La " forêt fantôme " : un petit patrimoine forestier en Comminges

Nos forêts semblent intemporelles et nous imaginons peu à quel point les activités humaines les ont façonnées et les influencent encore. Pourtant, même dans le cas des forêts rurales, de petites dimensions et à l'histoire tourmentée, la jonction de l'étude historique et du travail d'écologie forestière permet de reconstituer l'évolution séculaire de ces boisements

Evolution of microstructure and impact-strength energy in thermally and thermomechanically aged 15-5 PH

Due to its outstanding mechanical resistance and resistance to corrosion, alloy 15-5 PH can be beneficially used for manufacturing aerospace structural parts. Following exposure to intermediate temperature, from300◦–400 ◦C, the alloy embrittles through the decomposition of the martensite into iron-rich and chromium-rich domains.Depending on the ageing time, these domains are either interconnected or unconnected with each other. The embrittlement results in a drastic drop of the impact strength-energy and an increase of the ductile-to-brittle transition temperature. The initial microstructure and mechanical properties can be recovered through a re-homogenization of the distribution of chromium and iron atoms in the material in the case where the decomposition of the matrix is not too pronounced. The application of a stress higher than 60 per cent of the yield strength further enhances the ageing kinetics in the case where the combined effect of temperature and time results in the spinodal decomposition of the martensite

Agroforestry landscapes and global change: landscape ecology tools for management and conservation

Forest ecosystems are impacted by multiple uses under the influence of global drivers, and where landscape ecology tools may substantially facilitate the management and conservation of the agroforestry ecosystems. The use of landscape ecology tools was described in the eight papers of the present special issue, including changes in forested landscapes due to agricultural and forestry activities, landscape changes due to recent intensification of agriculture, and the impacts of agroforestry as compared to natural forest ecosystems. Landscape ecology can improve the economic, environmental and social values of agroforestry, and this knowledge should help to develop new management alternatives for agroforestry. We believe that these papers will inform management at the landscape level, especially in agroforestry landscapes, offering new tools for management and conservation.EEA Santa CruzFil: Martínez Pastur, Guillermo José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas. Laboratorio de Recursos Agroforestales; ArgentinaFil: Andrieu, Emilie. Institut National de la Recherche Agronomique; FranciaFil: Iverson, Louis R. USDA Forest Service. Northern Research Station; Estados UnidosFil: Peri, Pablo Luis. Universidad Nacional de la Patagonia Austral; Argentina. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Santa Cruz; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Why are there so many small woodlots in southwestern France landscapes?

Despite a trend during the last century towards a disconnection between agriculture and forestry, small woodlots strongly associated to farming activities are still very common in south western France. To explain the origin of this particularity and its consequences, we engaged ethnological, biotechnical and ecological studies. The ethnological study showed that the ‘house-centred’ social system - which is characteristic in this region - has shaped landscapes and reinforced the need for scattered small woodlots. Due to a principle of self-sufficiency, each farm had to have a direct access on its property or in its vicinity to all the resources needed. Woodlots had been maintained on lands that might have been cultivated and they contain a large diversity of woody species - even in the dominant tree layer - corresponding to the species needed for the family uses. Even if they are less able to apply all the usual practices, small woodlots are still seen by farmers as important components of their resources and landscapes. Their management lead to a particularly fine-grained mosaic of stands with different historical trajectories. Ecological studies revealed that these woodlots, and especially their edges, are key components of processes impacting agricultural activities, such as pest regulation. We argue that the small woodlots maintained in rural landscapes in south western France are beneficial for agriculture, forestry and rural activities, especially in a global change perspective. The question is how to keep their characteristics when their managers are leaving because of the lack of support from policy makers

Strength of forest edge effects on litter-dwelling macro-arthropods across Europe is influenced by forest age and edge properties

International audienceAim: Forests are highly fragmented across Western Europe, making forest edges im ‐portant features in many agricultural landscapes. Forest edges are subject to strong abiotic gradients altering the forest environment and resulting in strong biotic gradi ‐ents. This has the potential to change the forest's capacity to provide multiple eco ‐system services such as nutrient cycling, carbon sequestration and natural pest control. Soil organisms play a key role in this perspective; however, these taxa are rarely considered in forest edge research.Location: A latitudinal gradient of 2,000 km across Western Europe.Methods: We sampled six dominant taxa of litter‐dwelling macro‐arthropods (car ‐abid beetles, spiders, harvestmen, centipedes, millipedes and woodlice) in forest edges and interiors of 192 forest fragments in 12 agricultural landscapes. We related their abundance and community composition to distance from the edge and the inter ‐action with forest age, edge orientation and edge contrast (contrast between land use types at either side of the edge).Results: Three out of six macro‐arthropod taxa have higher activity‐density in forest edges compared to forest interiors. The abundance patterns along forest edge‐to‐in‐terior gradients interacted with forest age. Forest age and edge orientation also influ ‐enced within‐fragment compositional variation along the forest edge‐to‐interior gradient. Edge contrast influenced abundance gradients of generalist predators. In general, older forest fragments, south‐oriented edges and edges along structurally more continuous land use (lower contrast between forest and adjacent land use) re ‐sulted in stronger edge‐to‐interior gradients while recent forests, north‐oriented edges and sharp land use edges induced similarity between forest edge and interior along the forest edge‐to‐interior gradients in terms of species activity‐density and composition.Main conclusions: Edge effects on litter‐dwelling macro‐arthropods are anticipated to feedback on important ecosystem services such as nutrient cycling, carbon se ‐questration and natural pest control from small forest fragments

