ALBERT

Notizen: Books reviewed in this article: Land Ecology: An Introduction to Landscape Ecology as a Base for Land Evaluation, Land Management, and Conservation. Isaac S. Zonneveld

Notizen: Density, age structure, and growth rates of wild brook trout (Salvelinus fontinalis)and brown trout (Salmo trutta)in Whetstone Brook in northcentral Massachusetts were monitored for 4 years before and 3 years during limestone treatment to mitigate acidic conditions. The population density of brook trout increased significantly during treatment. Liming did not have any significant effects on the growth rates of brook trout or brown trout. Actual survival rates of brook trout and brown trout were not calculated due to the low density of both species, but more older individuals of both species were captured during the treatment period. Fulton condition factors (an index of fish condition) increased significantly for both brook trout and brown trout during treatment. Seven-day in situ bioassays of brown trout and rainbow trout demonstrated that liming improved the chemical environment for fish in Whetstone Brook. During a pretreatment bioassay in 1987, 100% rainbow trout mortality was observed at both the control and treatment stations in Whetstone Brook. Brown trout mortality was 67% in the control station and 70% in the treatment station. The pH during the 1987 bioassay averaged 4.90 in the control station and 4.99 in the treated station. During a bioassay conducted in 1990 after treatment began, rainbow trout mortality was 100% in the control station and 0% in the treatment station. Brown trout mortality was 17% in the control station and 0% in the treatment station. The pH during the 1990 bioassay averaged 5.23 in the control station and 6.60 in the treatment station. Analysis of total aluminum in the gills of fish from the 1990 bioassay revealed higher levels in fish from the control station than in those from the treatment station.

Notizen: We monitored the invertebrate fauna in Whetstone Brook for 3 years before and after limestone treatment to mitigate low pH conditions caused by acid precipitation. Sampling was conducted during the spring, summer, and fall by both qualitative and quantitative methods. The fauna in Whetstone Brook in the control and treatment sections was dominated by chironomids (Diptera), simuliids (Diptera), Leuctra (Plecop-tera) and Hydropsyche (Trichoptera) in both pretreatment and treatment periods. The acid-sensitive mayfly genera Epeorus increased during liming in the treated section of the stream but also declined during the same period in the control section. Annelida increased during the treatment period in both sections of the stream. The chironomid and black fly populations were not affected by liming. The lack of impact to the black fly population was surprising because larvae are obligate filter-feeders and feed on suspended seston in the same size range as the limestone slurry that was used to treat Whetstone Brook. Treatment did not change species diversity and taxa richness in the treated section of Whetsone Brook, but both indices declined during the treatment period in the control section of Whetstone Brook. This decline was attributed to the poorer water quality of the untreated section of Whetstone Brook during the treatment period, which was due to higher-than-average precipitation. Percent community similarity analysis indicated that the community composition changed more in the treated section of Whetstone Brook than in the control section as a result of treatment. We conclude that the invertebrate fauna in the treated section of Whetstone Brook was not negatively affected by liming, but that population density and diversity did not increase.

Notizen: A protective limestone treatment was applied to an acid-sensitive lake in northeastern Minnesota as part of the Acid Precipitation Mitigation Program. This 6–year study evaluated the impact of that treatment on lakes in the upper Midwest that experience episodes of acid stress but have not lost basic species integrity and community structure. Several changes in the fish community can be directly or indirectly attributed to the addition of 4.6 tonnes of calcium carbonate early in the third year of the study. An almost 30–fold increase in the population of Pimephales promelas(fathead minnow) a year after liming, based on mark-recapture estimates from trap netting and snorkeling, was attributed to a pH increase and a three-fold increase in the calcium concentration of the epilimnion. After the initial increase, the abundance of fathead minnows declined in subsequent years, as did the elevated pH and calcium concentrations. The Salvelimis fontinalis(brook trout) population also increased in the lake following application of limestone, but this was due in part to closing the lake to fishing. An increase in survival of stocked brook trout to age 1+ and an increase in growth of older brook trout after liming were attributed to the increased forage that the fathead minnows provided. Fathead minnows may have also reduced predation pressure on young brook trout by older brook trout. This study demonstrated that liming of a slightly acidic lake did not adversely affect the integrity of the fish community, and in fact may have increased the abundance and biomass of the forage fish community and indirectly increased the survival, abundance, and growth of brook trout.

Notizen: Seedling emergence of 12 selected northern jarrah (Eucalyptus marginata Donn ex Smith) forest species were investigated to assist Alcoa of Australia Ltd. in maximizing the establishment of topsoil species in rehabilitated bauxite mining sites. The species, which encompassed a range of seed weights (0.024 mg to 87 mg), plant families, seed-storage types, life forms, and germination requirements, were placed on the soil surface and at depths of 1, 2, 5, 10, and 15 cm under controlled conditions in a glasshouse. Ability to emerge from deep burial was found to depend on seed size for species that annually release their seed to the topsoil but not for species that store their seed on the plant. All selected species were capable of emerging from 2 cm depth of burial, but eight of the 12 species were either unable to emerge from 5 cm or showed a significant reduction in emergence from 5 cm depth of burial compared to optimally buried seed. This group included two small-seeded species, Stylidium calcaratum and Chamaescilla corymbosa; the major forest dominant, Eucalyptus marginata; the serotinous canopy-borne seed of Hakea amplexicaulis; and the wind-dispersed seed of Xanthorrhoea gracilis. A few seeds of the legume species Kennedia coccinea, Acacia pulchella, and Bossiaea aquifolium established seedlings from depths of 15 cm. Currently, Alcoa removes the upper 15 cm of topsoil separately from the underlying soil prior to the commencement of mining. This topsoil is respread at a similar depth following mining as part of the rehabilitation procedure. It is recommended that Alcoa continue to strip topsoil to a depth of 15 cm but investigate the option of re-spreading topsoil onto rehabilitated pits at a shallower depth to maximize establishment via the soil seed bank.

Notizen: We summarize the findings of a two-year study of vegetation and streambank erosion on incised streams. We conducted the first year of the research during the sixth year of a drought. During the second year of study, precipitation totals ranged from normal to 200% of normal. The focus of the study was to determine if vegetation established on a bank affects the erosion of or deposition on that bank. During the drought year, most banks showed relatively little change. During the high water year, 27% of all vegetated and 32% of all bare lower banks retreated more than 250 mm. This similarity between vegetated and unvegetated banks indicates that, on the streams studied, vegetation had little effect on bank erosion. Bank retreat was not related to near-bank velocities or to bank steepness. It is possible that herbaceous vegetation showed no effect on the incised streams because the streams were too far from a new dynamic equilibrium. The energy of the hydraulic system may have been greater than the vegetation could withstand.

Notizen: We examine the nature of incentive schemes between the principal and the risk-neutral agent in the presence of the agent's limited liability and ex ante action choice. We consider alternative schemes when a simple rental contract is infeasible due to the limited liability of the agent and study the effectiveness of a performance bonus scheme in achieving the first-best outcome. We also discuss some implications of such schemes in real practices.

Notizen: Recent theories of vertical integration based on incomplete contracts assume perfect competition on at least one side of the market. As a result, the make-or-buy choice has no redistributive effect and will reflect efficiency considerations only. This paper introduces imperfect competition into an otherwise standard model of a vertical relationship with noncontractable specific investments. We assume that there are a finite number of potential input suppliers with private information about their costs. We first show that a monopoly buyer of such inputs will often prefer to own the seller's assets even though it would be more efficient for the seller's assets not to be so owned. We then show that an increase in the number of potential partners on either side of the market reduces this inclination towards vertical integration. With perfect competition on either side of the market, the make-buy decision will reflect only efficiency considerations.

Notizen: The paper studies managerial incentives in a model where managers choose product market strategies and make takeover decisions. The equilibrium contract includes an incentive to increase the firm's sales, under either quantity or price Competition. This result contrasts with previous findings in the literature, and hinges on the fact that when managers are more aggressive, rival firms earn lower profits and thus are willing to sell out at a lower price. However, as a side effect of such a contract, the manager might undertake unprofitable takeovers.

Notizen: For U.S. futures exchanges, controlling costs while maintaining market performance is an ongoing, difficult challenge. New market realities have made that challenge even more daunting in recent years as costs have escalated, competition has expanded, and the role of information technology has expanded. It is always difficult for regulatory statutes to keep pace with ever-changing markets. Futures markets are no exception. The basic statutory framework represented by the Commodity Exchange Act (CEA) was enacted in 1922, over seventy years ago. In order to maintain appropriate regulatory balance, periodic review and reform has been essential over the years. Our current federal regulatory systems were built for different markets with different competitive realities than we face today. Reforming the CEA to take into account those new market realities is vital to the survival of U.S. futures exchanges.

Notizen: We develop a game-theoretic version of the right-to-manage model of firm-level bargaining where strategic interactions among firms are explicitly recognized. Our main aim is to investigate how equilibrium wages and employment react to changes in various labor and product market variables. We show that our comparative statics results hinge crucially on the strategic nature of the game, which in turn is determined by the relative bargaining power of unions and managers.

Notizen: We develop a simple model in which there is both interfirm (or intraproduct) and intrafirm (or interproduct) competition. The purpose is to develop a classificatoy framework in order to understand product-range or diversification decisions alongside conventional competition. The equilibrium outcomes commonly involve a limited range of the available goods being produced. Deterrence equilibria and other strategic actions are also examined.

Notizen: DeGraba and Postlewaite (1992) show that the seller of a durable input can solve the time inconsistency problem by offering most-favored-customer (MFC) protection to buyers. McAfee and Schwartz (1994) show that if a supplier sells inputs to competing firms using two-part tariffs, MFC protection that allows a firm to replace its contract with a contract executed by any other firm will not solve the commitment problem, and argue this implies managers cannot use MFCs as a strategic commitment device in complex contracting situations. This paper shows that if the profits of the seller and the buyers are monotonic in each term of the contract, then applying MFC protection to each term of a contract allows a manager to solve his commitment problem in complex contacting situations. We show that “standard” contract arrangements (two-part tariffs, declining block tariffs, and royalties as a percentage of sales) meet this condition.

Notizen: Evaluating alternatives for restoring the Everglades involves analysis of a complex ecological and economic system for which current knowledge is limited. Uncertain benefits and impacts are analyzed probabilistically in this paper, following otherwise accepted principles of net present value (NPV) analysis. Ecological benefits and impacts were considered in monetary terms. Probabilities for selected uncertain parameters were found by maximizing entropy. The first ecological risk conceptual model for the Everglades ecosystem was developed to show ecological interactions. “Current Plans” for restoration involve discharge of phosphorus-enriched water from artificial wetlands to relatively pristine Everglades marshes for 3–10 years, risking conversion of the ecosystem to a eutrophic cattail marsh. For two of the three areas studied, alternative “Bypass Plans” were shown to avoid the loss of up to 3000 acres of sawgrass marsh at a cost that is probabilistically justified by the value of the ecosystem preserved. Sensitivity of the results to projected ecological changes, eutrophic marsh valuation, natural marsh valuation, and future values as represented in the discount rate, was examined.

