bluuebunny/crossref_metadata_2025 huggingface dataset:
Energy and the Confused Student II: Systems
Authors: Jewett John W.
Published: January 2008

Energy is a critical concept in physics problem-solving but is often a major source of confusion for students if the presentation is not carefully crafted by the instructor or the textbook. The first article1 in this series discussed student confusion generated by traditional treatments of work. In any discussion of work, it is important to state that work is done on a system by a force. This phrasing has two important components: (1) the identification of the force that is doing the work and (2) the identification of the recipient of the work as a system. Very few textbook or lecture presentations use a system-based approach when performing an energy problem. The first two steps in approaching any energy problem should be: 1) Identify the system; 2) Categorize the system
Kinematics of a Head-Neck Model Simulating Whiplash
Authors: Colicchia Giuseppe , Zollman Dean , Wiesner Hartmut , Sen Ahmet Ilhan
Published: January 2008

A whiplash event is a relative motion between the head and torso that occurs in rear-end automobile collisions. In particular, the large inertia of the head results in a horizontal translation relative to the thorax. This paper describes a simulation of the motion of the head and neck during a rear-end (whiplash) collision. A head-neck model that qualitatively undergoes the same forces acting in whiplash and shows the same behavior is used to analyze the kinematics of both the head and the cervical spine and the resulting neck loads. The rapid acceleration during a whiplash event causes the extension and flexion of the cervical spine, which in turn can cause dislocated vertebrae, torn ligaments, intervertebral disc herniation, and other trauma that appear to be the likely causes of subsequent painful headache or neck pain symptoms. Thus, whiplash provides a connection between the dynamics of the human body and physics. Its treatment can enliven the usual teaching in kinematics, and both theoretical and experimental approaches provide an interesting biological context to teach introductory principles of mechanics.
Bouncing Balls that Spin
Authors: Knipp Peter
Published: January 2008

When a ball bounces elastically against a floor, the vertical component (vy) of the velocity of the ball's mass-center changes sign. This is a special case of the elastic collision of two balls (i.e., two objects, neither of which is much more massive than the other), in which case the balls' post-collision relative velocity (= vy1 − vy2) is −1 times the balls' pre-collision relative velocity.
The Circle of Apollonius and Its Applications in Introductory Physics
Authors: Partensky Michael B.
Published: January 2008

The circle of Apollonius is named after the ancient geometrician Apollonius of Perga. This beautiful geometric construct can be helpful when solving some general problems of geometry and mathematical physics, optics, and electricity. Here we discuss two of its applications: localizing an object in space and calculating electric fields. First, we pose an entertaining localization problem to trigger students' interest in the subject. Analyzing this problem, we introduce the circle of Apollonius and show that this geometric technique helps solve the problem in an elegant and intuitive manner. Then we switch to seemingly unrelated problems of calculating the electric fields. We show that the zero equipotential line for two unlike charges is the Apollonius circle for these two charges and use this discovery to find the electric field of a charge positioned near a grounded conductive sphere. Finally, we pose some questions for further examination.
Optical Simulation of Debye-Scherrer Crystal Diffraction
Authors: Logiurato F. , Gratton L. M. , Oss S.
Published: January 2008

In this paper we describe and discuss simple, inexpensive optical experiments used to simulate x-ray and electron diffraction according to the Debye-Scherrer theory. The experiment can be used to address, at the high school level, important subjects related to fundamental quantum and solid-state physics.
Engaging Student Learning in Science Through Writing Tasks
Authors: Slater Timothy F.
Published: January 2008

Dr. Timothy F. Slater has been a frequent contributor to this column. His research focuses on student conceptual understanding in formal and informal learning environments, inquiry-based curriculum development, and authentic assessment strategies.
Effects of Molecular Memory and Bursting on Fluctuations in Gene Expression
Authors: Pedraza Juan M. , Paulsson Johan
Published: January 2008

Many cellular components are present in such low numbers per cell that random births and deaths of individual molecules can cause substantial “noise” in concentrations. But biochemical events do not necessarily occur in single steps of individual molecules. Some processes are greatly randomized when synthesis or degradation occurs in large bursts of many molecules during a short time interval. Conversely, each birth or death of a macromolecule could involve several small steps, creating a memory between individual events. We present a generalized theory for stochastic gene expression, formulating the variance in protein abundance in terms of the randomness of the individual gene expression events. We show that common types of molecular mechanisms can produce gestation and senescence periods that reduce noise without requiring higher abundances, shorter lifetimes, or any concentration-dependent control loops. We also show that most single-cell experimental methods cannot distinguish between qualitatively different stochastic principles, although this in turn makes such methods better suited for identifying which components introduce fluctuations. Characterizing the random events that give rise to noise in concentrations instead requires dynamic measurements with single-molecule resolution.
Coastal Ecosystem-Based Management with Nonlinear Ecological Functions and Values
Authors: Barbier Edward B. , Koch Evamaria W. , Silliman Brian R. , Hacker Sally D. , Wolanski Eric , Primavera Jurgenne , Granek Elise F. , Polasky Stephen , Aswani Shankar , Cramer Lori A. , Stoms David M. , Kennedy Chris J. , Bael David , Kappel Carrie V. , Perillo Gerardo M. E. , Reed Denise J.
Published: January 2008

