ALBERT

Notizen: Books reviewed in this article: Biotic Interactions and Global Change P. M. Kareiva, J. G., Kingsolver, and R. B. Huey, editors Defining Sustainable Forests G.H. Aplet, N. Johnson, J. T. Olson, and V. A. Sample, editors

Notizen: Despite this nation's massive effort during the past 90 years to build levees throughout the upper Mississippi Basin, mean annual flood damage in the region has increased 140% during that time. These levees exacerbate the flood damage problem by increasing river stage and velocity. Thus, rather than continuing to rely on structural solutions for flood control, it is time to develop a comprehensive flood management strategy that includes using wetlands to intercept and hold precipitation where it falls and store flood waters where they occur. History testifies to the truth of this premise: it was the rampant drainage of wetlands in the nineteenth century that gave rise to many of today's water resources management problems. The 1993 flood verifies the need for additional wetlands: the amount of excess water that passed St. Louis during the 1993 flood would have covered a little more than 13 million acres —half of the wetland acreage drained since 1780 in the upper Mississippi Basin. By strategically placing at least 13 million acres of wetlands on hydric soils in the basin, we can solve the basin's flooding problems in an ecologically sound manner.

Notizen: We consider the general problem of price discrimination with nonlinear pricing in an oligopoly setting where firms are spatially differentiated. We characterize the nature of optimal pricing schedules, which in turn depends importantly upon the type of private information the customer possesses–either horizontal uncertainty regarding brand preference or vertical uncertainty regarding quality preference. We show that as competition increases, the resulting quality distortions decrease, as well as price and quality dispersions. Additionally, we indicate conditions under which price discrimination may raise social welfare by increasing consumer surplus through encouraging greater entry.

Notizen: We model an internal labor market in which employee behavior and compensation are affected by the firm's financial position and the threat of hostile takeover or other exercise of shareholder “voice.” We show how good past performance can result in excessively generous promotion and pay decisions. While the threat of shareholder activism will remove this “slack,” activists optimally face a positive cost barrier, which in turn varies across firms. The cost barrier is higher when cooperation or “helping” between employees is more important, and is lower when employees receive efficiency wages due to an inability to “pay” for their jobs. Since the importance of helping is associated with pay compression and “flat” pay ladders, such firms should also exhibit a greater degree of management entrenchment.

Notizen: The literature on the incentives for R & D cooperation with spillovers typically deals only with the factors affecting cooperative profits. This paper focuses on the incentives to cheat and the stability of such cooperative agreements in a repeated game framework. It is shown that the stability of cooperation is influenced by the nature and magnitude of spillovers, relative to the nature and degree of product market competition. While cooperative profits are higher with large positive (exogenous, unintended) know-how spillovers, such as in fundamental research, our anslysis shows that it may be easier to sustain cooperation in areas with lower spillovers, such as applied research, because of the smaller incenfives to cheat on the initial agreement, at least when firms produce substitutes. Alternatively, the possibility of technology sharing (i.e., intended or endogenous spillovers), besides R&D coordination, not only increases cooperative profits but also reduces the incentives to defect from a cooperative equilibrium.

Notizen: In a moral hazard setting, we model the fact that the agent may get private signals about the final outcome of his effort before the public realization of this outcome. Actions affect both the distribution of the outcome and the quality of the agent's private information. We compare simple contracts, based on output only, with revelation contracts, based on output and messages about signals. Revelation contracts give the agent some discretionary power during the course of the relationship; they are optimal if and only if lowering effort does not increase the quality of private information in the sense of Blackwell (1953). In the context of managerial compensation schemes, the revelation contracts we analyze can be viewed as allowing the agent to exercise an option on the final profits before the realization of these profits. The theory thus provides an alternative justification of the widespread use of stock options in managerial compensation schemes, as opposed to compensation schemes that rely only on salary, bonus, and (restricted) stock plans.

Notizen: Analysis of seven wholesale and retail markets for long-distance telephone services since the AT & T divestiture indicates that service provider concentration declined in the later 1980s and then stabilized in the 2990–1993 period. In addition to this stability in market shares, a number of other conditions established since 1990 have been conducive to the development of market sharing rather than significant price competition. The most important of these conditions has been the tarifing process of the Federal Communications Commission by which MCI and Sprint replicate ATGT's price announcements. As market shares stabilized and became more equal, and as regulation formalized the price-setting process, the price-cost margins of the three large carriers increased and became more nearly identical. These results are consistent not with price competition but rather with emerging tacit collusion among AT&T, MCI, and Sprint.

Notizen: The Federal Communications Commission held its first auction of radio spectrum at the Nationwide Narrowband PCS Auction in July 1994. The simultaneous multiple-round auction, which lasted five days, was an ascending bid auction in which all licenses were offered simultaneously. This paper describes the auction rules and how bidders prepared for the auction. The full history of bidding is presented. Several questions for auction theory are discussed. In the end, the government collected $617 million for ten licenses. The auction was viewed by all as a huge success an excellent example of bringing economic theory to bear on practical problems of allocating scarce resources.

Notizen: This study examines the investment patterns of all large local exchange telephone companies in the United States over time. It identifies how different regulatoy environments have influenced the recent historical pattern of investment in modern infrastructure equipment. It focuses exclusively on the postdivestiture experience of local telephone exchange companies (LECs). It examines the growth of fiber-optic deployment and of complementary equipment associated with the modernization of today's information infrastructure. The study estimates the influence of different regulatory structures on infrastructure deployment by LECs. The study is unique in that if relates individual LEC investment patterns to LEC-specific regulatory, demographic, and economic characteristics. Thus, it isolates the contribution of state regulatory policies from that of other demographic and economic factors in the determination of infrastructure deployment at the state LEC rather than at the corporate level. Its main findings are as follows: First, price regulation (and, in particular, price caps) is a more potent regulatory mechanism than the standard earnings sharing scheme. Second, when associated with an earnings sharing scheme, price regulation is less effective in triggering infrastructure deployment than when it is implemented by itself. These results raise questions about the effectiveness of a popular regulatory instrument-earnings sharing schemes-and highlight the effectiveness of generic price-cap regulation. These results have implications for the design of regulatory policy at both the state and federal levels. In particular, given the importance currently being placed on the development of the information superhighway, regulatory emphasis should be focused more on price regulation than on regulating profits.

