bluuebunny/crossref_metadata_2025 huggingface dataset:
Repeated challenge with prion disease: The risk of infection and impact on incubation period
Authors: Gravenor Mike B. , Stallard Nigel , Curnow Robert , McLean Angela R.
Published: September 2003

Natural exposure to prion disease is likely to occur throughout successive challenges, yet most experiments focus on single large doses of infectious material. We analyze the results from an experiment in which rodents were exposed to multiple doses of feed contaminated with the scrapie agent. We formally define hypotheses for how the doses combine in terms of statistical models. The competing hypotheses are that only the total dose of infectivity is important (cumulative model), doses act independently, or a general alternative that interaction between successive doses occurs (to raise or lower the risk of infection). We provide sample size calculations to distinguish these hypotheses. In the experiment, a fixed total dose has a significantly reduced probability of causing infection if the material is presented as multiple challenges, and as the time between challenges lengthens. Incubation periods are shorter and less variable if all material is consumed on one occasion. We show that the probability of infection is inconsistent with the hypothesis that each dose acts as a cumulative or independent challenge. The incubation periods are inconsistent with the independence hypothesis. Thus, although a trend exists for the risk of infection with prion disease to increase with repeated doses, it does so to a lesser degree than is expected if challenges combine independently or in a cumulative manner.
Hypogonadotropic hypogonadism due to loss of function of the KiSS1-derived peptide receptor GPR54
Authors: de Roux Nicolas , Genin Emmanuelle , Carel Jean-Claude , Matsuda Fumihiko , Chaussain Jean-Louis , Milgrom Edwin
Published: September 2003

Hypogonadotropic hypogonadism is defined as a deficiency of the pituitary secretion of follicle-stimulating hormone and luteinizing hormone, which results in the impairment of pubertal maturation and of reproductive function. In the absence of pituitary or hypothalamic anatomical lesions and of anosmia (Kallmann syndrome), hypogonadotropic hypogonadism is referred to as isolated hypogonadotropic hypogonadism (IHH). A limited number of IHH cases are due to loss-of-function mutations of the gonadotropin-releasing hormone receptor. To identify additional gene defects leading to IHH, a large consanguineous family with five affected siblings and with a normal gonadotropin-releasing hormone receptor coding sequence was studied. Homozygosity whole-genome mapping allowed the localization of a new locus within the short arm of chromosome 19 (19p13). Sequencing of several genes localized within this region showed that all affected siblings of the family carried a homozygous deletion of 155 nucleotides in the
GPR54
gene. This deletion encompassed the splicing acceptor site of intron 4–exon 5 junction and part of exon 5. The deletion was absent or present on only one allele in unaffected family members. GPR54 has been initially identified as an orphan G protein-coupled receptor with 40% homology to galanin receptors. Recently, a 54-aa peptide derived from the KiSS1 protein was identified as a ligand of GPR54. The present study shows that loss of function of GPR54 is a cause of IHH, and it identifies GPR54 and possibly KiSS1 protein-derived peptide as playing a major and previously unsuspected role in the physiology of the gonadotropic axis.
Selective contribution of IFN-α/β signaling to the maturation of dendritic cells induced by double-stranded RNA or viral infection
Authors: Honda Kenya , Sakaguchi Shinya , Nakajima Chigusa , Watanabe Ai , Yanai Hideyuki , Matsumoto Misako , Ohteki Toshiaki , Kaisho Tsuneyasu , Takaoka Akinori , Akira Shizuo , Seya Tsukasa , Taniguchi Tadatsugu
Published: September 2003

A complex mechanism may be operational for dendritic cell (DC) maturation, wherein Toll-like receptor and other signaling pathways may be coordinated differently depending on the nature of the pathogens, in order for DC maturation to be most effective to a given threat. Here, we show that IFN-α/β signaling is selectively required for the maturation of DCs induced by double-stranded RNA or viral infection
in vitro
. Interestingly, the maturation is still observed in the absence of either of the two target genes of IFN-α/β,
TLR3
and
PKR
(double-stranded-RNA-dependent protein kinase R), indicating the complexity of the IFN-α/β-induced transcriptional program in DCs. We also show that the DCs stimulated
in vivo
by these agents can migrate into the T cell zone of the spleen but fail to mature without the IFN signal. The immune system may have acquired the selective utilization of this cytokine system, which is essential for innate antiviral immunity, to effectively couple with the induction of adaptive immunity.
Economic Valuation of Ozone‐Related School Absences in the South Coast Air Basin of California
Authors: Hall Jane V. , Brajer Victor , Lurmann Frederick W.
Published: September 2003