A common assumption is that ecosystem services respond linearly to changes in habitat size. This assumption leads frequently to an “all or none” choice of either preserving coastal habitats or converting them to human use. However, our survey of wave attenuation data from field studies of mangroves, salt marshes, seagrass beds, nearshore coral reefs, and sand dunes reveals that these relationships are rarely linear. By incorporating nonlinear wave attenuation in estimating coastal protection values of mangroves in Thailand, we show that the optimal land use option may instead be the integration of development and conservation consistent with ecosystem-based management goals. This result suggests that reconciling competing demands on coastal habitats should not always result in stark preservation-versus-conversion choices.
The Subduction Zone Flow Field from Seismic Anisotropy: A Global View
Authors: Long Maureen D. , Silver Paul G.
Published: January 2008

Although the morphologies of subducting slabs have been relatively well characterized, the character of the mantle flow field that accompanies subduction remains poorly understood. To analyze this pattern of flow, we compiled observations of seismic anisotropy, as manifested by shear wave splitting. Data from 13 subduction zones reveal systematic variations in both mantle-wedge and subslab anisotropy with the magnitude of trench migration velocity |
V
t
|. These variations can be explained by flow along the strike of the trench induced by trench motion. This flow dominates beneath the slab, where its magnitude scales with |
V
t
|. In the mantle wedge, this flow interacts with classical corner flow produced by the convergence velocity
V
c
; their relative influence is governed by the relative magnitude of |
V
t
| and
V
c
.
A Localized Negative Genetic Correlation Constrains Microevolution of Coat Color in Wild Sheep
Authors: Gratten J. , Wilson A. J. , McRae A. F. , Beraldi D. , Visscher P. M. , Pemberton J. M. , Slate J.
Published: January 2008

The evolutionary changes that occur over a small number of generations in natural populations often run counter to what is expected on the basis of the heritability of traits and the selective forces acting upon them. In Soay sheep, dark coat color is associated with large size, which is heritable and positively correlated with fitness, yet the frequency of dark sheep has decreased. This unexpected microevolutionary trend is explained by genetic linkage between the causal mutation underlying the color polymorphism and quantitative trait loci with antagonistic effects on size and fitness. As a consequence, homozygous dark sheep are large, but have reduced fitness relative to phenotypically indistinguishable dark heterozygotes and light sheep. This result demonstrates the importance of understanding the genetic basis of fitness variation when making predictions about the microevolutionary consequences of selection.
Dual Positive and Negative Regulation of Wingless Signaling by Adenomatous Polyposis Coli
Authors: Takacs Carter M. , Baird Jason R. , Hughes Edward G. , Kent Sierra S. , Benchabane Hassina , Paik Raehum , Ahmed Yashi
Published: January 2008

The evolutionarily conserved Wnt/Wingless signal transduction pathway directs cell proliferation, cell fate, and cell death during development in metazoans and is inappropriately activated in several types of cancer. The majority of colorectal carcinomas contain truncating mutations in the adenomatous polyposis coli (APC) tumor suppressor, a negative regulator of Wnt/Wingless signaling. Here, we demonstrate that
Drosophila
Apc homologs also have an activating role in both physiological and ectopic Wingless signaling. The Apc amino terminus is important for its activating function, whereas the β-catenin binding sites are dispensable. Apc likely promotes Wingless transduction through down-regulation of Axin, a negative regulator of Wingless signaling. Given the evolutionary conservation of APC in Wnt signal transduction, an activating role may also be present in vertebrates with relevance to development and cancer.
Lhx2 Selector Activity Specifies Cortical Identity and Suppresses Hippocampal Organizer Fate
Authors: Mangale Vishakha S. , Hirokawa Karla E. , Satyaki Prasad R. V. , Gokulchandran Nandini , Chikbire Satyadeep , Subramanian Lakshmi , Shetty Ashwin S. , Martynoga Ben , Paul Jolly , Mai Mark V. , Li Yuqing , Flanagan Lisa A. , Tole Shubha , Monuki Edwin S.
Published: January 2008

The earliest step in creating the cerebral cortex is the specification of neuroepithelium to a cortical fate. Using mouse genetic mosaics and timed inactivations, we demonstrated that
Lhx2
acts as a classic selector gene and essential intrinsic determinant of cortical identity. Lhx2 selector activity is restricted to an early critical period when stem cells comprise the cortical neuroepithelium, where it acts cell-autonomously to specify cortical identity and suppress alternative fates in a spatially dependent manner. Laterally, Lhx2 null cells adopt antihem identity, whereas medially they become cortical hem cells, which can induce and organize ectopic hippocampal fields. In addition to providing functional evidence for Lhx2 selector activity, these findings show that the cortical hem is a hippocampal organizer.
Clonal Integration of a Polyomavirus in Human Merkel Cell Carcinoma
Authors: Feng Huichen , Shuda Masahiro , Chang Yuan , Moore Patrick S.
Published: January 2008