Notizen: The House and Senate of the United States Congress recently passed legislation that directs the FCC to establish a system for using auctions to allocate the use of radio spectrum for personal communications services. There is a unique and unprecedented set of issues that arise in this context, which are of interest to economists, industry analysts, regulators, and policymakers. We discuss these issues and evaluate their likely impact on the outcome of the spectrum auctions. In addition, we argue that there may be pitfalls in the auction procedure adopted by the FCC, and we discuss possible alternative procedures.

Notizen: Royalty payments from a franchisee to a franchisor serve as incentive for the franchisor to provide appropriate levels of quality and brand, name investment. However, since they also distort the service provided by the franchisee, we should expect relatively lower royalty rates in franchises that are primarily service-oriented. Casual examination of royalty rates across product-oriented and service-oriented franchises shows that the opposite is true, with service-type franchises enjoying higher royalty rates. We resolve this apparent puzzle. The basic argument we put forth is that in product-type franchises, a franchisor can charge a wholesale price on goods transferred to the franchisee, thus using an alternative instrument that also serves as an incentive for the franchisor. Moreover, in general, a franchisor will use both wholesale price and royalty to minimize distortions in retail price and service at the retail level. We then test the predictions of our model on different industries and find confirmation for the same.

Notizen: This paper reviews the events leading to the channelization of the Kissimmee River, the physical, hydrologic, and biological effects of channelization, and the restoration movement. Between 1962 and 1971, in order to provide flood control for central and southern Florida, the 166 km-long meandering Kissimmee River was transformed into a 90 km-long, 10 meter-deep, 100 meter-wide canal. Channelization and transformation of the Kissimmee River system into a series of impoundments resulted in the loss of 12,000–14,000 ha of wetland habitat, eliminated historic water level fluctuations, and greatly modified flow characteristics. As a result, the biological communities of the river and floodplain system (vegetation, invertebrate, fish, wading bird, and waterfowl) were severely damaged. Following completion of the canal, the U.S. Geological Survey released a report documenting the environmental concerns associated with channelization of the river. This action led to the 1971 Governor's Conference on Water Management in South Florida that produced a consensus to request that steps be taken to restore the fish and wildlife resources and habitat of the Kissimmee basin. In 1976, the Florida Legislature passed the Kissimmee River Restoration Act. As a result, three major restoration and planning studies (first federal feasibility study [1978–1985], the Pool B Demonstration Project [1984–1990], and the second federal feasibility study [1990-present] were initiated (1) to evaluate measures and provide recommendations for restoring flood-plain wetlands and improving water quality within the Kissimmee basin, (2) to assess the feasibility of the recommended dechannelization plan, and (3) to evaluate implementation of the dechannelization plan. The recommended plan calls for the backfilling of over 35 km of C-38, recarving of 14 km of river channel, and removal of two water-control structures and associated levees. Restoration of the Kissimmee River ecosystem will result in the reestablishment of 104 km2 of river-floodplain ecosystem, including 70 km of river channel and 11,000 ha of wetland habitat, which is expected to benefit over 320 species of fish and wildlife.

Notizen: Two groups of waterbirds have been chosen to assist in measuring the success of restoration of the traditional channel configuration, hydrologic regimes, and floodplain wetlands of the Kissimmee River: waterfowl (Anseriformes) and waders (Ciconiiformes). Waterfowl are dominant, swimming omnivores that use seeds, foliage, and invertebrates; waders are mainly walking predators that eat fish of various sizes. Both can be censused by well-established air and ground techniques, and both can be used to compare post-restoration with channelized or pre-channelization population data (waterfowl) or bird use of channelized versus restored wetlands (waders). In addition to use of population data, species richness and regularity of occurrence should provide a basis for assessing restoration of biological integrity. Conceptual models of avian habitat use for nesting and feeding demonstrate patterns of segregation that will aid assessments for some species. Other species show high overlap in foods and habitats and will require additional measures of response. To understand these patterns and reasons underlying waterbird use, measurements of habitat type, vegetation structure, and food resources will be essential. Integration of these high trophic-level guilds with evaluations of other system components will ensure an ecosystem perspective. Predicted responses to restoration suggest an increase in species richness and number of individuals of many species.

Notizen: Survival and height growth of tree seedlings and rooted cuttings introduced into artificially shaded and unshaded plots in a degraded dry forest were measured at intervals for nine months. Ten tree species were selected to represent a range of ecological characteristics of the dry–forest plant community on St. John, U.S. Virgin Islands. Of three propagule types – seeds, seedlings, and rooted cuttings – introduced to field plots, seedlings survived best (52%) over the initial nine-month period. Cuttings of six species rooted successfully in a shadehouse, but only two of these species survived the nine–month field experiment. Seed germination was low, under 11% for eight of ten species tested, and four species did not germinate. Subsequent mortality of seedling recruits was moderately high. Plumeria alba was the only species for which seedling height growth was not significantly greater than cutting height growth. Shading treatment (25% of full sun) significantly increased seedling survivorship (p= 0.03) but suppressed growth slightly for some species. Shading enhanced survival of seedlings produced from broadcast seeds, but not seed germination. Mortality occurred during dry periods, apparently from drought stress. Results suggest (1) that seedling introductions are the preferred propagule type (over seeding or rooted cuttings) for ecological restoration of degraded tropical dry forests, and (2) that some level of shading is required to increase the survivorship of many dry-forest species or to avert complete mortality of some species. This study suggests that early secondary dry forest may be best restored by underplanting within the existing vegetation. Sufficient shading suitable for growth of native dry-forest trees may be attained using a nurse crop of fast-growing leguminous trees.