Notizen: The motivation of the present work is to provide an auxiliary tool for the decision-maker (DM) faced with predictive model uncertainty. The tool is especially suited for the allocation of R&Dresources. When taking decisions under uncertainties, making use of the output from mathematical or computational models, the DM might be helped if the uncertainty in model predictions be decomposed in a quantitative-rather than qualitativefashion, apportioning uncertainty according to source. This would allow optimal use of resources to reduce the imprecision in the prediction. For complex models, such a decomposition of the uncertainty into constituent elements could be impractical as such, due to the large number of parameters involved. If instead parameters could be grouped into logical subsets, then the analysis could be more useful, also because the decision maker might likely have different perceptions (and degrees of acceptance) for different kinds of uncertainty. For instance, the decomposition in groups could involve one subset of factors for each constituent module of the model; or one set for the weights, and one for the factors in a multicriteria analysis; or phenomenological parameters of the model vs. factors driving the model configuratiodstructure aggregation level, etc.); finally, one might imagine that a partition of the uncertainty could be sought between stochastic (or aleatory) and subjective (or epistemic) uncertainty. The present note shows how to compute rigorous decomposition of the output's variance with grouped parameters, and how this approach may be beneficial for the efficiency and transparency of the analysis.

Notizen: The concept of vulnerability of complex industrial systems is defined and discussed in relation to risk and system survivability. The discussion is illustrated by referring to a number of previous industrial accidents. The various risk factors, or threats, influencing an industrial system's vulnerability are classified and discussed. Both internal and external threats are covered. The general scope of vulnerability analysis is compared to traditional risk analysis approaches and main differences are illustrated. A general procedure for vulnerability analysis in two steps, including building of scenarios and preparation of relevant worksheets, is described and discussed.

Notizen: The current safety criteria for a high hazard dam focus on protecting the dam during a large flood. While protecting the dam does help to protect downstream people and property, the two objectives are not the same. Instead, the criteria should focus on lowering property damage (including damage to the dam) and preventing flood deaths.High hazard dams must survive a design flood in the current safety criteria. However, experts don't agree on the size of the peak flow that meets this criteria.Statistical hydrologists have proposed an alternative to using professional judgment to specify the design flood. Unfortunately, peak flow distributions cannot be estimated with confidence for extreme floods given available data.A major safety goal is to prevent deaths from floods. Preventing deaths is a major reason for constructing the spillway to handle extreme floods so that the dam doesn't fail due to overtopping. However, even if the dam doesn't fail, the spilled floods could cause many deaths. A better approach is to warn people to get them out of harm's way if a flood is coming.Retrofitting existing dams that could pass a “probable maximum flood” (PMF) when built is almost never a good use of funds. Instead, funds would be spent better by focusing on preventing damage from small floods, lowering the damage from medium-sized floods, and warning people in the event of a flood that could pose risks to life.

Notizen: This paper describes and illustrates the architecture of computer-based Dynamic Risk Management Systems (DRMS) designed to assist real-time risk management decisions for complex physical systems, for example, engineered systems such as offshore platforms or medical systems such as patient treatment in Intensive Care Units. A key characteristic of the DRMSs that we describe is that they are hybrid, combining the powers of Probabilistic Risk Analysis methods and heuristic Artificial Intelligence techniques. A control module determines whether the situation corresponds to a specific rule or regulation, and is clear enough or urgent enough for an expert system to make an immediate recommendation without further analysis of the risks involved. Alternatively, if time permits and if the uncertainties justify it, a risk and decision analysis module formulates and evaluates options, including that of gathering further information. This feature is particularly critical since, most of the time, the physical system is only partially observable, i.e., the signals observed may not permit unambiguous characterization of its state. The DRMS structure is also dynamic in that, for a given time window (e.g., 1 day or 1 hour), it anticipates the physical system's state (and, when appropriate, performs a risk analysis) accounting for its evolution, its mode of operations, the predicted external loads and problems, and the possible changes in the set of available options. Therefore, we specifically address the issue of dynamic information gathering for decision-making purposes. The concepts are illustrated focusing on the risk and decision analysis modules for a particular case of real-time risk management on board offshore oil platforms, namely of two types of gas compressor leaks, one progressive and one catastrophic. We describe briefly the DRMS proof-of-concept produced at Stanford, and the prototype (ARMS) that is being constructed by Bureau Veritas (Paris) based on these concepts.

Notizen: Identifying the causes of accidents is a necessary prerequisite for preventive action. Some research suggests however that the analysis of accidents does not only differ between experts and laymen but that it is also linked to certain characteristics inherent in the analyst and in the social group to which he belongs: beliefs, value systems, norms, experiences in common, attitudes, roles, social and technical practices, etc. Culturally determined bias seems to affect the perception of risk and the causes of accidents. This article presents a certain number of thoughts and results based upon research carried out on causal attributions of traffic accidents in The Ivory Coast (West Africa) and discusses the importance of culture in risk-taking and accident prevention. It shows in particular that fatalistic beliefs and mystical practices influence the perception of accidents and consequently incite one to take more risks and neglect safety measures.

Notizen: Since substantial bias can result from assigning some type of mean exposure to a group, risk assessments based on epidemiological data should avoid the grouping of data whenever possible. However, ungrouped data are frequently unavailable, and the question arises as to whether an arithmetic or geometric mean is the most appropriate summary measure of exposure. It is argued in this paper that one should use the type of mean for which the total risk that would result if every member of the population was exposed to the mean level is as close as possible to the actual total population risk. Using this criterion an arithmetic mean is always preferred over a geometric mean whenever the dose response is convex. In each of several data sets examined in this paper for which the dose response was not convex, an arithmetic mean was still preferred based on this criterion.

Notizen: Developmental anomalies resulting from prenatal toxicity can be manifested in terms of both malformations among surviving offspring and prenatal death. Although these two endpoints have traditionally been analyzed separately in the assessment of risk, multivariate methods of risk characterization have recently been proposed. We examined this and other issues in developmental toxicity risk assessment by evaluating the accuracy and precision of estimates of the effective dose (ED05) and the benchmark dose (BMD05) using computer simulation. Our results indicated that different variance structures (Dirichlet-trinomial and generalized linear model) used to characterize overdispersion yielded comparable results when fitting joint dose response models based on generalized estimating equations. (The choice of variance structure in separate modeling was also not critical.) However, using the Rao-Scott transformation to eliminate overdispersion tended to produce estimates of the ED05 with reduced bias and mean squared error. Because joint modeling ensures that the ED05 for overall toxicity (based on both malformations and prenatal death) is always less than the ED05 for either malformations or prenatal death, joint modeling is preferred to separate modeling for risk assessment purposes.

Notizen: Nineteen Senior Managers of a major chemical company in the United Kingdom participated in a survey to determine their attitudes, beliefs, and perceptions regarding risks from chemicals. Similar surveys had previously been conducted with toxicologists and members of the general public in the United States and Canada. In general, the Senior Managers tended to judge risks to be quite small for most chemicals. Moreover, they had lower risk perceptions than did members of the British Toxicological Society and even far lower perceptions of risk than a comparison group of members of the Canadian public. The managers held views that were similar to British toxicologists working in industry and government and dissimilar to the views of toxicologists working in academia. The observed differences between views of managers, toxicologists, and the public must be recognized and understood in order to facilitate communication and constructive efforts to manage chemical risks.

Notizen: The construction industry is both the largest civilian industry and the most unique in terms of fragmentation and its approach to controlling risk. Structural specifications establish nominal safety factors and design criteria for engineered structures such as buildings, bridges, dams, and power facilities. The goal is satisfactory strength capacity to safely and economically meet the demands of structural performance. Structures must resist the highly uncertain effects of combined gravity, earthquakes, wind, and snow loads supported by natural and human-made materials. The public's expectation is that structures should last a long time and have low lifetime risk of structural failure. Historically, specifications have contained safety factors which evolved from past experiences and provided adequate safety or low risk. Due to pressures of economy and the need to optimize structural performance, structural specifications have recently been developed and accepted by industry based on structural reliability and risk-assessment principles. This paper reviews developments of probabilistic applications in structural specifications including specification format, database, implementation examples, target risk levels, present research activities, and future goals for establishing optimal risk-design procedures.

Notizen: Importance measures have been useful in the process of extracting insights from risk analyses. Importance measures have also been suggested for use in component classification. However, there are difficulties of interpretation associated with component classification based on importance measures. This paper briefly reviews an alternative method, “Top Event Prevention Analysis,” and, based on a simple example, compares its key characteristics to those of conventional applications of importance measures. The methods are compared with respect to the task of formulating a safety case for a complex and potentially hazardous facility, in which component classification plays an important role. A key subtask is identification of a collection of design elements that is necessary and sufficient to achieve the desired level of protection of the public, the workers, and the environment. At the design stage, identifying this set helps to determine what elements to include in the final design. Separately, a similar selection process could be used in order to justify limiting the scope of regulatory oversight to a subset of design elements, on which a safety case is to be based. This step could be taken during initial review of a design, or later as part of an effort to justify relief from regulatory requirements that are burdensome but provide little actual risk reduction.〈section xml:id="abs1-1"〉〈title type="main"〉SUMMARYA safety case should arguably be based on a collection of design elements that combine to provide satisfactory plant response to important safety challenges, and provide this response with the desired reliability (achieved through redundancy and diversity in design, and programmatic support activities as necessary in implementation). The key property of such a collection resides in the set as a whole, and not in any single element: the implications of including or not including any given design element in the collection depend strongly on what other design elements are included. Given a logic model that comprehensively addresses plant response, reflecting all components under consideration, and a defense-in-depth safety standard of the kind discussed above, TEPA is capable of choosing prevention sets: subsets of components that have the desired defense-in-depth property, and are suitable candidates for serving as the nucleus of a safety case.Single-event importance measures cannot capture considerations like this, except perhaps as part of an arduous iterative reformulation of a logic model to successively remove and restore combinations of events in a trial-and-error approach to a self-consistent design solution. No method of applying conventional importance measures has been shown to produce solutions that are feasible in the sense of completing pathsets, nor is one expected. Interpreting the upper portion of a ranked list of components as a safety case would therefore be a misapplication of the importance measure concept.However, given a prevention set, one could apply importance measures to fine-tune the allocation of resources within this set. That is, one could compute importances within a model that took credit only for elements of the prevention set, and reason from there. Even in this case, some iteration might be required in order to achieve a self-consistent allocation (one for which the reliability credit taken for each component is commensurate with the resources allocated to it). In order to draw valid conclusions in an application of this type, one must recall that all importance measures are predicated on credit for all modeled components; it is invalid to infer that components can be dropped from a safety case on grounds of low calculated importance. In short, application of importance measures is valid when (a) the selection problem has been solved by other means, (b) the importances are calculated with credit only for selected components, and (c) the resources allocated to each component are commensurate with the level of credit taken for the component (e.g., credit for a component's availability is backed up by an appropriate test schedule.).A byproduct of this work is the observation that whether or not TEPA itself is applied to choose prevention sets, a useful litmus test to be applied to a safety case is simply whether it is based on a union of complete success paths. As discussed above, thinking of the safety case in this way has other benefits, in helping to identify unmodeled components and in helping to specify the demands that must be met by each component, so that programmatic activities necessary to ensure its function can be identified and carried out. This formulation of the safety case helps in thinking about the relationship between component performance and resources allocated to that component. Understanding this relationship is essential to optimizing the use of safety resources.The number of combinations (possible prevention sets) that must be examined grows very rapidly as the number of design elements and minimal cutsets increases. Therefore, many realistic problems will be very demanding computationally. To some extent, this could be considered a drawback of TEPA, but it should be understood that the underlying problem is combinatorially very difficult, and actual solutions to it should not be expected to come easily in all cases. Fortunately, as illustrated by the practical applications summarized above, many real large-scale problems have specific features that permit their solution by adaptations of the general approach.

