bluuebunny/crossref_metadata_2025 huggingface dataset:
EBIT charge-exchange measurements and astrophysical applications
Authors: Wargelin B J , Beiersdorfer P , Brown G V
Published: March 2008

The past decade has seen a surge of interest in astrophysical charge exchange (CX). The impetus was the discovery of X-ray emission from comets in 1996, soon followed by the observation of CX emission in planetary atmospheres and throughout the heliosphere. Geocoronal and heliospheric CX are now recognized as contributing a considerable fraction of the soft X-ray background, and stellar-wind charge exchange is expected to occur in the astrospheres surrounding many stars. CX may also contribute to X-ray line emission in supernova remnants, the Galactic Center, and the Galactic Ridge. This article summarizes the key aspects of CX X-ray emission and its astrophysical relevance, and reviews related laboratory measurements and theoretical predictions with particular attention to spectroscopy experiments conducted on electron beam ion traps.PACS Nos.: 32.30.Rj, 34.70.+e, 39.10.+j, 95.30.Dr
Cometary X-ray emission: theoretical cross sections following charge exchange by multiply charged ions of astrophysical interest
Authors: Otranto S , Olson R E , Beiersdorfer P
Published: March 2008

The classical trajectory Monte Carlo (CTMC) method is used to calculate emission cross sections following charge exchange collisions involving highly charged ions of astrophysical interest and typical cometary targets. Comparison is made to experimental data obtained on the EBIT machine at Lawrence Livermore National Laboratory (LLNL) for O8+ projectiles impinging on different targets at a collision energy of 10 eV/amu. The theoretical cross sections are used together with ion abundances measured by the Advanced Composition Explorer as well as those obtained by a fitting procedure using laboratory emission cross sections to reproduce the X-ray spectrum of comet C/LINEAR S4 measured on 14 July 2001.PACS Nos.: 34.70+e, 32.30.Rj, 32.70.Fw, 95.30.Ky
Black holes in the varying speed of light theory
Authors: Shojaie H , Farhoudi M
Published: March 2008

We consider the effect of the varying speed of light theory on nonrotating black holes. We show that in any varying-c theory, the Schwarzschild solution is neither static nor stationary. For a no-charged black hole, the singularity in the Schwarzschild horizon cannot be removed by coordinate transformation. Hence, no matter can enter the horizon, and the interior part of the black hole is separated from the rest of the Universe. If ċ < 0, then the size of the Schwarzschild radius increases with time. The higher value of the speed of light in the very early Universe may have caused a large reduction in the probability of the creation of the primordial black holes and their population. The same analogy is also considered for charged black holes.

PACS No.: 04.70.–s
An overview of EBIT data needed for experiments on laser-producedplasmas
Authors: Schneider M B , Mancini R , Widmann K , Fournier K B , Brown G V , Chung H -K , Baldis H A , Cone K , Hansen S B , May M J , Thorn D , Beiersdorfer P
Published: March 2008

Data produced by an electron beam ion trap (EBIT) can be crucial for interpreting spectra from plasmas created by long-pulse lasers. Four example spectra are considered: (i) the spectra from the hot gold plasma in the laser deposition region of a hot hohlraum, (ii) the He-β spectra from an argon-doped imploding core of an inertial confinement fusion capsule, (iii) the polarization in spectral lines produced by hot electrons generated by laser-plasma parametric instabilities, and (iv) the spectra of the underdense plasma from an aerogel X-ray source. The EBIT data needed for these cases are: (i) the line positions for 3 → 2 transitions in open M shell gold ions, (ii) the Li-like satellite lines for the K-β transition in open L shell argon ions, (iii) the polarization of suitable X-ray lines at 30 keV, and (iv) the precise wavelengths of K lines of highly charged Si ions and the precise wavelengths of L and K lines of highly charged Ge ions.PACS Nos.: 52.25.Os, 52.38.–4, 52.38.Bv, 52.57.–z, 52.57.Fg, 52.59.Px, 52.70.–m 52.70.La
Deformation of ice under low stresses
Authors: Sego David C. , Morgenstern Norbert R.
Published: March 2008

This study confirms the existence of two flow laws for polycrystalline ice. One describes the behaviour of ice before the inflection point of a constant stress test, and one the behaviour well into the tertiary portion of the strain–time curve. Each flow law may be represented by a power law with an exponent of 3.0.The inflection point in constant stress experiments and the peak in constant strain rate experiments is shown to occur at about 1% strain in experiments conducted in the ductile material behaviour range. A Cottrell–Aytekin relationship has been used to fit the strain–time material behaviour up to the inflection point.The flow law of ice valid below 1% strain is shown to be dependent on the grain size ratio of the ice. The grain size ratio is a measure of the size effect of the sample tested. The temperature influence on the flow law is best described by using the inverse temperature relationship described by Voytkovskiy. Keywords: ice, creep deformation, long-term, failure strain.
The permeability of natural soft clays. Part II: Permeability characteristics
Authors: Tavenas F. , Jean P. , Leblond P. , Leroueil S.
Published: March 2008