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 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: 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: 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: 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: Native grasses may be used for multiple, sometimes conflicting, goals in revegetation projects. Woody plants are frequently desired for moose browse and timber in Alaska, but naturally occurring Calamagrostis canadensis (bluejoint reedgrass) hinders the establishment of these desired species. Seven grass cultivars of Alaskan origin were evaluated for their ability (1) to stabilize the soil, (2) to reduce regeneration of C. canadensis, (3) to allow openings for natural colonization, and (4) to permit establishment of desirable rooted cuttings. Cultivars tested are “Arctared” Festuca rubra (red fescue), “Alyeska”Arctagrostis latifolia (polar-grass), “Nugget”Poa pratensis (bluegrass) “Norcoast”Deschampsia beringensis (Bering hairgrass), “Nortran”Deschampsia caespitosa (tufted hairgrass), “Gruening” Poa alpina (alpine bluegrass), and “Sourdough” Calamagrostis canadensis. These were tested as single species and in multi-species mixtures, with two seeding rates of the multi-species mixture (0.5, 0.25 seeds/cm2). Experimental plots included unfertilized, unfertilized with rooted Salicaceae cuttings, and fertilized (350 kg/ha 20:20:10). A control plot was not seeded. After three growing seasons, Nortran D. caespitosa and Arctared F. rubra were the most successful cultivars. They provided 87% to 98% of the seeded-species cover for soil stabilization and suppressed C. canadensis on the fertilized subplots without reducing species diversity. Gruening Poa alpina was less than 3 cm tall, and it helped stabilize the site without interfering with woody plant establishment. Although cuttings were shorter under some seed treatments compared to the nonseeded control, heights of cuttings were not related to cover of seeded cultivars (r = 0.09, p 〉 0.55) but were positively correlated with total vascular plant cover (r= 0.61, p 〈 0.001).

Notizen: Throughout tropical moist climates, Dicranopteris linearis fernlands can develop as a result of rain forest clearance followed by frequent burning. In Sri Lanka, D. linearis fern-lands are capable of suppressing the regeneration of rain forest. Field experiments were conducted at Sinharaja Man and Biosphere Reserve, a rain forest where fernlands occupy substantial areas of the reserve boundary. The experiment's objective was to identify methods for initiating forest regeneration in fernlands dominated by D. linearis Three disturbance treatments were used to initiate seedling regeneration: clean weed, root removal, and till. We hypothesized that increasing the severity of the soil disturbance would establish vegetation with higher species richness and diversity, greater above-ground dry biomass, and higher percentage cover and seedling density. Results indicate only partial support for this hypothesis. Dry biomass was greatest in till treatments, the most severe soil disturbance. By comparison, species richness and diversity, seedling density, and percentage cover were greatest in root-removal treatments, though in many instances the differences were not significant. The study clearly demonstrated that any kind of soil disturbance can facilitate the establishment of herbs, shrubs, and trees in a fernland dominated by D. linearis. Results showed that herbs, sedges, grasses, and pioneer shrubs represented greater proportions of seedling recruits than did pioneer trees. Seedlings of primary-forest tree species were nearly nonexistent. In general, results showed that soil disturbance can play an important role in site preparation for the purpose of initiating non-fern vegetation in fernlands dominated by D. linearis.

Notizen: The effect of a pipeline corridor constructed through an ecological reserve in Southern California was investigated by assessing plant species composition and soil chemistry. A homogeneous plant community comprised primarily of exotic annuals was found along the entire length of the corridor. This community has low similarity to the adjacent native plant communities. Soil organic matter was significantly less on the disturbed corridor than in contiguous undisturbed areas. Both available nitrogen and extractable phosphorus values were greater in the disturbed corridor. By contrast, total nitrogen was significantly higher outside the pipeline. The more labile litter of the exotic annuals allows increased mineralization along the corridor than does the more recalcitrant litter of the native perennial shrubs in the undisturbed areas. Once established, the weedy exotic annual litter may completely turn over organic matter and nitrogen, favoring the persistence of the weedy annuals. These exotic annuals appear to be moving into three of the native communities - grassland, coastal sage, and oak woodland - that have less organic matter and a more open plant canopy. Poor restoration efforts can lead to the establishment of such exotics, subsequent invasion into the surrounding undisturbed habitat, and degradation of the reserve.

Notizen: A critical element of the ongoing effort to restore the ecological integrity of Florida's Kissimmee River ecosystem is the reestablishment of pre-channelization habitat structure and function. Restoration of habitat will form the basis for responses by most biological components of the ecosystem and will provide a key indicator of the success of the restoration effort. This paper evaluates the relative importance of a range of abiotic and biotic habitat parameters in the existing and historic Kissimmee River ecosystem and provides a conceptual framework for predicting expected spatial and temporal responses of river and floodplain habitats to the restoration project. Among the ecological factors and process that influenced the development, dynamics, and maintenance of river and floodplain habitat structure, hydrology is expected to be of central importance in eliciting restoration responses in the Kissimmee River Ecosystem. Based on the assumption that the restoration plan will reestablish historic hydrologic characteristics, predictions are made of expected responses by geomorphic and vegetative components of the Kissimmee River's habitat structure. Recommendations are made regarding key habitat parameters requiring long term tracking and analysis and utilization of a geographic information system(GIS). A hierarchical habitat classification scheme is provided as a foundation for all components of the restoration evaluation program.

Notizen: When the Kissimmee River was channelized in the 1960s and 1970s and placed under stage-fluctuation management, the dynamic interactions between the river and the flood-plain were essentially removed. Correspondingly, aquatic invertebrate life in the river and floodplain ecosystem shifted from a riverine to a more lacustrine fauna. A relinkage of the Kissimmee River with the floodplain following restoration will result in numerous changes to such ecologically important factors as streamflow, substrate composition, food quality and quantity, and water quality, all of which will influence invertebrate communities. These factors and their function in the ecosystem as the fauna shifts from predominantly lacustrine back to riverine are presented in a conceptual model. As an integral component of all aquatic ecosystems and a key link between primary producers and higher trophic levels, aquatic invertebrates are a valuable group with which to evaluate the recovery of the Kissimmee River. Utilization of a geographic information system mapping approach linking expected increased habitat heterogeneity and invertebrate richness with restoration efforts is suggested as an economical means of monitoring recovery of the Kissimmee River ecosystem.

Notizen: Despite the critical role insects play in ecosystem functioning, there has been little study of factors affecting their reestablishment in restored ecosystems. The goals of this research were to quantify the nectar resources provided by reclaimed coal surface mines and to examine the role nectar resources play in determining butterfly community composition on these sites. Adult butterfly communities and nectar resources were sampled on 18 reclaimed coal surface-mined sites and five unmined hardwood sites in southwestern Virginia. Recently, reclaimed sites provided an average of 300 times the nectar abundance of the surrounding hardwoods, and nectar abundance and species richness decreased with time since reclamation. Total nectar abundance was highly correlated with total butterfly abundance and species richness for the entire flight season; these variables were also significantly correlated among sites during most of the 12 sampling periods during the flight season. In only a few cases, however, were butterfly and nectar abundance and species richness significantly correlated within individual sites during the flight season. These results suggest that, although adults of many butterfly species move in response to nectar availability, nectar resources are not sufficiently limiting that their life histories have evolved to maximize nectar resources temporally. While planting species in restored areas that provide abundant nectar will likely attract adult butterflies, this is only one of a number of habitat variables that must be considered in efforts to restore butterfly populations. Finally, adult butterflies appear to have limited utility as indicators of revegetation success.