Merkel cell carcinoma (MCC) is a rare but aggressive human skin cancer that typically affects elderly and immunosuppressed individuals, a feature suggestive of an infectious origin. We studied MCC samples by digital transcriptome subtraction and detected a fusion transcript between a previously undescribed virus T antigen and a human receptor tyrosine phosphatase. Further investigation led to identification and sequence analysis of the 5387–base-pair genome of a previously unknown polyomavirus that we call Merkel cell polyomavirus (MCV or MCPyV). MCV sequences were detected in 8 of 10 (80%) MCC tumors but only 5 of 59 (8%) control tissues from various body sites and 4 of 25 (16%) control skin tissues. In six of eight MCV-positive MCCs, viral DNA was integrated within the tumor genome in a clonal pattern, suggesting that MCV infection and integration preceded clonal expansion of the tumor cells. Thus, MCV may be a contributing factor in the pathogenesis of MCC.
Differential Regulation of Dynein and Kinesin Motor Proteins by Tau
Authors: Dixit Ram , Ross Jennifer L. , Goldman Yale E. , Holzbaur Erika L. F.
Published: January 2008

Dynein and kinesin motor proteins transport cellular cargoes toward opposite ends of microtubule tracks. In neurons, microtubules are abundantly decorated with microtubule-associated proteins (MAPs) such as tau. Motor proteins thus encounter MAPs frequently along their path. To determine the effects of tau on dynein and kinesin motility, we conducted single-molecule studies of motor proteins moving along tau-decorated microtubules. Dynein tended to reverse direction, whereas kinesin tended to detach at patches of bound tau. Kinesin was inhibited at about a tenth of the tau concentration that inhibited dynein, and the microtubule-binding domain of tau was sufficient to inhibit motor activity. The differential modulation of dynein and kinesin motility suggests that MAPs can spatially regulate the balance of microtubule-dependent axonal transport.
Complicated Catheter-Associated Urinary Tract Infections Due toEscherichia coliandProteus mirabilis
Authors: Jacobsen S. M. , Stickler D. J. , Mobley H. L. T. , Shirtliff M. E.
Published: January 2008

Catheter-associated urinary tract infections (CAUTIs) represent the most common type of nosocomial infection and are a major health concern due to the complications and frequent recurrence. These infections are often caused byEscherichia coliandProteus mirabilis. Gram-negative bacterial species that cause CAUTIs express a number of virulence factors associated with adhesion, motility, biofilm formation, immunoavoidance, and nutrient acquisition as well as factors that cause damage to the host. These infections can be reduced by limiting catheter usage and ensuring that health care professionals correctly use closed-system Foley catheters. A number of novel approaches such as condom and suprapubic catheters, intermittent catheterization, new surfaces, catheters with antimicrobial agents, and probiotics have thus far met with limited success. While the diagnosis of symptomatic versus asymptomatic CAUTIs may be a contentious issue, it is generally agreed that once a catheterized patient is believed to have a symptomatic urinary tract infection, the catheter is removed if possible due to the high rate of relapse. Research focusing on the pathogenesis of CAUTIs will lead to a better understanding of the disease process and will subsequently lead to the development of new diagnosis, prevention, and treatment options.
Transmission of Tropical and Geographically Restricted Infections during Solid-Organ Transplantation
Authors: Martín-Dávila P. , Fortún J. , López-Vélez R. , Norman F. , Montes de Oca M. , Zamarrón P. , González M. I. , Moreno A. , Pumarola T. , Garrido G. , Candela A. , Moreno S.
Published: January 2008

In recent years, the increasing number of donors from different regions of the world is providing a new challenge for the management and selection of suitable donors. This is a worldwide problem in most countries with transplantation programs, especially due to the increase in immigration and international travel. This paper elaborates recommendations regarding the selection criteria for donors from foreign countries who could potentially transmit tropical or geographically restricted infections to solid-organ transplant recipients. For this purpose, an extensive review of the medical literature focusing on viral, fungal, and parasitic infections that could be transmitted during transplantation from donors who have lived or traveled in countries where these infections are endemic has been performed, with special emphasis on tropical and imported infections. The review also includes cases described in the literature as well as risks of transmission during transplantation, microbiological tests available, and recommendations for each infection. A table listing different infectious agents with their geographic distributions and specific recommendations is included.
Molecular Pathogenesis ofShigellaspp.: Controlling Host Cell Signaling, Invasion, and Death by Type III Secretion
Authors: Schroeder Gunnar N. , Hilbi Hubert
Published: January 2008

Shigellaspp. are gram-negative pathogenic bacteria that evolved from harmless enterobacterial relatives and may cause devastating diarrhea upon ingestion. Research performed over the last 25 years revealed that a type III secretion system (T3SS) encoded on a large plasmid is a key virulence factor ofShigella flexneri. The T3SS determines the interactions ofS. flexneriwith intestinal cells by consecutively translocating two sets of effector proteins into the target cells. Thus,S. flexnericontrols invasion into EC, intra- and intercellular spread, macrophage cell death, as well as host inflammatory responses. Some of the translocated effector proteins show novel biochemical activities by which they intercept host cell signal transduction pathways. An understanding of the molecular mechanisms underlyingShigellapathogenesis will foster the development of a safe and efficient vaccine, which, in parallel with improved hygiene, should curb infections by this widespread pathogen.
From Clinical Microbiology to Infection Pathogenesis: How Daring To Be Different Works forStaphylococcus lugdunensis
Authors: Frank Kristi L. , del Pozo José Luis , Patel Robin
Published: January 2008

