Besprechungen

The Science of Nature -     

On the origins of informal hierarchy: The interactive role of formal leadership and task complexity

Informal hierarchies are a common and important feature of many groups, yet we know little about the antecedent conditions that determine the strength of such hierarchies. Building on theory that has depicted hierarchy as a mechanism for reducing uncertainty and creating structure, we posit that informal hierarchies emerge most strongly in situations that are ambiguous, ill‐defined, and unstructured. Three independent studies confirm this notion, demonstrating that groups develop particularly strong informal hierarchies in situations characterized by both a lack of strong formal leadership and high task complexity. These findings support the theoretical notion that formal and informal hierarchies are closely related, but only under conditions of high task complexity in which the structuring functions of hierarchies are most crucial.     

Food access,food security and community gardens in Rockford,IL

Urban agriculture projects seek to ameliorate issues of food access and food security for people living in areas with low access to fresh foods, including food deserts. Within this discourse, community gardens have been promoted as vehicles to reclaim unused urban space, produce food locally and connect populations to their food sources and larger community. A variety of community garden models exist; in the Midwestern city of Rockford, Illinois, many community gardens grow food for donation to food pantries as part of a programme to benefit socioeconomically disadvantaged persons in the city. However, the ability of these gardens to involve neighbourhood participants and provide the social capital-related benefits attributed to community gardens in the literature is uncertain. Here we examine community gardens in Rockford, IL to assess the extent to which they contribute to residents’ ability to obtain fresh produce as well as other social benefits. Data for this project come from a combination of interviews with gardeners, focus groups with food pantry users and a survey of pantry users. We find that while non-gardening community members are benefitting from the increased produce that the gardens provide, they are not receiving all of the social and communal benefits associated with actively participating in a garden.     

Synthesis of the DDT metabolite 2,4-dichloro-1-[2-chloro-1-(4-chlorophenyl)ethenyl]benzene (o-Cl-DDMU) and its detection in abiotic and biotic samples

Environmental Science and Pollution Research - Technical dichlorodiphenyltrichloroethane (DDT) has been used worldwide as a pesticide since the beginning of the 1940s. Due to its persistence, DDT...     

Persistence of azadirachtin A and B in soil: Effects of temperature and microbial activity

Abstract

The persistence of two insecticidally active compounds from the neem tree, azadirachtin A and B, was determined at two different temperatures (15 and 25°C) in the laboratory after application of the commercial neem insecticide, Margosan‐O, to a sandy loam soil. The influence of microbial activity on degradation was also examined by comparing autoclaved and non‐autoclaved soils also at 15 and 25°C. Temperature influenced degradation rates. The DT ₅₀ (time required for 50% disappearance of the initial concentration) for azadirachtin A was 43.9 and 19.8 d for non‐autoclaved soil kept at 15 and 25°C, respectively. The DT ₅₀ for azadirachtin B was 59.2 and 20.8 d for non‐autoclaved soil kept at 15 and 25°C, respectively. Microbial activity was also responsible for faster degradation because DT ₅₀ ’s for autoclaved soil were much longer than for non‐autoclaved soils. DT ₅₀ ‘_s for azadirachtin A in autoclaved soil were 91.2 (15°C) and 31.5 d (25°C). DT50’s for azadirachtin B in autoclaved soil were 115.5 (15°C) and 42.3 d (25°C). Two degradation products of azadirachtin were detected, but were not identified. Higher levels of the two degradation products were detected in non‐autoclaved soil.     

Assessing the impact of the Indian Ocean tsunami on households: a modified domestic assets index approach

This paper offers a potential measurement solution for assessing disaster impacts and subsequent recovery at the household level by using a modified domestic assets index (MDAI) approach. Assessment of the utility of the domestic assets index first proposed by Bates, Killian and Peacock (1984) has been confined to earthquake areas in the Americas and southern Europe. This paper modifies and extends the approach to the Indian sub‐continent and to coastal surge hazards utilizing data collected from 1,000 households impacted by the Indian Ocean tsunami (2004) in the Nagapattinam district of south‐eastern India. The analyses suggest that the MDAI scale is a reliable and valid measure of household living conditions and is useful in assessing disaster impacts and tracking recovery efforts over time. It can facilitate longitudinal studies, encourage cross‐cultural, cross‐national comparisons of disaster impacts and inform national and international donors of the itemized monetary losses from disasters at the household level.     

An adaptive plan for prioritizing road sections for fencing to reduce animal mortality

Mortality of animals on roads is a critical threat to many wildlife populations and is poised to increase strongly because of ongoing and planned road construction. If these new roads cannot be avoided, effective mitigation measures will be necessary to stop biodiversity decline. Fencing along roads effectively reduces roadkill and is often used in combination with wildlife passages. Because fencing the entire road is not always possible due to financial constraints, high-frequency roadkill areas are often identified to inform the placement of fencing. We devised an adaptive fence-implementation plan to prioritize road sections for fencing. In this framework, areas along roads of high, moderate, and low levels of animal mortality (respectively, roadkill hotspots, warmspots, and coldspots) are identified at multiple scales (i.e., in circles of different diameters [200–2000 m] in which mortality frequency is measured). Fence deployment is based on the relationship between the amount of fencing being added to the road, starting with the strongest roadkill hotspots, and potential reduction in road mortality (displayed in mortality-reduction graphs). We applied our approach to empirical and simulated spatial patterns of wildlife–vehicle collisions. The scale used for analysis affected the number and spatial extent of roadkill hot-, warm-, and coldspots. At fine scales (e.g., 200 m), more hotspots were identified than at coarse scales (e.g., 2000 m), but combined the fine-scale hotspots covered less road and less fencing was needed to reduce road mortality. However, many short fences may be less effective in practice due to a fence-end effect (i.e., animals moving around the fence more easily), resulting in a trade-off between few long and many short fences, which we call the FLOMS (few-long-or-many-short) fences trade-off. Thresholds in the mortality-reduction graphs occurred for some roadkill patterns, but not for others. Thresholds may be useful to consider when determining road-mitigation targets. The existence of thresholds at multiple scales and the FLOMS trade-off have important implications for biodiversity conservation.