Notizen: The restoration of the northern jarrah (Eucalyptus marginata) forest after bauxite mining is a major objective of Alcoa of Australia Limited. The typically variable and sometimes low emergence of broadcast seed of jarrah-forest plant species may relate to microclimatic changes associated with mining disturbance. This study examined the effect of the presence and absence of a canopy and topographic position in the post-mining landscape on the emergence of four canopy species (E. marginata, E. calophylla, E. patens, and E. diversicolor) and related these patterns to detailed measures of surface soil temperature and moisture. The absence of a canopy in the restoration appeared to result in adverse microclimatic conditions for the successful early establishment of E. marginata and E. calophylla from seed, particularly in the low topographic regions of the restoration. Emergence beneath a canopy compared to that in the open was 17% and 6%, respectively, for E. marginata and 23% and 2%, respectively, for E. calophylla. For both species, emergence was also greater at upland than at lowland open restoration sites (9% and 3%, respectively, for E. marginata; 4% and 0.3%, respectively, for E. calophylla). In contrast, canopy removal and position on the topographic landscape did not reduce the early establishment success of E. patens and E. diversicolor. Field measurements revealed that soils were drier and that diurnal temperature fluctuations were wider in the open restoration sites than beneath a canopy. Furthermore, cold conditions were more frequent at lowland than at upland restoration sites, suggesting the occurrence of cold-air drainage to Jew-lying areas. It is therefore possible that the field emergence patterns reflected the lower tolerance of E. marginata and E. calophylla than both E. diversicolor and E. patens to cold and dry surface-soil conditions. The ecological significance and practical implications of the results are discussed.

Notizen: River and stream restoration projects are increasingly numerous but rarely subjected to systematic post-project evaluation. The few such evaluation studies conducted have indicated a high percentage of failures. Thus, post-project evaluation (and dissemination of results) is essential if the field of river restoration is to advance. Effective evaluation of project success should include: (1) Clear objectives, essential to identity potential incompatibilities among project objectives and to provide a framework for design of project evaluation. (2) Baseline data, needed as an objective basis for evaluating change caused by the project and encompassing as long a pre-project period as possible (including a detailed historical study). (3) Good study design, to demonstrate the effects of restoration projects in the complex riverine environment. (4) Commitment to the long term, to detect effects evident only years following project completion; in general, monitoring should continue for at least a decade, with surveys conducted after each flood above a predetermined threshold. (5) Willingness to acknowledge failures, or rather to recognize that each restoration project constitutes an experiment, so that a failure can be just as valuable to the science as a success, provided we can learn from it (which requires objective, robust post-project evaluation).

Notizen: Festuca idahoensis (Idaho fescue) was a common native perennial bunchgrass in the sagebrush steppe of the western United States until the introductions of domestic livestock and alien plants. Restoration of Idaho fescue to degraded sites will likely involve reseeding, and one of the factors affecting reseeding success is germinability of the seeds employed. We investigated effects of after-ripening and storage temperature on germinability of Idaho fescue seeds collected from a central Oregon site. Six months of after-ripening were required before maximum germination was obtained. Storage of dry seeds at either room temperature (20°C) or at cooler, alternating temperatures (5/15°C) did not alter the rate at which dormancy was lost. Storage at the warmer temperature promoted rapid germination in seeds that had broken dormancy. Seed longevity varied greatly from year to year. Seeds produced in a very dry year had poorer germination and shorter longevity than seeds produced during a year with near normal precipitation. Because seed dispersal occurs in late July and early August for Idaho fescue in central Oregon, a six-month after-ripening requirement ensures that the greatest potential germination coincides with the spring period most likely to provide sufficient moisture for seedling establishment.

Notizen: We conducted an experiment with the dual aims of (1) examining the feasibility of establishing a species-rich grassland using a commercially available grass and wild-flower seed mixture and (2) examining the effects of different defoliation and fertilizer managements on the productivity, species richness, diversity, and composition of a species-rich grassland established on a site reclaimed after opencast coal mining. The use of the seed mixture successfully established a sward of some 18–25 species per square meter. The species composition was enriched to some extent by recruitment of unsown species, principally from the soil seed bank. Hay-type defoliation management produced greater dry matter yield and species richness than grazing defoliation, but grazing defoliation produced greater species diversity. Fertilizer application had no significant effect on dry matter production but reduced species diversity. Ordination analysis revealed that both defoliation and fertilizer management significantly affected species composition. The response obtained by individual species was explicable largely by their comparative biology.

Notizen: Books reviewed in this article: World Soil Erosion and Conservation. D. Pimentel, editor Environmental Impacts of Mining: Monitoring, Restoration and Control. M. Sengupta

Notizen: We investigate why different states in the United States choose different regulatory plans in their telecommunications industry. We present a simple theoretical model and an empirical analysis of the issue. We find that a state is more likely to replace rate-of-return regulation with incentive regulation when: (1) residential basic local service rates have historically been relatively high; (2) allowed earnings under rate-of-return regulation in the state have been either particularly high or particularly low; (3) the state's leaders tend to come from both major political parties, rather than from a single party; (4) the state's urban population is growing relatively rapidly; and (5) the bypass activity of competitors in the state is less pronounced.

Notizen: After the initial breakthrough in the research phase of R&D, a new product undergoes a process of change, improvement, and adaptation to market conditions. We model the strategic behavior of firms in this development phase. We emphasize that a key dimension to this competition is the innovation that leads to product differentiation and quality improvement. In a duopoly model with a single adoption choice, we derive endogenously the level and diversity of product innovations. We demonstrate the existence of equilibria in which one firm enters early with a low-quality product while the other continues to develop the technology and eventually markets a high-quality good. In such an equilibrium, no monopoly rent is dissipated and the later innovator makes more profits. Incumbent firms may well be the early innovators, contrary to the predictions of the “incumbency inertia” hypothesis.

