Competition, resources, and vegetation during 10 years in native grassland

A 10-year experiment tested for variation in competition intensity over time in a natural grassland at the northern edge of the Great Plains. Growing-season precipitation varied fivefold during the study. All ecosystem-level variables varied significantly among years, and most covaried in expected ways. The covers of all common grasses possessing the C3 photosynthetic pathway varied significantly among years; in contrast, all common species with traits associated with drought tolerance (a C4 grass, a lichen, a spikemoss, and a subshrub) did not vary. Annual transplant experiments measured the competitive effects of neighbors on the growth of individuals of the native grass Bouteloua gracilis. A significant interaction between year and competition showed that competition intensity varied among years. The size of this effect, however, was small (eta2 = 0.074) relative to the size of the direct effect of competition (eta2 = 0.20) or the year in which the experiment was conducted (eta2 = 0.51). Further, competition intensity was not significantly related to any variable describing standing crop or resources, or species richness. Species richness was highest in years with high precipitation, standing crop, and individual growth, due to the recruitment of rare species that were absent from dry years. In summary, variation in competition intensity was statistically significant but had small effects relative to the direct effects of climate.     

Monitoring dissolved copper concentrations in Chesapeake Bay,U.S.A.

Dissolved copper and selected water chemistry parameters were monitored for 11 months in Chesapeake Bay, U.S.A. Dissolved copper concentrations in four recreational marinas, a large harbor, two major river systems, and a heavily used shipping canal ranged from below detectable levels to 80 g L^-1 (\-X=11.7 g L^-1). Dissolved copper was detected >91% of the time at five locations. Lowest copper concentrations were found in Potomac River, Baltimore Harbor, Pier One Marina, and C & D Canal (\-X=6–10 g L^-1; slightly higher levels of dissolved copper were found in Choptank River (\-X=12 g L^-1). Highest levels of copper were detected in Port Annapolis, Hartge, and Piney Narrows Marinas (\-X=13–18 g L^-1), with the highest values observed in the study (70 and 80 g L^-1) found in two of these marinas. Copper in the three marinas with highest dissolved copper levels could have been toxic to some of the more sensitive aquatic species. Intensive study of one marina indicated that a likely source of dissolved copper was the recreational boats housed in the marina.     

Shifts within ecological modernization in South Africa: Deliberation, innovation and institutional opportunities

Sustainable development is now widely accepted as a policy framework in planning and development both internationally and in South Africa. Within this framework, technocentric scientific approaches to environmental management, which are reflective of weak ecological modernization, have dominated environmental practice both in the developed and developing world. South Africa is a country in transition and as a result environmental law and policy have undergone significant reform. However, implementation and practice remains embedded within a weak ecological modernization approach. Through the lens of two case studies reflecting changing approaches and practices within state institutions, this paper explores the shifts taking place in the construction, adaptation and application of policy frameworks and tools used in the drive towards sustainability in South Africa. The research uses critical approaches to ecological modernization (Hajer, 1995; Christoff, 1996) and deliberative policy analysis (Hajer and Wagenaar, 2003; Hajer, 2003, 2003; Hajer, 2004) to explore these shifts. It suggests that the shift towards strong ecological modernization has taken place as a result of the adaptation of international practice to the South Africa context, the global acceptance of more integrated approaches, the opportunities for change that 'institutional ambiguity' and 'multi-signification' create, and pockets of innovation that have developed when intellectual actors shift the boundaries of environmental practice.     

Clarifying conditions and decision points for mediational type inferences in Organizational Behavior

Although mediational designs and analyses are quite popular in Organizational Behavior research, there is much confusion surrounding the basis of causal inferences. We review theoretical, research design, and construct validity issues that are important for drawing inferences from mediational analyses. We then distinguish between indirect effects, and partial and full mediational hypotheses and outline decision points for drawing inferences of each type. An empirical illustration is provided using structural equation modeling (SEM) techniques, and we discuss extensions and directions for future research. Copyright © 2006 John Wiley & Sons, Ltd.     