Air quality in the South Coast Air Basin of southern California has improved significantly over the past decade, although pollution levels continue to exceed health‐based standards on a significant number of days. This study estimates the decline in ozone‐related school absences in southern California over the 1990s, reported as differences in the number of days of respiratory illness–related absences, the number of days of all illness‐related absences, and the economic loss to families of those absences. The study reports differences in the number of these effects for the intervals 1990–92 to 1997–99, for rolling three‐year intervals to 1997–99 across that period, and for expected future reductions in ozone. The baseline population is the cohort aged 5–18 residing in the South Coast Air Basin in 1998. For the interval 1990–92 to 1997–99, the economic value of fewer school absences ranges from $156 million annually to more than $330 million annually, with a best estimate of $245 million. This represents a benefit of nearly $75, on average, for every school‐age child in the region. (JEL I10, I12, Q2, Q25)
Injecting Competition into Public‐Sector Return to Work: Prospects for the “Ticket to Work” Initiative
Authors: Dean David H. , Dolan Robert C. , Schmidt Robert M.
Published: September 2003

The Ticket to Work legislation (1999) introduces private‐sector competition into the provision of return‐to‐work services for persons with disabilities who receive Disability Insurance (DI) payments. This article examines the likely effects of the Ticket to Work initiative using data from the Social Security Administration's Project NetWork experiment (1993–98). The analysis demonstrates that the efficacy of the Ticket to Work program will depend on whether the private sector replaces the vocational rehabilitative services currently provided by the public sector, or whether it expands the delivery of services—both in terms of the level and range of services provided, as well as increasing the portion of DI beneficiaries receiving services. (JEL H4, I0, J2)
Issues in marketing enterprise initiatives within a university culture and framework
Authors: Collins Amanda , Robertson Martyn
Published: September 2003

Enterprise initiatives come in a number of guises but, whether they are grant‐funded or a commercial aspect of a university’s business, the key driver is output. This usually means numbers – of students, of businesses, of ideas developed and sold, of financial gain and reputations made. A critical element impeding progress to the successful development of enterprise is marketing. This is something of a misnomer within organisations as amorphous as universities. The ability to develop products and services and to market them effectively to what should be a captive audience can prove even more trying than dealing with the mountain of paper work that accompanies most, if not all, enterprise initiatives. This paper describes the difficulties experienced by Business Start‐Up@Leeds Met in marketing enterprise at Leeds Metropolitan University, lessons learned and the future direction in terms of marketing approach.
Pollution‐free energy production by a proper misuse of finite element analysis
Authors: Okrouhlik Miloslav , Ptak Svatopluk
Published: September 2003

Notes that what applied scientists in classical continuum mechanics are doing is based on knowledge established by Newton, Cauchy, Euler, Rayleigh and others, and no really fundamental laws or principles in continuum mechanics have been “discovered” since. Newtonian mechanics provides a vital tool, which is still valid in all manners of ways from engineering to astronomy. Illustrates that we are not inventing completely new concepts of the world – rather, we are dealing with more and more precise models designed within the scope of Newtonian continuum mechanics. Nowadays, material non‐linearities, large strains and deformations, high‐velocity impact problems and others are routinely treated by sophisticated discrete tools, for example boundary elements, finite elements as expressed in Eulerian, Lagrangian and/or ALE formulations. Notes that modern methodologies are based on progress that is constantly being reported in finite element technology areas and that we should not believe in free‐energy production.
The effect of the third invariant in computational plasticity
Authors: Pivonka Peter , Willam Kaspar
Published: September 2003

In this paper, we examine the influence of the third invariant in computational plasticity. For this purpose we consider the extended Leon model, an elasto‐plastic model for concrete materials which accounts for the difference of shear strength in triaxial compression and triaxial extension. Consequently, the deviatoric trace of the loading surface is no longer circular like in von Mises and Drucker‐Prager plasticity. In the limit it approaches the triangular shape of the Rankine condition of maximum direct stress. Thereby, elliptic functions describe the out‐of‐roundness of the circular trace in terms of C1‐continuous functions of the Lode angle. The algorithmic aspects of the third invariant considerably complicate the computational implementation since the radial return method of J2‐plasticity does no longer maintain normality leading to loss of deviatoric associativity. The paper will focus on the computational issues near the three regions with high curvature at the compressive meridians with special attention on the lack of convergence of the plastic return algorithm and its slow rate of convergence in these regions. The algorithmic discussion at the constitutive level will be augmented by the axial plane‐strain compression test in order to illustrate the effect of the third invariant at the structural level of finite element analysis.
Re‐engineering a construction supply chain: a material flow control approach
Authors: Childerhouse Paul , Lewis Jayne , Naim Mohamed , Towill Denis R.
Published: September 2003

