bluuebunny/crossref_metadata_2025 huggingface dataset:
Regioselective SO vs. CO bond cleavage in sulfenate ester radical anions
Authors: Stringle Donald LB , Workentin Mark S
Published: January 2006

The electron transfer (ET) reduction of benzyl benzenesulfenate ester (1) and tert-butyl benzenesulfenate ester (2) was investigated using electrochemical techniques. Analysis of the cyclic voltammetry of each compound suggests that the ET reduction proceeds via a stepwise dissociative mechanism. The voltammograms of 1 are similar to those of diaryl disulfides and it was found through controlled potential electrolysis (CPE) product studies that ET reduction leads to SO bond cleavage. The voltammograms of 2 are dramatically different with a sharper dissociative wave occurring at a more negative peak potential. CPE experiments indicate products that result from ET leading to CO bond cleavage in this case. DFT calculations of the singly occupied molecular orbitals (SOMOs) of 1 and 2 were performed and offer a rationale for the different reactivity of the two radical anions.Key words: sulfenate esters, dissociative electron transfer, electrochemistry, radical anions.
The mechanisms of hydrolysis of alkyl N-alkylthioncarbamate esters at 100 °C
Authors: Humeres Eduardo , M. Sanchez Maria de Nazaré , Lobato Conceição ML , Debacher Nito A , Souza Eduardo P. de
Published: January 2006

The hydrolysis of ethyl N-ethylthioncarbamate (ETE) at 100 °C was studied in the range of 7 mol/L HCl to 4 mol/L NaOH. The pHrate profile showed that the hydrolysis occurred through specific acid catalysis at pH < 2, spontaneous hydrolysis at pH 26.5, and specific basic catalysis at pH > 6.5. The Hammett acidity plot and the excess acidity plot against X were linear. The BunnettOlsen plot gave a negative slope indicating that the conjugate acid was less hydrated than the neutral substrate. It was concluded that the acid hydrolysis occurred by an A1 mechanism. The neutral species hydrolyzed with general base catalysis shown by the Brønsted plot with β = 0.48 ± 0.04. Water acted as a general base catalyst with (pseudo-)first-order rate constant, kN = 3.06 × 107 s1. At pH > 6.5 the rate constants increased, reaching a plateau at high basicity. The basic hydrolysis rate constant of ethyl N,N-diethylthioncarbamate, which must react by a BAc2 mechanism, increased linearly at 13 mol/L NaOH with a second-order rate constant, k2 = 2.3 × 104 (mol/L)1 s1, which was 10 times slower than that expected for ETE. Experiments of ETE in 0.6 mol/L NaOH with an excess of ethylamine led to the formation of diethyl thiourea, presenting strong evidence that the basic hydrolysis occurred by the E1cb mechanism. In the rate-determining step, the E1cb mechanism involved the elimination of ethoxide ion from the thioncarbamate anion, producing an isothiocyanate intermediate that decomposed rapidly to form ethylamine, ethanol, and COS.Key words: alkylthioncarbamate esters, ethyl N-ethylthioncarbamate, ethyl N,N-diethylthioncarbamate, hydrolysis, mechanism.
Deuterium kinetic isotope effects on the thermal isomerizations of deuteriocyclopropane to deuterium-labeled propenes
Authors: Baldwin John E , Singer Stephanie R
Published: January 2006

The gas-phase thermal isomerizations of deuteriocyclopropane to the four possible monodeuterium-labeled propenes have been followed at 435 °C. The observed distribution of products provides estimates of two deuterium kinetic isotope effects, the secondary [Formula: see text] for the carboncarbon bond cleavage leading to trimethylene diradical reactive intermediates and the primary [Formula: see text] ratio for a [1,2] shift of a hydrogen or deuterium leading from the diradical to a labeled propene. The values determined are [Formula: see text] = 1.09 ± 0.03 and [Formula: see text] = 1.55 ± 0.06. The experimental [Formula: see text] value found agrees well with some, but not all, earlier calculated values and conjectures. Key words: cyclopropane, thermal rearrangement, kinetic isotope effects.
Mechanism of the lithiumiodine exchange in an iodothiophene
Authors: Reich Hans J , Whipple Wesley L
Published: January 2006

Solutions of 2-lithio-5-methylthiophene (4) were characterized using DNMR techniques and shown to be a mixture of monomer and dimer in THFEt2O (3:2). The hypervalent iodine ate complex 5 (Ar2ILi+), a presumed intermediate in the LiI exchange with 2-iodo-5-methylthiophene, was observed by 13C and 7Li NMR spectroscopy at low temperatures (130 °C). At higher temperatures, the ate complex coalesced with 2-lithio-5-methylthiophene. A kinetic scheme was developed, which accounts for the exchange of the monomer 4M, dimer 4D, and 2-iodo-5-methylthiophene (6) with the ate complex 5. The rates of the various exchanges were obtained through a DNMR analysis of the variable temperature 13C and 7Li NMR spectra, and the thermodynamic and activation parameters were calculated. The monomer 4M and the ate complex 5 have similar reactivity as aryl donors in the LiI exchange reaction, but 4M is at least 1000 times as reactive as the dimer 4D towards the iodide.Key words: halogenmetal exchange, lithium iodinate, iodine ate complex, lithium reagent, aggregate reactivity.
Reaction intermediates in organic chemistry  The “big picture”
Authors: Andraos John
Published: January 2006

