The heterogeneity of wooded-agricultural landscape mosaics influences woodland bird community assemblages

Context Landscape heterogeneity (the composition and configuration of different landcover types) plays a key role in shaping woodland bird assemblages in wooded-agricultural mosaics. Understanding how species respond to landscape factors could contribute to preventing further decline of woodland bird populations. Objective To investigate how woodland birds with different species traits respond to landscape heterogeneity, and to identify whether specific landcover types are important for maintaining diverse populations in wooded-agricultural environments. Methods Birds were sampled from woodlands in 58 2 x 2 km tetrads across southern Britain. Landscape heterogeneity was quantified for each tetrad. Bird assemblage response was determined using redundancy analysis combined with variation partitioning and response trait analyses. Results For woodland bird assemblages, the independent explanatory importance of landscape composition and landscape configuration variables were closely interrelated. When considered simultaneously during variation partitioning, the community response was better represented by compositional variables. Different species responded to different landscape features and this could be explained by traits relating to woodland association, foraging strata and nest location. Ubiquitous, generalist species, many of which were hole-nesters or ground foragers, correlated positively with urban landcover while specialists of broadleaved woodland avoided landscapes containing urban areas. Species typical of coniferous woodland correlated with large conifer plantations. Conclusions At the 2 x 2 km scale, there was evidence that the availability of resources provided by proximate landcover types was highly important for shaping woodland bird assemblages. Further research to disentangle the effects of composition and configuration at different spatial scales is advocated

Urban Biodiversity and Landscape Ecology: Patterns, Processes and Planning

Effective planning for biodiversity in cities and towns is increasingly important as urban areas and their human populations grow, both to achieve conservation goals and because ecological communities support services on which humans depend. Landscape ecology provides important frameworks for understanding and conserving urban biodiversity both within cities and considering whole cities in their regional context, and has played an important role in the development of a substantial and expanding body of knowledge about urban landscapes and communities. Characteristics of the whole city including size, overall amount of green space, age and regional context are important considerations for understanding and planning for biotic assemblages at the scale of entire cities, but have received relatively little research attention. Studies of biodiversity within cities are more abundant and show that longstanding principles regarding how patch size, configuration and composition influence biodiversity apply to urban areas as they do in other habitats. However, the fine spatial scales at which urban areas are fragmented and the altered temporal dynamics compared to non-urban areas indicate a need to apply hierarchical multi-scalar landscape ecology models to urban environments. Transferring results from landscape-scale urban biodiversity research into planning remains challenging, not least because of the requirements for urban green space to provide multiple functions. An increasing array of tools is available to meet this challenge and increasingly requires ecologists to work with planners to address biodiversity challenges. Biodiversity conservation and enhancement is just one strand in urban planning, but is increasingly important in a rapidly urbanising world

Remote detection of invasive alien species

The spread of invasive alien species (IAS) is recognized as the most severe threat to biodiversity outside of climate change and anthropogenic habitat destruction. IAS negatively impact ecosystems, local economies, and residents. They are especially problematic because once established, they give rise to positive feedbacks, increasing the likelihood of further invasions and spread. The integration of remote sensing (RS) to the study of invasion, in addition to contributing to our understanding of invasion processes and impacts to biodiversity, has enabled managers to monitor invasions and predict the spread of IAS, thus supporting biodiversity conservation and management action. This chapter focuses on RS capabilities to detect and monitor invasive plant species across terrestrial, riparian, aquatic, and human-modified ecosystems. All of these environments have unique species assemblages and their own optimal methodology for effective detection and mapping, which we discuss in detail

ADAPTATION D'UN DISPOSITIF DU TYPE HOPKINSON-KOLSKY À L'ÉTUDE DU COMPORTEMENT MÉCANIQUE DE MATÉRIAUX EXPLOSIBLES EN TEMPÉRATURE

On présente une adaptation d'un dispositif du type Hopkinson-Kolsky permettant de déterminer le comportement en compression dynamique d'un matériau explosible, pour des vitesses de déformation élevées (< 3000 s-1) à des températures comprises entre -70° et + 150°C.This paper presents an apparatus derivated from a split Hopkinson pressure bar, allowing the determination of the dynamic compression behaviour of high explosives for high strain rate (< 3000 s-1) at temperature ranging from - 70°C to 150°C

Thematic and taxonomic relations in preschoolers: The development of flexibility in categorization choices

International audienceTwo experiments examined the development of flexibility of categorization in children aged from 3 to 5, using a picture-matching task. During a pre-test, spontaneous matches were observed. Children were next presented with a scene aimed at inducing an alternative match. Finally, they were given a post-test identical to the pre-test to assess whether they would maintain their initial choice. Both experiments showed that preschoolers were able to produce different types of categorization choices. In Experiment 1, children had to choose between a thematic and a taxonomic option. Five-year-olds; showed flexibility and changed their mode of response more often in the presence of the scenes (experimental group) than in their absence (control group). In contrast, 3-year-olds' responses seemed to reflect spontaneous variability since their switches were not related to contextual information. In Experiment 2, two more choice options were added. Three-year-olds' data replicated the findings of Experiment 1. However, a majority of 4-year-olds were consistent on the thematic mode of response and adapted their responses to the scenes only to a limited extent. Overall, the data suggest a developmental path from spontaneous variability to flexibility, via a predominance of one mode of response

CARACTÉRISATION DE LA TENSION LIMITE DE RUPTURE PAR ÉCAILLAGE DE MATÉRIAUX EXPLOSIBLES

Des essais d'écaillage sur un explosif composite à fort taux de charge ont été réalisés à l'aide d'un canon à gaz. Les échantillons testés ont été analysés par radiographie et par microscopie électronique. L'amplitude des chocs engendrés dans les matériaux a été mesurée par des jauges piezorésistives. Une simulation numérique des essais a été effectuée. L'ensemble de ces investigations permet de déterminer la tension limite de rupture par écaillage des explosifs composites ou par extension de tous matériaux présentant une structure du même type.A light gas gun has been used to performe planar impact experiments where spalling of a cast-cured plastic bonded explosive has been studied. After experiment samples were observed by means of X-radiography and electron microscopy. The unreacted Hugoniot was measured for stresses of 180 - 300 MPa using piezoresistive gauges. A numerical simulation of our experiments was performed. Thus with these experiments, the minimum stress that leads to the spalling of a high explosive sample can be determined