From the arguably poor platforms described by the Egan, Latham, and Royal Academy of Engineering reports on the construction sector, there is now evidence that the supply chain revolution experienced over the last decade in the electronics products and automotive sectors is impacting on housebuilding in the UK. This case study describes how a first‐tier supplier has applied “best practice” to design and implement a BPR programme. In total span the resulting change covers a baseline of traditional operations to the present status of agile response. Essentially the BPR programme has been conceived around the need for streamlined material flow through internal processes and both supplier and customer interfaces. The paper highlights the BPR stages necessary for enabling change, which is audited in terms of assessment of improved material flow. Finally, the “bottom‐line” impact of the BPR programme is documented, and demonstrates that substantial benefits have accrued.
Automatic query taxonomy generation for information retrieval applications
Authors: Chuang Shui‐Lung , Chien Lee‐Feng
Published: September 2003

It is crucial for information retrieval systems to learn more about what users search for in order to fulfil the intent of searches. This paper introduces query taxonomy generation, which attempts to organise users’ queries into a hierarchical structure of topic classes. Such a query taxonomy provides a basis for the in‐depth analysis of users’ queries on a larger scale and can benefit many information retrieval systems. The proposed approach to this problem consists of two computational processes: hierarchical query clustering to generate a query taxonomy from scratch, and query categorisation to place newly‐arrived queries into the taxonomy. The results of the preliminary experiment have shown the potential of the proposed approach in generating taxonomies for queries, which may be useful in various Web information retrieval applications.
Management and Business Ethics: A Critique and Integration of Ethical Decision‐making Models
Authors: Bartlett Dean
Published: September 2003

This paper critically reviews the literature relating to the management of ethics within organizations and identifies, in line with other authors, a gap between theory and practice in the area. It highlights the role of management (both as an academic discipline and from a practitioner perspective) in bridging this gap and views managers, with their sense of individual ethical agency, as a key locus of ethics within organizations. The paper aims to address the theory–practice gap by surveying the business ethics literature in order to identify, draw together and integrate existing theory and research, with a particular emphasis upon models of ethical decision‐making and their relationship to work values. Such an endeavour is necessary, not only because of the relative neglect of management practice by business ethics researchers, but also because of the current lack of integration in the field of business ethics itself. The paper outlines some of the main methodological challenges in the area and suggests how some of these may be overcome. Finally, it concludes with a number of suggestions as to how the theory–practice gap can be addressed through the development of a research agenda, based upon the previous work reviewed.
The Influence of Regular Work Systems on Compensation for Contingent Workers
Authors: Lautsch Brenda A.
Published: September 2003

Using data from a nationally representative survey of U.S. establishments, this article explores how features of regular work influence outcomes for contingent workers. The results show that firms combine regular and contingent work in varied ways: Some managers design contingent work to achieve performance objectives not possible with the regular workforce, whereas managers in other cases create contingent jobs to reinforce the same goals as regular work. In the latter case, contingent workers are more likely to be integrated with regular workers and to receive benefits. Benefit provision for contingent workers is also influenced by traditional internal labor market rules and by spillover effects in which efficiency or regulatory requirements lead benefits to be extended to contingent staff once offered to regular workers.
The Evolution of the Office of Management and Budget Under President Reagan
Authors: Mathiasen David G.
Published: September 2003

This article introduces a series of retrospective articles on the Reagan administration. The Office of Management and Budget became a major actor in the budget debate over the last eight years. The Reagan administration has seen a change in OMB’s role from that of an advisor to the president, to an agency with a central role to play in the development of the president’s foreign and domestic policy within budgetary constraints. The article focuses on how OMB has reacted to these changes producing budget conventions and techniques unique to the 1980s.
Fiscal Centralization in the American States: Findings From Another Perspective
Authors: Stonecash Jeffrey M.
Published: September 2003

Studies of the determinants of fiscal centralization have produced conflicting results. The difficulty may lie in reliance on cross‐section analyses and their presumptions of the sources and nature of change. Studies of the current relative positions of political units ignore historical factors which may have “pushed” units away from some sort of normal position. An historical analysis of the American states demonstrates these points.
Budgeting Rights: The Case of Jail Litigation
Authors: Straussman Jeffrey D. , Thurmaier Kurt
Published: September 2003

Judicial decisions are one element in the erosion of local government budgetary discretion. For example, litigation concerning constitutional rights forces local government officials to allocate resources toward the rights‐based population. While rights‐based allocation decisions may narrow the budgetary discretion of public officials, some managers may, paradoxically, be “better‐off”—defined as the ability to protect and defend their budgets — when discretion is reduced. This thesis is tested through a case study of jail overcrowding litigation in a county government.
Dynamics of the Greenbelt Amenity Effect on the Land Market—The Case of Seoul's Greenbelt
Authors: Lee Chang‐Moo , Linneman Peter
Published: September 2003