Staphylococcus lugdunensishas gained recognition as an atypically virulent pathogen with a unique microbiological and clinical profile.S. lugdunensisis coagulase negative due to the lack of production of secreted coagulase, but a membrane-bound form of the enzyme present in some isolates can result in misidentification of the organism asStaphylococcus aureusin the clinical microbiology laboratory.S. lugdunensisis a skin commensal and an infrequent pathogen compared toS. aureusandS. epidermidis, but clinically, infections caused by this organism resemble those caused byS. aureusrather than those caused by other coagulase-negative staphylococci.S. lugdunensiscan cause acute and highly destructive cases of native valve endocarditis that often require surgical treatment in addition to antimicrobial therapy. Other types ofS. lugdunensisinfections include abscess and wound infection, urinary tract infection, and infection of intravascular catheters and other implanted medical devices.S. lugdunensisis generally susceptible to antimicrobial agents and shares CLSI antimicrobial susceptibility breakpoints withS. aureus. Virulence factors contributing to this organism's heightened pathogenicity remain largely unknown. Those characterized to date suggest that the organism has the ability to bind to and interact with host cells and to form biofilms on host tissues or prosthetic surfaces.
Impact of insect root herbivory on the growth and nitrogen and carbon contents of white clover (Trifolium repens) seedlings
Authors: Murray P. J. , Hatch D. J. , Cliquet J. B.
Published: January 2008

The impact of root herbivory by larvae of the weevil Sitona flavescens (Marsh.) on the growth and carbon and nitrogen economies of seedlings of white clover (Trifolium repens L.) and the nature and extent of nitrogenous compounds found in the root exudates taken from the rhizosphere were investigated. The seedlings were grown in sand culture in a system of microlysimeters that enabled sequential sampling of root exudates. Weevil infestation significantly reduced foliar biomass and total N and C contents and impaired N-fixation. The C:N ratios of the infested plants were significantly increased compared with those of uninfested seedlings. The most abundant amino acids in the exudates were aspartic acid and serine. Keywords: nitrogen fixation, Sitona spp., root exudates, white clover.
Voluntary and Evoked Muscle Contractile Characteristics in Active Men and Women
Authors: Behm David G. , Sale Digby G.
Published: January 2008

Eight men and 8 women were tested for voluntary and isometric evoked contractions of the dorsiflexors. Maximal voluntary contractions were conducted isometrically (30° plantarflexion) and isokinetically. Men produced greater peak torques at all but the highest isokinetic velocity. They exceeded women in measures of absolute voluntary isometric (33.8%), tetanic (46.3%), and twitch (37.9%) peak torque. Men demonstrated a higher tetanus/MVC ratio (17.8%). This ratio disparity would indicate that gender differences in peak torque in this study were more dependent upon muscle mechanisms. Although men exceeded women in measures of absolute voluntary maximum rate of torque development (MRTD) (38.7%), tetanic MRTD (39.1%), twitch MRTD (27.9%), voluntary maximum rate of torque relaxation (MRTR) (46.9%), and tetanic MRTR (41.9%), there were no significant gender differences in percentage rates of torque development or relaxation with voluntary or evoked contractions. Therefore the central and peripheral mechanisms controlling MRTD and MRTR may be similar between the sexes. Key words: gender strength differences, muscle contraction, rate of torque, tetanus, twitch
Prolonged Recovery From Eccentric Versus Concentric Exercise
Authors: Thomas Tom R. , Londeree Ben R. , Lawson Deborah A.
Published: January 2008

In order to determine whether exercise mode affects recovery energy expenditure, 7 active men (average age 25 yrs) performed a control rest and three submaximal exercise bouts in counterbalanced order in separate weeks. The bouts, designed to involve three levels of eccentric muscular activity, included 60% [Formula: see text] jog (60 J), 60% downhill (−5%) jog (60 DH), 60% cycling (60 C), and a control session. Following a 24-hr period of regulated activity and diet, subjects exercised for 60 min. [Formula: see text] and RER were assessed during 48 hrs of regulated recovery. Total energy use was elevated following 60 C and 60 DH versus control, and fat energy use was elevated following 60 J, 60 DH, and 60 C versus control. For combined trials, the total energy use was higher at 1, 2, and 9 hrs postexercise. These results do not support the hypothesis that eccentric muscular activity affects the magnitude of recovery energy expenditure. Key words: energy expenditure, fat energy expenditure, excess postexercise oxygen consumption, exercise mode
Biomass allocation and multiple resource limitation in tree seedlings
Authors: Canham C.D. , Berkowitz A.R. , Kelly V.R. , Lovett G.M. , Ollinger S.V. , Schnurr J.
Published: January 2008