The permeability characteristics of a number of intact natural soft clays from Québec, the USA, and Sweden have been investigated in the laboratory. The variation of permeability with void ratio is best represented in terms of a linear e vs. lg k relation which is generally valid in the range of volumetric strains encountered in engineering practice.The permeability at the in-situ void ratio is shown to be a complex function of such parameters as the void ratio, the clay fraction, the plasticity index, and the fabric of the clay. Permeability anisotropy is negligible in marine clays.The e vs. lg k relationships of the various clays tested are well ordered in terms of an empirical parameter (IP + clay fraction), irrespective of the geological origin of the clay. The slope of the e vs. lg k relationship, referred to as permeability change index Ck, is simply related to the initial void ratio by Ck = 0.5eo. Keywords: permeability, clays, laboratory tests, permeability anisotropy, permeability – void ratio relations.
Interpretation of cone penetration tests. Part I: Sand
Authors: Robertson P. K. , Campanella R. G.
Published: March 2008

Significant advances have been made in recent years in research, development, interpretation, and application of cone penetration testing. The addition of pore pressure measurements during cone penetration testing has added a new dimension to the interpretation of geotechnical parameters.The cone penetration test induces complex changes in stresses and strains around the cone tip. No one has yet developed a comprehensive theoretical solution to this problem. Hence, the cone penetration test provides indices which can be correlated to soil behaviour. Therefore, the interpretation of cone penetration data is made with empirical correlations to obtain required geotechnical parameters.This paper discusses the significant recent developments in cone penetration testing and presents a summarized work guide for practicing engineers for interpretation for soil classification, and parameters for drained conditions during the test such as relative density, drained shear strength, and deformation characteristics of sand. Factors that influence the interpretation are discussed and guidelines provided. The companion paper, Part II: Clay, considers undrained conditions during the test and summarizes recent developments to interpret parameters for clay soils, such as undrained shear strength, deformation characteristics of clay, stress history, consolidation characteristics, permeability, and pore pressure. The advantages and use of the piezometer cone are discussed as a separate topic in Part II: Clay. The authors' personal experiences and current recommendations are included. Keywords: static cone penetration testing, in situ, interpretation, shear strength, modulus, density, stress history, pore pressures.
Emergency drainage system at the dam 3 – Outardes 4 development
Authors: Dascal O. , Comeau W.
Published: March 2008

A sudden increase (outburst) in the seepage discharge was recorded at the downstream toe of dam 3 of the Outardes 4 project. The normal rate of seepage of about 22.5 L/min increased suddenly to 18 000–22 500 L/min. The flow seems to have increased to its maximum rate in a period of not more than a few hours, followed subsequently by a gradual decrease to about 45 L/min in about 20 days.The rockfill dam, with a slightly inclined till core, has a maximum height of about 30 m and rests directly on a very competent bedrock. The quality of the grouted bedrock and the properties of the dam's construction material make it extremely unlikely that seepage through the rock or piping through the core and the transition zones could have caused this event.The presence of a roadfill or "berm" on the downstream rockfill zone, used as a temporary access road during construction and composed of a variety of unselected overburden and rock materials, could have acted as a barrier at the downstream toe of the dam. Thus, the recorded water outburst most likely has been caused by storage of the normal seepage water in the voids of the downstream rock shell and the sudden opening of a drainage channel through this roadfill barrier.Considering the risk of a such ponding in the downstream shell, an emergency drainage system was installed to avoid the repetition of a similar event in the future.The present paper deals with the design and construction of the drainage system whose major component was a tunnel excavated in the bedrock under the dam and illustrates the results of the tests carried out to monitor the ponding tendency in the downstream shell. Keywords: rockfill dam, drainage, tunnel (excavation), blasting (controlled).
Methods of improving the performance of drilled piers in weak rock
Authors: Horvath R. G. , Kenney T. C. , Kozicki P.
Published: March 2008

Investigations were made of two methods to improve the load–displacement performance of concrete piers socketed into very weak rock. Results of load tests on six full-size piers are reported.One method involved cutting grooves into the socket wall to roughen the pier–rock interface and thus increase the shaft resistance component of load support. Two types of piers were tested: piers with a void at the base (shaft resistance only) and piers having both shaft resistance and end-bearing resistance. In the latter case, flatjack load cells were installed to measure base loads. The test results indicated that increasing the roughness of the socket wall can cause important increases in shaft resistance.The second method involved the application of preload to the socket base to increase the end-bearing component of load support at small displacements. The test results showed that preloading the socket base resulted in a stiffer load–displacement behaviour of the pier–socket system.The initial portions of the load–displacement curves from all the tests were linear, reflecting elastic behaviour of the pier–socket system. This elastic behaviour did not appear to rely on socket roughness. Beyond the limit of proportionality, the load–displacement behaviour of each pier departed from that of an elastic system, and this departure was more rapid for the piers with smooth sockets than for those with roughened socket walls. Preloading the socket base caused the elastic range of loading to be extended.Two design approaches, limit-state analysis and elastic-state analysis, are discussed. Keywords: drilled piers and caissons, large-bored piles, shaft resistance, grooved shaft, load transfer, preload, shale, weak rock.
On the stability and settling of suspended solids in settling ponds. Part I. Piece-wise linear consolidation analysis of sediment layer
Authors: Yong Raymond N. , Siu Steven K. H. , Sheeran Donald E.
Published: March 2008