Notizen: This paper addresses the strategic commitment value of various price and nonprice vertical contracts. Assuming contract offers are sufficiently public to have strategic importance, we focus on commitment as a necessary and separable condition to be met. The analysis has two components. First, considering the relationship between a monopolist manufacturer and his imperfectly competing retailers, enforcement conditions necessary for alternative vertical contracts to have commitment value are identified in the static (reputation-free) context. It is shown that external help (i.e., enforcement by nonsignatories) is necessary for bilateral minimum resale price maintenance (price floors) and exclusive territory contracts to have commitment value, whereas maximum resale price maintenance (price ceilings) do not require such help (i.e., they are internally enforcing). Second, the paper provides an analysis of the U.S. case law and discusses the empirical validity of the “external enforcement” assumption that is shown to underlie recent proposals to make certain vertical restraints illegal.

Notizen: . Experimental evidence has been gathered to show that the life cycle of the myxozoan gallbladder parasite Zschokkella nova Klokacewa, 1914, which infects the fish Carassius carassius, has a complex life cycle with alternation of two hosts (fish and Oligochaeta) and two developmental phases (myxosporean and actinosporean). The gut epithelium of the oligochaete, Tubifex tubifex, exposed experimentally to Z. nova, obtained from C. carassius, became infected with organisms resembling Actinosporea. The spore structure and cube-like network of the interconnected spores is reminiscent of Siedleckiella silesica Janiszewska, 1952, although the spores are very different in size and number of sporoplasm nuclei. The life cycle of Z. nova resembles that of the whirling disease agent Myxosoma cerebralis described by Wolf and Markiw, which also alternates between fish and oligochaete hosts.

Notizen: . Organisms in the phylum Apicomplexa appear to have a large extrachromosomal DNA which is unrelated to the mitochondrial DNA. Based on the apparent gene content of the large (35 kb) extrachromosomal DNA of Plasmodium falciparum, it has been suggested that it is a plastid-like DNA, which may be related to the plastid DNA of rhodophytes. However, phylogenetic analyses have been inconclusive. It has been suggested that this is due to the unusually high A + T content of the Plasmodium falciparum large extrachromosomal DNA. To further investigate the evolution of the apicomplexan large extrachromosomal DNA, the DNA sequence of the organellar ribosomal RNA gene from Toxoplasma gondii, was determined. The Toxoplasma gondii rDNA sequence was most similar to the large extrachromosomal rDNA of Plasmodium falciparum, but was much less A + T rich. Phylogenetic analyses were carried out using the LogDet transformation to minimize the impact of nucleotide bias. These studies support the evolutionary relatedness of the Toxoplasma gondii rDNA with the large extrachromosomal rDNA of Plasmodium falciparum and with the organellar rDNA of another parasite in the phylum Apicomplexa, Babesia bovis. These analyses also suggest that the apicomplexan large extra-chromosomal DNA may be more closely related to the plastid DNA of euglenoids than to those of rhodophytes.

Notizen: . Seabottom sediments from a discontinued Philadelphia-Camden 40-Mile ocean sewage disposal site were cultured for cyst-forming free-living amoebae. Barge delivered wastes were discharged at the site from 1973 until 1980 when the site was closed. One station at the southeast margin of the site was sampled at a depth of approximately 50 m, twice in 1978 and once in 1982, 1983 and 1984. Sediment from the 1978 collection yielded Acanthamoeba polyphaga, Vahlkampfia sp., and an unknown amoeba with stellate endocysts similar to those of A. astronyxis. Trophozoites and cysts of the isolate were typical of those described for the genus Acanthamoeba. Biochemical tests employing enzyme electrophoresis and morphological studies on live and stained specimens showed that the isolate was distinct from other well-described species within the family Acanthamoebidae Sawyer & Griffin, 1975.

Notizen: . Alexandrium tamarense (Lebour) Balech (=Gonyaulax tamarensis Lebour) has been widely distributed and occasionally abundant in coastal waters of Long Island, New York in recent years. However, the distribution on the New Jersey coast has been sparse and this fact cannot be explained by this dinoflagellate's ability to migrate, or by its nutritional and physiological characteristics, or by the region's general suitability for phytoplankton. Therefore, the possibility that New Jersey coastal waters might be chemically exclusionary for A. tamarense seemed worth exploring. In a limited approach, we tested for water quality detrimental to the species in one New Jersey site (Great Bay) with a series of annual assays. Parsonage Creek, Long Island, New York, was assayed for comparison; this creek is assumed to have had at least marginal suitablity for A. tamarense, based on its reported long-term presence. Results provide tentative support for our working hypothesis, i.e. Great Bay chemical water quality is generally unfavorable for A. tamarense. Inhibition of A. tamarense growth, or culture decline, occurred in both assay series, but was substantially greater in Great Bay water. Inimical water quality was the most important factor distinguishing the two sites. Chelation with EDTA had greatest overall benefit in Great Bay assays, suggesting that lower availability of a natural chelator in the bay could be a secondary factor. Assay metal response is problematic, but we believe it permits speculation that essential metals could be partially limiting to A. tamarense in Great Bay, but would not be a critical regulator.

Notizen: . Experimental transmission of two bacterial endosymbionts to symbiont-free isolates of Acanthamoeba spp. was studied to determine specificity of the host-symbiont relationship. Both symbionts originated from amoebic isolates displaying an identical mitochondrial DNA EcoRI fingerprint (group AcUW II). Symbioses were readily established in one amoebic isolate which displayed a homologous mtDNA fingerprint (group AcUW II). Exposure of a heterologous amoebic isolate (group AcUW IV) to the two symbionts resulted in either cell death or encystation without the establishment of symbioses. While symbioses were established with an amoebic isolate from a second heterologous group (AcUW I), a unique membranous sheath appeared and persisted around one of the symbionts which did not exist in the original host. An isolate representing a third heterologous amoebic group (AcUW VI) was variable in its susceptibility with one symbiont unable to infect the host and the other becoming established only after an initial reaction in which trophozoites rounded-up and floated off the substrate. These studies suggest that a specific recognition system exists between particular isolates of Acanthamoeba and their symbionts, and that the appearance of a killer phenotype is related to contact between mismatched, though recognized, pairs.