Seoul's greenbelt has been maintained for twenty years with little change, although Seoul has grown rapidly. Therefore, Seoul's greenbelt is interesting to examine for the dynamic impacts of a greenbelt regulation in a growing city. These impacts are examined in this article which also exploits a unique time series of Seoul property values (1970–1989). The results show that the amenity value of Seoul's greenbelt is quite high. However, the marginal value of greenbelt accessibility has been decreasing since 1980, in notable contrast to earlier years. A simple welfare analysis demonstrates that as the city grows, the greenbelt eventually loses its efficiency as a policy tool, even though earlier it may have achieved economic efficiency.
Housing Market Conditions, Listing Choice and MLS Market Share
Authors: Dale‐Johnson David , Hamilton Stanley W.
Published: September 2003

In some housing markets, a seller may hire a broker to multiple list or exclusively list a property for sale or may bypass the brokerage industry and list the property privately as a “sale by owner.” This article introduces a new model that illustrates the factors which will impact on the broker's and seller's preferred type of listing. An implication of the model is that if the choice is available, sellers and real estate brokers will employ a multiple listing service more often during slower market periods where the volume of sales is low and properties are more difficult to sell. An empirical analysis of Vancouver data yields results consistent with these arguments.
An Analysis of the Ex Ante Probabilities of Mortgage Prepayment and Default
Authors: Yang Tyler T. , Buist Henry , Megbolugbe Isaac F.
Published: September 2003

Observed mortgage prepayment and default rates have been far different than the ruthless option exercise rates predicted by contingent claims models of mortgage pricing. The discrepancies have been attributed to both the competing‐risk nature of prepayment and default and to transactions costs. This paper tries a different means of reconciliation. We introduce a third stochastic process, household income, into the usual pricing model that includes only the spot interest rate and the house price. The presence of income allows considering consumption‐theoretic determinants of termination. The role of mortgage underwriting rules in restricting optimal prepayment is also explicitly modeled. Numerical ex ante prepayment and default rates based on the theoretical model come much closer to historical experience.
Selling Time and Selling Price: The Influence of Seller Motivation
Authors: Glower Michel , Haurin Donald R. , Hendershott Patric H.
Published: September 2003

We consider the role that seller motivation plays in determining selling time, list price and sale price. A new survey of home sellers suggests that sellers are heterogeneous in their motivation to sell. Our findings are that a seller who, at the time of listing, has a planned date to move sells more quickly than one who does not. Also, the shorter the planned time until a move at the time of listing, the shorter the actual duration of marketing time. We find that seller motivation affects sale price, but not the list‐price markup. Our results suggest that theoretical models of the housing search process should be recast to allow for heterogeneous sellers.
Do Real Estate Prices and Stock Prices Move Together? An International Analysis
Authors: Quan Daniel C. , Titman Sheridan
Published: September 2003

The relationship between stock prices and real estate prices has been the subject of substantial debate in both the academic and practitioner literatures. Existing studies have focused on the time series of stock and real estate returns using data from a single country, such as the U.S. By necessity, these studies examine return and price changes over short intervals, creating a bias when property values are smoothed from year to year. Using data from 17 different countries over 14 years, this paper examines the relation between stock returns and changes in property values and rents. Consistent with other country‐specific studies, we find that, with the exception of Japan, the contemporaneous relation between yearly real estate price changes and stock returns is not statistically significant. However, when the data are pooled across countries and when we look at longer measurement intervals, a significant relation between stock returns and both rents and value changes becomes apparent. Real estate prices are also found to be significantly influenced by GDP growth rates and provide a good long‐term hedge against inflation but a poor year‐to‐year hedge.
Buyer Brokers: Do They Make a Difference? Their Influence on Selling Price and Search Duration
Authors: Elder Harold W. , Zumpano Leonard V. , Baryla Edward A.
Published: September 2003

This study focuses on the role of buyer brokers in the home‐buying process by examining the effects of brokerage representation on home selling prices and search duration. The results of this study indicate that real estate brokers, no matter the type, have no independent effect on home prices. The principal effect of broker intermediation is a reduction in buyer search time, compared to for‐sale‐by‐owner transactions. The most important finding, however, is that buyer agents are more effective at reducing search time for their clients than more traditional seller agents or non‐agent facilitators.
Random Walks and the Cointegration of the ACLI and NCREIF
Authors: Shilton Leon
Published: September 2003