The resultant large overall strains resulting from the consolidation of low solids content slurry sediments, such as those obtained in settling ponds, are predicted and compared with actual results for two sludge settling ponds. The computer technique developed in association with the piece-wise linear consolidation model permits inclusion of self-weight and eliminates restrictions such as small strains, constant load, and constant material consolidation parameters by solving the governing equations using the finite difference iterative technique. Good agreement between predicted and measured field values for the two ponds has been obtained. Keywords: large-strain consolidation, settling ponds, sediments, piece-wise linear consolidation, finite difference, iterative technique.
Influence factors for settlement estimates of footings on finite layers
Authors: Taylor Brian B. , Matyas Elmer L.
Published: March 2008

The estimation of the settlements of surface footings on finite layers is examined for values of Poisson's ratio ranging from 0 to 0.5. Influence factors based on Steinbrenner's approximate method were evaluated and were found to be in good agreement with influence factors obtained by a more rigorous and difficult evaluation by Giroud. This study confirms the findings by Christian and Carrier that the Janbu, Bjerrum, and Kjaernsli chart for the estimation of elastic settlements (v = 0.5) is incorrect. Keywords: elasticity, footings, settlement analysis.
A coring device suitable for paleomagnetic sampling of unconsolidated subsurface deposits
Authors: Barendregt René W. , Vreeken W. J.
Published: March 2008

Research in paleomagnetism requires the collection of continuous, undisturbed, and oriented cores from fine-grained sub-surface deposits. The authors have found the Giddings coring machine to be a suitable device which offers a rapid and accurate alternative to hand-cut sampling from natural outcrops. This hydraulic machine collects undisturbed and oriented cores to a maximum depth of 16 m. It has been widely used in the study of soil engineering and hydraulic properties as well as in other geotechnical investigations of fine-grained materials. Keywords: paleomagnetism, coring, oriented sampling.
A centrifugal model study of slope instability in Ottawa area Champlain Sea clay
Authors: Goodings D. J. , Schofield A. N.
Published: March 2008

Problems of serious slope instability in quick Champlain Sea clay, also known as Leda clay, found in eastern Canada, have been the subject of debate regarding mechanisms of failure and relevant strength characteristics. Eight intact samples of Ottawa area Champlain Sea clay were retrieved, formed into 19 different slope configurations, and tested as reduced-scale models on the Cambridge University 4.25 m diameter 150 g geotechnical centrifuge. Of these, 14 showed some manner of slope instability, ranging from deep intact slope movement, to slope degradation, to flowsliding. Speculation is made on the importance of time-dependent horizontal stress release, on the possibility that prototype failure is not circular and rotational, and that uplift may affect subsequent retrogressions in prototypical landslides but not initial failure. Inconsistencies in the behaviours of models were attributed in part to certain possible limitations on reduced-scale modelling; these included the effects of the unscaled network of fissures and the loss of strength as a function of displacement rather than of strain. Key words: centrifuge, clays, failures, simulation models, slope stability.
Theoretical study on NO3-initiated oxidation of acenaphthene in the atmosphere
Authors: Qu Xiaohui , Zhang Qingzhu , Wang Wenxing
Published: March 2008

Acenaphthene is widespread and toxic, and thus of substantial environmental concern. The reaction with NO3 radicals is an important atmospheric loss process of acenaphthene at night time. In this work, the mechanism for the NO3-initiated atmospheric oxidation reaction of acenaphthene has been studied using high level molecular orbital theory. Geometries of all the related species have been optimized at the MPWB1K level with the 6–31G(d,p) basis set. The single-point energy calculations have been carried out at the MPWB1K/6–311+G(3df,2p) level. The possible secondary reactions were also studied. Several energetically favorable reaction pathways were revealed for the first time.Key words: acenaphthene, NO3 radicals, reaction mechanism, product information, oxidation degradation.
Evaluating and understanding the hydrothermal stability of alumina aerogel doped with yttrium oxide and used as a catalyst support for the thermo-catalytic cracking (TCC) process
Authors: Al-Yassir Nabil , Mao Raymond Le Van
Published: March 2008