Notizen: This paper raises two questions, i.e., Are some people more prone to perceive hazards than others embedded in the same dangerous working environment?, and—if so—Is it possible to find distinguishing characteristics allowing us to profile this worker segment? A survey study was conducted among catering personnel working on a drilling platform at the continental shelf in the North sea. It was observed that some people more than others perceived hazards in their working environment. By contrasting the extreme groups, i.e., the high and low hazards perceivers it was found that sociodemographics, e.g., gender, marital status, age and working experience possessed no descriptive power. However, the findings revealed that the worker segment prone to perceive high hazards also reported higher degree of burnout, anxiety and depression than did the low hazards perceivers. They (the high hazards perceivers) were also less satisfied with their stay on the platform, and they reported more health problems as well. The findings indicate that hazards perceptions of hazards go beyond mere “cold cognition,” also tapping into negatively feelings and emotional states. Theoretical and practical implications are highlighted.

Notizen: This paper presents estimates of daily average per capita fish consumption by age and gender for the 48 conterminous states. The estimated consumption rates are reported for three fish habitats: freshwater/estuarine fish, marine fish, and all fish. The estimates were generated from the combined 1989, 1990, and 1991 Continuing Survey of Food Intake by Individuals (CSFII), a national food consumption survey conducted by the United States Department of Agriculture (USDA). Point and interval estimates of per capita fish consumption were generated from the empirical distribution of daily average per capita consumption. The point estimates include the mean, 50th, 75th, 90th, 95th, and 99th percentiles. Ninety percent confidence intervals are provided for the estimated mean and 90% bootstrap intervals are provided for percentile estimates. Information in a recipe file provided by USDA was used to calculate the amount of fish in recipes which contain fish. The estimated consumption rates are based on the weight of fish in its prepared or “as consumed” condition. The estimated mean consumption rate for all fish for the U.S. population of the 48 conterminous states was 15.65 grams/person/day (C.I.:14.67–16.63) of which 4.71 grams/person/day (C.I.:4.17–5.25) was freshwater/estuarine fish and 10.94 grams/person/day (C.I.: 10.14–11.73) was marine fish.

Notizen: The combination of radon and smoking produces a synergistic risk of lung cancer. Lay understanding of this risk was examined from the perspectives of mental models theory, the psychometric approach to risk perception, and optimistic bias. As assessed by interview, participants (N= 50) had more extensive mental models for the risks of smoking than for the risks of radon or the combination of radon and smoking; 32% knew little or nothing about radon. Despite reading an informational brochure, their risk-perception ratings of the three hazards showed no perception of the synergy between smoking and radon risk, although the combined hazard was rated as less familiar but more controllable than the average of the single hazards (p 〈 .01). No evidence of optimistic bias for the health consequences of radon, or the combination of radon and smoking was observed. Participants appeared to be combining the single-hazard risks subadditively to arrive at their combined-hazard risk perceptions. Further research on the integration of perceived risks would be beneficial for designing optimal communications about synergistic risk.

Notizen: This paper investigates the role that performance-based regulations can play in linking a firm's environmental, health, and safety concerns with their corporate strategy. The specific focus is on the performance standards required by the Clean Air Act Amendments (CAAA) which require firms that store or use certain chemicals to develop a Risk Management Plan (RMP) for reducing the likelihood and impact of accidents at their plants. Data from a series of case studies and interviews of executives in chemical firms reveal that proactive companies integrated many of the requirements of the CAAA into their management systems prior to the regulatory requirements. Most of these firms tend to be large ones. Small firms often lack the resources to implement these regulations and hence have tended to have a more difficult time with compliance.

Notizen: Coexisting Ca-poor and Ca-rich pyroxenes in granulites at Cape Riche, in the Precambrian Albany-Fraser Province, Western Australia, are dominantly chemically homogeneous within individual samples, suggesting a major episode of equilibration. However, occasional grains in a few samples contain exsolved domains interpreted as relics of an earlier, higher-T assemblage. Pyroxene pairs in ten, presumably isothermal, samples from a restricted area are used to (i) assess the suitability of several versions of the two-pyroxene thermometer for application to metamorphic rocks, and (ii) determine the thermal history of the Cape Riche pyroxenes.The various versions of the two-pyroxene thermometer applied to the well-equilibrated homogeneous pyroxene grains show poor to good precision and yield mean temperatures varying widely from 683° to 893°C, in the following order of increasing T: Lindsley (1983; opx version), 683°± 11°C; Kretz (1982; KD version), 705°± 19°C; Ross & Huebner (1975), 709°± 30°C; Kretz (1982; solvus version), 735°± 24°C; Fonarev & Graphchikov (1982; opx version), 〈750°C; Lindsley (1983; cpx version), 784°± 40°C; Fonarev & Graphchikov (1982; cpx version), ~820°± 30°C; Wood & Banno (1973), 849°± 16°C; Powell (1978), 854°± 23°C; Wells (1977), 893°± 10°C. Independent T estimates, based on mafic assemblages and garnet-biotite thermometry, suggest that the major episode of metamorphism occurred at 700-800°C (P ~ 5 kbar). Therefore the Wells, Powell, Wood & Banno and Fonarev & Graphchikov (cpx) temperatures are almost certainly too high. In the absence of a more precise independent T estimate it is difficult to assess the relative merits of the results obtained from the remaining versions of the two-pyroxene thermometer, none of which can be unequivocally demonstrated to be seriously in error, though the Lindsley (opx) T is probably too low. Other significant shortcomings evident in the results include the relatively poor precision obtained from the three methods based on purely graphical representation of the augite limb of the solvus (i.e., the Ross & Huebner, Fonarev & Graphchikov (cpx) and Lindsley (cpx) versions), and the apparent dependence of derived T on Mg/Fe2+ ratio for the Powell, Wood & Banno and Lindsley (cpx) methods.For the bulk compositions of exsolved domains, the different versions of the two-pyroxene thermometer yield mean temperatures 23° to 82°C (overall mean, 65°C) higher than for homogeneous grains in the same samples. These exsolved domains are interpreted as relics of a higher-T (peak?) metamorphic assemblage, rather than an igneous precursor.

Notizen: Abstract We have deduced the steady-state lithospheric geotherm at c. 1 Ga in the south Indian shield area using the available data on the concentration of radioactive elements, and the P-T conditions of Proterozoic mantle xenoliths in the south Indian kimberlites as constraints. The geotherm was adjusted back to 2.5 Ga by keeping the surface temperature constant and calculating the temperature change at the top of convecting upper mantle. The reduced or mantle heat flux, which was treated as an adjustable parameter, was 20.9–21.3 mW/m2 at 1–2.5 Ga. Comparison of the calculated steady-state geotherm with the available P-T data of the Archaean (c. 2.5 Ga) charnockites and granulites from southern India suggests that the granulite facies metamorphism in this region had resulted from a major thermal perturbation, which was c. 400° C at 25 km.Seismic tomographic and gravity data essentially preclude any significant magma underplating of the granulitic crust in southern India. Previous workers have suggested that the formation of charnockites in this region was associated with copious CO2 influx from a deep-seated source, possibly the mantle. In this work, we have evaluated both the transient and steady-state thermal effects of the heat convected by CO2 outgassing from upper mantle. It is shown that the thermobarometric array of charnockites and granulites can be produced by the convective perturbation of the steady-state geotherm, and that a flux of CO2 of ±90 mol/m2 yr (corresponding to Darcy velocity of ±0.30 cm/yr) for a period of ±30 Ma was needed to produce the required perturbation. This is c. 150 times the average CO2 flux through the tectonically active area of the Earth's crust at the present time. There is, however, an uncertainty of a factor of 3 in this value.Seismic tomographic and gravity data independently suggest thickening of the crust beneath the granulite terrane compared with the adjacent Dharwar craton. This suggests thermal perturbation due to overthrusting as a major potential cause for the granulite facies metamorphism in south India. Overthrusting of a 30–35-km-thick thrust block was needed to produce the required thermal effect. The estimated thickness of the original crust from geobarometric and seismic tomographic data south of the orthopyroxene isograd or ‘transition zone’is compatible with the emplacement of a thrust block of this magnitude. However, the latter fails to match the estimated pre-uplift crustal thickness at the transition zone, if it is assumed that the crust has not thinned by non-erosional processes since the Archaean. Thus, we propose a combination of overthrusting and CO2 fluxing from a deep-seated source as the cause for the formation of charnockites in this zone. The required focusing of CO2 in this case is c. 40% of that estimated in the model where CO2 fluxing was considered to be the sole reason for thermal perturbation. This combined thrusting—CO2 fluxing model also helps explain the development of patchy charnockites in the transition zone from amphibolite facies rocks.

Notizen: Abstract End-member, continuous and degenerate reactions are derived for the multisystem with the six components Na2O, CaO, (Mg/Fe)O, Al2O3, SiO2, H2O among the phases plagioclasess, garnetss, amphiboless, cpx, opx, olivine, spinel, quartz and an aqueous fluid. The chemography of this system is degenerate due to the co-linearity 2Opx = Ol + Qtz. This co-linearity has its implications both on reaction space and phase equilibria.From a total of 28 reaction systems, reaction space is derived for nine subsystems (phases in parentheses are absent): Case A1: (Cpx,Ol) (Cpx,Opx) and (Cpx,Qtz), Case A2: (Spl,Ol) (Spl,Opx) and (Spl,Qtz), Case B: (Ol,Opx) (Ol,Qtz) and (Opx,Qtz).In the absence of either cpx or spl (case A), three reactions form an invariant point, either [Cpx] or [Spl], where the co-linear phases olivine, opx and quartz coexist on the transformation line 2Opx = Ol + Qtz. Changing mineral compositions force invariant points to move along the line with the different reaction curves changing their relative position according to Schreinemakers’rules. Zero contours, i.e. the location where (a) phase(s) disappear(s) in reaction space correspond to singular points in phase diagrams. Two types are distinguished; singular points of indispensable and of substitutable phases. In the first case the phase disappears from the entire bundle while in the second it disappears from a single reaction. In the specific case where the substitutable phases are also the co-linear ones, two of the three co-linear phases disappear simultaneously. Two of the three reaction curves coincide.In the system including Cpx and Spl (Case B) three reactions, (Ol,Opx) (Ol,Qtz) and (Opx,Qtz), oppose three invariant points, [Ol], [Opx] and [Qtz]. Invariant points no longer move along the line 2Opx = Ol + Qtz. The coincidence of the zero contours of all three co-linear phases in reaction space-the result of the chemographic degeneracy-causes the respective singular points to coincide in the phase diagrams. This is the location where curves must be rearranged in a bundle to conform Schreinemakers’rules.The reaction Grs1Prp2= 2 Ol + An is fourth order degenerate and part of all nine subsystems (cases A and B). It can be used to relate the different phase diagrams to one another.

