Bats aloft: variability in echolocation call structure at high altitudes

Bats alter their echolocation in response to changes in ecological and behavioral conditions, but little is known about how they adjust call structure in response to changes in altitude. We examined altitudinal variation in the echolocation of Brazilian free-tailed bats, Tadarida brasiliensis, a species known to fly to altitudes of 3,000 m above the ground. From 50.2 h of recordings, we analyzed 113 high-quality echolocation call sequences recorded from 0 to 862 m above ground level. Bats flying near the ground used shorter, higher-frequency, broader-bandwidth calls compared to bats at higher altitudes, an effect likely due to the greater levels of echo-producing clutter (i.e., vegetation, buildings) found near the ground. When ground-level recordings are excluded, bats continue to shift towards the use of longer-duration, lower-frequency, narrower-bandwidth calls with increasing altitude. We propose that the observed high-altitude changes in call structure are a response to changing acoustic attenuation rates and/or decreasing insect densities at higher altitudes.     

Sorption and bioavailability of arsenic in selected Bangladesh soils

The bioavailability of arsenic (As) in the soil environment is largely governed by its adsorption–desorption reactions with soil constituents. We have investigated the sorption–desorption behaviour of As in four typical Bangladeshi soils subjected to irrigation with As-contaminated groundwater. The total As content of soils (160 samples) from the Laksham district ranged from <0.03 to approximately 43 mg kg⁻¹. Despite the low total soil As content, the concentration of As in the pore water of soils freshly irrigated with As-contaminated groundwater ranged from 0.01 to 0.1 mg l⁻¹. However, when these soils were allowed to dry, the concentration of As released in the pore water decreased to undetectable levels. Remoistening of soils to field moisture over a 10-day period resulted in a significant (up to 0.06 mg l⁻¹) release of As in the pore water of soils containing >10 mg As kg⁻¹ soil, indicating the potential availability of As. In soils containing <5 mg As kg⁻¹, As was not detected in the pore water. A comparison of Bangladeshi soils with strongly weathered long-term As-contaminated soils from Queensland, Australia showed a much greater release of As in water extracts from the Australian soils. However, this was attributed to the much higher loading of As in these Australian soils. The correlation of pore water As with other inorganic ions (P, S) showed a strongly significant (P < 0.001) relationship with P, although there was no significant relationship between As and other inorganic cations, such as Fe and Mn. Batch sorption studies showed an appreciable capacity for both As^V and As^III sorption, with As^V being retained in much greater concentrations than As^III.     

Antecedents and consequences of basic versus career enrichment benefit satisfaction

Using a sample of 250 medical technologists (MTs) over a four‐year time period, this study presents initial evidence for differentiating two different facets of benefit satisfaction—basic and career enrichment. Basic benefit satisfaction exhibited stronger relationships to subsequent general benefit satisfaction, organizational withdrawal intent, and turnover behavior, while career enrichment benefit satisfaction exhibited a stronger relationship to subsequent affective organizational commitment. Copyright © 2001 John Wiley & Sons, Ltd.     

Consequences of niche overlap for ecosystem functioning: an experimental test with pond grazers

While the number of studies investigating the effects of species diversity on ecosystem properties continues to expand, few have explicitly examined how ecosystem functioning depends quantitatively on the degree of niche complementarity among species. We report the results of a microcosm experiment where similarity in habitat use among aquatic snail species was evaluated as a predictor of changes in community and ecosystem properties due to increasing species richness. Replicate microcosms with all possible one- and two-species combinations of a guild of six snail species were stocked with identical initial snail biomass. Microcosms with two species of snails had greater final snail biomass, lower attached algae biomass, and less total organic matter than monocultures. Snail species differed in their use of five distinct habitat types in the microcosms. Similarity in habitat use between a species pair was negatively related to the magnitude of change (e.g., deltaEF [change in ecosystem function]) in dissolved oxygen. periphyton biomass, and accrual of organic matter with a change in diversity. However, using the most stringent criterion for complementarity effects (e.g., Dmax [proportional deviation of the total polyculture yield from the highest yielding monoculture]), a relationship between species' niche similarity and changes in function with increasing species richness was only observed for dissolved oxygen. The identity of snail species present in the microcosms had strong effects on total organic matter, snail biomass, dissolved oxygen, periphyton biomass, and sedimentation rate. In this study, herbivore identity, sampling effects, and niche complementarity all appear to contribute to species richness effects on pond ecosystem properties and community structure. The analytical approach employed here may profitably be used in other systems to quantify the role of niche complementarity in species richness-ecosystem function relationships.     

AGRICULTURAL WATER MODELING AND ECONOMIC INFORMATION NEEDS UNDER THE MODEL WATER CODE1

ABSTRACT: Economic information for efficient water allocation is difficult and costly to acquire under administrative water systems evolving under the Model Water Code. One approach to obtaining more information is to use a simulator like the Florida AGWATER model. The advantage of AGWATER is the potential for realistic prediction, because it operates at the field and day levels, using detailed information for each crop and tract. Unfortunately, such simulators are complex and require large amounts of costly input data. A better solution to the information problem may be to use markets for the marketable goods associated with water, because information is inherent in such a process. This approach will allow limited modeling and management resources to be put into using water models to generate information for the goods dependent on water that are difficult to market, like wildlife services.     

Cognitive and motivational effects of participation: A mediator study

Previous experimental studies of participation have typically examined its motivational (especially commitment) benefits. These studies showed that these benefits are neither large nor consistent. The present study focused on the cognitive benefits of participation in decision making (pdm) and on the role of a different motivational mediator, self-efficacy. Unlike previous research which claimed to study the cognitive (informational) effects of participation, the present experiment: (a) allowed the information concerning task strategies to emerge from group discussion rather than being manipulated by the experimenter; (b) measured the actual strategies that were developed and used by subjects in the pdm condition; and (c) measured self-efficacy which was associated with the discovery and use of these strategies. It was found that the strategies developed by the subjects and their self-efficacy completely mediated the effect of participation on performance. Further, participation in setting goals, consistent with previous studies, did not affect performance but did affect self-efficacy.     

Integrating pollution prevention into the manufacturing process

An Integrated Manufacturing and Environmental (IME) approach to pollution prevention offers the opportunity to achieve regulatory compliance and substantial operational efficiencies. It is accomplished by realizing the simple fact that waste represents a quality defect and adapting traditional manufacturing industry analytical methods to also consider environmental factors. The author outlines techniques and procedures entailed by this approach that are applicable to both large and small facilities as part of an overall Total Quality Management program. Several case examples are provided.