The current work presents results concerning the hydrothermal stability of yttria-doped alumina aerogel, which was prepared by the sol–gel method using a supercritical drying technique. The influence of atmospheric steam at 750 and 1000 °C on the rate of sintering of yttria-doped alumina aerogel with various yttria contents was investigated. BET N2 adsorption measurements, X-ray diffraction, thermogravimetric analysis, FTIR of adsorbed pyridine, and 1H and 27Al MAS NMR were used for characterization of solid samples. It was found that the hydrothermal stability of yttria-doped alumina aerogel was greatly improved compared with alumina aerogel and conventional alumina. This was evident from the decrease in the loss of surface area and pore volume, and the minimization of structural transformations. These significant improvements were attributed to the combined effect of sol–gel method and the presence of yttrium ions. Yttria-doped alumina aerogel with various yttria loadings, when compared with undoped alumina aerogel, exhibited lower concentrations of surface –OH groups, higher amounts of bridged –OH groups, and lower degrees of crystallinity with smaller particle sizes. It was also observed that the thermal and hydrothermal stabilities of both yttria-impregnated alumina aerogel and conventional alumina were improved but to a much lower extent. These improvements were attributed to the presence of yttria, and subsequently the formation of surface yttrium aluminate. This structure was found to be more thermally stable than bare alumina owing to the presence of less surface defects and –OH groups. Therefore, it was concluded that to observe the most effective role of yttria, it is quite essential to incorporate it into the alumina structure via the sol–gel technique.Key words: thermo-catalytic cracking (TCC), yttria-doped alumina aerogel, yttria-impregnated alumina, hydrothermal stability, surface –OH groups, Lewis sites.
Gaseous ions and chemical mass spectrometry
Authors: Böhme Diethard K
Published: March 2008

The intrinsic chemical reactivities of ions can be monitored in the gas phase using mass spectrometers that are coupled to appropriate ion sources and reaction cells. Here the author surveys his own experiences over the past 40 years as an ion chemist. He used flow-tube techniques for room temperature measurements of the intrinsic chemical reactivities of a large variety of positive and negative ions, including bare atomic ions, ions found in solution, biological ions, carbonaceous ions, and interstellar, cometary, and ionospheric ions. Progress in the measurement of chemical reactions of these ions with flow-tube mass spectrometry in the author’s laboratory was been driven largely by developments in techniques of ion injection into the flow tube and of ion production (e.g., by electron impact, plasma ionization, and electrospray ionization). Chemical topics that are covered include: acid-base and nucleophilic displacement reactions that have bridged the gap between the gas phase and solution; interstellar ions and their role in molecular synthesis such as the synthesis of amino acids; the chemistry of fullerene cations as a function of charge state; fundamentals and applications of the chemistry of atomic cations with an emphasis on transition metal and lanthanide cations; atomic metal-ion catalysis; and chemical reactions of singly and multiply charged biological anions and cations in the gas phase.Key words: ions, mass spectrometry, kinetics, ion chemistry.
Novel chiral fluorescent chemosensors for malate and acidic amino acids based on two-arm thiourea and amide
Authors: Huang Xiao-Huan , He Yong-Bing , Chen Zhi-Hong , Hu Chen-Guang , Qing Guang-Yan
Published: March 2008

The charge neutral anthracene based chiral fluorescent receptors 4a and 4b containing thiourea and amide groups were synthesized by simple steps in good yields, and their enantioselective recognition for chiral dicarboxylic anions (L/D-malate, L/D-aspartate, and L/D-glutamate) were examined by UV–vis, fluorescence, and 1H NMR spectroscopy. The sensor 4a exhibited an excellent enantioselective recognition ability towards malate (Kass (L)/Kass (D) = 9.65).Key words: enantioselective recognition, chiral chemosensor, fluorescence, malate.
Diastereoselective bismuth triflate catalyzed Claisen rearrangement of 2-alkoxycarbonyl-substituted allyl vinyl ethers
Authors: Ollevier Thierry , Mwene-Mbeja Topwe M
Published: March 2008

In the presence of a catalytic amount of bismuth triflate, 2-alkoxycarbonyl-substituted allyl vinyl ethers as a mixture of enol ether double bond isomers were smoothly converted into the β,γ-alkyl-substituted α-keto esters. The isomerization reaction proceeded rapidly to afford smoothly the α-keto esters in good to excellent yields using catalytic amounts of Bi(OTf)3·4H2O (1 mol%). (Z,Z)-2-iso-Propyloxycarbonyl-substituted allyl vinyl ethers 3Z,Z afforded the corresponding β,γ-alkyl-substituted α-keto esters 4 with very good syn diastereoselectivity.Key words: bismuth; bismuth(III) triflate; Claisen rearrangement; allyl vinyl ethers.
Resolution of non-proteinogenic amino acids via microbial lipase-catalyzed enantioselective transesterification
Authors: Miyazawa Toshifumi , Mio Motoe , Watanabe Yuko , Yamada Takashi
Published: March 2008

A number of non-proteinogenic amino acids bearing aliphatic side chains were resolved with moderate to good enantioselectivities (E = 15–42) through the Burkholderia cepacia lipase-catalyzed enantioselective transesterification of the 2,2,2-trifluoroethyl esters of their N-benzyloxycarbonyl derivatives with methanol as a nucleophile in diisopropyl ether.Key words: non-proteinogenic amino acids, microbial lipases, Burkholderia cepacia lipase, 2,2,2-trifluoroethyl ester, enantioselective transesterification, enantioselectivity.
Asymmetric nitroaldol reaction with a chiral copper complex derived from D-tartaric acid
Authors: Gan Changsheng
Published: March 2008