Notizen: Abstract We report structural and metamorphic data from a c. 25-km transect across the eastern Grenville Front Tectonic Zone (GFTZ) to the Britt domain at the northern end of Georgian Bay near Key Harbour, Ontario. Constrasting Grenvillian structural and fabric elements characterize the eastern GFTZ, northern Britt domain and a narrow Transition Zone between them.Moderately to steeply dipping foliations with strong down-dip lineations in all three divisions appear to be associated with NW-directed thrusting. In the Transition Zone and northern Britt domain, early S = L fabrics with steep lineations are overprinted by younger structures (S 〉 L) with shallow, SE-SSE-plunging lineations in which sparse, dominantly (but not exclusively) normal-sense kinematic indicators are recognized. Pressure and temperature estimates from Grenvillian metamorphic assemblages in metadi-abase indicate that conditions of P ± 12 kbar and T c 800° C were achieved before or during the thrust-related deformation, with P-T-t paths that indicate near-isothermal decompression to P c. 4 kbar and T c. 700° C. Correlation of fabric elements with points on the P-T-t paths suggests that exhumation occurred during two stages, the first associated with thrusting (≥1035 Ma) and the second with extension and thrusting (pre-1003 Ma).The GFTZ contains steeply to moderately dipping, thrust-related fabrics and lacks shallow, extensional structures; the latest episode of thrusting in the GFTZ is inferred to have taken place at 990-980 Ma. The data are interpreted in terms of a tectonic model involving two stages of propagation of the Grenville orogen towards its foreland (≥1035 Ma and ≥980 Ma), with an intervening period of extension, although the tectonic regime probably remained compressional on the scale of the orogen.

Notizen: Abstract 40Ar/39Ar data (on hornblende, muscovite and K-feldspar) are presented for samples from the western Grenville Province taken along a 140-km traverse from the Grenville Front into the Britt domain. Our interpretation is based on 28 new analyses, synthesized with 20 previously reported from the traverse area.In regions where comparisons are possible, muscovite and (large domain) K-feldspar apparent ages appear similar (at c. 920–930 Ma), but throughout the traverse, these are c. 60–70 Myr younger than the hornblende ages. The inferred cooling rate over the c. 350–500°C temperature range, c.2°C Myr-1, is appropriate for exhumation controlled by post-orogenic erosional unroofing. At the Grenville Front Tectonic Zone (GFTZ) — Britt domain boundary there is a c. 25-Myr offset in both hornblende and muscovite/K-feldspar ages. We interpret the lower ages in the Britt domain to reflect variations in crustal thickness and geothermal gradient between the flank and interior of a thick orogen.The argon data from the GFTZ are interpreted in the context of an asymmetric crustal-scale antiformal structure developed during a late episode of convergence. Hornblende from rocks on either side of the core of the antiform has an apparent age of c. 990 Ma, our estimate of the age of the compressional event. In the west, we infer that these date the short-lived thermal event associated with the development of the crustal-scale antiform previously postulated. In the east, the ages reflect the cooling of material brought toward the surface in the flank of the antiform. Hornblendes from the antiform core appear to contain excess radiogenic argon. We suggest that this was the ambient argon in rocks transported from depth that was subsequently trapped when the rocks cooled rapidly.

Notizen: Abstract Three generations of mylonites discovered in the northern Prince Charles Mountains (nPCM) are associated with episodes of crustal thickening and thinning. First-generation mylonites (MY1) are shallow thrusts which pre-date both folding and peak metamorphic conditions, and formed during early crustal thickening. Second-generation mylonites (MY2) are significant subvertical normal faults that formed at conditions of c. 5 kbar and 700° C, and throughout the nPCM consistently display NW-block uplift. It is argued that MY2 uplift was rapid in the north-west, produced exhumation of approximately 6–7 km, and caused re-equilibration of most nPCM assemblages at lower pressures. It is suggested that features of this terrane may be reconciled with a tectonic model involving simultaneous crustal thickening and lithospheric thinning; MY2 uplift may reflect isostatically induced uplift. In contrast, the adjacent east Lambert Glacier Region (eLGR) was unaffected by MY2 uplift and remained at lower crustal levels. P-T trajectories across this oblique terrane thus reflect a gradual transition in uplift rates: nPCM paths preserve mostly cooling after partial MY2 exhumation, while those in the eLGR are dominated by slower uplift which facilitated the retrograde growth of coronas and symplectites at amphibolite facies conditions. Amphibolite facies third-generation mylonites, MY3, post-date the preserved P-T segments and are low-angle normal faults which indicate consistent easterly transport across the entire terrane. It is proposed that they are related to tectonic collapse.

Notizen: Abstract Five whole-rock 40Ar/39Ar plateau ages from low-grade sectors of the Sambagawa belt (Besshi nappe complex) range between 87 and 97 Ma. Two whole-rock phyllite samples from the Mikabu greenstone belt record well-defined 40Ar/39Ar plateau ages of 96 and 98 Ma. Together these ages suggest that a high-pressure metamorphism occurred in both the Sambagawa and Mikabu belts at c. 90–100 Ma. The northern Chichibu sub-belt may consist of several distinct geochronological units because metamorphic ages increase systematically from north (c. 110 Ma) to south (c. 215 Ma). The northern Chichibu sub-belt is correlated with the Kuma nappe complex (Sambagawa belt). Two whole-rock phyllite samples from the Kurosegawa terrane display markedly older metamorphic ages than either the Sambagawa or the Chichibu belts.Accretion of Sambagawa-Chichibu protoliths began prior to the middle Jurrasic. Depositional ages decrease from middle Jurassic (Kuma-Chichibu nappe complex) to c. 100 Ma (Oboke nappe complex) toward lower tectonostratigraphic units. The ages of metamorphic culmination also decrease from upper to lower tectonostratigraphic units. The Kurosegawa belt and the geological units to the south belong to distinctly different terrances than the Sambagawa-Chichibu belts. These have been juxtaposed as a result of transcurrent faulting during the Cretaceous.

Notizen: Abstract 40Ar/39Ar data collected from hornblende, muscovite, biotite and K-feldspar constrain the P-T-t history of the Cordillera Darwin metamorphic complex, Tierra del Fuego, Chile. These data show two periods of rapid cooling, the first between c. 500 and c. 325° C at rates ≥25° C Ma-1, and the second between c. 250 and c. 200°C. For high-T cooling, 40Ar/39Ar ages are spatially disparate and depend on metamorphic grade: rocks that record deeper and hotter peak metamorphic conditions have younger 40Ar/39Ar ages. Sillimanite- and kyanite-grade rocks in the south-central part of the complex cooled latest: 40Ar/39Ar Hbl = 73–77 Ma, Ms = 67–70 Ma, Bt = 68 Ma, and oldest Kfs = 65 Ma. Thermobarometry and P-T path studies of these rocks indicate that maximum burial of 26–30 km at 575–625° C may have been followed by as much as 10 km of exhumation with heating of 25–50° C. Staurolite-grade rocks have intermediate 40Ar/39Ar ages: Hbl = 84–86 Ma, Ms = 71 Ma, Bt = 72–75 Ma, and oldest Kfs = 80 Ma. Thermobarometry on these rocks indicates maximum burial of 19–26 km at temperatures of 550–580° C. Garnet-grade rocks have the oldest ages: Ms = 72 Ma and oldest Kfs = 91 Ma; peak P-T conditions were 525–550° C and 5–7 kbar. Regional metamorphic temperatures for greenschist facies rocks south of the Beagle Channel did not exceed c. 300–325° C from 110 Ma to the present, although the rocks are only 2 km from kyanite-bearing rocks to the north.One-dimensional thermal models allow limits to be placed on exhumation rates. Assuming a stable geothermal gradient of 20–25° C km-1, the maximum exhumation rate for the St-grade rocks is c. 2.5 mm yr-1, whereas the minimum exhumation rate for the Ky + Sil-grade rocks is c. 1.0 mm yr-1. Uniform exhumation rates cannot explain the disparity in cooling histories for rocks at different grades, and so early differential exhumation is inferred to have occurred. Petrological and geochronological comparisons with other metamorphic complexes suggest that single exhumation events typically remove less than c. 20 km of overburden. This behaviour can be explained in terms of a continental deformation model in which brittle extensional faults in the upper crust are rooted to shallowly dipping ductile shear zones or regions of homogeneous thinning at mid- to deep-crustal levels. The P-T-t data from Cordillera Darwin (1) are best explained by a ‘wedge extrusion’model, in which extensional exhumation in the southern rear of the complex was coeval with thrusting in the north along the margin of the complex and into the Magallanes sedimentary basin, (2) suggest that differential exhumation occurred initially, with St-grade rocks exhuming faster than Ky + Sil-grade rocks, and (3) show variations in cooling rate through time that correlate both with local deformation events and with changes in plate motions and interactions.

Notizen: Abstract The Rand and Pelona Schists consist of eugeoclinal rock types overlain by continental basement along the Vincent-Chocolate Mountains (VCM) faults. Both schists display inverted metamorphic zonation, defined in part by a systematic variation in composition of calcic to sodic-calcic amphibole in mafic schist structurally upward. The compositional progressions include increase of total A1, A1IV and Ti, but decrease in the ratios of Na/(Na + Ca) to A1/(A1 + Si), and NaM4 to (A1VI+ Fe3++ Ti). These variations imply that structurally high rocks belong to a lower-pressure metamorphic fades series than those at depth. This result is consistent with previous views that the inverted metamorphic zonations represent intact structural sequences.Amphibole composition is dependent not only on structural position (i.e. P-T), but also upon bulk-rock composition. The important controls are whole-rock Mg/(Mg + Fe2++ Mn) and Fe3+/Fe2+. The greatest impact of these factors, however, is on the absolute values of Na and Al, rather than their ratio. Thus, interpretation of facies series is not seriously hindered by compositional variability.Sodic amphibole in epidote blueschists from the Rand Schist is extensively replaced by sodic-calcic amphibole. Sodic-calcic amphibole in the Rand Schist and Pelona Schist is, itself, rimmed by actinolitic amphibole. Similar blueschist to greenschist transitions in other metamorphic terranes are typically attributed to exhumation. In the Rand and Pelona Schists, the sequence probably formed during burial.

Notizen: Abstract 40Ar/39Ar step-heating and single-grain laser fusion ages from phengites from the polydeformed and polymetamorphosed blueschist-greenschist facies Nome Group fall into two groups. Samples from the upper part of the structural section that have experienced a relatively weak metamorphic and deformational post-blueschist facies overprint and one sample from the Cape Nome orthogneiss yield plateau ages of 116-125 Ma. More intensely overprinted samples yield hump-shaped spectra with minimum ages of 123 Ma and maximum ages of 334 Ma. Samples with hump-shaped spectra are derived from a greater structural depth than most samples with plateau ages. Unreasonably old maximum ages from some of the disturbed spectra suggest that the hump-shaped spectra result from the incorporation of excess 40Ar. This interpretation conflicts with previous interpretations of similarly disturbed spectra from the Brooks Range, which have been argued to provide minimum ages for blueschist facies metamorphism. Since the maximum temperatures achieved by all samples were probably above the blocking temperature of Ar in phengite, the 116-125 Ma plateau ages are a minimum age for blueschist facies metamorphism on the Seward Peninsula, Alaska.