Investigating activated sludge flocs using microanalytical techniques: demonstration of environmental scanning electron microscopy and time-of-flight secondary ion mass spectrometry for wastewater applications.

Environmental scanning electron microscopy (ESEM) with an energy-dispersive X-ray spectrometer (EDS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were demonstrated to be useful analytical tools for investigating surface and bulk components of individual floc particles from both full- and bench-scale activated sludge systems. Detailed surface imaging of various hydrated biological floc particles by ESEM revealed substantial differences in surface features between treatment systems, while EDS identified spatial differences in the iron and the aluminum distributions. The ToF-SIMS spectra had signature fragments of protein and polysaccharide material from the floc surface, suggesting that this technique is capable of surface profiling extracellular polymeric substances. Principal-component analysis of the positive ion ToF-SIMS spectra from the mixed-liquor-suspended solid (MLSS) samples and reference aquatic organic materials found slight differences between the full- and bench-scale MLSS surface properties but substantial differences among MLSS and treated effluent from the same facility.     

The effects of graduated driver licensing on hospitalization rates and charges for 16-and 17-year-olds in North Carolina

OBJECTIVE: To mitigate the high risk of motor vehicle crashes for young beginning drivers, over 40 states and the District of Columbia have implemented graduated driver licensing (GDL) systems that gradually and systematically ease teen drivers into higher risk driving conditions. Evaluations of GDL programs using motor vehicle crash data have demonstrated marked declines in crashes. The objective of this study is to examine the association between the implementation of the North Carolina GDL program and the rate of hospitalization, as well as hospital charges, for 16-and 17-year-old drivers. METHODS: Data were obtained from the North Carolina Hospital Discharge Database for the 26 months before and 46 months after the December 1, 1997, implementation of the GDL program. ARIMA interrupted time series analyses were used to model monthly hospitalization rates, controlling for the hospitalization rates of 25-to 54-year-old drivers. ARIMA analyses were also used to determine whether changes occurred in monthly total hospital charges. RESULTS: Among the 568 16-year-old hospitalized drivers, GDL was associated with a 36.5% decline in the hospitalization rate per population and a 31.2% decline in the total monthly driver hospitalization charges. Although a 12% reduction in the rate of hospitalizations was observed among the 615 17-year-old drivers, the analysis lacked sufficient power to be statistically reliable. No consistent change was observed in the 16-year-old driver total monthly hospital charges. CONCLUSIONS: The North Carolina GDL program was associated with a marked decline in the rate of hospitalizations and hospital charges for 16-year-old drivers. Following the implementation of GDL, over $650,000 in hospital charges have been averted each year for 16-year-old drivers. Analyses suggest these reductions were primarily the result of reduced exposure rather than an improvement in teen driving.     

Controlling impaired driving through vehicle programs: an overview

The growing recognition of the problem presented by illicit vehicle operation by those whose license has been suspended for driving while intoxicated (DWI) has led to the increasing use of vehicle sanctions. These sanctions include vehicle impoundment and forfeiture, vehicle registration cancellation, and vehicle interlocks as penalties for DWI and driving while suspended (DWS). This article reviews the current information available on the use and effectiveness of vehicle sanctions for reducing offender recidivism. In the United States, 14 states have impoundment laws that are widely used as sanctions for both DWI and DWS, with the length of the impoundment increasing with the number of previous offenses. These laws have been shown to reduce recidivism while the vehicle is in custody and, to a lesser extent, even after the vehicle has been released. Vehicle impoundment is also widely used in Canada and New Zealand. Although a larger number of U.S. states have laws providing for vehicle forfeiture for DWI or DWS, this sanction tends to be limited to multiple offenders and therefore impacts fewer drivers. Cancellation of the vehicle registration and the confiscation of the vehicle plates are increasing in popularity because the vehicle tags are the property of the state, rather than the vehicle owner. Vehicle alcohol interlocks have proven to be an effective method for reducing DWI offender recidivism while they are on the car, but appear to produce only limited post-treatment behavior change. Interlocks are widely used in the United States and Canada and are beginning to be implemented in Europe and Australia. The issues that arise in implementing vehicle sanction programs are discussed and the actions taken by states to deal with them are described.     

