C. japonica. We concluded that snow pressure gradient on a sloping topography strongly influences the regeneration success of C. japonica, restricting its distribution to ridges in natural forests in snowy regions.
Nitrogen fertilization of trembling aspen seedlings grown on soils of different pH
Authors: DesRochers Annie , Driessche R van den , Thomas Barb R
Published: March 2003

Seedlings from three open-pollinated aspen (Populus tremuloides Michx.) families were grown in a greenhouse with four nitrogen (N) sources, each at two N levels and three pH levels. Nitrogen sources were ammonium sulfate ((NH4)2SO4), calcium nitrate (Ca(NO3)2), ammonium nitrate (NH4NO3), and urea ((NH2)2CO); N levels were 50 and 200 mg·L1 (100-mL aliquots three times per week); and pH levels were 5, 6, and 7. Shoot dry mass and leaf area increased with pH in (NH4)2SO4 and (NH2)2CO treatments, but were greatest at pH 6 in the NH4NO3 and Ca(NO3)2 treatments as a result of a pH × N source interaction. N level was directly related to growth, net assimilation, water-use efficiency, and leaf carbon isotope ratio, while N source had no effect on these parameters. Seedlings from families 2 and 3 grew larger than seedlings from family 1, which allocated relatively more dry matter to roots. Growth of the three families interacted with soil pH so that family 1 was largest at pH 7, but families 2 and 3 were largest at pH 6. Seedling boron (B) uptake was reduced by increasing pH and by the Ca(NO3)2 fertilizer. These results were interpreted to show that although the three families seemed well adapted to all the N and pH conditions to which they were exposed, growth could be increased by selection of a fertilizer most suitable to the pH and availability of other nutrients in the soil.
Multiplication végétative de l'Acer saccharum: contribution à la micropropagation
Authors: Brassard N , Richer C , Tousignant D , Rioux J A
Published: March 2003

For the first time, all stages required for the micropropagation of sugar maple (Acer saccharum Marsh.) have been successfully completed. Buds of more than 200 seedlings of two-year-old sugar maple trees were stripped of their scales and cultured on media containing Murashige and Skoog salts with Bourgin and Nitsch organic elements, all diluted to 33%, with or without growth regulator. Survival rate after induction was higher in media without growth regulator. Stem formation and multiplication succeeded in media of the same composition but containing 0.01 or 0.025 mg·L1thidiazuron, as well as 6-(γ, γ-dimethylallylamino)purine, 6-(γ, γ-dimethylallylamino)purine riboside, or phenylacetic acid (PAA). Stem elongation took place in media with 0.3 mg·L1PAA. Root induction was achieved in media containing 0.3 mg·L1PAA with naphthaleneacetic acid. A few shoots rooted when transferred into vermiculite. Although the overall rate of success is still low, rooted shoots were produced by bud multiplication.
Population dynamics of Glaucomys sabrinus and Tamiasciurus douglasii in old-growth and second-growth stands of coastal coniferous forest
Authors: Ransome Douglas B , Sullivan Thomas P
Published: March 2003

Habitat preferences and population dynamics of northern flying squirrels (Glaucomys sabrinus Shaw) and Douglas squirrels (Tamiasciurus douglasii Audubon and Bachman) were examined in old-growth and mature second-growth stands in British Columbia, Canada. Using markrecapture techniques to estimate population dynamics, we tested the hypothesis that old-growth stands provided higher-quality habitat than second-growth stands for these species. Populations were monitored in two old-growth and two mature second-growth stands from August 1995 to May 1999. We were unable to detect major differences in movement, density, recruitment, mass of males, survival, percentage of the population breeding, and the duration that individuals remained on the study plots between stand types for G. sabrinus. Similarly, with the exception of recruitment, we were unable to detect major differences in these parameters between stand types for T. douglasii. Recruitment of T. douglasii was higher in second-growth than in old-growth stands. Old-growth stands were not higher-quality habitat than second-growth stands for either species for the period of enquiry and the parameters we measured. We also presented evidence of late fall  early winter breeding for G. sabrinus, as well as seasonal fluctuations in mass and trappability, larger movement by males than females, and the age of some squirrels exceeding 3.5 years.
Establishment and dynamics of the balsam fir seedling bank in old forests of northeastern Quebec
Authors: Parent Sylvain , Simard Marie-Josée , Morin Hubert , Messier Christian
Published: March 2003