Notizen: Abstract Granitic orthogneiss is widespread throughout the metamorphic core of the Brooks Range in both the ductilely deformed blueschist/greenschist facies Schist Belt and the lower grade Central Belt (= Skajit allochthon) to the north. Orthogneiss occurs as large metaplutonic massifs and in small bodies enclosed within metasedimentary rocks. Crystallization ages for the granitic protoliths range from Proterozoic through Devonian (U-Pb zircon); the K-Ar system was reset during Cretaceous metamorphism. Mineral assemblages of the orthogneisses reflect nearly complete re-equilibration during Jurassic-Cretaceous collisional orogenesis in northern Alaska. The most common metamorphic paragenesis in orthogneiss is: Qtz + Kfs + Ab + Phe + Bt ± Ep, Ttn, Rt, Ap, Chl, Cal.Constituent minerals from 16 Brooks Range orthogneiss samples were analysed with the electron microprobe. Phengite from the Schist Belt samples is highly enriched in Al-celadonite, with Si values up to 3.50 per formula unit (on an 11-oxygen basis). Central Belt samples contain phengite with lower Si content (±3.38 p.f.u.). In nearly all samples, Si content of phengite varies considerably, reflecting partial re-equilibration to lower pressure and/or higher temperature conditions. Metamorphic conditions were estimated using the Phe-Bt-Kfs-Qtz barometer and the two-feldspar solvus thermometer. The results indicate that the Schist belt underwent high-pressure/low-temperature metamorphism (generally 9-12 kbar at 375-430° C), consistent with the widespread development of glaucophane + epidote/clinozoisite and lawsonite pseudomorphs in other rock types. The Central Belt also experienced a relatively high P-T metamorphism, with most samples yielding pressure estimates in the range 5-8 kbar (at 325-415° C). These results confirm the existence of two metamorphic belts in the core of the Brooks Range that differ in metamorphic conditions by up to 5 kbar. The range in Si content in phengite from Schist Belt samples is consistent with isothermal decompression of up to 5 kbar.

Notizen: This work presents the results of a fluid inclusion study of an amphibolite-granulite facies transition in West Uusimaa, S.W. Finland. Early fluid-inclusions in the granulite facies area are characteristically carbonic (CO2), in contrast to predominantly aqueous early inclusions in the amphibolite facies area. These early inclusions can be related to peak metamorphic conditions (750-820°C and 3-5 kbar for peak granulite facies metamorphism). Relatively young CO2 inclusions with low densities (〈0.8g/cm3) indicate that the first part of the cooling history of the rocks was characterized by a near isothermal uplift.N2-CH4 inclusions, with compositions ranging between pure CH4 and pure N2 (Raman spectral analysis), were found in the whole area. They are probably syn- or even pre-early inclusions. Only nearly critical homogenizing inclusions have been found (low density). Pressure estimates, based on densities of early fluid inclusions, show that the rapid transition of amphibolite towards granulite facies metamorphism is virtually isobaric. Granulite facies metamorphism in West Uusimaa is a thermal event, probably induced by the influx of hot, CO2-bearing fluids.

Notizen: Multisystems of n+k (k 〉 3) phases are very complicated and knowledge of them has suffered as a result. The successful solution of the topological relationships in n+ 3 phase multisystems by Zen (1966, 1967) and Zen & Roseboom (1972) has aroused much interest regarding what will happen in a multisystem of more than n+ 3 phases. Since 1979, some important research results on this topic have been published. These results have expounded the substantial rules governing the appearance of phase relations in phase diagrams of n - k (k 〉 3) phase multisystems. The most significant conclusions include: (1) It is impossible to incorporate all the possible phase relations in an n+k (k 〉 3) phase multisystem in a single closed net. Therefore, it is no longer enough to use only a single closed net to depict the topological relations involved in these types of multisystems. Instead, one or more groups of closed nets, namely the complete system(s) of closed nets are necessary for this purpose. (2) A principle called the Combination Principle has been proposed and proved. It states: Any closed net of one n+k (k 〉 3) phase multisystem must be a combination of two or more distinct n+ 3 order submultisystem closed nets belonging to the given n+k phase multisystem, if it is not one of the n+ 3 order submultisystem closed nets itself. The combination principle provides both a theoretical basis and a practical method for the construction of closed nets and, hence, for the derivation of the real phase diagrams for any n+k (k 〉 3) phase multisystem. (3) A theorem on divariant-assemblage-characteristic-stability-polygons is also important to our understanding of the n+k (k± 3) phase multisystem closed nets. This theorem can be stated as follows: A divariant assemblage of an n+k (k± 3) phase multisystem will be stable in an l-polygon lacking diagonals in an appropriate set of closed-net-diagrams, and this l-polygon may be at least a triangle, and at most a k-polygon. In addition, the closed-net-diagrams of unary and binary n+ 4 phase multisystems derived respectively by Guo (1980b, 1980c, 1981a) and by Roseboom & Zen (1982) have also been summarized. The combination principle is applied to a practical petrological problem in this paper, dealing with 7 phases in the system FeO-Fe2O3-SiO2.

Notizen: Abstract The stability of quartz-chloritoid-staurolite-almandine-cordierite and aluminium silicates is used to constrain both metamorphic conditions and pressure-temperature trajectories for two localities within the 2700 Ma Archaean Yilgarn Block in Western Australia. Available experimental data are used to calculate thermodynamic data for a self-consistent set of equilibria between these minerals. A lower amphibolite facies locality from the margin of a lower strain area contains assemblages including quartz-chloritoid-staurolite-garnet-biotite with altered cordierite replacing chloritoid, quartz-staurolite-andalusite, and quartz-cordierite-andalusite-biotite. This locality was heated to 530–560°C in the andalusite field, at 4.2 kbar. A sample from a mid- to upper-amphibolite facies, highly strained locality contains relict staurolite enclosed by andalusite, in turn replaced by cordierite and muscovite with biotite and sillimanite in the matrix. The assemblage was heated isobarically from conditions near the maximum experienced by the lower grade locality of 560°C at 4.2 kbar to temperatures in excess of the andalusite-sillimanite transition but within the quartz plus muscovite stability field (600–650°C). The higher grade locality is close to a granitoid dome and sections based on gravity profiles reveal that this locality is underlain by granitoid at shallow depths. The higher grade metamorphism apparently reflects superposition of the thermal aureole on regional metamorphic conditions similar to those in the lower grade areas.

Notizen: Abstract A major system of steep Caledonian shear zones, of regional extent, has been identified in NE Scotland. The shear zones affect a wide range of lithologies, including Argyll and Southern Highland Group Dalradian, ‘Younger Basic’intrusives and their hornfelses, and also the earlier of the more acid intrusions. The observed fabrics and parageneses are consistent with low-pressure amphibolite facies metamorphism. These shear zones represent a phase of movement which occurred in the 490-465 Ma interval when ambient temperatures were still high, and it is concluded that this is the principal control on the metamorphic grade achieved within the shear zones, although local anomalies may exist.

Notizen: Abstract An experimental study of the system CaCO3–MgCO3–FeCO3 was undertaken in order to calibrate the iron correction to the calcite–dolomite geothermometer, which is based on the solubility of magnesium in calcite in the assemblage calcite + dolomite. The experiments, at 450°C and lower temperatures, resulted in products with a very small grain size and incomplete equilibration. However, application of a carefully-devised automatic data processing algorithm to analyses of the phases in experimental charges, combined with a thermodynamic analysis, results in geothermometer diagrams which should be preferred to previous theoretical predictions.

Notizen: Abstract Biotite, garnet, staurolite and kyanite isograds in pelitic metasedimentary rocks are developed as a result of thermal metamorphism around syntectonic granitoids in Eastern Rouergue (France). Temperature estimates range between 400°C and 650°C at about 6.5 kbar. Geothermobarometry shows a steep isobaric T gradient which is consistent with the interpretation that the metamorphic highs are thermal aureoles. High grade rocks show evidence of two staurolite forming reactions in the presence of plagioclase and the absence of chlorite that have not been described previously in the literature. The reaction that occurs in the middle staurolite zone, alm-rich ga + Ca-rich pla + Na-rich mu gro-rich ga + Na-rich pla + st + Na-poor mu, is considered to be prograde, whereas the reaction that occurs in the kyanite zone, alm-rich ga + Ca-rich pla + w st + Ca-rich ga + Na-rich pla + qz, is retrograde. The topology of these reactions is illustrated in terms of end member compositions for the systems KNaFASH and KCaFASH, respectively.

Notizen: During the last two decades Chlamydotis undulata (houbara bustard) has declined drastically throughout its range, due primarily to over-hunting and severe habitat degradation. The threatened extinction of local populations led the National Commission for Wildlife Conservation and Development of Saudi Arabia to implement ex- and in-situ conservation measures: (1) a captive breeding program initiated in 1986, which achieved production of a self-sustaining breeding flock as well as a surplus for reintroduction by 1992; (2) establishment of a 13,775-km2 protected area around the last known breeding population in Saudi Arabia; (3) studies of wild birds, to determine densities, feeding ecology, and habitat requirements; and (4) studies on different release techniques (adult releases, sub-adult releases, feather-cut sub-adult releases, and covey releases), carried out since 1991 within the 2,300-km2 fenced and protected area of the Mahazat as-Sayd reserve.

Notizen: The unique marine ecosystems of coral reefs express varying levels of degradation as a result of increasing anthropogenic pressures. This is the main reason why more than 200 coral reef localities were proclaimed as natural reserves or marine parks under varying legislation, rules, and monitoring and management programs. Ironically, the conventional management plans increased accessibility to many reef localities and enhanced dramatically the impact of tourism on reef habitats. Recreational activities including SCUBA and skin diving, fishing, human trampling, sediment re-suspension, and other damage caused by “innocent” visitors are causing a rapid deterioration of many reefs. Their destruction requires years and decades for full recovery. I propose to rehabilitate such damaged habitats by the alternate strategy of “gardening coral reefs” with asexual and sexual recruits. Coral branches, colony fragments, and whole small colonies (asexual recruits) and laboratory or in situ settled planula-larvae (sexual recruits) are designed to be transplanted into denuded reefs for restoration. This approach is further improved when the sexual and asexual recruits are maricultured in situ within special protected areas, before being transplanted. The use of sexual recruits ensures an increase in genetic diversity. I discuss several methodologies and results already accumulated showing the applicability of this gardening strategy for rehabilitation of denuded coral reefs. This restoration strategy should be integrated with proper management similar to that of already established reforestation in terrestrial habitats. The best candidates for employing this strategy are the fast-growing coral species, usually branching forms and species that brood their planulae larvae.