An overview of the discovery of reaction intermediates and associated concepts in physical organic chemistry is presented. Particular attention is paid to chronology of ideas, frequency of occurrence of reaction intermediates in the library of organic reactions used in organic synthesis, and the lexicon of scientific terms used in the language of physical organic chemistry. General logic decision trees are presented for the unique or near unique identification of reaction intermediates based on experimental techniques and common patterns of reactivity documented in the literature over the last century. Contributions made by scientists working in laboratories at Canadian universities and at the National Research Council of Canada are noted throughout.Key words: physical organic chemistry, mechanistic chemistry, reaction intermediates.
A computational study of the 1,3-dipolar cycloaddition reaction mechanism for nitrilimines
Authors: Mawhinney Robert C , Muchall Heidi M , Peslherbe Gilles H
Published: January 2006

The [3+2] and [1+2] cycloaddition pathways between ethene and a series of 13 nitrilimines (R1CNNR2) have been examined by density functional theory [PBE0/6-311++G(2df,pd)] calculations. All reactions have low barriers ranging from 14.14 (R1 = CH3, R2 = H) to 1.01 (R1 = R2 = F) kcal mol1, and large reaction exothermicities consistent with the transient nature of nitrilimines. The [3+2] and [1+2] transition-state structures are very similar, mainly differing in the relative orientation of their fragments and the newly forming CC bond distance, and exhibit only minor deviations from the structures of the reactants. Both reaction pathways are concerted and asynchronous, but the [1+2] reaction has a greater degree of asynchronicity. Examination of the frontier molecular orbitals reveals that both the [3+2] and [1+2] barrier heights are related to two sets of orbital interactions, with the interaction between the lowest unoccupied molecular orbital π [Formula: see text] of nitrilimine and the highest occupied molecular orbital of ethene in common. The second interaction in both cases is carbene-like. A relationship between the weights of the 1,3-dipolar resonance contribution in the various nitrilimines and the corresponding [3+2] barrier heights was not found, but a good correlation could be found between the [1+2] barrier heights and both the 1,3-dipolar and carbene contributions. Inspection of the potential energy surface in the vicinity of the two transition states for the reaction between unsubstituted nitrilimine and ethene suggests that the observed [3+2] product is a result of an initial carbene-like approach of the two fragments followed by a ridge bifurcation that leads to the [3+2] product minimum. Key words: nitrilimines, 1,3-dipole, carbene, [3+2] cycloaddition, [1+2] cycloaddition, density functional theory (DFT).
Enhancement of aqueous solubility of itraconazole by complexation with cyclodextrins using supercritical carbon dioxide
Authors: Shehatta Ibrahim , Al-Marzouqi Ali Hassan , Jobe Baboucarr , Dowaidar Ali
Published: January 2006

The formation of inclusion complexes between itraconazole, a highly hydrophobic drug, and α-, β-, γ-, and hydroxylpropyl-β-cyclodextrin (HP-β-CD) were assessed using phase-solubility techniques. The solubility of itraconazole increased as a function of cyclodextrin concentration showing an AL phase diagram indicating the formation of soluble complexes with 1:1 stoichiometry. The Gibbs free energies of transfer of the drug from aqueous solution to the cavity of cyclodextrin are negative and increase in magnitude with increasing cyclodextrin concentration. The solubility of itraconazole, as well as the stability constant of its complex with HP-β-CD, are found to be affected by the pH of the medium. The HP-β-CD cavity was found to have a greater affinity for the unionized itraconazole than the protonated one. It was found that the interaction between the drug and the cyclodextrin is weakened as the medium becomes more apolar by the addition of methanol. Also, the size of the cavity of the cyclodextrins plays an important role in the association process. Furthermore, the thermodynamic parameters of the complexation process were calculated, by monitoring the isothermic solubility diagrams of itraconazoleHP-β-CD and itraconazoleβ-CD at various temperatures, to gain information on the driving forces for the formation of inclusion complexes. Drug formulations of itraconazole were prepared by complexation of the drug into different cyclodextrins using supercritical carbon dioxide in a static mode. The effects of cyclodextrins on the prepared inclusion complexes were studied and characterized by differential scanning calorimetry.Key words: cyclodextrin, itraconazole, inclusion complex, solubility, stability constant.
The mechanism of 1,3-dipolar cycloaddition reactions of cyclopropanes and nitrones  A theoretical study
Authors: Wanapun D , Van Gorp K A , Mosey N J , Kerr M A , Woo T K
Published: January 2006

The 1,3-dipolar cycloaddition reaction of cyclopropanes and nitrones to give tetrahydro-1,2-oxazine has been studied with density functional theory calculations at the B3LYP/6-31+G(d,p) level of theory. Realistic substituents were modelled including those at the 2-, 3-, 4-, and 6-positions of the final oxazine ring product. The strained σ bond of the cyclopropane was found to play the role of an alkene in a conventional [3+2] dipolar cycloaddition. Two distinct, but similar, reaction mechanisms were found  an asymmetric concerted pathway and a stepwise zwitterionic pathway. The reaction barriers of the two pathways were nearly identical, differing by less than ~1 kcal/mol, no matter what the substituents were. The effect of a Lewis acid catalyst was examined and found to have a very large effect on the calculated barriers through coordination to the carbonyl oxygen atoms of the diester substituents on the cyclopropane. The reaction barrier was found to decrease by as much as ~19 kcal/mol when using a BF3 molecule as a model for the Lewis acid catalyst. Solvent effects and the nature of the regiospecificity of the reaction were also examined. Trends in the calculated barriers for the reaction were in good agreement with available trends in the reaction rates measured experimentally. Key words: 1,3-dipolar cycloaddition, cyclopropane, nitrone, tetrahydro-1,2-oxazines, ab initio quantum chemistry, mechanism.
Chemoselective thioacetalization with odorless 2-(1,3-dithian-2-ylidene)-3-oxobutanoic acid as a 1,3-propanedithiol equivalent
Authors: Yu Haifeng , Dong Dewen , Ouyang Yan , Liu Qun
Published: January 2006