This study examines balsam fir (Abies balsamea (L.) Mill.) recruitment in old fir stands. Studying the regeneration of these stands is essential to understand the regeneration dynamic of the species in the absence of stand-destroying disturbances. The objectives were (1) to obtain substrateseedling associations for different age-classes and according to the presence or absence of adventitious roots; (2) to evaluate the contribution of the seed rain to seedling recruitment; (3) to re-examine age structures using the most appropriate method that minimizes estimation errors due to the presence of adventitious roots. A total of 90 quadrats (1 m2) were established along transects. In each quadrat, subtrates were characterized (type and topography) and their area was estimated. All balsam fir seedlings (<50 cm tall) present in the quadrats were located, harvested whole (root and shoot), and described (age, height, presence of adventitious roots, etc). Fir seedlings were strongly associated with woody mounds covered with thin mats of mixed mosses and Pleurozium shreberi (Bird.) Mitt. but negatively associated with flat topography particularly dominated by Hylocomium splendens (Hedw.) B.S.G. The presence of adventitious root is related to seedling age more than substrate type or topography. The age structure is in agreement with seed production and disturbance regime.
Vitality and chemistry of roots of red spruce in forest floors of stands with a gradient of soil Al/Ca ratios in the northeastern United States
Authors: Wargo Philip M , Vogt Kristiina , Vogt Daniel , Holifield Quintaniay , Tilley Joel , Lawrence Gregory , David Mark
Published: March 2003

Number of living root tips per branch, percent dead roots, percent mycorrhizae and mycorrhizal morphotype, response of woody roots to wounding and colonization by fungi, and concentrations of starch, soluble sugars, phenols, percent C and N and C/N ratio, and Al, Ca, Fe, K, Mg, Mn, and P were measured for 2 consecutive years in roots of red spruce (Picea rubens Sarg.) in stands in the northeastern United States (nine in 1993 and two additional in 1994) dominated by red spruce and with a gradient of forest floor exchangeable Al/Ca ratios. Root vitality was measured for nonwoody and coarse woody roots; chemical variables were measured for nonwoody (<1 mm), fine woody (1 to <2 mm), and coarse woody (2 to <5 mm) roots. There were significant differences among sites for all variables, particularly in 1993, although few were related to the Al/Ca ratio gradient. Percent mycorrhizae decreased, while some morphotypes increased or decreased as the Al/Ca ratio increased. In nonwoody roots, N increased as the Al/Ca ratio increased. Most sampled trees appeared to be in good or fair health, suggesting that an adverse response of these root variables to high Al concentrations may be apparent only after a significant change in crown health.
An 1800-year record of the spatial and temporal distribution of fire from the west coast of Vancouver Island, Canada
Authors: Gavin Daniel G , Brubaker Linda B , Lertzman Kenneth P
Published: March 2003

Charcoal records from lake sediments may show changes in fire frequency over thousands of years, but such records are ambiguous with regard to the actual locations of fires. Using a comparison of fire dates from an 1800-year lake sediment record from the west coast of Vancouver Island (British Columbia, Canada) and dates of last fire from 38 sites in the same watershed using tree-ring and soil-charcoal 14C dates, we estimated the source area that contributes to charcoal peaks and determined the degree to which fires were biased to certain locations. Twenty-three charcoal peaks, likely corresponding with individual fire events, were objectively identified from the sediment record. Comparison of fire dates from charcoal peaks in the sediment record with fire dates from points near the lake suggests that the charcoal source area is within 500 m of the lake edge. Fire occurrence within this charcoal source area increased sharply at AD 1100 from ca. 50 to ca. 300 years between charcoal peaks, coeval with the first "Little Ice Age" cooling. Soil-charcoal radiocarbon dates revealed that 37% of the charcoal source area had not burned over the last 1800 years and that the 23 fires identified in the sediment record were restricted to south-facing slopes near the lake. This spatial pattern may result only if fire is >25 times more likely to occur on susceptible sites (south-facing slopes) than on less susceptible sites. This strong bias in fire location ensured the millennial-scale persistence of large areas of late-successional forest through past climatic periods.
Distillation in a boreal mossy forest floor
Authors: Carleton T J , Dunham K M.M
Published: March 2003

The feathermoss-dominated floor of coniferous boreal forests can experience midsummer drought. From ecophysiological studies, based on single shoots, it is unclear how the live moss carpet can survive such stress. External capillary wicking from the lowest, moist organic layers is one possibility. Another is evaporation from the same source followed by condensation on the upper, live moss shoots (distillation). A laboratory wicking experiment showed that, under ideal conditions, much of the organic forest floor profile can be supplied with moisture by capillarity from below. However, the uppermost live moss shoots could not be hydrated by this mechanism. In contrast, a gravimetric field experiment indicated nocturnal mass gain by turves of live moss shoots, placed in situ on the forest floor, during dry-down conditions. For turf treatments with an underlying vapour barrier, no such mass gain was evident. Turf treatments with a vapour barrier on top were little different from controls. It is concluded that nocturnal distillation occurs during all summer dry-downs and that this is likely to ensure moss shoot survival during diurnal periods of drought stress. Limited microclimate monitoring indicated that nocturnal cooling at the forest floor surface was sufficient to bring the moss shoot surfaces to the dew point and to reverse the daytime temperature gradient through the organic forest floor profile. This appears to be most noticeable late in the growing season when the lowermost organic layers have progressively warmed throughout the summer.
Evaluation of U.S. southern pine stumpage market informational efficiency
Authors: Prestemon Jeffrey P
Published: March 2003