Do NCREIF returns influence commercial mortgage underwriters when they adjust capitalization rates? Are the ACLI capitalization series and the NCREIF return series cointegrated at the national and the smaller geographic sub‐division levels? This research uses a two‐step procedure to test for cointegration. First, the Phillips–Perron unit‐root procedure must show that each series is a unit‐root random walk. Previous research usually has assumed that these series are random walks, with the implication that the commercial mortgage market is efficient. Second, the Phillips–Ouliaris test of the residuals of a function of the two series determines the possibility of cointegration. At the national level and for the Northeast and Pacific regions the two series are random walks and cointegrated. In other geographic sub‐divisions, neither or only one series is a random walk and therefore the data does not support a relationship. The lack of functional relationships in four of the six smaller geographic regions suggests that underwriters are not obtaining the NCREIF information or are ignoring it. The lack of random walks with the implication about capital‐market efficiency invites further research.
Inter- and Intraclonal Diversity of the
Pseudomonas aeruginosa
Proteome Manifests within the Secretome
Authors: Wehmhöner Dirk , Häussler Susanne , Tümmler Burkhard , Jänsch Lothar , Bredenbruch Florian , Wehland Jürgen , Steinmetz Ivo
Published: September 2003

The proteomes of cultured
Pseudomonas aeruginosa
isolates from chronically infected cystic fibrosis (CF) lungs were compared by using genetically divergent clones and isogenic morphotypes of one strain. Cellular extracts gave very similar protein patterns in two-dimensional gels, suggesting that the conserved species-specific core genome encodes proteins that are expressed under standard culture conditions in vitro. In contrast, the protein profiles of extracts of culture supernatants were dependent on the growth phase, and there were significant differences between clones. The profiles also varied within clonally related morphotypes from one CF patient, including a hyperpiliated small-colony variant. Mass spectrometry revealed that this variant overexpressed proteins secreted by the type I secretion system (including proteins involved in iron acquisition) and by the type III secretion system. Furthermore, the proteins in the supernatant extracts from the small-colony variant which were recognized by sera from different CF patients varied greatly. We concluded that the secretome expression is a sensitive measure of
P. aeruginosa
strain variation.
A Novel Outer Membrane Protein, Wzi, Is Involved in Surface Assembly of theEscherichia coliK30 Group 1 Capsule
Authors: Rahn Andrea , Beis Kostantinos , Naismith James H. , Whitfield Chris
Published: September 2003

Escherichia coligroup 1 K antigens form a tightly associated capsule structure on the cell surface. Although the general features of the early steps in capsular polysaccharide biosynthesis have been described, little is known about the later stages that culminate in assembly of a capsular structure on the cell surface. Group 1 capsule biosynthesis gene clusters (cps) inE. coliandKlebsiella pneumoniaeinclude a conserved open reading frame,wzi. Thewzigene is the first of a block of four conserved genes (wzi-wza-wzb-wzc) found in all group 1 K-antigen serotypes. Unlikewza,wzb, andwzchomologs that are found in gene clusters responsible for production of exopolysaccharides (i.e., predominantly cell-free polymer) in a range of bacteria,wziis found only in systems that assemble capsular polysaccharides. The predicted Wzi protein shows no similarity to any other known proteins in the databases, but computer analysis of Wzi predicted a cleavable signal sequence. Wzi was expressed with a C-terminal hexahistidine tag, purified, and used for the production of specific antibodies that facilitated localization of Wzi to the outer membrane. Circular dichroism spectroscopy indicates that Wzi consists primarily of a β-barrel structure, and dynamic light scattering studies established that the protein behaves as a monomer in solution. A nonpolarwzichromosomal mutant retained a mucoid phenotype and remained sensitive to lysis by a K30-specific bacteriophage. However, the mutant showed a significant reduction in cell-bound polymer, with a corresponding increase in cell-free material. Furthermore, examination of the mutant by electron microscopy showed that it lacked a coherent capsule structure. It is proposed that the Wzi protein plays a late role in capsule assembly, perhaps in the process that links high-molecular-weight capsule to the cell surface.
Modeling the role of papermill sludge in the organic carbon cycle of paper products
Authors: Mabee W , Roy D N
Published: September 2003

Fundamental information about the chemistry of sludge, published rates of sludge generation, and models of paper production and wastepaper recycling were combined to create a predictive model. The goal of the modeling exercise was to determine and project global sludge production until the year 2050. It was predicted that a global shift in paper and paperboard production would result in the Asia-Pacific region emerging as a major producer of papermill sludge. Global production of papermill sludge was predicted to rise over the next 50 years by between 48 and 86% over current levels. Sludge was found to contain a large amount of woody organic material, but the proportion of this material in the sludge was found to drop as recycling programs were implemented. Sludge was also found to contain a large amount of woody carbon, which comprised about 30% of the total sludge solids. The presence of such a large proportion of woody carbon may become important if a system of carbon crediting is implemented for the forest industry. Key words: carbon cycle, forests, papermill sludge, modeling, life cycle analysis.
Natural emissions of mercury to the atmosphere in Canada
Authors: Richardson G M , Mitchell I A , Mah-Paulson M , Hackbarth T , Garrett R G
Published: September 2003