Odorless 2-(1,3-dithian-2-ylidene)-3-oxobutanoic acid (1c) was prepared and investigated in the thioacetalization of carbonyl compounds as a 1,3-propanedithiol equivalent. The results showed that the thioacetalization of various carbonyl compounds 2 with 1c proceeded smoothly and afforded the corresponding dithioacetals 3 in high yields (up to 99%) in the presence of acetyl chloride at room or reflux temperatures. Moreover, the thioacetalization exhibited high chemoselectivity between aldehydes and ketones. Key words: chemoselectivity, 2-(1,3-dithian-2-ylidene)-3-oxobutanoic acid, α-oxo ketene dithioacetal, 1,3-propanedithiol equivalent, thioacetalization.
Ionic liquid promoted simple and efficient synthesis of β-enamino esters and β-enaminones from 1,3-dicarbonyl compounds  One-pot, three-component reaction for the synthesis of substituted pyridines
Authors: Karthikeyan Ganesan , Perumal Paramasivan T
Published: January 2006

A facile enamination of 1,3-dicarbonyl compounds with amines has been developed that affords good to excellent yields of β-enamino esters and β-enaminones using Brønsted acidic ionic liquid 1-methylimidazolium trifluoroacetate ([Hmim]+Tfa) at room temperature. This methodology has been extended for the synthesis of substituted pyridines in excellent yield by a one-pot, three-component reaction of 1,3-dicarbonyl compounds, ammonium acetate, and alkynone in the presence of [Hmim]+Tfa.Key words: ionic liquid, β-enaminones, β-enamino esters, 1,3-dicarbonyl compounds, amines, pyridines.
Triazene derivatives of (1,x)-diazacycloalkanes. Part V.1 Synthesis and characterization of 4-ethyl-3-({6-ethyl-3-[2-aryl-1-diazenyl]hexahydro-1-pyrimidinyl}methyl)-1-[2-aryl-1-diazenyl)hexa- hydropyrimidines from the reaction of diazonium salts with mixtures of formaldehyde and 1,3-diaminopentane
Authors: Tingley Reid , Peori M Brad , Church Ryan , Vaughan Keith
Published: January 2006

A new series of bistriazenes has been synthesized from a general reaction of diazonium salts with a mixture of 1,3-diaminopentane (DYTEK® EP diamine) and formaldehyde, which affords the 4-ethyl-3-({6-ethyl-3-[2-aryl-1-diazenyl]hexahydro-1-pyrimidinyl}methyl)-1-[2-aryl-1-diazenyl]hexahydropyrimidines (1). Each of the molecules of type 1 is built up of two equivalent 3-(aryldiazenyl)-6-ethylhexahydro-1-pyrimidinyl groups attached to a central methylene group. The importance of this study is in part due to the fact that the formaldehyde1,3-diaminopentane system has not previously been investigated. All new compounds have been characterized by IR and NMR spectroscopy, with elemental analysis for selected compounds; one example from the series has been unequivocally characterized by X-ray crystallography. Although analysis of the NMR spectra is made somewhat difficult because of broadness and coalescence of signals due to the rotational dynamics of the NN single bonds, it is possible to fully assign the proton spectra of all compounds and to detect 94% of all carbon signals. The fine structure within the proton spectra illustrate the diastereotopic nature of the methylene group protons because of the presence of a stereocenter in each hexahydropyrimidine ring. The general conclusion of this study is that alkanediamines with three carbon atoms in the spacer link between the nitrogen atoms give rise to the linear bicyclic molecules of type 1, 2, and 3, in contrast to the case of ethylenediamine (spacer link has two carbon atoms), which affords molecules of type 7 that exemplify the bridged bicyclic bistriazene structure. The new compounds of series 1 represent an extension of a broad ranging study of the synthesis of new bistriazene derivatives of (1,x)-diazacycloalkanes.Key words: triazene, diazonium coupling, hexahydropyrimidine, diaminopentane, diazacycloalkanes, stereocenter, diastereotopic protons.
Linear free energy relationship and kinetic isotope effects as measures for the transition-state variation  A case of the neophyl system
Authors: Ammal Salai Cheettu , Yamataka Hiroshi
Published: January 2006

Ab initio calculations at the MP2/6-31G* level and density functional theory (B3LYP/6-311+G**) calculations have been performed on acid-catalyzed ionizations of substituted neophyl alcohols to investigate whether a variation of the transition-state (TS) structure is reflected in the kinetic isotope effects (KIE) and linear free energy relationship. The effect of substituents on KIEs, TS structures, and activation and reaction energies was calculated. This study revealed that a curved Brønsted-type plot could arise for a single-step process from the variation of TS structure with the substituent, whereas the Hammett plots with a dual-parameter treatment can not detect such TS variation. The variation of KIEs at various positions of neophyl alcohol reflects the variation of TS structures in a manner consistent with the More O'Ferrall  Jencks type reaction diagram analyses.Key words: transition-state variation, substituent effect, kinetic isotope effect, linear free energy relationship.
Forest landowner decisions and the value of information under fire risk
Authors: Amacher Gregory S , Malik Arun S , Haight Robert G
Published: January 2006