A novel catalytic enantioselective Henry reaction has been developed using a tetradentate copper complex derived from D-tartaric acid to give β-nitroalkanols in moderate to high enantioselectivities.Key words: Henry reaction, D-tartaric acid, enantioselective, β-nitroalkanols.
Mapping fuels at multiple scales: landscape application of the Fuel Characteristic Classification SystemThis article is one of a selection of papers published in the Special Forum on the Fuel Characteristic Classification System.
Authors: McKenzie D. , Raymond C.L. , Kellogg L.-K.B. , Norheim R.A. , Andreu A.G. , Bayard A.C. , Kopper K.E. , Elman E.
Published: March 2008

Fuel mapping is a complex and often multidisciplinary process, involving remote sensing, ground-based validation, statistical modelling, and knowledge-based systems. The scale and resolution of fuel mapping depend both on objectives and availability of spatial data layers. We demonstrate use of the Fuel Characteristic Classification System (FCCS) for fuel mapping at two scales and resolutions: the conterminous USA (CONUS) at 1 km resolution and the Wenatchee National Forest, in Washington State, at 25 m resolution. We focus on the classification phase of mapping — assigning a unique fuelbed to each mapped cell in a spatial data layer. Using a rule-based method, we mapped 112 fuelbeds onto 7.8 million 1 km cells in the CONUS, and mapped 34 fuelbeds onto 18 million 25 m cells in the Wenatchee National Forest. These latter 34 fuelbeds will be further subdivided based on quantitative spatial data layers representing stand structure and disturbance history. The FCCS maps can be used for both modelling and management at commensurate scales. Dynamic fuel mapping is necessary as we move into the future with rapid climatic and land-use change, and possibly increasing disturbance extent and severity. The rule-based methods described here are well suited for updating with new spatial data, to keep local, regional, and continental scale fuel assessments current and inform both research and management.
Accounting for surveyor inconsistency and bias in estimation of tree density from presettlement land survey records
Authors: Kronenfeld Barry J. , Wang Yi-Chen
Published: March 2008

Presettlement land survey records provide baseline data on forest characteristics prior to major European settlement, but questions regarding surveyor bias and methodological consistency have limited confidence in quantitative analyses of this important data source. We propose new correction factors, calculated from bearings, distances, and species of bearing trees, to account for the effects of (i) inconsistency in quadrant configuration, (ii) bearing angle bias, and (iii) species bias on forest density and species composition estimated from presettlement land survey records. Computer simulations confirmed accuracy in random and nonuniform density forests, with moderate bias in very clustered and dispersed forests. A case study of township and quarter-section corners surveyed by the Holland Land Company in western New York demonstrates the potential magnitude of errors caused by surveyor inconsistency/bias in estimation of density and relative species frequency. The influence of nonuniform density, clustering, and dispersal on plotless density estimators remains an important obstacle to quantitative analysis of Presettlement land survey records. However, by accounting for uncertainties regarding surveyor methodology, the proposed correction factors add confidence to conclusions made regarding presettlement forest structure and composition.
Pricing the social contract in the British Columbian forest sector
Authors: Niquidet Kurt , Nelson Harry , Vertinsky Ilan
Published: March 2008

In this paper, we investigate the impact of various socioeconomic conditions on the value of timber tenures in the province of British Columbia. Two timber tenure models were created, one for short-term timber sale licenses and the other for longer term forest licenses. The short-term model revealed that timber sales that were awarded according to a combination of employment, revenue, and manufacturing criteria yielded $8.63/m3 less revenue than timber sales awarded based on revenue alone. Similarly, the long-term model indicates that manufacturing and employment conditions significantly reduce the bid on forest licenses. In both instances, we suggest that such conditions distort the use of timber, labour, and capital. Therefore, we conclude that recent forest policy changes in the province that removed several of these conditions greatly improved economic efficiency. Nevertheless, distribution impacts are likely to be important because resource rents have potentially been redistributed away from rural communities to the provincial government.
Unrestricted guided transect sampling for surveying sparse species
Authors: Ringvall Anna , Snäll Tord , Ekström Magnus , Ståhl Göran
Published: March 2008

We present a modification of an earlier presented method using prior auxiliary information in the layout of survey strips. The idea is to imitate a skilled surveyor who purposively seeks the species of interest. Yet, the method “unrestricted guided transect sampling” (UGTS) is a probability sampling method. In comparison with a strip survey using no auxiliary information, UGTS gave 11%–64% lower standard errors for estimates of species population size in three simulated forest types. In a test in six stands where European aspen ( Populus tremula L.) and an epiphytic moss ( Orthotrichum speciosum Nees) had been mapped, UGTS gave a small improvement in some stands but considerably higher standard errors in other stands with kNN estimates of volume of deciduous trees derived from satellite images as covariate values. With covariates values simulated from aspen basal area, UGTS gave 8%–75% lower standard error than a strip survey using no auxiliary information. The study shows a gain in precision by using auxiliary information both in the design and in estimation when surveying sparse species but also that the correlation between the covariate and the variable of interest has to be relatively strong to make the method worthwhile.
Measurement variability error for estimates of volume change
Authors: Westfall James A. , Patterson Paul L.
Published: March 2008

