A Conceptual Model of Spatially Heterogeneous Nitrogen Leaching from a Welsh Moorland Catchment

Soil- and stream-water data from the Plynlimon research area, mid-Wales, have been used to develop a conceptual model of spatial variations in nitrogen (N) leaching within moorland catchments. Extensive peats, in both hilltop and valley locations, are considered near-complete sinks for inorganic N, but leach the most dissolved organic nitrogen (DON). Peaty mineral soils on hillslopes also retain inorganic N within upper organic horizons, but a proportion percolates into mineral horizons as nitrate (NO ₃ ^– ), either through incomplete immobilisation in the organic layer, or in water bypassing the organic soil matrix via macropores. This NO ₃ ^– reaches the stream where mineral soilwaters discharge (via matrix throughflow or pipeflow) directly to the drainage network, or via small N-enriched flush wetlands. NO ₃ ^– in hillslope waters discharging into larger valley wetlands will be removed before reaching the stream. A concept of catchment nitrate leaching zones is proposed, whereby most stream NO ₃ ^– derives from localised areas of mineral soil hillslope draining directly to the stream; the extent of these zones within a catchment may thus determine its overall susceptibility to elevated surface water NO ₃ ^– concentrations.     

The design of child restraint system (CRS) labels and warnings affects overall CRS usability

A study was conducted that assessed the effectiveness of different child restraint system (CRS) label/warning designs on users' installation performance. Forty-eight paid participants installed a convertible CRS in a vehicle, and two child test dummies in a CRS, using one of four label conditions. The label conditions were: (1) no labels, (2) the manufacturer's labels that were already affixed to the CRS ("Current"), (3) labels that were designed according to a combination of the current U.S. regulations concerning CRS labels and recently proposed changes to these regulations ("Proposed"), and (4) labels that were designed according to human factors principles and guidelines, and that were based on a hierarchical behavioral task analysis ("Optimal"). Results demonstrated that, overall, the Optimal labels resulted in higher usability ratings and better task performance. This indicates that labels designed using human factors and task analyses that identify critical task information requirements for label features will result in increased user compliance with instructions, higher usability, and improved task performance. Surprisingly, having no labels on the CRS resulted in better installation performance than when either the Current or the Proposed label conditions were used. This indicates that label design can decrease task performance; the actual physical design of a CRS may be just as critical as label content in the installation choices provided to the user. Collectively, results suggest that implementation of the proposed changes to the U.S. regulations concerning CRS labeling would likely not result in increased performance or usability compared to existing manufacturer labels that follow the current guidelines. In order to achieve significantly better ease-of-use and task performance, it would be necessary to implement features of the Optimal label condition.     

Female choice and the quality of parental care in the great tit Parus major

Summary Previous work on great tits suggested that female mate choice was based on the characteristics of the male rather than the quality of his territory. The aim of this paper was to see whether females were deriving any direct benefits as a result of such choice by comparing male plumage colouration (the size of the central black breast-stripe) with the quality of parental care provided by both members of the pair. Males with large stripes were more likely to defend their broods because their nest attentiveness was higher increasing the chances of predator detection. Males with large stripes produced heavier fledglings primarily as a result of faster growth early in the nestling period. Previous work on great tits has shown that heavier fledglings have a higher survival probability than lighter ones. The results of this study can more easily be explained by differences in parental quality between males rather than as a result of variation in female or territory quality. Therefore, female great tits could increase their reproductive success by pairing with males with a large stripe because such males appear to be better quality parents. This suggests that female choice in the great tit may concern, at least in part, the quality of male parental care.     

Antioxidant alteration ofGlycine max (Fabaceae) defensive chemistry: Analogy to herbivory elicitation

Summary The water-soluble antioxidant, L-ascorbic acid (vitamin C), proved elicitory to alterable anti-herbivory inGlycine max againstTrichoplusia ni larvae. Elicitation by vitamin C was influenced especially by dose, time after elicitation and space in the plant. Results allow an analogy between antioxidant and herbivory elicitation. Elicitation apparently involves a sulfhydryl-protein-dependent redox mechanism which can be significantly affected by antioxidants. Findings would also support a proposed common redox-based mechanism, involving the plasma membrane, for communication between plant and animal cells and their environments.     

Female choice and the evolution of the conspicuous plumage coloration of monogamous male great tits

Summary The conspicuous male plumage coloration of many avian species is often regarded as the result of sexual selection through female choice. In general terms such plumage characters may evolve in monogamous species if males bearing them pair with high quality females and so reproduce more successfully than males lacking the character. Male great tits have a conspicuous, central black breast stripe which varies in size between individuals. The stripe is also present in the female although it is smaller in size. Male great tits with large stripes paired with females which laid large clutches. Furthermore, in one of three years, females paired with such males commenced breeding earlier in the season than other females. Individual females were significantly more consistent in their clutch size and laying date between years than were nesting boxes. Males with large stripes paired with females which had previously laid a large clutch. Although there was evidence that territory quality may affect female reproductive success by influencing nesting success and nestling quality, there was no significant relationship between the stripe size of a male and the quality of his territory. Therefore, the results suggest that female great tits are choosing the characteristics of the male rather than the quality of his territory. The evidence thus suggests that female choice may be important in the evolution of male secondary sexual characteristics in great tits.     

Including model uncertainty in estimating variances in multiple capture studies

We present bootstrap-based methods which incorporate model uncertainty in estimating variances in multiple capture studies. Each of our three methods has a specific set of properties, and we discuss when each method should be used. Our first method can be used in any multiple capture setting, but it gives an estimate of the variance conditional on the number of observed animals. Our other two methods yield estimates of the unconditional variance; they require good estimates of part or all of the specific probability model, respectively. Smoothed estimated cell probabilities are utilized by the latter method. We contrast the three methods on a real-life data set, and then conduct simulations for a simple setting. Finally, we detail the use of our methodology for specific settings and discuss adaptations for tag-return studies.     

Temporal analysis of airborne particulate matter reveals a dose-rate effect on mortality in El Paso: indications of differential toxicity for different particle mixtures

One of two topics explored is the limitations of the daily average in summarizing pollutant hourly profiles. The daily average of hourly measurements of air pollutant constituents provides continuity with previous studies using monitoring technology that only provided the daily average. However, other summary statistics are needed that make better use of all available information in 24-hr profiles. The daily average reflects the total daily dose, obscuring hourly resolution of the dose rate. Air pollutant exposures with comparable total daily doses may have very different effects when occurring at high levels over a few hours as opposed to low levels over a longer time. Alternative data-based choices for summary statistics are provided using principal component analysis to capture the exposure dose rate, while preserving ease of interpretation. This is demonstrated using the earliest hourly particle concentration data available for El Paso from archived records of particulate matter (PM)10. In this way, a significant association between evening PM10 exposures and nonaccidental daily mortality is found in El Paso from 1992 to 1995, otherwise missed using the daily average. Secondly, the nature and, hence, effects of particles in the ambient aerosol during El Paso sandstorms is believed different from that of particles present during still-air conditions resulting from atmospheric temperature inversions. To investigate this, wind speed (ws) is used as a surrogate variable to label PM10 exposures as Low-ws (primarily fine particles), High-ws (primarily coarse particles), or Mid-ws (a mixture of fine and coarse particles). A High-ws evening is significantly associated with a 10% lower risk of mortality on the succeeding third day, as compared with comparable exposures at Low- or Mid-ws. Although this analysis cannot be used to form firm conclusions because it uses a very small data set, it demonstrates the limitations of the daily average and suggests differential toxicity for different particle compositions.