We estimate the value of three types of information about fire risk to a nonindustrial forest landowner: the relationship between fire arrival rates and stand age, the magnitude of fire arrival rates, and the efficacy of fuel reduction treatment. Our model incorporates planting density and the level and timing of fuel reduction treatment as landowner decisions. These factors affect, among other things, the loss a landowner incurs should fire arrive before harvesting. The value of information depends on the nature and combination of mistakes a landowner makes, the relationship between fire arrival and stand age, and on whether the landowner undertakes fuel treatment and values nontimber benefits. Information of various types is of most value to a landowner who does not undertake fuel treatment. The value of information about the magnitude of fire risk is also more than twice as high when the landowner underestimates fire risk, rather than overestimating it. For a landowner who undertakes fuel treatment but makes multiple mistakes, the asymmetry between overestimating and underestimating fire risk and efficacy of fuel reduction is even more pronounced.
Characterization of damage and biotic factors associated with the decline of Eucalyptus wandoo in southwest Western Australia
Authors: Hooper Ryan J , Sivasithamparam K
Published: January 2006

Crown decline of wandoo, Eucalyptus wandoo, in southwest Western Australia has escalated over the last 10 years, so very few unaffected stands remain. To assess the canopy-damage characteristics of trees in decline a destructive, partial-harvest method was used to sample branches in natural mixed-age stands. Necrosis of common cankers was closely associated with type-1 borer damage, characterized by "longitudinal" gallery structure on declining trees only. Cankers were found to be consistently more severe on declining trees, with decay regions affecting a greater proportion of sapwood tissue. Several infestations causing type-1 borer damage that varied in age were found on declining branches, providing evidence of cyclical damage events. Type-2 borer damage characterized by "ring-barking" gallery structure caused extensive damage in canopies, but was not always associated with decline. Interactions between foliage density and canker score showed that 17.8% and 63.1% of the variability in foliage-density ratios was accounted for in declining intermediate-health and unhealthy classes, respectively. The relationship was negligible for the healthy class (9.9%), providing strong evidence that cankers are causing foliage loss in declining canopies. Evidence suggests that an interaction between type-1 borer infestations and decay-causing fungi is responsible for the decline in E. wandoo wandoo canopies.
Spring and summer hydraulic conductivity of 14 woody species of the sub-boreal forest in British Columbia
Authors: Wang Jian R
Published: January 2006

Four hydraulic properties of the xylem, the Huber value (HV), hydraulic conductivity (Kh), and specific (Ks) and leaf-specific hydraulic conductivity (K1) were studied during the spring before leaf-out and during the summer after full leaf-out for 14 co-occurring tree and shrub species in the sub-boreal mixedwood forests of central British Columbia. The 14 studied species were divided into deciduous and evergreen angiosperm and gymnosperm groups, including one deciduous gymnosperm species, the tamarack, Larix laricina (Du Roi) K. Koch. I tested whether species with different life forms and classification divisions have different hydraulic properties. HVs were statistically similar for all angiosperms but significantly different among gymnosperms. Long-lived, late-successional species had higher HVs than pioneer and early-successional species. Ks and K1 values for all species except one, subalpine fir, Abies lasiocarpa var. lasiocarpa (Hook.) Nutt., were significantly higher in the spring than in the summer. Conductivity was higher in angiosperms than in gymnosperms in both the spring and the summer, and was highest in deciduous species in both seasons. The results indicate that requirements for mechanical strength may account for the high HVs in conifers, and that the high HVs compensate for low Ks and K1 values. The high hydraulic conductivities observed in the spring coincide with high water availability and high water demand by trees with emerging leaves. The subsequent reduction in Ks and K1 values could be caused by drought-induced embolism and cavitation in early summer.
Comparative in vitro and early nursery performance of adventitious shoots from cryopreserved cotyledons and axillary shoots from epicotyls of the same zygotic embryo of control-pollinatedPinus radiata
Authors: Hargreaves Cathy L , Grace Lynette J , van der Maas Susan A , Menzies Mike I , Kumar Satish , Holden D Grant , Foggo Martin N , Low Charlie B , Dible Mike J
Published: January 2006

This is the first published report comparing production and performance of adventitious shoots from cryopreserved cotyledons, with axillary shoots formed from epicotyls of the same zygotic embryo of radiata pine (Pinus radiata D. Don). Genotypes from 10 control-pollinated families of P. radiata in two treatments were compared for shoot initiation, in vitro growth, rooting, and early nursery performance. Plant growth in nursery beds was assessed by measuring height after 2 and 7 months. After 8 months in nursery beds, the physiological ages of genotypes were assessed before field planting. Genotype capture was higher from the cryopreserved cotyledons than from the epicotyls. This technique has the advantage of preserving juvenile material while field testing is done. Early shoot multiplication in both treatments was good. After four transfer cycles, epicotyl cultures showed improved elongation and higher multiplication rates. After 6 months of in vitro growth, shoots from both treatments were given auxin pulses. Shoots of adventitious origin were slower to root than epicotyl-derived shoots. Overall rooting rates were satisfactory. Plants of adventitious origin were shorter when planted into nursery beds and when transferred to field trials. Assessment of relative physiological age indicated that all plants of adventitious origin showed some increase.
Trembling aspen response to a mixed-severity wildfire in the Black Hills, South Dakota, USA
Authors: Keyser Tara L , Smith Frederick W , Shepperd Wayne D
Published: January 2006