We conducted a greenhouse experiment to determine how differences among tree species in allocation of biomass to roots versus shoots affected their responses to different combinations of light, water, and soil nutrients. Across a full range of light levels, we were specifically interested in examining the sensitivity of tree seedlings to additional reductions in aboveground growth due to soil resource limitation, and the relative sensitivity of seedlings to water versus nutrient stress under different light regimes. The four tree species used in our experiment included two species that are the most common initial tree invaders of abandoned agricultural lands (old fields) in the Hudson Valley (red maple (Acerrubrum L.) and white pine (Pinusstrobus L.)) and two species that are less frequently found in old fields, but that are dominant forest species, and are noted for their tolerance of either light stress or water stress (sugar maple (Acersaccharum Marsh.) and red oak (Quercusrubra L.), respectively). At the lowest light levels (2% of full sun), there was no effect of variation in soil resource availability on shoot growth of any of the four species. At the 9% full sun light level, red maple seedlings showed clear evidence of simultaneous limitation by light, water, and nitrogen. At higher light levels (20–100% of full sun), all four species responded to variation in at least one of the two soil resources. The four species showed two contrasting patterns of allocation of biomass to roots. Red maple and white pine responded to an increase in soil resource availability by reducing relative allocation to roots and increasing aboveground growth. Sugar maple and red oak had much more conservative root allocation patterns: root allocation was high (58–75% of added biomass allocated to roots) and did not vary in response to soil resource availability. Allocation to roots was affected more strongly by variation in soil nitrogen availability than it was by soil moisture availability.
Direct canopy nitrogen uptake from 15N-labeled wet deposition by mature red spruce
Authors: Boyce Richard L. , Friedland Andrew J. , Chamberlain C. Page , Poulson Simon R.
Published: January 2008

We applied 15N-labeled ammonium and nitrate to individual branches of red spruce (Picearubens Sarg.) to examine the importance of canopy N assimilation in the field. Levels of labeled N were highest in the youngest foliage and youngest twigs, and twig ammonium assimilation exceeded nitrate assimilation. Approximately 5% of the ammonium and 1% of the nitrate applied to each branch was assimilated; because of throughfall interactions with multiple branches, canopy assimilation rates are expected to be 3–6 times larger. Twig 15N levels exceeded foliar levels for the younger age-classes in the ammonium-labeled treatments, suggesting that twigs play an important role in ammonium assimilation. Comparisons of these results with data from trees that assimilated 15N through their roots showed that the pattern of canopy N assimilation differs from root assimilation, primarily by the assimilation of large amounts of N by twigs. Our results directly demonstrate for the first time that canopy assimilation is a pathway for uptake of N in these high-elevation trees. Canopy assimilation of atmospherically deposited N may represent 2–8% of the total N requirement for spruce in the high-elevation forest. While canopy N assimilation may thus reflect only a minor anthropogenic alteration of N acquisition in these forests, the long-term fate of this N needs to be determined.
A method for the identification of trees with unusually colored foliage
Authors: Innes John L. , Ghosh Sucharita , Schwyzer Andreas
Published: January 2008

A method is presented for recognizing trees with unusually colored foliage, based on the use of Munsell plant color charts. Color assessments are made by scoring the crown of each tree for hue, value, and chroma. These values are plotted in three-dimensional space for each species, and a threshold is identified marking the border of an ellipsoid. Trees with foliage outside this ellipsoid are considered as unusual. The method means that assessments of discoloration can cover a range of colors and moves the decision over the color status of a tree from a subjective field decision to a statistically defined decision at the analytical stage. It takes into account that a tree may still be classified as green (previously classed as without discoloration) when its color of green lies outside the normal expectation for the species. The method represents a significant improvement on the discoloration assessments currently being used in large-scale inventories of crown condition in Europe.
The influence of hardwood content on balsam fir defoliation by spruce budworm
Authors: Su Qiong , Needham Ted D. , MacLean David A.
Published: January 2008

Changing stand composition by increasing hardwood content has been suggested as a long-term method for reducing susceptibility and vulnerability of balsam fir (Abiesbalsamea (L.) Mill.) to spruce budworm (Choristoneurafumiferana (Clem.)). Twenty-five mixed balsam fir–hardwood stands were selected in northern New Brunswick, with five stands in each 20% hardwood class (0–20, 21–40%, etc.). Defoliation each year from 1989 to 1993 was significantly (p < 0.0001) related to hardwood content, with r2 ranging from 0.57 to 0.81. As hardwood content increased, defoliation of balsam fir decreased. From 1989 to 1992, the years of moderate to severe defoliation, balsam fir stands with <40% hardwoods sustained 58–71% defoliation, on average, versus 12–15% defoliation in stands with >80% hardwood. A generalized model combining hardwood content and the estimated defoliation in pure softwood stands in a given year explained 77% of the variation in defoliation over stands and years. This study indicated that mixed balsam fir–hardwood stand management, with hardwood content >40%, could substantially reduce losses during spruce budworm outbreaks. Further research is warranted to elucidate the mechanism involved, but our working hypothesis is that greater hardwood content increased the diversity or populations of natural enemies such as birds and parasitoids.
Growth, nutrient dynamics, and interspecific competition of nutrient-loaded black spruce seedlings on a boreal mixedwood site
Authors: Malik V. , Timmer V.R.
Published: January 2008