Notizen: . Microsporidian spores were developed from cells which were grown in vitro from a human liver lesion which was due to larval Echinococcus multilocularis. The microsporidian spores developed in the same fashion as an Encephalitozoon cuniculi. The Encephalitozoon-like spores were completely separated on Percoll gradients. The separated spores contained DNA capable of amplification by two different primer sets designed for the polymerase chain reaction (PCR) of E. multilocularis DNA. However, the cell DNA from which microsporidium developed was thoroughly insensitive to the PCR using the E. multilocularis primer sets. The results strongly suggested that Encephalitozoon should be taken into consideration, when DNA isolated from larval E. multilocularis is analyzed.

Notizen: . We have used the anti-phosphoprotein antibody MPM-2 to examine changes in phosphorytation of cortical proteins during cilia regeneration in Tetrahymena thermophila. Although numerous cortical proteins are phosphorylated in both nondeciliated and deciliated cells, deciliation induces a dramatic increase in the phosphorylation of a 90-kDa cortical protein. The 90-kDa protein remained phosphorylated during cilia regeneration and then gradually became dephosphorylated. The 90-kDa protein was phosphorylated and dephosphorylated normally in Tetrahymena mutants that assemble short cilia, suggesting that achievement of full length is not the signal that triggers dephosphorylation of the 90-kDa protein. When initiation of cilia assembly is blocked, the 90-kDa protein becomes phosphorylated and remains phosphorylated for an extended period of time, suggesting that initiation of cilia elongation triggers eventual dephosphorylation of the 90-kDa protein, regardless of how long the cilia actually become.

Notizen: . Giardia lamblia trophozoites express on their surfaces one of a set of cysteine-rich antigenically variant proteins, called variant-specific surface proteins, which comprise the majority of proteins detected by surface labeling. While these VSP proteins may be immunodominant proteins important in the host immune response to G. lamblia, the ability to switch expression from one VSP to another may provide a means for the trophozoites to avoid the host immune response. The first VSP characterized, VSPA6 (from the A6 clone of the WB isolate, originally termed CRP170), contains 18–23 copies of a 65 amino acid repeat. We have now used the repeat as a probe to isolate from a WBA6 genomic library two genes related to vspA6 (called vspA6-S1, vspA6-S2). Sequence analysis of the vspA6-S1 gene revealed nearly two complete copies of the 195 bp repeat and substantial nucleotide and translated amino acid similarity in the coding regions 5’and 3’to the repeats. The vspA6-S2 gene, while still related, showed greater divergence from vspA6 than vspA6-S1 in the nonrepeat coding region and contained nearly four copies of a 201 bp repeat that was 75% identical to the 195 bp vspA6 repeat. These results suggest that gene duplication followed by divergence has played a key role in the generation of the vsp gene repertoire.

Notizen: . The glycerophosphate oxidase (GPO), the unique terminal oxidase of bloodstream trypanosome (TAO), appears to be functionally similar to the alternative oxidases of some plants and higher fungi. Immunoblotting of mitochondrial proteins of bloodstream trypomastigotes of Trypanosoma brucei brucei with monoclonal or polyclonal antibodies to Sauromatum guttatum (voodoo lily) and Symplocarpus foetidus (skunk cabbage) alternative oxidases respectively revealed two proteins of about 33 kDa (p33) and 68 kDa (p68). These proteins are not present in procyclic trypomastigotes. Electrophoresis under rigorous denaturing conditions indicated p68 to be the dimer of p33. Indirect immunofluorescent studies of bloodstream and procyclic trypomastigotes with monoclonal antibody to plant alternative oxidase also showed the localization of 33 kDa protein in the mitochondria of the bloodstream trypomastigotes. The functional TAO activity could be solubilized efficiently from the mitochondrial membrane of the bloodstream trypomastigotes by 1% NP-40 or 10 mM lauryl maltoside. When fractionated by Superose 12 gel filtration chromatography, p33 was co-purified with the TAO enzymatic activity. The apparent molecular size of the active enzyme complex was found to be 160 kDa. Gradual disappearance of the 33 kDa protein and the TAO enzymatic activity were well correlated during in vitro differentiation of the bloodstream to procyclic trypomastigotes. This study implies that the net biosynthesis of p33, an essential subunit of TAO, is decreased during differentiation from bloodstream to procyclic trypomastigotes.

Notizen: . The microsporidium, Enterocytozoon bieneusi, causes a severe, debilitating, chronic diarrhea in patients with the acquired immunodeficiency syndrome. Specific diagnosis of intestinal microsporidiosis, especially due to Enterocytozoon, is difficult and there is no known therapy that can completely eradicate this parasite. Preliminary studies indicate that a short term (about 6 months) in vitro culture of this parasite yielding low numbers of spores, may be established by inoculating human lung fibroblasts and/or monkey kidney cell cultures with duodenal aspirates and or biopsy from infected patients. The cultures may subsequently be used for the isolation and molecular analysis of parasite DNA.

Notizen: . A new Myxosporea, Ceratomyxa sparusaurati n. sp., was found in the gall bladder and bile of cultured gilthead sea bream (Sparus aurata L.) from different Spanish fish farms. It is clearly different from all the previously reported Ceratomyxa from sparids, and it is distinguished from other members of the genus by the shape and size of the spores. Prevalence of infection was 2.15% in an Atlantic farm, 48.7% in a Mediterranean farm and 28.6% in the facilities of the Instituto de Acuicultura de Torre de la Sal. The cell-in-a-cell pattern was found through all the sporogenesis and the general ultrastructure resembled other Myxosporea. Primary cells with two developing spores, harbored other secondary cells. Disporous sporoblasts contained numerous membrane-bound inclusions, a few lipid droplets and polysaccharides as evidenced by cytochemistry. In mature spores, binucleate sporoplasmic cells contained abundant Thièry-negative sporoplasmosomes.