Trembling aspen (Populus tremuloides Michx.) regeneration dynamics including sprout production, growth, and clone size were measured to determine the effects of fire on small aspen clone persistence following a mixed-severity wildfire in the Black Hills, South Dakota. Four years postfire, 10 small, isolated aspen clones per low and high fire severity classes were compared with 10 unburned clones. Regardless of severity, fire did not cause an increase in the area occupied by individual aspen clones. Clones affected by high severity fire had the greatest suckering response producing an average of 31 930 sprouts·ha1; more than double the sprout density in unburned clones and 67% greater than the sprout density in clones affected by low severity fire. Sprout growth in high severity clones was 135% and 60% greater than sprout growth in unburned and low severity clones. The succession of these clones to more shade-tolerant ponderosa pine was delayed in clones affected by high severity fire as high severity fire caused significant pine mortality within and surrounding the clone, whereas, without further disturbance, pine encroachment and dominance will likely continue in clones affected by low severity fire.
An ecogeographic framework for in situ conservation of forest trees in British Columbia
Authors: Hamann Andreas , Smets Pia , Yanchuk Alvin D , Aitken Sally N
Published: January 2006

We present a comprehensive approach to carry out community-wide assessments of in situ conservation of forest trees based on basic botanical and ecological data. This is a first step, resulting in a consistent framework to set priorities for collection and inclusion of species- specific biological and genetic information. We use botanical sample data to generate high-resolution distribution maps as a basis for a gap analysis of how well each species is represented in protected areas. To account for adaptive genetic variation of tree species we stratify populations by ecological zones that represent different macroclimates. In a detailed example for Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), we show that under certain conditions this approach can pinpoint gaps at the level of genetically differentiated populations without actually using genetic data. In a comprehensive case study, evaluating the outcome of a major protected area expansion between 1991 and 2001 for British Columbia, we demonstrate how extensive results from a community-wide GIS analysis can be summarized and presented for decision-making. We provide methods to identify and efficiently cope with in situ conservation gaps, where lack of data or low protected area coverage requires additional conservation efforts or collection of better data.
Does thinning intensity affect the tracheid dimensions of Norway spruce?
Authors: Jaakkola Tuula , Mäkinen Harri , Sarén Matti-P , Saranpää Pekka
Published: January 2006

The effect of thinning intensity on the growth rate and tracheid dimensions of Norway spruce (Picea abies (L.) Karst) was studied in two long-term thinning experiments (Heinola and Punkaharju) in southeastern Finland. The stand age was 86 and 67 years in Heinola and Punkaharju, respectively. Thinning intensities in this study were lower and higher than recommended in the 1960s for forestry practice in Finland. An increase in tree growth rate (31% in Heinola and 37% in Punkaharju) caused by the high thinning intensity resulted in slightly shorter tracheids (9% in Heinola and 4% in Punkaharju) than with the low thinning intensity. Increased growth rate had no pronounced effect on tracheid cell wall thickness and lumen diameter. A faster growth rate slightly decreased the average cell wall thickness of an annual ring, but the changes in average lumen diameter were small. The effect of thinning intensity was similar in earlywood and latewood. Variation in fiber properties between and within individual trees and annual rings was large. In conclusion, the current thinning intensities used in Finnish forestry practice enhance growth rate but have a rather small effect on tracheid dimensions.
Tree growth response to climate change at the deciduousboreal forest ecotone, Ontario, Canada
Authors: Goldblum D , Rigg L S
Published: January 2006

We consider the implications of climate change on the future of the three dominant forest species, sugar maple (Acer saccharum Marsh.), white spruce (Picea glauca (Moench) Voss), and balsam fir (Abies balsamea (L.) Mill.), at the deciduousboreal forest ecotone, Ontario, Canada. Our analysis is based on individual species responses to past monthly temperature and precipitation conditions in light of modeled (general circulation model) monthly temperature and precipitation conditions in the study area for the 2080s. We then consider the tree species sensitivity to past climate with predicted conditions for the 2080 period. Sugar maple, located at its northern limit in the study area, shows the greatest potential for increased growth rates under the predicted warming and altered precipitation regime. White spruce is likely to benefit less, while the understory dominant balsam fir is likely to experience a decrease in growth potential. These projected changes would enhance the future status of sugar maple at its northern limit and facilitate range expansion northward in response to global warming.
Logging impacts on forest carabid assemblages in Japan
Authors: Osawa Naoya , Terai Atsumi , Hirata Keiichi , Nakanishi Asami , Makino Ayumi , Sakai Shinjiro , Sibata Shozo
Published: January 2006