Nutrient-loaded and conventionally fertilized containerized black spruce (Piceamariana (Mill.) BSP) seedlings were planted on a boreal mixedwood site in the Greater Clay Belt of Ontario to study their growth and interaction with natural vegetation. At planting, nutrient-loaded seedlings were similar in height and biomass to conventionally fertilized seedlings, but contained 39, 69, and 22% more tissue N, P, and K content, respectively. After two field growing seasons, nutrient-loaded seedlings attained 15–18% more height and 16–39% more biomass, resulting in 15–27% reduction in the biomass of neighbouring vegetation. Aboveground biomasses of seedlings and neighbouring vegetation were inversely related. Interspecific competition was more intense in the second year than in the first year of outplanting. Nutrient loading prior to planting stimulated nutrient uptake and root growth after planting, and reduced soil N availability by 6–20% during the first season, suggesting greater preemption of belowground nutrient resources. The enhanced competitive ability of loaded seedlings over naturally occurring vegetation was probably due to the contrasting nutrient utilization traits induced by greenhouse fertilization. Nutrient-loaded seedlings translocated more nutrients to actively growing parts from reserves built up during the greenhouse preconditioning phase than did conventionally fertilized seedlings. First-season growth and nutrient responses in the field and in previous greenhouse trials were significantly correlated, demonstrating the effectiveness of using intact bioassays to simulate and predict short-term field responses to competition treatments.
Radial growth trends of loblolly pine in the Virginia Coastal Plain
Authors: Reams Gregory A.
Published: January 2008

A number of recent studies have shown reduced individual-tree growth throughout the 1970s and early 1980s in natural loblolly pine (Pinustaeda L.) stands in the southeastern United States. This study updates radial growth trends of loblolly pine in the Virginia Coastal Plain through 1989. Ring-width series were initially grouped into two age-classes (<50 or ≥50 years) and a clustering procedure was used to identify common radial growth patterns. These data suggest that radial growth trends of loblolly pine are cyclic and support previous findings of reduced growth in the 1970s. A reversal in trend has occurred since the early 1980s with radial growth increasing since then for both old and young trees. This change to increased growth corroborates the finding of increased growth of loblolly pine identified in the most current Forest Inventory and Analysis (FIA) survey cycle for the Virginia Coastal Plain.
The precolonial 19th century forest of the Upper St. Lawrence Region of Quebec; a record of its exploitation and transformation through notary deeds of wood sales
Authors: Simard Hélène , Bouchard André
Published: January 2008

A method based upon the use of wood sales, recorded by notary deeds, was used to describe how the precolonial forest of the Upper St. Lawrence Region of Québec changed during the 19th century. The notary deeds, covering the period of 1800 to 1880, are conserved in the National Archives of Quebec, in Montréal. Wood sales of the different species were compared, for each decade, as well as the fluctuations of volumes sold in relation to price. The results show a succession of species, appearing and disappearing, in the recorded wood sales. The sales began, in the early 1800s, with bur oak (Quercusmacrocarpa Michx.), eastern white cedar (Thujaoccidentalis L.), white pine (Pinusstrobus L.), sugar maple (Acersaccharum Marsh.), yellow birch (Betulaalleghaniensis Britton), and American beech (Fagusgrandifolia Ehrh.). Oak sales reached their highest level in the first decade of the century, but this species was rapidly exhausted and disappeared completely from the market by the end of the 1840s. Similarly, pine was sold mostly during the 1820s. Sugar maple, yellow birch, and beech, sold for firewood during the 1820s and 1830s, were replaced gradually in the following decades by other species also used for firewood, such as black spruce (Piceamariana (Mill.) BSP), tamarack (Larixlaricina (Du Roi) K. Koch), hemlock (Tsugacanadensis (L.) Carrière), "plaine" (a mix of Acerrubrum L. and Acersaccharinum L.), American elm (Ulmusamericana L.), and ash (Fraxinus). The most valuable species were the first exploited for wood sales, and as they were depleted from the forest, they were replaced by others of less value. Throughout the 19th century, under the influence of this harvesting, the composition of the Upper St. Lawrence forest changed to become what it is today.
Changes in dinitrogen fixation in maturing stands of Casuarinaequisetifolia and Leucaenaleucocephala
Authors: Parrotta John A. , Baker Dwight D. , Fried Maurice
Published: January 2008

Biological dinitrogen fixation in Casuarinaequisetifolia J.R. & G. Forst. and Leucaenaleucocephala (Lam.) de Wit was evaluated using the 15N-enrichment technique under field conditions in single-species and mixed-species plantings (with a nonfixing reference species, Eucalyptus ×robusta J.E. Smith) between 1.0 and 3.5 years of age in Puerto Rico. Following periodic labelling of trenched and untrenched plantation quadrats with 15N-enriched ammonium sulfate, analyses of foliar and whole-tree (weighted average) N-isotopic ratios and total biomass N were used to estimate the proportion of nitrogen derived from biological dinitrogen fixation (PNDFA) and total nitrogen derived from fixation (TNDFA) in C. equisetifolia and L. leucocephala. The 15N-enrichment technique yielded accurate estimates of dinitrogen fixation in maturing stands of these two tree species provided the reference species (Eucalyptus) was grown in close proximity to the N-fixing species in trenched, mixed-species plots. Changes in the 15N/14N ratio of soil-available nitrogen in single-species plots of the N-fixing and reference were found to yield inaccurate estimates of dinitrogen fixation in the single-species plots of C. equisetifolia and L. leucocephala after 2 years of age. The results confirm earlier findings that foliar sampling is a useful nondestructive alternative to whole-tree biomass sampling for the 15N-enrichment protocol. Between 1.0 and 3.5 years after plantation establishment, PNDFA in C. equisetifolia remained relatively constant between 50 and 60%, while PNDFA in L. leucocephala declined from nearly 100% at 1 year to less than 40% at 3.5 years. The rate of dinitrogen fixation (kg•ha−1•year−1) did not decline as the stands matured. Cumulative dinitrogen fixation (TNDFA) estimates at 3.5 years were very similar between species: 73 in C. equisetifolia and 74 kg N•ha−1•year−1 in L. leucocephala.
Use of the ectomycorrhizal fungus Laccarialaccata in forestry. I. Consistency between isolates in effective colonization of containerized conifer seedlings
Authors: Molina Randy
Published: January 2008