The effectiveness of home-study driver education compared to classroom instruction: the impact on student knowledge and attitudes

PROBLEM: Home-study driver education programs exist in several states, but none have been scientifically evaluated to determine if such courses are as effective as classroom courses for teaching driver education. METHOD: Over 1,300 students were randomly assigned to classroom instruction, or CD ROM, workbook, or Internet/workbook home-study courses and compared on proctored exit examination knowledge and attitude scores, and written knowledge test outcomes. RESULTS: Few differences were found on exit examination knowledge and attitude scores, but they tended to favor the CD and Internet/workbook home-study courses over the classroom or workbook courses. Differences favoring the classroom on written knowledge test outcomes likely reflect a bias in classroom courses toward teaching test-specific material. DISCUSSION: The findings present no compelling evidence that home-study courses are less effective than classroom courses for teaching driver education. IMPACT ON INDUSTRY: The findings could result in more widespread use of home-study courses. Also, the use of low-cost home-study courses as the first course of a two-stage driver education and training system could make integrating such programs with graduated driver licensing more feasible and acceptable to the public.     

Biota Connect Aquatic Habitats throughout Freshwater Ecosystem Mosaics

Freshwater ecosystems are linked at various spatial and temporal scales by movements of biota adapted to life in water. We review the literature on movements of aquatic organisms that connect different types of freshwater habitats, focusing on linkages from streams and wetlands to downstream waters. Here, streams, wetlands, rivers, lakes, ponds, and other freshwater habitats are viewed as dynamic freshwater ecosystem mosaics (FEMs) that collectively provide the resources needed to sustain aquatic life. Based on existing evidence, it is clear that biotic linkages throughout FEMs have important consequences for biological integrity and biodiversity. All aquatic organisms move within and among FEM components, but differ in the mode, frequency, distance, and timing of their movements. These movements allow biota to recolonize habitats, avoid inbreeding, escape stressors, locate mates, and acquire resources. Cumulatively, these individual movements connect populations within and among FEMs and contribute to local and regional diversity, resilience to disturbance, and persistence of aquatic species in the face of environmental change. Thus, the biological connections established by movement of biota among streams, wetlands, and downstream waters are critical to the ecological integrity of these systems. Future research will help advance our understanding of the movements that link FEMs and their cumulative effects on downstream waters.     

Random forest models to estimate bankfull and low flow channel widths and depths across the conterminous United States

Channel dimensions (width and depth) at varying flows influence a host of instream ecological processes, as well as habitat and biotic features; they are a major consideration in stream habitat restoration and instream flow assessments. Models of widths and depths are often used to assess climate change vulnerability, develop endangered species recovery plans, and model water quality. However, development and application of such models require specific skillsets and resources. To facilitate acquisition of such estimates, we created a dataset of modeled channel dimensions for perennial stream segments across the conterminous United States. We used random forest models to predict wetted width, thalweg depth, bankfull width, and bankfull depth from several thousand field measurements of the National Rivers and Streams Assessment. Observed channel widths varied from <5 to >2000 m and depths varied from <2 to >125 m. Metrics of watershed area, runoff, slope, land use, and more were used as model predictors. The models had high pseudo R² values (0.70–0.91) and median absolute errors within ±6% to ±21% of the interquartile range of measured values across 10 stream orders. Predicted channel dimensions can be joined to 1.1 million stream segments of the 1:100 K resolution National Hydrography Dataset Plus (version 2.1). These predictions, combined with a rapidly growing body of nationally available data, will further enhance our ability to study and protect aquatic resources.