The literature on informational efficiency of southern timber markets conflicts. Part of this conflict is because of differences in how efficiency was tested. In this paper, price behavior tests are based on deflated ("real") southern pine (Pinus spp.) sawtimber stumpage prices, using some of the same data and tests used in previous research and some new data and tests. Here, different results are found in many cases regarding price behavior, as compared with the existing literature. Using a valid and consistent data-based model selection procedure, augmented DickeyFuller tests cannot reject a null of a unit root for most deflated monthly and all quarterly southern pine timber price series evaluated. Regressions of long-term deflated timber price ratios on their own lags lead to results similar to those offered by other authors when not corrected for bias but produce fewer similarities when bias is addressed. The results of those regressions support a contention that most of the monthly series contain nonstationary as well as stationary components and that quarterly prices tested in this framework using data through 2001 are closer to pure nonstationary processes. These results have implications for harvest timing approaches that depend on serial dependence of timber prices, provide support for certain kinds of policy and catastrophic shocks modeling procedures, and address the validity of statistical approaches best suited to evaluating interconnections among timber markets.
Combining remote sensing, data from earlier inventories, and geostatistical interpolation in multisource forest inventory
Authors: Tuominen Sakari , Fish Stuart , Poso Simo
Published: March 2003

Multisource forest inventory with two-phase sampling offers several advantages in the forest management planning when compared with the traditional visual inventory by stands. For example, by combining data from remote sensing imagery with field measurements, it is possible to estimate the forest characteristics of large areas at a more reasonable cost than by using the traditional visual inventory by stands. In this study, the k-nearest-neighbours estimation (k-nn), stand inventory data, and geostatistical interpolation were combined for estimation of five forest variables (mean diameter, mean height, mean age, basal area, and volume) per sample plot and stand. Digitized aerial photograph features, visually interpreted aerial photograph features, and updated stand inventory data were used as the auxiliary data sources in the estimation of forest variables. The results show that, at the sample plot level, the k-nn estimates based on the auxiliary data sources were more accurate than the updated stand inventory data transferred to the plot level. At the stand level, the updated stand inventory data were more accurate than the k-nn estimates. When the k-nn estimates were combined with the updated stand inventory data, the accuracy of the estimates was significantly improved at both the sample plot and stand level. The geostatistical interpolation, which was tested on the stand level estimation, did not result in any further improvement in the accuracy of the estimates.
Early development of root rot in young Norway spruce planted on sites infected by Heterobasidion in southern Finland
Authors: Piri Tuula
Published: March 2003

Root rot infections in Norway spruce (Picea abies (L.) Karst.) regeneration, planted after the clear-cutting of spruce on sites infested by Heterobasidion, were investigated on 21 experimental plots in eight 2- to 23-year-old plantations. Heterobasidion root rot became evident about 10 years after planting and the proportion of infected spruces increased steadily with plantation age. The average number of planted spruces infected per old decayed stump was 0.2 trees in 2- to 9-year-old plantations, 0.8 trees in 11- to 15-year-old plantations, and 1.8 trees in 20- to 23-year-old plantations. About 10 and 20 years after planting, 7 and 23% of the planted spruces in the disease centers were infected by Heterobasidion. Heterobasidion parviporum Niemelä & Korhonen, and Heterobasidion annosum (Fr.) Bref. s. str. caused 98 and 2% of the Heterobasidion infections in the previous spruce rotation, and 96 and 4% in the spruce regeneration, respectively. In all, 71% of the infected regeneration trees were attacked by a Heterobasidion genet that was also isolated from the stumps of the previous tree stand. Armillaria species (Armillaria borealis Marxmüller & Korhonen and Armillaria cepistipes Velenovský) were isolated from 7% of the planted spruces.
Positional influence on rooting of shoots forced from the main bole of swamp white oak and northern red oak
Authors: Fishel D W , Zaczek J J , Preece J E
Published: March 2003