Notizen: Large areas of North American prairie have been planted with grasses introduced from Eurasia. We examined three strategies (herbicide, tilling, and nitrogen manipulation) for enhancing the establishment of seedlings of native species and suppressing the introduced grasses Agropyron cristatum (crested wheat grass) and Bromus inermis (smooth brome). Plots (5 × 15 m) were subjected to one of three levels of tilling (none, intermediate, complete) and four levels of nitrogen (none, intermediate, high, and sawdust added to immobilize nitrogen). Treatments were applied in a factorial design with twelve treatments and ten replicates. Seeds of 41 native species were drilled into the plots in May 1992. Following the failure of seeds to establish in 1992, a subplot (5 × 13 m) within each main plot was sprayed with the herbicide glyphosate in April 1993. The nitrogen treatments were repeated in Spring 1993. In August 1993, the density of native seedlings in sprayed subplots was 20 times that in unsprayed subplots. Within sprayed subplots, native seedling density and the cover of bare ground decreased significantly with increasing nitrogen availability. Plots receiving sawdust had significantly higher mean cover of bare ground and significantly lower concentrations of soil available nitrogen. Native seedling density was significantly higher in plots receiving the highest intensity of tilling. The responses of native seedlings to all these factors point to the importance of neighbor-free establishment sites as a prerequisite for prairie restoration.

Notizen: At least 43 agriculture fields were built in south Louisiana wetlands between 1900 and 1920 using pumps and levees. All but one project is now abandoned as a result of soil subsidence, financial difficulties, or multiple levee failures. Some are now in flood-protected urban zones, and the remainder are mostly open water. The total area of abandoned agricultural fields in 1990 is large (〉 80,000 ha), and their levees continue to deteriorate naturally. Ten failed or abandoned coastal agricultural impoundments (22,680 ha) were examined to determine recent wetland restoration or regression rates from 1978 to 1988. Wetland area and levee length were determined from aerial photography for 1978,1983,1985, and 1988. Average wetland change rates for all areas ranged from −4.28 to +2.54% per year from 1978 to 1988. One site gained wetland area between 1978 and 1988 (77 ha/yr), and four sites gained wetland area between 1985 and 1988 (range 14–439 ha/yr). Wetland area in the other sites either remained stable or declined during the study period. The results from a multiple regression model indicate that restoration is inversely related to impoundment size and directly related to levee reduction. Results from a multiple regression model indicate that active levee removal will probably enhance wetland restoration rates at a very favorable cost (〈 $1/ha) and will be sustainable with little additional management.

Notizen: Interest in using native grass species for restoration is increasing, yet little is known about the ecology and genetics of native grass populations or the spatial scales over which seed can be transferred and successfully grown. The purpose of this study was to investigate the genetic structure within and among populations of Elymus glaucus in order to make some preliminary recommendations for the transfer and use of this species in revegetation and restoration projects. Twenty populations from California, Oregon, and Washington were analyzed for allozyme genotype at 20 loci, and patterns of variation within and among populations were determined. Allozyme variation at the species level was high, with 80% of the loci polymorphic and an average expected heterozygosity (an index of genetic diversity) of 0.194. All but two of the populations showed some level of polymorphism. A high degree of population differentiation was found, with 54.9% of the variation at allozyme loci partitioned among populations (Fst= 0.549). A lesser degree of genetic differentiation among closely spaced subpopulations within one of the populations was also demonstrated (Fst= 0.124). Self-pollination and the patchy natural distribution of the species both likely contribute to the low level of gene flow (Nm= 0.205) that was estimated. Zones developed for the transfer of seed of commercial conifer species may be inappropriate for transfer of E. glaucus germplasm because conifer species are characterized by high levels of gene flow. Limited gene flow in E. glaucus can facilitate the divergence of populations over relatively small spatial scales. This genetic differentiation can be due to random genetic drift, localized selective pressures, or both. In order to minimize the chances of planting poorly adapted germplasm, seed of E. glaucus may need to be collected in close proximity to the proposed restoration site.

Notizen: The restoration of the high botanical diversity of the premining jarrah (Eucalyptus marginata) forest is a major priority of rehabilitation following bauxite mining in southwestern Australia. This study investigated the effects of different ripping, seeding, and scarifying dates on the establishment of plants from propagules stored in the topsoil and from applied seed on areas being rehabilitated after mining. Seed stored in the topsoil, rather than applied seed, was the major contributor to plant diversity. Ripping late (April) or scarifying in June significantly reduced the number of species and numbers of individual plants that established from propagules in the topsoil. Species originating from broadcast seed were most numerous when the seed was broadcast in April or after scarifying in June. Scarifying before seeding, particularly in June, increased the establishment of species from the broadcast seed. To make best use of the applied seed, without jeopardizing the establishment of species from the topsoil, pits should be ripped and sown by April. We list a number of strategies that can help maximize plant numbers and botanical diversity on rehabilitated bauxite mines, which may also be of more general application for restoring the original native vegetation on disturbed sites.

Notizen: Annual legumes are often used as nurse plants for restoration projects, but two commonly used legume species were competitors at all densities with Artemisia californica (California sagebrush), a dominant shrub of southern California coastal sage scrub. Survival of Artemisia was not reduced by the lowest densities of the native Lupinus succulentus (arroyo lupine) at ratios of Artemisia to Lupinus of 1:1 or 1:3 or by the exotic Trifolium hirtum (rose clover) at the 1:1 density, but its survival was as low as 4% at the highest densities of Trifolium (1:16) and 1:32). Overall, Trifolium was more detrimental to survival of Artemisia, but the biomass of Artemisia was reduced by 90% or more in mixtures with both legumes even at the lowest densities of 1:1. The total soil nitrogen either did not change or decreased in two of the mixtures between planting and harvest dates, indicating that the legumes not only did not add nitrogen to the soil within one growing season but even depleted it in these two cases. Whereas Lupinus had greater aboveground bio-mass than Trifolium, it had a lower root density than Trifolium. The Artemisia root system was more shallow than either Trifolium or Lupinus, possibly explaining the poor growth of Artemisia in mixtures, The legumes were one to two orders of magnitude greater in aboveground biomass than Artemisia at the 1:1 ratio and therefore may be inappropriate choices as nurse plants. There is no evidence from this study that either of these legumes can act as nurse plants, even at the lowest ratio of one nurse plant to on shrub. Nurse plants are probably more important in harsher environments than in coastal sage scrub.

Notizen: Over the last 150 years butterflies have declined rapidly in both distribution and abundance in Britain. The majority of species declines can be linked with widespread habitat destruction that has occurred over the same period. The resulting concern for their conservation has provided many examples of attempts at restoration, most of which have been unsuccessful. The most common reasons for failure appear to be unsuitability of the habitat or lack of knowledge of the species' requirements, but in many cases the recording of the attempt is inadequate for any assessment to be made. Case studies of recent restoration efforts for four butterfly species are used to illustrate that successful restoration depends on detailed study of the species1 ecology and–particularly–habitat requirements, the ability and the resources to manage the habitat to provide those requirements, and a formal scientific approach that maximizes the information gained from the restoration process. As more land in Britain is taken out of intensive agricultural use, opportunities will increase for restoration programs. Prominent and popular species indicative of particular habitats can act as a focus for restoration of the habitat as a whole.

Notizen: The role of tree plantations as facilitators of tropical forest restoration in degraded lands has been explored recently, but there are few data on the effect of different tree species on invasion of the plant understory. We evaluated early patterns of understory composition in three-year-old native tree plantations in lowland Costa Rica using two pure-species treatment (Jacaranda copaia and Vochysia guatemalensis) and one mixed-species treatment (J. copaia, V. guatemalensis, Stryphnodendron microstachyum, and Calophyllum brasiliense). We also monitored woody invasion in unplanted control areas dominated by grasses. The understory of the different plantation treatments differed in light environment, woody-plant growth and recruitment, and quantity and quality of woody regeneration. Forest tree invasion appeared to be enhanced under Vochysia, while shrubs were more abundant under the Jacaranda and mixed-species treatments. Woody plant growth, herbaceous cover, and understory light availability were highest under Jacaranda, intermediate under mixed species, and lowest under Vochysia. Soil-stored seeds seemed an important source for woody plant recruitment in Jacaranda and mixed species and of minimal importance under Vochysia, probably due to light suppression. It appears that competition from grasses is a major factor influencing early woody invasion in our study area. We found no woody recruitment after one year in the unplanted controls. We suggest that to promote the use of plantations as tools of forest restoration, there is a need to gather basic ecological information on how different tree species may influence patterns of plant understory colonization.

Notizen: Prescribed burns are increasingly being used in ecological restoration and vegetation management. Despite the accumulation of scientific information on fire behavior and fire effects, however, in many cases fires are prescribed without consideration of such information and often simply because of evidence of past fires. Rather than basing fire management plans on ideas of the historical “natural” occurrence of fire, we present the case for fire management being based on the fire effects desired. Effective fire management and development of proper fire prescriptions require an understanding of fire processes and heat transfer that explain fire behavior characteristics, as well as an understanding of how fire behavior is coupled to specific fire effects. We provide a basic introduction to these concepts and processes, which will help in understanding the importance of having a more technical understanding of fire. The discussion includes the processes of heat transfer and the relative role of various fuel variables in these processes, as well as the concepts of fire intensity, rate of spread, fuel consumption, duff consumption, fire frequency, and the ecological effects associated with variation in these characteristics of fire behavior.

Notizen: Restoration ecologists are increasingly aware of the potential to re-create chalk grassland on abandoned farmland. Success is often hampered by lack of desirable species in the seed bank and by poor dispersal from nearby sites. In certain schemes, the input of seed may be essential. Locally collected seed is desirable but availability is limited. We examined whether lower sowing rates than currently recommended may be successfully utilized, facilitating more-efficient use of available seed. Experimental plots on former agricultural land were sown at different rates in a randomized complete block, and the vegetation was surveyed for two years. We compared species richness and cover for chalk grassland plants and weeds - species not associated with chalk grassland communities. Values for cover and abundance were matched with data for communities of the British National Vegetation Classification (NVC). Species richness for chalk grassland plants increased with sowing rate and with time, although after two years there was no significant difference between the treatments sown at 0.4, 1.0, and 4.0 grams of seed per square meter. Weed species decreased with increasing rate and time. After two seasons, the vegetation on all treatment plots was similar to that of recognized NVC chalk grassland communities, while the controls were dominated by weeds and showed signs of developing into species-poor grassland. Higher rates rapidly eliminated weeds, but even a small inoculum of seed seemed to significantly enhance establishment of desirable plants and to reduce weed cover. We conclude that lower sowing rates would enable the desired vegetation to become established successfully, under appropriate conditions and management regimes. Lower rates allow for the re-creation of sizable areas using local seed, and they minimize damage to donor sites.