We hypothesized that small-area logging (<1 ha) would greatly affect microhabitats of carabid beetles. To test this hypothesis, we studied the carabid assemblages at Kamigamo Experimental Station, Kyoto, Japan, from June 1999 to May 2001. From the analysis of the number of individuals and niche breadth, the numbers of large carnivores (Carabus dehanii Chaudoir, Carabus maiyasanus Bates, and Carabus yaconinus Bates) and large insectivores (Chlaenius posticalis Motschulsky and Haplochlaenius costiger (Chaudoir)) decreased because of logging, whereas the small carabids, Synuchus arcuaticollis (Motschulsky) and Synuchus cycloderus (Bates), may not have been negatively influenced by logging. The mass of the FH layer significantly affected the total number of Pterostichus latemarginatus (Straneo) and marginally affected the number of S. cycloderus. However, soil water content (%) and the mass of the L layer did not affect the total number of individuals in any species. The results of this study imply that (1) the richness of the FH layer and vegetation, that is, the potential food abundance and habitat richness, is involved in determining species richness and the density of the carabid assemblages and (2) even small-area logging may have a negative impact on the density of the large predatory carabids, which are sensitive indicators of forest disturbance.
Soil respiration in pure and mixed stands of European beech and Norway spruce following removal of organic horizons
Authors: Borken Werner , Beese Fritz
Published: January 2006

Soil respiration was measured in adjacent pure and mixed stands of European beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) Karst.) at Solling, Germany. Forest type had a significant effect on soil respiration, which was highest in the pure beech stand and lowest in the pure spruce stand. Both throughfall and soil temperature increased with the proportion of beech. Additionally, microbial respiration and biomass in the organic (O) horizons increased sequentially from the pure spruce to the pure beech stand, suggesting that abiotic and biotic factors enhanced the decomposition of litter under beech. Because the spruce litter decomposition rate was low, carbon (C) stocks of the O horizons increased with the proportion of spruce, from 1.6 to 5.1 kg C·m2. The removal of the O horizons decreased soil respiration by 31%45%, indicating a large contribution of the mineral soil and roots to total soil respiration. Turnover times of organic C in the O horizons ranged between 5.5 years in the pure beech stand and 20.6 years in the pure spruce stand. Our results suggest that tree species conversion may alter the turnover of soil organic matter, and thus the sequestration of organic C in the O horizons.
Estimation of whole-tree kraft pulp yield of Eucalyptus nitens using near-infrared spectra collected from increment cores
Authors: Schimleck Laurence R , Kube Peter D , Raymond Carolyn A , Michell Anthony J , French Jim
Published: January 2006

Eucalyptus nitens (Deane and Maiden) Maiden (shining gum) is widely grown for kraft pulp production. Improving the kraft pulp yield of E. nitens increases plantation profitability but traditional assessment is slow and expensive, which hinders improvement. Near-infrared (NIR) spectroscopy provides a rapid and inexpensive method for estimating pulp yield, but studies have been limited to estimating whole-tree pulp yield using whole-tree composite samples obtained destructively. For whole-tree pulp-yield calibrations to be used non-destructively they must be applied to increment cores. In this study we used a Tasmanian E. nitens whole-tree pulp yield calibration to estimate the whole-tree pulp yields of trees from a site not included in the calibration. This was done using NIR spectra from increment cores and whole-tree composite chips. Predictions of whole-tree pulp yield based on increment cores were better than those obtained using whole-tree composite chips. The accuracy of pulp-yield predictions was greatly improved by adding a small number of prediction-set samples to the calibration sets. Calibrations for estimating whole-tree pulp yield were also obtained using NIR spectra from milled cores and whole-tree composite chips. The calibrations had similar statistics, indicating that it is possible to obtain calibrations for estimating whole-tree pulp yield based on increment-core NIR spectra.
Micropropagation with a novel pattern of adventitious rooting in Formosan sweetgum
Authors: Ďurkovič Jaroslav , Pichler Viliam , Lux Alexander
Published: January 2006

Cultures of the Formosan sweetgum (Liquidambar formosana Hance) were established from axillary buds of intact plants and from petiole segments of in vitro grown leaves. Petiole segments were generally slower than axillary buds to form multiple shoot cultures. Thidiazuron in combination with 6-benzylaminopurine produced on average up to 9.4 shoots per explant. Shoot elongation was significantly affected by the concentration of 6-benzylaminopurine, regardless of auxin addition to the medium. Adventitious rooting occurred up to 90%. An unexpected pattern of adventitious rhizogenesis was observed from the aerial parts of microshoots not in contact with the rooting medium, including leaf blades and petiole axils. In vitro adventitious root formation from the leaf blade was associated with parenchyma cells surrounding the main vein. The regenerated plants established ex vitro did not show any detectable morphological variation and no aerial roots were formed.
Response of small mammals to clear-cutting and precommercial thinning in mixed forests of southeastern Quebec
Authors: Etcheverry Pierre , Ouellet Jean-Pierre , Crête Michel
Published: January 2006

The impacts of forest management on habitat characteristics, species richness, and population dynamics of small mammals remain ambiguous. We studied the response of small-mammal populations, including snowshoe hares, to clear-cutting with protection of advanced regeneration and soils (CPRS) and precommercial thinning (PCT). We compared stands recently treated by CPRS or PCT with established stands dominated by deciduous or coniferous trees in two large blocks of mixed forests. We measured habitat components and abundance of small mammals in the four stand types. Trees (DBH ≥ 9 cm) became very rare in CPRS stands and remained at low density in PCT stands, which stimulated the growth of herbs and seedlings, resulting in increased lateral cover. Tree harvest also generated coarse woody debris in CPRS stands, which did not persist in PCT stands. Small mammals responded to these disturbances in a species-specific manner but, overall, relative abundance and species richness of small mammals were lower in PCT stands than in CPRS and closed stands. Our results suggest that forest managers should exclude some stands from PCT following CPRS or natural perturbations, to maintain ecosystem diversity at the landscape level.
Nutrient cycling in a mixed-species plantation ofEucalyptus globulusandAcacia mearnsii
Authors: Forrester David I , Bauhus Jürgen , Cowie Annette L
Published: January 2006