The transition of ontogenetic maturity was assessed in two oak species by forcing softwood shoots from main bole stem sections in the greenhouse and from intact crowns, stumps, and hedged trees in situ and subsequently subjecting the new shoots to rooting trials. Mean shoot production was greater from forced stem sections of northern red oak (Quercus rubra L.) than from those of swamp white oak (Quercus bicolor Willd.) (14.6 and 4.6 shoots/m, respectively). Northern red oak stem sections exhibited a vertical gradient in the number of forced shoots; greater numbers originated from basal and juvenile sections of trees than from distal and mature sections. Rooting of swamp white oak shoots was low, 1.4% for forced shoots and none from hedged trees. Rooting of northern red oak was greater but variable, averaging 40.3% from greenhouse forced shoots and 0-35% from field-grown trees. Moreover, percent rooting was greatest for forced shoots originating from basal stem sections and declined with increasing distance from the tree base. The results suggest that ontogenetic maturation gradually increases, and rooting response decreases, along the bole of northern red oak trees.
Growth responses of Picea abies and Larix decidua to elevation in subalpine areas of Tyrol, Austria
Authors: Li Mai He , Yang Jian , Kräuchi Norbert
Published: March 2003

Microsites related to microenvironmental conditions, including microclimate, seem to be a key factor for the restoration of forests in the subalpine area. Tree growth was studied in Picea abies (L.) Karst. (Norway spruce) and Larix decidua Mill. (European larch) on 30 plots located at different microsites (i.e., different elevations and micro top o graphies combined) within the subalpine zone (16801940 m) of the Schmirn Valley (Tyrol, Austria). The age of the trees studied was 27 years for larch and 28 years for spruce. The mean height and biomass growth decreased significantly with increasing elevation. The effect of elevation and microtopography on growth varied with tree size (age): (1) elevation had little effect on growth of trees less than 0.5 m in height; (2) both elevation and microtopography affected tree growth significantly when the tree height was between 0.5 and 3 m; (3) as trees exceed 3 m in height, tree canopies can fully cover the ground surface and create a forest microclimate causing growth to decline with increasing elevation, irrespective of microtopography. We conclude that the microclimate, associated with microsite, controls growth during the early stages of tree development, but following canopy closure, the local climate (mesoclimate) associated with topography begins to determine tree growth.
Substrate and litterfall effects on conifer seedling survivorship in southern boreal stands of Canada
Authors: Simard Marie-Josée , Bergeron Yves , Sirois Luc
Published: March 2003

Most conifer seeds die as seeds or seedlings within 5 years after dispersal. Understanding what factors keep a few of them alive is essential if natural regeneration is to be maintained in managed forests. For example, decaying logs and the conifer seedlings that often grow on them are rare under certain canopies such as deciduous trembling aspen (Populus tremuloides Michx.). We conducted a seeding experiment to evaluate the role of certain substrates, and litterfall, on early conifer survivorship. Seeds of balsam fir (Abies balsamea (L.) Mill.), white spruce (Picea glauca (Moench) Voss), and eastern white-cedar (Thuja occidentalis L.) were sown during 2 consecutive years on mineral soil, relocated logs, and litter in deciduous aspen and coniferous (Thuja occidentalis dominated) stands. Seedling survivor ship was monitored at the end of the first growing season and 1 year after each sowing. Conifer seedling survivorship was equivalent or greater under aspen than under cedar-dominated canopies. Picea and Thuja survivorship was highest on decaying logs of approximately 9 cm high (compared with logs buried at forest floor level) and lowest on forest floor litter during both the first growing season and the following autumnwinter. Abies survivorship was little affected by substrate type, except for low autumnwinter survival on litter. Thuja autumnwinter survival was significantly reduced by litterfall in both deciduous and coniferous stands.
Évolution de la structure diamétrale et de la composition des peuplements mixtes de sapin baumier et d'épinette rouge de la forêt primitive après une coupe à diamètre limite sur l'Aire d'observation de la rivière Ouareau
Authors: Fortin Mathieu , Bégin Jean , Bélanger Louis
Published: March 2003

Using data from 41 plots, the diameter structure and composition of old-growth mixed stands composed mainly of balsam fir (Abies basalmea (L.) Mill.) and red spruce (Picea rubens Sarg.) were characterized. The stand table was organized in five groups of diameter classes, and we characterized the basal area of four tree species in each group. Analysis showed that diameter structure tends toward a reverse J-shaped curve. Red spruce and yellow birch (Betula alleghaniensis Britt.) were more abundant among large diameter trees while balsam fir was more abundant among saplings. A comparison with 18 permanent plots from a diameter-limit cutting showed that plots had come back to a structure similar to that of the old-growth forest 47 years after cutting. However, spruce ratios had decreased while those of balsam fir and paper birch (Betula papyrifera Marsh.) had increased. Red spruce decrease is not due to a lack of regeneration but to overcutting. Single-tree selection method would be a suitable treatment if aimed at protecting red spruce trees up to a given diameter.