Notizen: Books reviewed in this article: Ecology of Greenways — Design and Function of Linear Conservation Areas. Daniel S. Smith and Paul Cawood Hellmund, editors Reconstruction of Fragmented Ecosystems: Global and Regional Perspectives. D. Saunders, R. Hobbs, and P. Ehrlich, editors Defining Sustainable Forests G. H. Aplet, N. Johnson, J. T. Olson, and V. A. Sample, editors

Notizen: Seed bank experiments are described to assess the species richness potential of coal slurry ponds reclaimed as wetlands (ranging from 6 to more than 40 years old). Experimental treatments test the drawdown and flooded conditions characteristic of the vegetation dynamics of emergent wetlands in the Upper Mississippi Valley. More seedlings, primarily annuals, emerged from exposed wet sediments (freely drained) than under continuous flooded sediments in cold ponds (339 versus 136 seedlings m−2, respectively) and in natural ponds (163 versus 47, respectively). More seeds were produced by plants established in freely drained conditions than under flooded conditions from sediments in the coal ponds (26546 versus 1842 seeds m−2, respectively) and the natural ponds (28430 versus 4526, respectively). Similarly, more biomass was also produced by these plants in freely drained than under flooded conditions in coal ponds (118 versus 47 g m−2, respectively) and natural ponds (118 versus 52, respectively). Fertilization (NPK) did not affect germination for the most part, but it did affect seed set and biomass production, especially for C4 annuals such as Echinochloa crusgalli and Panicum dichotomiflorum. I propose that lime (calcium carbonate) and fertilizer be applied during the first few scheduled drawdowns for these coal slurry ponds reclaimed as wetlands to increase the number of species and to allow their more rapid development as self-sustaining systems.

Notizen: Efforts to restore fish communities of the Kissimmee River will require carefully defined criteria for assessing success. A goal of regaining communities mirroring those in the historical river may not be an appropriate target because the ecological conditions of the river before channelization are poorly known. The Kissimmee River is in a biogeographic region historically low in fish diversity, and no comparable rivers in that region remain substantially unaltered by human activity to permit their use as reference sites indicative of conditions in the Kissimmee before channelization. I propose alternative criteria for assessing restoration success emphasizing expectations for ecosystem function in similar floodplain rivers. Assessing ecosystem function will be less simple than assessing criteria such as fish condition or density of selected species. But criteria based solely on fish-population characteristics cannot be justified quantitatively. Information integrated from several levels of biotic organization (individuals, populations, communities, and systems) should be drawn upon in making conclusions about restoration success. I develop a conceptual model to outline aspects of ecosystem function that could serve as a basis for evaluation of the restoration of fish communities of the Kissimmee River. The model focuses on the dynamics of the flux of floodplain-channel nutrients and the movement of larvae, juvenile, and adult fishes and macroinvertebrates. The present community may be dominated more by species tolerant of low-oxygen conditions, such as gar and bowfin, than the restored community will be. I propose that nest sites may be the limiting recruitment success of substrate spawning species in the channelized river and that these species, including sunfish and large-mouth bass, will increase in abundance after restoration. Also, species relying on floodplain habitats, including sun-fish species, darters, and some minnows, may also increase in frequency with restoration of floodplain-channel hydro-logical conditions and habitats. The observation that no species are known to have disappeared from the Kissimmee River, and its relatively simple community structure compared to rivers of comparable size elsewhere, are encouraging for prospects of successful restoration.

Notizen: Restoration of the Kissimmee River and floodplain ultimately will involve restoring 70 km of river channel and riparian zone and 11,000 ha of wetland over a period of two decades. Restoring ecosystem integrity is a crucial goal of the project, and the evaluation program is designed to assess the success of this endeavor. Major components of the riverine and floodplain ecosystem will be evaluated, guided by conceptual models of their structure and function. These studies will be referenced to historic conditions of the past and to present-day conditions in the channelized system. Enhanced connectivity and interactions between the river and floodplain, the interplay of abiotic and biotic variables, and interactions between trophic levels will restructure the channelized river and the largely drained floodplain that now exist. The key to evaluating the success of this ambitious project will be selecting measurements of the structure and function of the river and floodplain ecosystems that are responsive to this large-scale manipulation. The timing and duration of floodplain inundation, improved dissolved oxygen conditions, germination and establishment of wetland vegetation, and enhancement and expansion of rheophilic benthic invertebrate populations are critical initial elements of restoration. Further expected outcomes are an increase in the primary productivity of the ecosystem, expansion of the fish community into the reopened channels and onto the reflooded floodplain, and improved visitation and use by waterbirds in the restored regions. We highlight predictions of some of these key linkages and primary structural and functional attributes of the restored river and floodplain that should be measured.

Notizen: Beach nourishment is an engineering solution to erosion of beaches. As in any restoration project, the goals of beach nourishment are the restoration of habitat to promote survival of plants and animals and to maintain aesthetically pleasing sites for humans. Unfortunately, beach nourishment sometimes alters parameters of the natural beach, decreasing the reproductive success of sea turtles. Engineers have recognized this problem and are working to improve nourishment practices. Biologists must specify problems incurred by sea turtles as a result of beach nourishment so that they may be addressed. A review of the literature on sea turtles and beach nourishment found certain problems repeatedly identified. For nesting females, characteristics induced by nourishment can cause (1) beach compaction, which can decrease nesting success, alter nest-chamber geometry, and alter nest concealment, and (2) escarpments, which can block turtles from reaching nesting areas. For eggs and hatchlings, nourishment can decrease survivorship and affect development by altering beach characteristics such as sand compaction, gaseous environment, hydric environment, contaminant levels, nutrient availability, and thermal environment. Also, nests can be covered with excess sand if nourishment is implemented in areas with incubating eggs. The extent and implication of each problem are discussed, and future research initiatives are proposed.

Notizen: We investigated the role of artificially introduced Panicum virgatum (switch grass) on the sequential natural revegetation of 15- and 35-year-old tailings in the Adirondack region of northern New York. Switch grass covered approximately 48% of the 15-year-old Chaumont Tailings. Establishment of switch-grass stands improved the fertility of the site by adding organic matter, raising pH, and elevating cation exchange capacity and concentrations of major nutrients (N, P, and K). Switch-grass stands also aided the initial recruitment of such pioneer species as Populus spp. (aspens), Salix spp. (willows), and Betula spp. (birches). This facilitation of recruitment of woody species is explained as follows: (1) robust switch-grass stands physically captured the wind-disseminated seeds of these species; (2) switch grass acted as a “nurse crop” for these species, thus these species were able to increase their density vigorously through root or stem sprouting; (3) a combination of both. Switch grass decreased its cover (14%), however, as observed in the 35-year-old South Tailings. As switch grass declined, such vigorous “root-suckering” species as aspens increased in dominance, followed by the invasion of Prunus pensylvanica (pin cherry).

Notizen: The purpose of this study was to clarify the effect of grazing exclosures on the recovery and rehabilitation of overgrazed steppe vegetation on varying slope aspects in the Loess Plateau of northwest China. The annual precipitation in the area studied was 400–480 mm. Soil samples were taken on nine slopes in the five-year exclosure and on five slopes outside the exclosure after a vegetation survey; they were then analyzed chemically. Mean number of species recorded per 0.25 m2 was lower on the south-facing slope than all other slopes. The reverse trend was observed for aerial biomass. Species diversity estimated by information content was higher in the grazing zone than in a 3200-ha protected zone within an exclosure. From species ordination by principal component analysis, species with lower coverage in the grazing zone were Poa sphondylodes, Roegneria purpurascens, Hierochloe odorata, and Potentilla bifurca, which are all recognized as indicator species for rehabilitation efforts. In the soil surface layer, calcium contents were low, and the total contents of carbon and nitrogen were high on the north-facing slope in the exclosure. The protection by exclosure of overgrazed steppe was seen to be effective because the accumulation of soil organic matter increased and water balance improved.

Notizen: Theoretical work on population viability and extinction probabilities, empirical data from Canis lupus (gray wolf) populations, and expert opinion provide only general and conflicting conclusions about the number of wolves and the size of areas needed for conservation of wolf populations. There is no threshold population size or proven reserve design that guarantees long-term (century or more) survival for a gray wolf population. Most theoretical analyses of population viability have assumed a single, isolated population and lack of management intervention, neither of which is likely for wolves. Data on survival of actual wolf populations suggest greater resiliency than is indicated by theory. In our view, the previous theoretical treatments of population viability have not been appropriate to wolves, have contributed little to their conservation, and have created unnecessary dilemmas for wolf recovery programs by overstating the required population size. Nonetheless, viability as commonly understood may be problematic for small populations at the fringe of or outside the contiguous species range, unless they are part of a metapopulation. The capability of existing nature reserves to support viable wolf populations appears related to a variety of in situ circumstances, including size, shape and topography of the reserve; productivity, numbers, dispersion, and seasonal movement of prey; extent of poaching inside; degree of persecution outside; exposure to enzootica; attitudes of local people; and proximity to other wolf populations. We estimate that a population of 100 or more wolves and a reserve of several thousand square kilometers may be necessary to maintain a viable population in complete isolation, although 3000 km2 or even 500–1000 km2 may be adequate under favorable circumstances. In most cases, management intervention is probably necessary to assure the viability of relatively small, isolated populations. Because most reserves may be inadequate by themselves to ensure the long-term survival of wolf populations, favorable human attitudes toward the species and its management must be recognized as paramount, and cooperation of neighboring management jurisdictions will be increasingly important.

Notizen: Dieout of Ammophila breviligulata— death of the major dune-stabilizing plants — has been observed along the north and mid-Atlantic coast of the United States for the past decade and a half. Pathogenic nematodes have been identified as the probable causal agents; they can bring about a complete dieout of sand dune vegetation, with Ammophila breviligulata being the first species to die. Typically, such an area would remain barren for up to five years before plants could be successfully introduced. Applications of fertilizer and dolomitic limestone were tested in the field as a possible management strategy to alleviate the vulnerability of a denuded dune to erosion by making it possible to plant such a site earlier than usual. These applications were also tested in an area of weakened and dying plants to determine if the vegetation could be saved before complete dieout occurred. By creating soil conditions conducive to vigorous plant growth, it was hypothesized that the plants could better withstand the stress of nematode attack. The addition of N-P-K macronutrient fertilizer resulted in increased growth and spread of plants introduced into a site where the grass had been dead for only one to two years. Results indicate that application of fertilizer would be necessary only every other year at most. Micronutrient application, at the concentration used in this study, had little or a somewhat detrimental effect. The addition of dolomitic limestone increased the survival of newly introduced plants. It was also found that the application of macronutrients to a site of moribund vegetation could not only rescue the plants in that site, but could also increase their growth, vigor, and spread, thereby preventing further loss of plant cover essential to dune stabilization.

Notizen: Our objectives were to evaluate the use of microcatchments in the establishment of Leucaena retusa (little-leaf leadtree) and Atriplex canescens (four-wing saltbush) and their role in the initiation of autogenic landscape restoration processes on a shallow semiarid site. Three six-month-old seedlings of either Leucaena retusa or Atriplex canescens were planted in 1.5-m2 microcatchments. An equal number of seedlings was planted in control plots (unmodified soil surface). The water collection effects on shrub survival, standing biomass, and the natural immigration of herbaceous vegetation were determined over 42 months. Planting in microcatchment basins doubled Leucaena seedling survival and resulted in a five-fold increase in standing biomass, compared to the control, during the first growing season. There was a significant increase in soil organic matter in the microcatchment basins within 32 months. At the same time, microcatchments planted with Atriplex canescens seedlings had a ten-fold increase in seedling standing biomass compared to the control. Forty-two months after transplanting, the herbaceous standing crop was significantly greater near Atriplex canescens or in microcatchment basins than in plots with unmodified surface soil. Basins containing Atriplex produced significantly more herbaceous vegetation than basins containing Leucaena, and empty basins produced the least herbaceous vegetation of three basin treatments. These data suggest that landscape-scale procedures that concentrate scarce resources (water, organic matter, nutrients, and propagules), establish keystone species, and ameliorate microenvironmental conditions can initiate autogenic restoration of degraded semiarid ecosystems.