A doubling of aboveground biomass production has been observed in mixtures of Eucalyptus globulus Labill. and Acacia mearnsii de Wildeman when compared with monocultures after 11 years of growth. This study examined to what extent increased nitrogen (N) availability and accelerated rates of nutrient cycling may contribute to increased growth in mixtures. Monocultures of E. globulus (E) and A. mearnsii (A) and mixtures of these species were planted in a species replacement series: 100% E, 75% E + 25% A, 50% E + 50% A, 25% E + 75% A, and 100% A. Litterfall mass increased with aboveground biomass production and was highest in 50:50 mixtures and lowest in monocultures. Owing to higher N concentrations of A. mearnsii litter, N contents of annual litterfall were at least twice as high in stands containing A. mearnsii (32-49 kg·ha1·year1) as in E. globulus monocultures (14 kg·ha1·year1). Stands with A. mearnsii also cycled higher quantities of phosphorus (P) in annual litterfall than E. globulus monocultures. This study demonstrated that mixing A. mearnsii with E. globulus increased the quantity and rates of N and P cycled through aboveground litterfall when compared with E. globulus monocultures. Thus, mixed-species plantations appear to be a useful silvicultural system to improve nutrition of eucalypts without fertilization.
Evaluation of Weibull-based parameter prediction equation systems for black spruce and jack pine stand types within the context of developing structural stand density management diagrams
Authors: Newton P F , Amponsah I G
Published: January 2006

The objective of this study was to evaluate the predictive ability of Weibull-based parameter prediction equation (PPE) systems developed for natural (density unregulated) and managed (density regulated) black spruce (Picea mariana (Mill.) BSP) and jack pine (Pinus banksiana Lamb.) stand types (n = 6), using (1) seemingly unrelated regression (SUR) employing a recursive system specification, (2) cumulative density function regression (CDFR) in which the location parameter was estimated indirectly employing a minimum diameter function (denoted CDFR(1)), and (3) CDFR in which the location parameter was estimated directly from stand-level variables (denoted CDFR(2)). An Ontario-based calibration data set consisting of diameter frequency distributions and associated stand-level variables derived from 1591 permanent sample plot (PSP) measurements was used to develop SUR-based, CDFR(1)-based, and CDFR(2)-based PPE systems. The calibration data set and an Ontario-based independent test data set, which consisted of stand-level variables and associated diameter frequency distributions derived from 244 PSP measurements, were used to evaluate the resultant PPE systems. Based on the approximate equivalency among the PPE systems in terms of (1) goodness-of-fit indices, (2) lack-of-fit statistics, (3) prediction error indices, and (4) stand-level product value prediction error, all three parameterization methods were found to be of equal utility, irrespective of stand type.
Correlations between soil nutrient availability and fine-root biomass at two spatial scales in forested wetlands with contrasting hydrological regimes
Authors: Neatrour Matthew A , Jones Robert H , Golladay Stephen W
Published: January 2006

We investigated the relationship between soil nutrients and fine-root biomass at broad (among ecosystem types) and fine (within a 20 m × 20 m plot) spatial scales in forested wetlands of the southeastern United States. We selected three replicates each of high-fertility floodplain swamps, low-fertility depressional swamps, and intermediate-fertility river swamp sloughs and measured soil nutrient availability (NO3-N, NH4-N, and PO4-P) and fine-root biomass. At one replicate of each wetland type, a dense network of sampling points was used to measure variability (variance and coefficient of variation) of soil nutrients and fine-root biomass. At the broad scale, fine-root biomass was lower in floodplain swamps than in either river swamp sloughs or depressional swamps. Also, multiple linear regression and Spearman's rank correlations indicated a negative relationship between soil nutrient availability and fine-root biomass. Fine-scale correlates between soil nutrient availability and fine-root biomass were generally weak. Fine-scale variability of NO3-N and NH4-N was greatest in the floodplain swamps, but nutrients were not spatially patchy at any of the sampled sites. We conclude that soil nutrient availability may control fine-root biomass at the broad scale, but it is unclear if the same is true at fine spatial scales.
Dendrochronological responses to the 24 October 1992 tornado at Sunset Crater, northern Arizona
Authors: Sheppard Paul R , May Elizabeth M , Ort Michael H , Anderson Kirk C , Elson Mark D
Published: January 2006

This paper documents tree-ring responses to a historic tornado and reevaluates prehistoric tree-ring changes seen in archaeological wood of Wupatki Ruin used to date the 11th-century eruption of Sunset Crater. The historic tornado occurred at Sunset Crater, northern Arizona, on 24 October 1992, and trees within areas damaged by the tornado survived the event and continue living today. The objectives of this research were to document their ring-growth changes and to consider the possibility of tornadoes as a candidate disturbance for the prehistoric ring-growth changes of Wupatki. About half of the trees sampled within areas damaged by the tornado show one or more dendrochronological responses to that event, including ring-width release, reaction wood, ring-width suppression, and (or) reduced latewood. Tornado damage is not a likely candidate for having caused the abrupt ring-width changes at AD 10641065 seen at Wupatki. However, five living ponderosa pines (Pinus ponderosa Dougl. ex P. & C. Laws.) at Sunset Crater experienced abrupt and severe suppressions in ring growth beginning decades ago and continuing today. No single disturbance seems obvious for causing these growth suppressions, but further research is merited to find the cause of these modern suppressions to propose a new candidate explanation for the AD 1064 suppression.
Using satellite imagery as ancillary data for increasing the precision of estimates for the Forest Inventory and Analysis program of the USDA Forest Service
Authors: McRoberts Ronald E , Holden Geoffrey R , Nelson Mark D , Liknes Greg C , Gormanson Dale D
Published: January 2006