Four isolates of the ectomycorrhizal fungus Laccarialaccata (Scop. ex Fr.) Berk and Br. were inoculated singly onto containerized Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), ponderosa pine (Pinusponderosa Dougl. ex Laws.), Sitka spruce (Piceasitchensis (Bong.) Carr.), and western hemlock (Tsugaheterophylla (Raf.) Sarg.) seedlings to detect ecotypic variation in colonization success and effects on seedling growth. All isolates formed well-developed ectomycorrhizae on all inoculated seedlings. Abundance ratings of short roots colonized did not differ between the four isolates for any conifer species; most inoculated seedlings developed ectomycorrhizae on over 80% of their short roots. There were also no differences between isolates in affecting seedling height, stem diameter, and dry weight of tops and roots for all conifer species. Inoculations did not improve seedling growth over uninoculated controls. Uninoculated controls of Douglas-fir and ponderosa pine had significantly greater dry weight than their inoculated seedlings; growth of Sitka spruce and western hemlock seedlings was not affected by any inoculation treatment. Laccarialaccata vigorously colonized the entire container rooting substrate and appears a prime candidate for artificial ectomycorrhizal inoculation of containerized western conifers.
Development of dwarf mistletoe in western hemlock regeneration in southeast Alaska
Authors: Shaw III Charles G.
Published: January 2008

Western hemlock (Tsugaheterophylla (Raf.) Sarg.) regenerated within 9.14 m of old-growth hemlock severely infected with dwarf mistletoe, Arceuthobiumtsugense ((Rosendahl) G.N. Jones), and left standing on cutover sites in southeast Alaska were felled and examined for infection. The percentage of understory trees infected among the 3429 examined averaged 9, 7, 5, and 17, respectively, in 17-, 19-, 35-, and 43-year-old stands. Ninety-two percent of all infections in the 17-, 19-, and 35-year-old stands were alive, but only 51% were alive in the 43-year-old stand. In all stands few trees had more than two live infections and few had any infections in their middle or upper crown. In all stands, advanced regeneration was more frequently infected and accounted for a significantly greater proportion of crop trees than new reproduction. A significantly higher proportion of hemlock crop trees were infected than non crop trees, but the number of infections on crop trees was consistently low. Most infections were established on host tissue 5 years or younger, but tissue up to 13 years old was infected. At a comparable age, young stands in Alaska appear to be less severely affected by A. tsugense than similar stands in Washington, Oregon, and British Columbia. Disease control strategies, developed for stands experiencing more severe infection intensities than those now known to prevail in southeast Alaska, will require modification to meet local conditions.
Estimating probability of intertree root contact in second-growth Douglas-fir
Authors: Reynolds K. M. , Bloomberg W. J.
Published: January 2008

The relationships of root attributes and tree, stand, and site factors to root contact between second-growth Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) were studied in excavated root systems. Type 1 contacts (tenuous) were positively related to root length and inversely related to root volume. Type 2–3 contacts (with slight to severe root deformation) were positively related to number of roots. Type 4 contacts (apparent grafts) were positively related to root number and cross-sectional area. Differentiation among groups containing no contacts. Type 1 contacts only or all contact types showed that intertree distance, tree diameter, rooting depth, soil gravel content, and percent slope were significant in determining probability of root contact.
A comparison of measurements of the standing crops of biomass and nutrients in a conifer stand in Nova Scotia
Authors: Freedman B. , Duinker P. N. , Morash R. , Prager U.
Published: January 2008

A comparison is made of the realized and potential harvest removals of biomass and nutrients (N, P. K. Ca, and Mg) in a red spruce (Picearubens Sarg.) dominated stand, as estimated by experimental harvest of two 0.5-ha plots, and through the use of biomass regressions and a stratified mean-tree approach. The latter two calculations gave estimates of potential harvest removal (standing crop) that were similar to each other, but that were higher than the removals estimated by the harvest method by an average of 29% for whole-tree biomass, 84% for N. 58% for P. 28% for K. 45% for Ca. and 41 % for Mg. The differences are attributed to incomplete recovery of aboveground biomass by the experimental harvests, and to a tendency of regression techniques to overestimate standing crops.
Mass, nutrient content, and decay rate of dead boles in rain forests of Olympic National Park
Authors: Graham Robin Lambert , Cromack. Jr. Kermit
Published: January 2008

Analysis of dead boles of Piceasitchensis (Bong.) Carr. and Tsugaheterophylla (Raf.) Sarg. in open- and closed-canopy forests of the Olympic Peninsula Washington, U.S.A., revealed that hemlock mortality in both forest types was due mainly to windthrow, whereas spruce typically died upright. The open forest contained 120 t/ha of dead bole wood; the closed forest contained 161 t/ha. Hemlock boles decayed more rapidly than the larger spruce boles, although both showed considerable variability. On a per-hectare basis, 146–223 kg of N, 147–197 kg of Ca. 39–61 kg of K, 18–29 kg of Mg, 6–14 kg of Na, and 17–29 kg of P were contained in dead boles of the open- and closed-canopy forests, respectively. Except for N and Mg, the nutrient concentrations of the wood were not significantly different after 33–68 years of bole decay. The N:P ratios increased with increasing decay for both species.
Application of the pipe model theory to predict canopy leaf area
Authors: Waring R. H. , Schroeder P. E. , Oren R.
Published: January 2008