Notizen: . The immobilization antigens (i-antigens) are a class of highly abundant surface membrane proteins found on a number of holotrich ciliates. In Ichthyophthirius multifiliis (an obligate parasite of fish) these antigens appear to be targets of the host immune response. While the i-antigens of Ichthyophthirius are predominantly membrane-associated proteins, we now find that they are released into the water surrounding the parasite in a highly enriched form. The membrane-associated and water soluble proteins appear indistinguishable by antigenic means, as well as by several biochemical criteria including peptide mapping, mobility in reducing and non-reducing SDS-polyacrylamide gels, and relative glycosylation. Antibodies raised against the membrane-associated antigens react with the water soluble proteins on Western blots. Not surprisingly, immunocytochemical localization studies show binding of these antibodies to surface membranes of the cell. In addition, however, antibody binding is also detectible on the membranes of a secretory organelle (that is, mucocysts) present in the cortical cytoplasm. The significance of these findings with regard to the potential role of the i-antigens in infection and immunity is discussed.

Notizen: . The complete nucleotide sequence has been established for two genes (maeA and maeB) coding for different subunits of the hydrogenosomal malic enzyme [malate dehydrogenase (decarboxylating) EC 1.1.1.39] of Trichomonas vaginalis. Two further genes (maeC and maeD) of this enzyme have been partially sequenced. The complete open reading frames code for polypeptides of 567 amino acids in length. These two open reading frames are similar with less than 12 percent pairwise nucleotide differences and less than 9 percent pairwise amino acid differences. The open reading frames of the two partially sequenced genes correspond to the amino-terminal part of the polypeptides coded and are similar to the corresponding parts of the completely sequenced ones. The deduced translation products of the two complete genes differ in their calculated pI values by 1.5 pH unit. The genes code for polypeptides which contain 12 or 11 amino-terminal amino-acyl residues not present in the proteins isolated from the cell. Other hydrogenosomal enzymes also have similar amino-terminal extensions which probably play a role in organellar targeting and translocation of the newly synthesized polypeptides. A comparison of 19 related enzymes from bacteria and eukaryotes with the maeA product revealed 34–45 percent amino acid identity. Phylogenetic reconstruction based on nonconservative amino acid differences with maximum parsimony (phylogenetic analysis using parsimony, PAUP) and distance based (neighbor-joining, NJ) methods showed that the T. vaginalis enzyme is the most divergent of all eukaryotic malic enzymes, indicating its long independent evolutionary history.

Notizen: Previous investigations have shown that the adhesion of T. cruzi plasma membrane vesicles (PMV) to monolayers of host cell myoblasts and to immobilized heart muscle sarcolemma membranes (PAM) on polyaerylamide beads is mediated by the interaction of T. cruzi attachment sites with the muscarinic cholinergic and β-adrenergic receptors of the host cell membrane. It has also been shown that this interaction is blunted by the specific antagonists of the mammalian receptors atropine and propranol, respectively. In the studies reported here, PAM also rapidly attached to swimming T. cruzi trypomastigotes in a complex, concentration-dependent fashion and binding isotherms showed that the equilibrium between free and bound PAM is rapidly reached within 2 minutes of incubation in physiologically balanced salt solutions. In this time frame, trypomastigote cAMP levels are significantly reduced from steady state values within 30 seconds of the addition of PAM in a buffer system containing a diesterase inhibitor. Maximal attenuation of cAMP levels was measured between 1 and 2 minutes of the addition of PAM to T. cruzi trypomastigotes. The degree of cAMP level attenuation was reduced by blocking PAM attachment with either atropine or propranol. On the basis of these results we propose that a likely pathway for the negative parasite signal generated upon adhesion of host muscle cell membranes to the surface of the flagellates is from the parasite's surface attachment sites directly to a Pertussis toxin sensitive inhibitory protein Gi, thereby blunting adenyl cyclase activity and cAMP formation.

Notizen: Morphology and morphogenesis of Onychodromus grandis (Hypotrichida, Ciliata) were studied in vivo and in protargolimpregnated preparations. The species was isolated from halophyte communities in astatic shallow waters of the Hortobágy National Park, Hungary. The species has two well developed dorsal horns. According to some characteristics (number and situation of ventral cirri) our findings differ from Stein's description in 1859. Individuals of the population studied had 9 ventral cirri in 3 rows. Nine rows of dorsal kineties were found on the back. It was found that the oral primordium develops in the vicinity of the transverse cirri. In O. grandis marginal primordia are formed in the marginal rows with the participation of parental cirri. This is also true for Laurentiella acuminata. Dorsal fragmentation of O. grandis displays similarity to that of L. acuminata, considering especially the development of the numerous small dorso-marginal kineties. There are certain similarities among O. quadricornutus, O. indica, L. acuminata, Stylonychia vorax and O. grandis in the development of the ventral and dorsal pattern and in some morphogenetical events. The remarkable differences in the interphase cells can be related simply to the significantly different numbers of cortical units (number of cirri). and also to the various cell sizes.

Notizen: Isotricha jalaludinii n. sp. found in the rumen of lesser mouse deer, Tragulus javanicus, in Malaysia was described and illustrated. This new species is characterized by the location and direction of the vestibulum, shape of the macronucleus, and absence of a dent at the vestibular opening. The presence of single peculiar isotrichid species in the rumen of mouse deer, which is recognized as one of the most primitive ruminants, suggests that the isotrichid ciliates similar to I. jalaludinii and Isotricha intestinalis were established at a fairly early period during the evolution of ruminants.

Notizen: We have generated a transformation marker for Paramecium using a Paramecium expression vector (pPXV) and the open reading frame (ORF) of the bacterial antibiotic resistance gene aminoglycoside 3'-phosphotransferase-II (APH-3'-II or neor) from the transposon Tn5. The expression vector contained a small multiple cloning site between the 5' and 3' non-coding regions of the calmodulin gene, and Tetrahymena telomere sequences for the stability of the plasmid in Paramecium. After the neor ORF was inserted, the plasmid was referred to as pPXV-NEO. Delivery of approximately 10–20 picoliters of linearized PXV-NEO at 〉 2000 copies/pl into the macronucleus effected 100% transformation. Southern and Northern blot hybridization showed the presence of neor-specific DNA and RNA, respectively, in all of the transformed clones but not in the untransformed clones. The degree of resistance to G-418, and the concentrations of neor-specific DNA and neor-specific RNA in the clones were proportional to the concentration of the vector injected. We have demonstrated that when the linearized plasmid was injected into the macronucleus, the prokaryotic sequence conferred an antibiotic resistance to Paramecium despite codon-usage differences.