Forest inventory programs report estimates of forest variables for areas of interest ranging in size from municipalities, to counties, to states or provinces. Because of numerous factors, sample sizes are often insufficient to estimate attributes as precisely as is desired, unless the estimation process is enhanced using ancillary data. Classified satellite imagery has been shown to be an effective source of ancillary data that, when used with stratified estimation techniques, contributes to increased precision with little corresponding increase in cost. Stratification investigations conducted by the Forest Inventory and Analysis program of the USDA Forest Service are reviewed, and a new approach to stratification using satellite imagery is proposed. The results indicate that precision may be substantially increased for estimates of both forest area and volume per unit area.
Exponential fertilization of Pinus monticola seedlings: nutrient uptake efficiency, leaching fractions, and early outplanting performance
Authors: Dumroese R Kasten , Page-Dumroese Deborah S , Salifu K Francis , Jacobs Douglass F
Published: January 2006

We evaluated nutrient uptake efficiency and subsequent leaching fractions for western white pine (Pinus monticola Dougl. ex D. Don) seedlings grown with exponentially increasing or conventional (constant) fertilization in a greenhouse. Conventional fertilization was associated with higher leachate electrical conductivity and greater nutrient losses, which were more pronounced for the more mobile NO3-N than for NH4-N. Exponential fertilization increased seedling nitrogen (N) uptake efficiency (75%), which helped reduce leaching losses compared to conventional fertilization (50%). Although exponentially fertilized plants received 45% less fertilizer (20 mg N·plant1) during the establishment and accelerated growth phases compared with conventional cohorts (36 mg N·plant1), seedling morphological characteristics and nutrient status were similar at the end of greenhouse culture and after 2 years of growth in the field, except that exponential fertilization increased root volume after the first year and also increased ectomycorrhizal colonization. Reduction of applied fertilizer quantities and enhanced fertilizer uptake efficiency through exponential fertilization allows for production of high-quality seedlings while simultaneously minimizing fertilizer inputs and mitigating potential environmental contamination.
INCOMPLETE FUSION IN THE EXCITATION FUNCTIONS OF 12C + 115In REACTIONS AT 4–7 MeV/NUCLEON
Authors: MUKHERJEE S. , SHARMA A. , SODAYE S. , GOSWAMI A. , TOMAR B. S.
Published: January 2006

We measured the excitation functions for nine evaporation residues for the 12C + 115In system in the energy range well beyond the Coulomb barrier. The experimental results are compared with the theoretical values calculated using the Monte Carlo simulation code PACE2. Several complete and incomplete fusion products are observed in the present study. It is observed that a definite amount of incomplete fusion contribution is present, even at the lowest energy. The results clearly show the incomplete fusion contributions in the iodine and antimony products.
RELATIVISTIC FIVE-QUARK EQUATIONS AND u, d-PENTAQUARK SPECTROSCOPY
Authors: GERASYUTA S. M. , KOCHKIN V. I.
Published: January 2006

The relativistic five-quark equations are found in the framework of the dispersion relation technique. The five-quark amplitudes for the low-lying pentaquarks including u, d quarks are calculated. The poles of the five-quark amplitudes determine the masses of the ududţ and uuuuţ pentaquarks. The calculated of pentaquark amplitudes estimates the contributions of four subamplitudes. The main contributions to the pentaquark amplitude are determined by the subamplitudes, which include the meson states M.
HANBURY-BROWN–TWISS INTERFEROMETRY WITH IDENTICAL BOSONS IN RELATIVISTIC HEAVY ION COLLISIONS: COMPARISONS WITH HADRONIC SCATTERING MODELS
Authors: HUMANIC THOMAS J.
Published: January 2006

Identical boson Hanbury-Brown–Twiss interferometry as applied to relativistic heavy-ion collisions is reviewed. Emphasis is placed on the use of hadronic scattering models to interpret the physical significance of experimental results. Interferometric studies with center-of-mass energies from <1 GeV/nucleon up to 5500 GeV/nucleon are considered.
CONDITIONS FOR THE APPLICABILITY OF THE PRINCIPAL COMPONENT ANALYSIS TO THE CHARACTERIZATION OF THE 1/f-NOISE
Authors: LÓPEZ-ALONSO JOSÉ MANUEL , ALDA JAVIER
Published: January 2006

Principal Component Analysis (PCA) has been applied to the characterization of the 1/f-noise. The application of the PCA to the 1/f noise requires the definition of a stochastic multidimensional variable. The components of this variable describe the temporal evolution of the phenomena sampled at regular time intervals. In this paper we analyze the conditions about the number of observations and the dimension of the multidimensional random variable necessary to use the PCA method in a sound manner. We have tested the obtained conditions for simulated and experimental data sets obtained from imaging optical systems. The results can be extended to other fields where this kind of noise is relevant.