Using quality assurance data, measurement variability distributions were developed for attributes that affect tree volume prediction. Random deviations from the measurement variability distributions were applied to 19 381 remeasured sample trees in Maine. The additional error due to measurement variation and measurement bias was estimated via a simulation study for various components of volume change. In comparison with sampling error, the error due to measurement variation was relatively small. When biases in measurements had contradictory effects on the calculation of individual tree volume, there was little additional error, however, systematic biases produced substantial error increases. The proportion of measurement variation error attributable to diameter at breast height and tree species classification was small relative to that attributable to bole (merchantable) height and percent cull attributes, which composed the preponderance of uncertainty due to measurement variation. The greatest impacts were associated with the accretion component, which was subject to measurement variation and bias at both the initial and subsequent measurements.
Coexistence of Abies mariesii and Abies veitchii in a subalpine fir-wave forest
Authors: Ugawa Shin , Iwamoto Kojiro , Fukuda Kenji
Published: March 2008

To clarify the mechanisms underlying the coexistence of Abies mariesii Masters and Abies veitchii Lindl. in a fir-wave forest, we surveyed the population dynamics of the two Abies species throughout stand development on Mount Shimagare, central Japan. We established three belt transects and found that, overall, A. veitchii dominated this fir-wave forest. However, A. mariesii dominated the canopy initially, whereas A. veitchii increased as stand development progressed; thus, dominant A. mariesii was eventually replaced by A. veitchii. This replacement was explained by the presence of an A. mariesii sapling bank that formed under the canopy of a mature stand and by the large A. veitchii seedling bank resulting from greater seed production. For ordinary canopy individuals, which are taller than midcanopy individuals, the increase in height suggested that taller individuals grow faster vertically regardless of species; moreover, height growth did not differ significantly between the two Abies species, which facilitated the growth of A. mariesii into the canopy and the production of seeds for the next generation. We concluded that the persistence of A. mariesii in this fir-wave forest is supported by its shade tolerance.
Increment and decay in Norway spruce and Scots pine after artificial logging damage
Authors: Mäkinen Harri , Hallaksela Anna-Maija , Isomäki Antti
Published: March 2008

The effects of depth, size, location, and season of artificial logging damage on increment and decay of Norway spruce ( Picea abies (L.) Karst.) and Scots pine ( Pinus sylvestris L.) trees were studied in long-term experiments in central Finland. Damage types applied were root damage, root collar damage, increment borer hole, and stem damage. In root collar and stem damages, two sizes (100 or 400 cm2) and depths (shallow or deep) were applied. Five to 20 years after damaging, the damages did not result in a decrease in radial, height, or volume increment. In Norway spruce, the frequency of decay in the root collar and stem damages was high. From large and deep damages, decay spread faster than from smaller and shallow ones. In Scots pine, a lower proportion of trees were decayed compared with Norway spruce. Increment coring resulted in decay in most of the trees, but the decay spread slowly. The effect of compass direction or the month of damaging was negligible. The most common decay fungus in Norway spruce was Stereum sanguinolentum (Alb. & Schwein. Fr.:) Fr. In Scots pine, only nondecay fungi were isolated. In general, logging damages decreased sawlog production through the rejection of butt logs containing decay or discoloration.
Examination of North American softwood lumber species substitution using discrete choice preferences and disaggregated end-use markets
Authors: Shook Steven R. , Soria Jorge A. , Nalle Darek J.
Published: March 2008

Over the past 20 years, four significant and contentious softwood lumber trade disputes have taken place between the United States and Canada. The US International Trade Commission (USITC), relying on aggregate market assessments using elasticity of demand estimation and cointegration methods, has ruled that all North American softwood lumber species are perfectly fungible. The objective of this study is to disaggregate the US softwood lumber market by estimating cross-price elasticity of demand for North American softwood lumber species and species groups in three major end-use markets (floor framing, roof framing, and wall framing products) using a discrete choice preference model. Specifically, this study utilizes a choice-based conjoint model to estimate species and species group preferences, market shares, and price-demand relationships for North American softwood lumber. Research results are compared with published aggregate market cross-price elasticity of demand estimates, such as those relied upon by USITC, to determine whether North American softwood lumber species and species groups are perfectly fungible in the three largest softwood lumber end-use markets. Results demonstrate that distinct differences exist in the substitutability between North American species and species groups of softwood lumber. The results provide notable implications in future USITC trade analyses of the US–Canadian softwood lumber trade issue.
Forest and economic impacts of alternative management strategies on Crown land in New Brunswick
Authors: Kennedy Michael I.L. , Lantz Van A. , MacLean David A.
Published: March 2008