High ecosystem service delivery potential of small woodlands in agricultural landscapes

Global forest loss and fragmentation have strongly increased the frequency of forest patches smaller than a few hectares. Little is known about the biodiversity and ecosystem service supply potential of such small woodlands in comparison to larger forests. As it is widely recognized that high biodiversity levels increase ecosystem functionality and the delivery of multiple ecosystem services, small, isolated woodlands are expected to have a lower potential for ecosystem service delivery than large forests hosting more species. We collected data on the diversity of six taxonomic groups covering invertebrates, plants and fungi, and on the supply potential of five ecosystem services and one disservice within 224 woodlands distributed across temperate Europe. We related their ability to simultaneously provide multiple ecosystem services (multiservice delivery potential) at different performance levels to biodiversity of all studied taxonomic groups (multidiversity), forest patch size and age, as well as habitat availability and connectivity within the landscape, while accounting for macroclimate, soil properties and forest structure. Unexpectedly, despite their lower multidiversity, smaller woodlands had the potential to deliver multiple services at higher performance levels per area than larger woodlands of similar age, probably due to positive edge effects on the supply potential of several ecosystem services. Biodiversity only affected multiservice delivery potential at a low performance level as well as some individual ecosystem services. The importance of other drivers of ecosystem service supply potential by small woodlands in agricultural landscapes also depended on the level of performance and varied with the individual ecosystem service considered. Synthesis and applications. Large, ancient woodlands host high levels of biodiversity and can therefore deliver a number of ecosystem services. In contrast, smaller woodlands in agricultural landscapes, especially ancient woodlands, have a higher potential to deliver multiple ecosystem services on a per area basis. Despite their important contribution to agricultural landscape multifunctionality, small woodlands are not currently considered by public policies. There is thus an urgent need for targeted policy instruments to ensure their adequate management and future conservation in order to either achieve multiservice delivery at high levels or to maximize the delivery of specific ecosystem services

High ecosystem service delivery potential of small woodlands in agricultural landscapes

Global forest loss and fragmentation have strongly increased the frequency of forest patches smaller than a few hectares. Little is known about the biodiversity and ecosystem service supply potential of such small woodlands in comparison to larger forests. As it is widely recognized that high biodiversity levels increase ecosystem functionality and the delivery of multiple ecosystem services, small, isolated woodlands are expected to have a lower potential for ecosystem service delivery than large forests hosting more species. We collected data on the diversity of six taxonomic groups covering invertebrates, plants and fungi, and on the supply potential of five ecosystem services and one disservice within 224 woodlands distributed across temperate Europe. We related their ability to simultaneously provide multiple ecosystem services (multiservice delivery potential) at different performance levels to biodiversity of all studied taxonomic groups (multidiversity), forest patch size and age, as well as habitat availability and connectivity within the landscape, while accounting for macroclimate, soil properties and forest structure. Unexpectedly, despite their lower multidiversity, smaller woodlands had the potential to deliver multiple services at higher performance levels per area than larger woodlands of similar age, probably due to positive edge effects on the supply potential of several ecosystem services. Biodiversity only affected multiservice delivery potential at a low performance level as well as some individual ecosystem services. The importance of other drivers of ecosystem service supply potential by small woodlands in agricultural landscapes also depended on the level of performance and varied with the individual ecosystem service considered. Synthesis and applications. Large, ancient woodlands host high levels of biodiversity and can therefore deliver a number of ecosystem services. In contrast, smaller woodlands in agricultural landscapes, especially ancient woodlands, have a higher potential to deliver multiple ecosystem services on a per area basis. Despite their important contribution to agricultural landscape multifunctionality, small woodlands are not currently considered by public policies. There is thus an urgent need for targeted policy instruments to ensure their adequate management and future conservation in order to either achieve multiservice delivery at high levels or to maximize the delivery of specific ecosystem services

Dynamique des arbres forestiers en contexte agricole : projet de recherche

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