Notizen: Environmental Effects of Mining Earle A. Ripley, Robert E. Redmann, and Adele A. Crowder. Managing Habitats for Conservation William J. Sutherland and David A. Hill, editors. The Ecology of Woodland Creation Richard Ferris-Kuan, editor.

Notizen: This paper interprets private label marketing as a retailer instrument for overcoming the double-marginalization problem inherent in the distribution of well-known manufacturer brands. Retailers with some degree of market power carry private label substitutes for popular national brands in order to capture more profit from the vertical structures they share with brand manufacturers. The net effect of private label marketing is to improve the performance of distribution channels. After presenting a formal model and deriving analytical results, the paper gathers some empirical evidence that supports these results.

Notizen: This paper studies the hypothesis that large firms have more bargaining power with suppliers than do small firms, using data from the cable television industry. Employing techniques from the “new empirical lo,” the effect of owner size on marginal costs is inferred from the effect of owner size on observable product market choices. In the cable industry, the downstream firms decide how many subscriptions of cable to sell and how many channels to offer in the cable package. lf large firms have lower costs than small firms, then large firms should be willing to supply more than small firms, at all prices. The effects of bargaining power are identified separately from the effects of scale economies by exploiting the structure of the cable industry. Scale economies, in the cable industry, are likely to stem from regional size, while bargaining power is likely to stem from national size. By controlling for regional size, estimates of the effect of owner national size on the willingness to supply cable subscriptions and to offer channels indicate that large downstream firms offer significantly more subscriptions and channels at all prices than do small downstream firms. These results provide some of the first systematic, industry-specific, evidence consistent with the bargaining-power hypothesis.

Notizen: The role of product warranty in segmentation of consumer durable product markets is highlighted. I demonstrate that consumer moral hazard and heterogeneity in product usage create variation in the valuation of product warranties by the different segments in the market. In this context, the firm, by offering a self-selecting menu of base warranty and extended warranties, satisfies the warranty demands of the various segments of the population. The consumer choice behavior prediction of the theory with regard to extended warranty is empirically validated with data from a survey of new car buyers.

Notizen: Research on durable goods has shown that because of a time inconsistency problem, a monopolist manufacturer prefers to rent rather than sell its product. We reexamine the relative profitability of renting versus selling from a marketing perspective. In particular, using a simple linear demand formulation, we assume a durable goods monopolist has to use downstream intermediaries to market its product. In contrast to the case of an integrated monopolist, we find that when the monopolist has to rely on intermediaries, then it prefers to go through an intermediary that sells rather than one that rents its product. Similarly, the intermediary that sells the product is more profitable than the intermediary that rents the product. However, if the monopolist can commit to a set of prices, then the intermediary that rents is more profitable than the intermediary that sells.

Notizen: Empirically validating and testing the specification of game theoretic models has received limited attention in the marketing literature. The authors provide an econometric framework for estimating the parameters of response functions when the observed data in the market place are the Nash equilibrium outcomes of an underlying dynamic duopoly game specification. Specifically, the estimation procedure accounts for the joint endogeneity of market shares and marketing efforts of market rivals using a system of simultaneous equations that included the market response function and the Nash equilibrium conditions. A formal statistical test is used to detect model misspecification. The empirical analysis is carried out using data from four product markets: pharmaceutical, soft drink, beer, and detergent. Comparisons are provided with conventional estimation of the response function parameters in which the equilibrium conditions are ignored in the estimation. Managerial implications of the empirical results are discussed.

Notizen: This paper develops a theory of capital structure based on the attempts of a firm to alleviate a holdup problem that arises in its bilateral relationship with a buyer. It is shown that by issuing debt to outsiders, the firm can improve its ex post bargaining position vis-a-vis the buyer and capture a larger share of the ex post gains from trade. Debt, however, is costly because the buyer may find the required price too high and refuse to trade. Since debt raises the payoff of claimholders, it strengthens the firm's incentive to make relationship-specific investments, and therefore alleviates the well-known underinvestment problem. A comparative static analysis yields a number of testable hypotheses regarding the firm's financial strategy.

Notizen: Whether vertical integration between a downstream oligopolist and an upstream oligopolist is profitable for an integrated pair of firms is shown to depend on whether one means by this that profits increase no matter what other firms do, that all integrated firms are better off when all firms are integrated than when none are, or simply that no downstream-upstream pair of firms has an incentive to deviate from a situation where all firms are integrated. It is also shown to depend on the number of firms in each oligopoly and on the type of interaction that is assumed between firms that are integrated and firms that are not. In particular, it is shown that if no restriction is put on trade between integrated and nonintegrated firms, integrated firms may continue to purchase inputs from the nonintegrated upstream firms, with the goal of raising their downstream rivals' costs. Furthermore, even though firms are identical, asymmetric equilibria, where integrated and nonintegrated firms coexist, may actually arise as an outcome of the integration game.

Notizen: This paper considers the incentives of a firm with power in a market for one good to tie in the sale of a complementary good even though the complementary good is produced in a zero profit market. If the zero-profit price of the tied good is greater than the marginal cost (which occurs for example when the technology is characterized by a fixed cost and a constant marginal cost), a firm will fie in order to increase the sales of the complementary good, which at the margin is profitable. We show that such tying will lower the effective prices paid by customers and increase welfare. This incentive exists if the firm with market power is a monopolist or one of several competing oligopolists.

Notizen: This paper examines the effect of a middleman on the search and trading behavior of the traders. It is shown that the buyer and seller types with middle valuations choose to search for each other, while the buyer and seller types with high or low valuations drop out of the search market and choose to trade directly with the middleman. The ask and bid prices of the middleman act as an outside option for the buyer and seller, and influence the outcome of the bargaining between the two. The model generalizes Gehrig (1993) by endogenizing the traders' search intensities, by allowing the traders to go to an intermediary even if thy have engaged in search, and by enabling the intermediary to provide the service of immediacy.

Notizen: This paper discusses the supplier power of medical specialists. We argue that a combination of factors, including the structure of health care delivery, reimbursement systems, the presence of option demand, and high consumer switching costs, create circumstances in which medical specialists may be able to exercise significant seller power. We explore the implications of this for the pricing and organization of medical care.

Notizen: This paper offers an exact definition of the value created by firms together with their suppliers and buyers. The “added value” of a firm is similarly defined, and shown under certain conditions to impose an upper bound on how much value the firm can capture. The key to a firm's achieving a positive added value is the existence of asymmetries between the firm and other firms. The paper identifies four routes (“value-based” strategies) that lead to the creation of such asymmetries. Our analysis reveals the equal importance of a firm's supplier and buyer relations. Cooperative game theory provides the underpinnings of the analysis.

Notizen: The recent emergence of total quality management (TQM) in the U.S. has spawned a great deal of interest in management circles as well as in the mass media. However, despite the growing number of firms that have adopted this management technique, few formal tests exist concerning the pattern of adoption as well as the changes that accompany the adoption of TQM. This paper contrasts models of production for TQM and non-TQM firms in order to explore reasons why some firms but not others have adopted the TQM approach to quality improvement. Predictions arising from such a comparison are tested using a unique data set that combines data on firms from three different sources. Our findings tend to support the proposed theory of systematic differences between firms that find it advantageous to adopt TQM and firms that do not. We also find evidence that firms adopting TQM experience greater growth in sales, employment, and capital stock.

Notizen: Private information creates a cost of operating a hierarchy, which becomes larger as the hierarchical distance between the information source and the decision maker increases. When information about a firm's capabilities is dispersed among the individuals in the firm, production is inefficient even though everyone behaves rationally. Because hierarchies need rents in order to function, a firm with a long hierarchy may not be viable in a competitive industry.

Notizen: A dynamic model of product rivalry is developed for a market in which firms choose price and advertising intensity. The model, a state-space game, is implemented using data that consist of weekly price, sales, and promotional activity for four brands of saltine crackers sold by four chains of grocery stores in a small town. A number of questions can be asked of this data. First, is advertising predatory (merely changing market shares) or cooperative (shifting out market demand)? Second, are price and advertising own and cross-strategic complements or substitutes? And finally, do investments in stocks of goodwill and in price reductions make firms tough and aggressive or soft and accommodating?

Notizen: Why are moving sales a successful and widespread phenomenon? How can it be optimal for a seller to disclose her low valuation for the item to be sold? We propose an explanation based on the “lemons problem” in bargaining with asymmetric information about quality. Disclosing a low valuation signals that there are significant gains from trade, so that trade takes place when it wouldn't otherwise, and all agents are made better off.

Notizen: I present tests of a competitive rationale for price promotions. In a model with a population of informed and uninformed customers, price competition yields a static equilibrium in which each seller draws a price from a specified density function. Price data on coffee and saltine crackers products are used to test whether the sample of prices on each product could have possibly come from the theoretically specified density function. The results suggest that some markets are indeed consistent with the marginal distributions of prices predicted by the model. Furthermore, in the process of testing this rationale for price promotions, estimates are obtained for the marginal cost of each product, the number of competing goods, and the percentage of informed consumers. The resulting excess variability of these estimates across competing brands can also raise questions with respect to the empirical validity of the model.

Notizen: It is common in catastrophic food-contamination events that consumers fail to adjust instantaneously to a normal consumption level. One explanation is that consumers only gradually accept new positive information as being trustworthy. The gradual establishment of the trustworthiness of the released information depends on both positive and negative media coverage over time. We examine the individual “trust” effects by extending the prospective reference theory (Viscusi, 1989) to include a dynamic adjustment process of risk perception. Conditions that allow aggregation of changes in risk perceptions across individuals are described. The proposed model describes a general updating process of risk perceptions to media coverage and can be applied to explain the temporal impact of media coverage on consumption of a broad range of goods (food or nonfood). A case study of milk contamination is conducted to demonstrate consumer demand adjustment process to a temporarily unfavorable shock. The results suggest that effects of positive and negative information to adjustment of consumption and risk perception are asymmetric over time.

Notizen: The scaling of administered doses to achieve equal degrees of toxic effect in different species has been relatively poorly examined for noncancer toxicity, either empirically or theoretically. We investigate empirical patterns in the correspondence of single oral dose LD, values across several mammalian species for a large number of chemicals based on data reported in the RTECSQ database maintained by the National Institute for Occupational Safety and Health. We find a good correspondence of LD, values across species when the dose levels are expressed in terms of mgadministered per kg of body mass. Our findings contrast with earlier analyses that support scaling doses by the 3/4-power of body mass to achieve equal subacute toxicity of antineoplastic agents. We suggest that, especially for severe toxicity, single- and repeated-dosing regimes may have different cross-species scaling properties, as they may depend on standing levels of defenses and rate of regeneration of defenses, respectively.