The only Canadian inventory of natural source emissions of mercury (Hg) was prepared in 1981, but is now considered unreliable. As a result, the primary reference relied upon by Canadian regulators concerning the relative contribution of natural sources to environmental Hg contamination is a global inventory that was published in 1989. The relevance to Canada of a global inventory that included volcanic emissions is questionable. Therefore, a new inventory of natural Hg emissions in Canada was undertaken. Consistent with earlier inventories, natural Hg emission sources included wind erosion of soil, sea salt spray, forest and brush fires, biogenic Hg vapour emissions from terrestrial vegetation, and evasion of vapour from soil, ocean surfaces (within territorial limits) and lakes and rivers. Meteoritic dust was also considered. Recognizing the variability and uncertainty in available data, probabilistic methods were employed to derive mean estimates with 90% confidence limits. Estimated total annual natural source emissions of Hg in Canada averaged 1.1 × 106 kg with lower and upper 90% confidence limits of 0.54 × 106and 2.3 × 106 kg. Evasion of Hg vapour from terrestrial vegetation and evasion from soil predominated as natural sources of Hg in Canada; other sources were minor or insignificant. The estimated mean annual emission was approximately one third of that estimated in 1981. It was impossible with currently-available data to quantitatively differentiate natural emissions of Hg from those that are re-emitted following previous anthropogenic release and deposition. Therefore, the estimates provided herein include an unquantifiable contribution by re-emitted anthropogenic Hg.Key words: natural, mercury, emissions, atmosphere, Canada.
Vegetation management and ecosystem disturbance: impact of glyphosate herbicide on plant and animal diversity in terrestrial systems
Authors: Sullivan T P , Sullivan D S
Published: September 2003

The conservation of biological diversity (biodiversity) is becoming an integral part of the sustainable management of forest- and agro-ecosystems. A vital part of these systems is weed control, or vegetation management, to enhance crop production. Because of its widespread use and environmental compatibility, this review was designed to evaluate glyphosate herbicide in terms of: (i) its role as a disturbance agent and (ii) a measure of its impact on species diversity of terrestrial plants and animals. Our analyses were based on 60 published studies of terrestrial plants and animals in temperate zone forest- and agro-ecosystems. Species richness and diversity of vascular plants was either unaffected or increased, particularly herbaceous species, in response to glyphosate. Responses of plant species in forest ecosystems differ from those in agro-ecosystems where glyphosate is used to repeatedly reduce non-crop vegetation in most situations. Richness and diversity of songbirds appeared little affected by glyphosate-induced habitat alteration. In studies on small mammal communities and glyphosate use, none found significant reductions in species richness or diversity. As for avian responses, some small mammal species declined temporarily whereas others increased in abundance. The impact of glyphosate on large mammalian herbivores was measured by abundance of animals and food plants and by habitat use. Hares (Lepus spp. L.) and deer (Odocoileus spp. Rafinesque and Capreolus capreolus L.) were little affected, whereas reductions in plant biomass and related moose (Alces alces L.) forage and habitat use generally occur for 15 years after treatment. Studies on terrestrial invertebrates covered a wide range of taxa with variable responses in abundance to glyphosate treatments. The magnitude of observed changes in mean species richness and diversity of vascular plants, birds, and small mammals, from the effects of herbicide treatment, were within the mean values of natural fluctuations of these variables. The biological significance of this impact is limited to shifts in species composition based on changes in floral composition and structure of habitats. Management for a mosaic of habitats within forest and agricultural landscapes, which provide a range of conditions for plant and animal species, should help ameliorate the short-term changes in species composition accompanying vegetation management with glyphosate.Key words: agro-ecosystems, forests, glyphosate, plants and animals, species richness and diversity, vegetation management.
Attributes and indicators of old-growth and successional Douglas-fir forests on Vancouver Island
Authors: Trofymow J A , Addison J , Blackwell B A , He F , Preston C A , Marshall V G
Published: September 2003