The pipe model theory presents the idea that a unit weight of tree foliage is serviced by a specific cross-sectional area of conducting sapwood in the crown. Below the crown, a large fraction of the tree bole may be nonconducting tissue, so the sapwood area would have to be known to estimate foliage. We applied the pipe model theory to the analysis of several western coniferous species to learn whether the distribution of canopy leaf area could be accurately estimated from knowledge of the sapwood cross-sectional area at various heights, including breast height (1.37 m). Results are excellent, but taper in the conducting area must be considered when sapwood area is measured below the crown.
Defoliation by spruce budworm: estimation by ocular and shoot-count methods and variability among branches, trees, and stands
Authors: MacLean David A. , Lidstone Roy G.
Published: January 2008

Ocular and shoot-count defoliation estimation techniques were compared for accuracy and precision at the levels of branches and crown position within trees, whole trees, plots, and stands. A shoot-count estimate of defoliation for a midcrown branch had the best relative accuracy (±7%), while the best ocular estimate was for the whole tree by an experienced observer (accuracy ±12%). Ocular estimates were biased towards ovcrestimation at low defoliation levels (error 20–30% defoliation), and previous defoliation caused the ovcrestimation of current defoliation by 30–40% on trees that had been previously severely defoliated. Observers were found to be consistent in their rating, but biased by about ±10%; experienced observers were about 5–10% more accurate than inexperienced observers. Intertree variance in defoliation was greater than intratree variance or variance between plots in a stand. It was concluded that ocular estimation of defoliation is a viable technique that can give accuracy within the limits required for surveys and many research applications, if the influence of observer experience, observer bias, and previous defoliation arc recognized, and adjusted for when necessary.
Distribution des gourmands sur les fûts de 25 essences en bordure de déboisement
Authors: Rey-Lescure Eric
Published: January 2008

Twenty-five species bordering clear-cut strips were classified according to their propensity to produce epicormic branches. The phenomenon occurred on 11 species, mostly on intermediate trees of average health and growing in medium density stands. Epicormic branching appeared generally below the crown on trees bordering the clear-cut. These results are consistent with the literature. They also verify the lack of correlation between the number of epicormic branches and tree mensuration data.
Root biomass and surface area in three successional tropical forests
Authors: Berish Cory W.
Published: January 2008

Total root biomass and surface area of fine roots (<5 mm diameter) were determined to a depth of 85 cm in 1-, 8-, and 70-year-old tropical forests on the same soil type (Typic Dystrandept) at Turrialba, Costa Rica. Root biomass and root area index (RAI) increased with age: biomass = 219, 1291, and 1555 g/m2, and RAI = 1.34, 4.66, and 5.28 in the 1-, 8-, and 70-year-old stands, respectively. Fine roots were most concentrated in the surface 5 cm of soil at all three sites, but especially so in the 70-year-old stand. The 1- and 8-year-old vegetations had proportionally more fine roots below 25 cm than the 70-year-old vegetation, but lacked the large-diameter roots characteristic of the 70-year-old stand.
Incidence of wounding and Echinodontium tinctorium infection in advanced white fir regeneration
Authors: Aho Paul E. , Filip Gregory M.
Published: January 2008

Incidence of wounding and Echinodontiumtinctorium E. & E. infection in advanced white fir (Abiesconcolor (Gord. & Glend.) Lindl. ex Hildebr.) regeneration were determined by a systematic survey of four stands in the Fremont National Forest, Oregon. Half of the 201 trees examined had one or more stem wounds, and 95% were more than 50 years old when sampled. Hymenomycetous fungi were isolated from 10 to 41 (24%) white firs dissected and examined in the laboratory; 9 (22%) had a total of 10 E. tinctorium infections; 6 infections occurred in healthy appearing wood and apparently were dormant; 4 infections were active (causing decay) and were in close proximity to injuries. Infection and decay processes by E. tinctorium in white fir are similar to those in western hemlock (Tsugaheterophylla (Raf.) Sarg.) and Pacific silver fir (A. amabilis Dougl. ex Forbes). Serious decay losses may occur in the four sampled stands before they become merchantable.
Variation among 21 Populus clones in tolerance to simazine and diuron
Authors: Akinyemiju O. A. , Dickmann D. I.
Published: January 2008

Clones of 21 cultivars from Populus sections Aigeiros and Tacamahaca were grown from cuttings in a greenhouse and assayed for tolerance to five dosages of simazine and diuron using a sand-eulture technique. Individual clones differed in their response to increasing dosages of the two herbicides. Each clone was classified as tolerant, intermediate, or intolerant to simazine and diuron based on the dosage required to cause a 20% reduction in plant dry weight (ED20). Pure Tacamahaca hybrids and intersectional crosses between Tacamahaca and Aigeiros were relatively intolerant of both herbicides. Pure Aigeiros clones were relatively tolerant to simazine and diurion, but even these clones were severely injured or killed by the highest dosages.