This study evaluated the long-run economic impacts of four alternative forest management strategies on New Brunswick’s Crown land forests: two volume-based strategies focused on business as usual (BAU) and intensive (INT) timber volume production and two value-based strategies focused on forest manufacturing sector contribution to gross domestic product (GDP) and government surplus (GOV). These were defined within an extended wood supply model that incorporated both economic indicators (logging sector profit, government surplus, forest manufacturing sector shipments, and forest manufacturing sector GDP) and timber supply indicators (harvest levels, operable growing stock, and products). Results showed that a number of indicator trade-offs emerge under each strategy. For instance, the GOV strategy produced the highest present value government surplus value (at $1.2 billion, exceeding INT, BAU, and GDP strategies by $352 million, $302 million, and $169 million, respectively) and logging sector profit (at $2.4 billion, exceeding BAU, INT, and GDP strategies by $4 million, $11 million, and $8 million, respectively) over an 80 year planning horizon. However, this strategy also produced the lowest forest manufacturing sector contribution to GDP (at $12.8 billion, below the GDP, INT, and BAU strategies by $4.3 billion, $1.6 billion, and $1.4 billion, respectively) and the lowest annual softwood volume harvest, operable growing stock, and silvicultural investment of all strategies. Thus, although these findings emphasize that value-based strategies can produce some favourable economic outcomes, a number of trade-offs emerge that need to be further investigated before such strategies can be supported.
Canopy characteristics and growth rates of ponderosa pine and Douglas-fir at long-established forest edges
Authors: Sherich Kelsey , Pocewicz Amy , Morgan Penelope
Published: March 2008

Trees respond to edge-to-interior microclimate differences in fragmented forests. To better understand tree physiological responses to fragmentation, we measured ponderosa pine ( Pinus ponderosa Dougl. ex P. & C. Laws) and Douglas-fir ( Pseudotsuga menziesii (Mirbel) Franco) leaf area, crown ratios, sapwood area, basal area (BA) growth rates, and BA growth efficiency at 23 long-established (>50 year) forest edges in northern Idaho. Trees located at forest edges had more leaf area, deeper crowns, higher BA growth rates, and more sapwood area at breast height than interior trees. Ponderosa pine had significantly higher BA growth efficiency at forest edges than interiors, but Douglas-fir BA growth efficiency did not differ, which may relate to differences in photosynthetic capacity and drought and shade tolerance. Edge orientation affected BA growth efficiency, with higher values at northeast-facing edges for both species. Edge effects were significant even after accounting for variation in stand density, which did not differ between the forest edge and interior. Although edge trees had significantly greater canopy depth on their edge-facing than forest-facing side, sapwood area was evenly distributed. We found no evidence that growing conditions at the forest edge were currently subjecting trees to stress, but higher leaf area and deeper crowns could result in lower tolerance to future drought conditions.
Backhauling in forest transportation: models, methods, and practical usage
Authors: Carlsson Dick , Rönnqvist Mikael
Published: March 2008

In this paper, we consider a tactical transportation planning problem in forestry to decide the destination of logs. This problem is generally solved by finding the flow between a set of supply points and demand points. It can be formulated as a linear programming problem involving direct flows between supply and demand points. However, better solutions can be found by using additional flow variables representing flow in potential backhaul routes. However, the number of such variables is often very large. In this article, we provide the basis for backhaul flow planning in forestry. This includes defining the underlying operations research models for both the flow problem and the subproblem to find backhaul routes. The size of the problem in terms of the number of variables increases rapidly with the number of supplies and demands and we describe a column generation approach for its solution. We report on some case studies and industrial systems where the approach has been used.
Bayesian estimation of a surface to account for a spatial trend using penalized splines in an individual-tree mixed model
Authors: Cappa Eduardo P. , Cantet Rodolfo J.C.
Published: March 2008

Unaccounted for spatial variability leads to bias in estimating genetic parameters and predicting breeding values from forest genetic trials. Previous attempts to account for large-scale continuous spatial variation employed spatial coordinates in the direction of the rows (or columns). In this research, we use an individual-tree mixed model and the tensor product of B-spline bases with a proper covariance structure for the random knot effects to account for spatial variability. Dispersion parameters were estimated using Bayesian techniques via Gibbs sampling. The procedure is illustrated with data from a progeny trial of Eucalyptus globulus subsp. globulus Labill. Four different models were used in the sequel. The first model included block effects and the three other models included a surface on a grid of either 8 × 8, 12 × 12, or 18 × 18 knots. The three models with B-splines displayed a sizeable lower value of the deviance information criterion than the model with blocks. Also, the mixed models fitting a surface displayed a consistent reduction in the posterior mean of σ2e, an increase in the posterior means of σ2A and h2DBH, and an increase of 66% (for parents) or 60% (for offspring) in the accuracy of breeding values.
Comparison of linear and mixed-effect regression models and a k-nearest neighbour approach for estimation of single-tree biomass
Authors: Fehrmann Lutz , Lehtonen Aleksi , Kleinn Christoph , Tomppo Erkki
Published: March 2008