The Douglas-fir forests of coastal British Columbia are within the most heavily modified forest ecosystem types in coastal BC and local land managers are developing new forestry practices to retain elements of old growth within the managed forest area. To determine how successful these practices are requires the selection and monitoring of appropriate attributes and knowledge on how they change with stand development. In this paper we summarize previously published results from an extensive data set on four Douglas-fir dominated sites located on eastern Vancouver Island. Data were collected as part of the Coastal Forest Chronosequences project which was addressing questions on (1) how does conversion to managed forests impact species and forest structural diversity and (2) how does this diversity recover in older second-growth stands. Each site contained four stands, a postharvest chronosequence: regeneration (R, 510 years), immature (I, 2545 years), and maturing (M, 7595 years) stands, and an old growth (O, >240 years) control stand. Over 20 attributes are summarized including structural attributes, and at three sites, detailed biodiversity and process attributes. All old-growth plots exceeded the minimum age criteria and some but not all of the minimum structural attribute criteria for old-growth Douglas-fir forests in the US Pacific Northwest, reflecting regional or site type differences. Most structural attributes showed their greatest change within the first 100 years, although older stands (M and O) still differed based on tree and snag sizes and tree mass or basal area. Most species abundance and richness attributes and process attributes clearly differentiated R from the forested stages but were of less value for differentiating among older (M and O) stands. Arboreal lichen abundance and species richness; the abundance of cryptogams, achlorophyllus plants, litter collembola, and specific species of fungi and carabids; litter fall and gap fraction were the exception, these attributes clearly differentiating M from O stands. In postharvest stands, the overall pattern of change with succession for most attributes, as inferred from the chronosequence, was confirmed to be very different from a previously published conceptual model for post-fire succession. Compared to the post-fire model, the greatest changes in the postharvest stands occurred early in stand development, associated with canopy closure. Although stand structural attributes can clearly be used to distinguish old-growth features in managed forest stands, none-the-less it is important to monitor and demonstrate, at least for a selection of nonstructural attributes, that forestry practices are effective in maintaining biodiversity and associated processes of old-growth forests in the managed forest area. Key words: old-growth forest, succession, Douglas-fir forest, criteria and indicators, biodiversity, managed forest.
Old growth in the Great Lakes forest
Authors: Carleton T J
Published: September 2003

The Great Lakes forest region is a bioclimatic zone between the northern boreal forest and the eastern deciduous forest of North America. Relatively warm, dry conditions prevailed during the first half of the Holocene, at which time pines (Pinus spp.) and oaks (Quercus spp.) were more prominent than during the second half. The contemporary Great Lakes forest is dominated by sugar maple (Acer saccharum Marsh.) on optimum sites but almost 50 other tree species occur over the spectrum of sites and disturbance regimes encountered throughout the region. Although gap-phase regeneration typifies the undisturbed forest, wildfire and destructive windfall, due to downbursts, are not uncommon. The incidence of forest fire is lower than that in the boreal zone, and the incidence of windfall is lower than that of the deciduous forest to the south and east. Age-structure reconstruction points to the fire-related origin of many Pinus- and Quercus-dominated forests. Paleoecological and neoecological evidence indicates subsequent succession to dominance by either eastern hemlock (Tsuga canadensis (L.) Carr.) or to sugar maple. However, it seems that these shade-tolerant forests remain stable over millennia, even though they may occupy similar sites. Species composition changes only after catastrophic disruption and death of the original cohort. The old-growth stage has been identified by features linked to forest stand age, including a heterogeneous physiognomy, high biomass, high woody necromass, and high species diversity. Assessment of each feature along chronosequences of forests dominated by eastern white (Pinus strobus) and red pine (Pinus resinosa Ait.) yielded a more complicated picture. Productive sites led to forests of much taller stature and earlier canopy breakup than on poor sites. Standing woody biomass aggraded to 120150 years and subsquently declined on all but the most productive sites, where it continued to increase with stand age. Snag volume tended to peak in the 90- to 125-year age range with subsequent decline. On the forest floor, coarse woody debris accumulated in a pattern similar to that of aboveground woody biomass. Plant species diversity was linked to the heterogeneity of substrata, much of which was attributed to woody necromass. These features persisted as legacies from stand growth before forest fire. Consequently, plant species diversity showed no correlation with postdisturbance stand age. The need to adopt a more dynamic view of the distribution and abundance of the Great Lakes forest flora is exemplified by the conservative understorey perennial, ground ginger (Asarum canadense L.) and cryptogamic epiphytes that indicate the continuity of old-growth forests with time. Key words: diversity, downbursts, fire, Holocene, necromass, old-growth criteria, pine chronosequence, site relations, succession.
Old growth in the boreal forest: A dynamic perspective at the stand and landscape level
Authors: Kneeshaw Daniel , Gauthier Sylvie
Published: September 2003