Notizen: . Four methods are commonly used to study cell cycle processes in Paramecium tetraurelia. These include stage frequency analysis in asynchronous cultures, hand selection of synchronous dividing cells, selection of newly divided cells by elutriation centrifugation, and the sister cell method. We have compared the timing and resolution of stages of oral morphogenesis and micronuclear mitosis with each method. The temporal resolution obtainable with the sister cell method was inadequate to position the timing of morphogenesis stages within the cell cycle. Both the asynchronous method and the hand-selected synchronous samples methods are prone to bias. Elutriation centrifuge synchronization provides large samples with resolution comparable to that of hand selected samples. The elutriation method is the least prone to bias when 〈5% of the parent culture of Paramecium is selected.

Notizen: . Norlevinea n. g. is established for microsporidia in which a uninucleate meront changes into a sporont by secreting a thin, membranous, sporontogcnetic and fragile sporophorous vesicle (pansporoblast membrane) in which four uninucleate sporoblasts are formed. In contrast to the genus Gurleya, the sporoblasts and later the spores are permanently joined into doublets, being laterally cemented by an electron-dense substance structurally identical to and continuous with the exospore layer. The polar filament is of the anisofilar type. The type species is Norlevinea daphniae (Weiser, 1947) n. comb., a parasite of the ovaries of Daphnia longispina occurring in several carp ponds in Czechoslovakia.

Notizen: . The microsporidian parasite known as Nosema helminthorum Moniez, 1887, parasitic in the tapeworm Moniezia expansa (Rudolphi, 1810), has been shown by electron microscopy to have two cycles of development, one with isolated nuclei, the other with paired nuclei (diplokarya). Both merogony and sporogony of the two separate sequences take place in direct contact with the host cell cytoplasm and ultimately give rise to unikaryotic and diplokaryotic sporoblasts. Sporogony is disporoblastic. The nuclear condition of the spores was not seen. The sequences, corresponding to those of the genera Unikaryon and Nosema, may be part of a single dimorphic life cycle and, if so, the species will have to be transferred to a new genus.

Notizen: . Sarcocystis falcatula Stiles, 1893 is re-described. Intermediate hosts of the parasite which was earlier described as Sarcocystis debonei Vogelsang, 1929 are species of passeriform, psittaciform, and columbiform birds. In these birds, muscle zoites are 6.88 × 2.19 (4.8-8.4 × 1.2-3.6) μm and are enclosed in a cyst wall with regular protrusions, 1-5 μm long. The convoluted primary wall has multiple thin areas in the osmiophilic layer. Microtubules originate in the ground substance and extend to the tips of the protrusions. The only known definitive host is the opossum, Didelphis virginiana; rats, cats, a dog, and a ferret could not be infected from muscle cysts. Sporocysts from opossums infected from five different infected avian sources measure 11.2 × 7.4 (9.6−12.0 × 6.0-8.4)μm.

Notizen: . Descriptions are given of two new species of Hepatozoon Miller, 1908 found in the pygmy squirrel, Idiurus macrotis, in the Ivory Coast. Gamonts of both are parasites of monocytes.The size and shape of the gamonts of one, H. normani n. sp., are similar to those of a number of gamonts of other species of rodent hemogregarines and the separate identity of the parasite is based on the host restriction of mammalian hemogregarines. The gamonts of the other species, H. dolichomorphon n. sp., are remarkably long and slender and are unlike those of any other known hemogregarine of mammals. Schizonts of this species were found in a smear prepared from heart blood.

Notizen: . The presence of nonvariant antigens (NVAs) limited to bloodstream forms of Trypanosoma brucei brucei and Trypanosoma brucei rhodesiense was demonstrated for the first time by immunodiffusion and Immunoelectrophoresis. Noncloned and cloned populations were employed in preparation of polyclonal antisera in rabbits and of antigens to be used in the immunologic reactions. The NVAs could be shown best in systems in which hyperimmune rabbit sera (adsorbed with procyclic forms to eliminate antibodies against antigens common to bloodstream form and procyclic stages) were reacted with trypanosomes characterized by heterologous variant-specific antigens (VSAs).The NVAs demonstrated in this study are very likely different from the common parts of VSAs. As has been suggested by experiments with living trypanosomes, at least a part of the NVAs appears to be located on the surface of the bloodstream forms. In these experiments involving the quantitative indirect fluorescent antibody test, the amount of fluorescence recorded for the heterologous system, i.e. ETat 5 trypanosomes incubated with anti-AmTat 1.1 serum, equalled ∼3.0% of the fluorescence emitted by the AmTat 1.1 bloodstream forms treated with their homologous antiserum. Evidently, only small amounts of NVAs are present on the surfaces of T. brucei bloodstream forms.In addition to the NVAs, the electrophoresis results suggested the presence of antigenic differences between procyclic stages belonging to different T. brucei stocks.

Notizen: . Late schizonts from continuous cultures of P. falciparum were concentrated over Percoll, inoculated to various experimental media at the rate of about 20 × 106 per 0.5 ml of medium, and incubated in a candle jar at 37° for 1 day. Controls in standard culture medium showed a heavy invasion with young rings in the previously uninfected red cells introduced with the inoculum of schizonts. In a medium of high potassium content containing a 33% extract of human erythrocytes, this invasion was inhibited and many free merozoites were present. If, however, this same medium was supplemented with both ATP, as the dipotassium salt at 1.6 mM, and sodium pyruvate at 3.6 mM, there appeared large numbers of extracellular forms resembling young rings. Examination of these by electron microscopy shows that they are indeed merozoites that have begun to differentiate extracellularly. This suggests that the trigger for differentiation of merozoites may not depend on the process of entry into a red cell but rather on specific factors within the red cell.

Notizen: . Opossums (Didelphis marsupialis), act as intermediate hosts for Besnoitia darlingi and could be infected orally with sporozoites (oocysts) and bradyzoites (tissue cysts), or intraperitoneally (i.p.) with tachyzoites. Infections could presumably be transmitted through cannibalism. Cats (Felis catus), the definitive host, could be infected only with bradyzoites but not sporozoites. Oocysts shed by cats measure about 12 × 12 μm, resemble similarly sized oocysts of Toxoplasma gondii and Hammondia hammondi, and must be differentiated by the appearance of tissue cysts after experimental infection of intermediate hosts. Cats did not form tissue cysts of B. darlingi. Tachyzoites from the related B. jellisoni could be used in the Sabin-Feldman dye test to determine the development of antibody to B. darlingi in opossums after infection.