Allometric biomass models for individual trees are typically specific to site conditions and species. They are often based on a low number of easily measured independent variables, such as diameter in breast height and tree height. A prevalence of small data sets and few study sites limit their application domain. One challenge in the context of the actual climate change discussion is to find more general approaches for reliable biomass estimation. Therefore, nonparametric approaches can be seen as an alternative to commonly used regression models. In this pilot study, we compare a nonparametric instance-based k-nearest neighbour (k-NN) approach to estimate single-tree biomass with predictions from linear mixed-effect regression models and subsidiary linear models using data sets of Norway spruce ( Picea abies (L.) Karst.) and Scots pine ( Pinus sylvestris L.) from the National Forest Inventory of Finland. For all trees, the predictor variables diameter at breast height and tree height are known. The data sets were split randomly into a modelling and a test subset for each species. The test subsets were not considered for the estimation of regression coefficients nor as training data for the k-NN imputation. The relative root mean square errors of linear mixed models and k-NN estimations are slightly lower than those of an ordinary least squares regression model. Relative prediction errors of the k-NN approach are 16.4% for spruce and 14.5% for pine. Errors of the linear mixed models are 17.4% for spruce and 15.0% for pine. Our results show that nonparametric methods are suitable in the context of single-tree biomass estimation.
Transaction evidence analysis: stumpage prices and risk in central Georgia
Authors: Sydor Tymur , Mendell Brooks C.
Published: March 2008

This paper uses hedonic regression techniques to analyze timber bid transactions in central Georgia. Softwood stumpage prices from pay-as-cut transactions are regressed against timber sale and stand characteristics. We identify observable factors that are statistically associated with the volatility of pine sawtimber stumpage prices in the market. The remaining price volatility, defined as market risk, characterizes undiversifiable price volatility in the market. Isolating market risk in this way has implications for relative price risk across predefined timber markets. Applications of this these techniques suggest that analyzing market price variability with total measures alone, such as standard deviation, may provide false senses of timber price risk.
Effects of freezing on Young’s modulus for twigs of coniferous and deciduous trees and shrubs
Authors: Umbanhowar, Charles E. , Lambert Allison M. , VanDelinder Lindsay
Published: March 2008

The mechanical behavior of frozen twigs may be important in understanding twig breakage during winter owing to wind or snow loading. While below 0 °C temperatures are known to increase the stiffness of wood, few studies have examined the effects of cold temperatures on the biomechanical properties of twigs of both coniferous and deciduous woody plants. In this study, we compared the effects of –11 to –14 °C temperatures on the Young’s modulus (E) of fine twigs of 14 species of woody plants. Twigs were 13%–304% stiffer when frozen than when thawed at room temperature (21 °C), with conifers showing the greatest percentage increase in stiffness. In general, more flexible twigs (when thawed) showed the greatest percentage increase in E when frozen. Greater stiffening of more flexible twigs may in part be the result of higher water contents but may also reflect differences in the relative importance of supercooling and extracellular freezing, with greater frozen stiffness associated with freezing. Our work suggests a direct link between cell physiology and whole organ biomechanics, and highlights reasons for differences in susceptibility to breakage due to wind or snow loading.
Effects of soil freezing on fine roots in a northern hardwood forest
Authors: Cleavitt Natalie L. , Fahey Timothy J. , Groffman Peter M. , Hardy Janet P. , Henry Karen S. , Driscoll Charles T.
Published: March 2008

We reduced early winter snowpack in four experimental plots at the Hubbard Brook Experimental Forest in New Hamphire for 2 years to examine the mechanisms of root injury associated with soil freezing. Three lines of evidence suggested that direct cellular damage, rather than physical damage associated with frost heaving, was the principal mechanism of root injury: (i) decreases in root vitality were not greater on sites with more frost heaving, (ii) in situ freezing damage was confined to first- and second-order roots in the organic horizons rather than entire root systems, and (iii) tensile strength of fine roots was not significantly compromised by experimental stretching to simulate ice lens formation. Although significant differences in the intensity of soil freezing (depth, rate, and minimum temperature) were observed across the plots, no clear effects of soil freezing intensity on root injury were observed. Snow manipulation had no effect on mycorrhizal colonization of sugar maple ( Acer saccharum Marsh.) roots. A significant increase in root growth was observed in the second summer after treatments, coincident with a significant pulse of soil nitrate leaching. Through their effects on fine roots, soil freezing events could play an important role in forest ecosystem dynamics in a changing climate.
Mass loss and nutrient dynamics of coarse woody debris in three Rocky Mountain coniferous forests: 21 year results
Authors: Herrmann Steffen , Prescott Cindy E.
Published: March 2008

Mass loss and changes in C, N, and P concentrations were measured in 20 cm long log segments of lodgepole pine ( Pinus contorta Dougl. ex Loud.), white spruce ( Picea glauca (Moench) Voss), and subalpine fir (Abies lasiocarpa (Hook.) Nutt.) that had been placed in three Rocky Mountain coniferous forests 21 years earlier. Pine, spruce, and fir lost 76%, 39%, and 64%, respectively, of their initial mass during the 21 years. The corresponding mean decay rates (k) were 0.072, 0.024 and 0.052·year–1. The decay patterns of pine and spruce were similar with the highest k between 6 and 14 years. Fir k increased during the course of decomposition with the highest rate between 14 and 21 years. The correlation between original dry mass and k was negative for pine (r = –0.28), positive for fir (r = 0.35), and not significant for spruce. C/N, C/P, and N/P ratios declined and converged to a similar value in relation to mass loss for all three species. The N/P ratios of logs of all three species stabilized at about 19. These findings indicate that patterns of wood decay are difficult to predict (even with 14 year data), and so models that incorporate wood-decay estimates will be associated with considerable uncertainty.