Old-growth forests have been identified as a potentially important stage of stand development for maintaining biodiversity in the landscape, yet they have also been targeted by the forest industry in their drive to regulate the forest. We will attempt to propose a definition of old growth, applicable throughout the North American boreal forest, that takes into account the dynamic nature of forest development and that could be useful for management and conservation purposes. We define the start of the old-growth stage as occurring when the initial post-disturbance cohort begins dying off, concurrent with understorey stem recruitment into the canopy. We propose that species longevity and the regional fire cycle can be used to assess the extent of this phase in different regions. Using published data on fire history, we show that the amount of old growth expected to occur in western and central Canada is less than in eastern Canada, where most stands (in area) escape fire for periods longer than that necessary to incur substantial mortality of the initial cohort. At the stand level, we show that the old-growth stage is characterized by small-scale disturbances that engender gap dynamics. Until recently, this process had not been studied in the boreal forest. The old-growth index we present suggests that the relationship between time since the last major disturbance and old-growth status varies most in areas that have not been disturbed for long periods. Both management and conservation strategies have to take into account that old-growth forests are dynamic. To be effective, reserves should contain all stages of development and should be sufficiently large to encompass rare but large disturbances. The abundance of old growth in many boreal regions of North America also suggests that forest management strategies other than even-aged, fully regulated systems have to be developed. Key words: old growth, old-growth index, boreal forest, conservation, forest management, stand development.
Perspectives on development of definitions and values related to old-growth forests
Authors: Frelich Lee E , Reich Peter B
Published: September 2003

Old-growth forests are those that meet some threshold(s) determined by a scientific and political process. The main issue is what criteria to use to determine these thresholds; they must be practical enough to allow managers to delimit and manage old-growth stands in the field. People value forests with old and (or) big trees and primary forests that have a continuous heritage of natural disturbance and regeneration, even though the latter may include all stages of stand development and succession. We advocate uniting these two and using "primary forest", also called "natural heritage forest", as the criterion for delimiting old growth in regions where primary forest still exists. This criterion recognizes that the stage of development with big, old trees is part of a cycle of development, and it is necessary to have all the parts to continue to produce new examples of the older stages. The best available second-growth stands can be used in regions where primary forests are not available. Alternatively, threshold criteria for delimiting old growth can be based on tree size and age, but arbitrary criteria based on human size and age scales should be avoided in favour of criteria that specify stands dominated by trees relatively large and old for the species and site. Such criteria allow for old growth to occur across a variety of levels of site productivity, with trees of widely varying stature and with varying life-history characteristics, such as longevity, shade tolerance, and successional status. In any case, managers and scientists should work together to make sure that definitions work in the field but also include the ecological processes necessary to maintain the unique biological resources of old growth. The biological resources present in old growth may help to restore the second-growth landscape and allow reconstitution of forests in new places after global warming. Old-growth forests provide a baseline for comparison of effects of logging and natural disturbance, with respect to resilience to climatic change and disturbance, maintenance of species richness, and natural genetic structure of tree populations, which respond to different selective regimes in old growth and harvested forests. The species in old-growth remnants, their interactions and the resilience of the system after disturbance are as important or perhaps more so than the age and size of the trees at a given point in time. Key words: dwarf forest, Minnesota, old-growth processes, tree height.
Characterization of old "wet boreal" forests, with an example from balsam fir forests of western Newfoundland
Authors: Thompson Ian D , Larson David J , Montevecchi William A
Published: September 2003

Wet boreal forests occur primarily in Atlantic Canada especially in Newfoundland, but examples are also found in Quebec and the northeastern U.S.A. These forests are dominated by balsam fir (Abies balsamea), which is susceptible to fire but flourishes in wetter environments where fire is absent. The major stand disturbances are caused by insects, primarily spruce budworm (Choristoneura fumiferana) and hemlock looper (Lambdina fiscellaria), followed by root rots and blowdown. Stands in Newfoundland were characterized by large amounts of dead standing and fallen wood, as a result of self-thinning processes and insect attacks. A comparison of 40-, 60-, and [Formula: see text]80-year-old forests in Newfoundland indicated that the oldest stage of balsam fir forests had a distinctly different structure, including more large dead and fallen wood, a more irregular canopy including gaps, a more diverse ground flora, more moss ground cover, a more variable tree height, taller snags, fewer white birch snags, and fewer deciduous small trees. These differences were reflected in various plant and animal faunas that were distinct in the old forest including: flowering plants, beetles, Collembola, oribatid mites, mammals, and birds. Several species of plants and animals were only found in the oldest forest stands, including a high percentage among the arthropods. Suggested indicator species at the stand level include black-backed woodpeckers (Picoides arcticus) and marten (Martes americana). Logging results in a larger mean patch size than that caused by natural insect disturbances, possibly affecting dispersal by soil organisms and plants within the new landscape. A portion of the landscape, keyed to species with the largest area requirements to maintain their populations, including marten, black-backed woodpeckers, and (or) boreal owls (Aegolius funereus) could guide the amount of old forest, and individual patch sizes, required across a landscape over time. Key words: old growth, biodiversity, species richness, forest management, balsam fir.