187 research outputs found
Geographical variation in the distributional constraints along a gradient of population aggregation
No full textFactors determining species distributions have frequently been shown to vary geographically, yielding spatially variable species–environment relationships when developing species distribution models. Using occurrence data for four bird species, we analysed to what extent position within the distribution range along a gradient of population aggregation determined geographical variation of distributional constraints. We built generalised linear models for the whole dataset (global models) and separately for each region within the species range with decreasing population aggregation (core, middle and peripheral). For both global and regional models, we compared species responses to habitat conditions showing an overall higher model fit in peripheral regions than in middle and core regions. Better model fit in peripheral regions was also found after including a spatial factor (i.e. an autocovariate estimating the proportion between the presences and total observations within a 10 km radius) into the global and regional models.The scattered availability of suitable habitat patches in a predominantly hostile landscape matrix seems to be the limiting factor for species distributions in peripheral regions. Conversely, the larger number of spatially dependent occurrences in core and middle region may favour source and sink population dynamics, yielding poorer relationships between habitat conditions and species occurrence. The role of the spatial factor after removing the co-variation with habitat conditions separately for each region suggests that endogenous processes such as dispersal vary throughout the species range but differently for each species. Geographical variation in distributional constraints can be interpreted as a consequence of the inherent spatial character of ecological processes and their interaction with varying environmental conditions throughout the species range. Overlooking the effects of spatial variation in distributional constraints may lead to erroneous management conclusions and inadequate estimation of the species’ response to environmental changes.<br/
Does fire increase the seasonal variability of bird communities ? A case in Mediterranean shrublands
No full textFire, a frequent phenomenon in Mediterranean landscapes, is a major ecological disturbance in terrestrial ecosystems. We hypothesized that bird communities undergo greater seasonal changes in burnt areas than in unbumt ones. Using the point-count method we assessed bird species composition and abundance in three zones (unbumt, burnt in 1982, and burnt in 1994) during the breeding and wintering seasons of 1997 and 1998.
From the breeding to the wintering seasons, burnt zones showed an increase in forest species, whereas the bird community of the unbumt zone remained stable in the gradient open-forest species. Moreover, the seasonal turnover of communities was higher in burnt zones than in the unbumt ones, although this did not imply that the former varied in richness through the year. The pattern of bird abundance in the unbumt zone was similar during the two study years, in contrast with that of burnt zones, suggesting higher annual cyclicity in resource availability in unbumt areas. These findings suggest that fire increases the seasonal variability of bird communities.Les incendies, phénomènes habituels dans les paysages méditerranéens, sont l’une des principales perturbations écologiques des systèmes terrestres. On a cherché à vérifier l’hypothèse selon laquelle les variations saisonnières des communautés d’oiseaux augmenteraient dans les zones brûlées. En utilisant la méthode des points d’écoute pendant la période de nidification et l’hiver 1997 et 1998, on a déterminé la composition et l’abondance de ces communautés dans trois zones (non-brûlée, brûlée en 1982 et brûlée en 1994).
Entre ces deux saisons, les zones incendiées ont montré un accroissement du nombre d’espèces forestières, tandis que dans la zone intacte la communauté est restée stable le long du gradient forêt-milieux ouverts. De plus, le turn-over saisonnier fut supérieur dans les zones brûlées sans que ceci implique une variation de la richesse spécifique au long de l’année. Contrairement aux zones brûlées, les parties intactes n’ont pas montré de grandes fluctuations d’abondance des espèces, ce qui y suggère une plus forte cyclicité annuelle de la disponibilité des ressources. Ces résultats indiquent que le feu augmenterait la variabilité saisonnière des communautés d’oiseaux.Herrando Sergi, Brotons Lluis, Llacuna Santiago. Does fire increase the seasonal variability of bird communities ? A case in Mediterranean shrublands. In: Revue d'Écologie (La Terre et La Vie), tome 57, n°2, 2002. pp. 151-163
Modelización y simulación dinámica de un automóvil utilitario de tracción delantera
No full text[ES] Este proyecto consiste en la modelización mecánica de un Austin MINI Cooper del año 1964, el cual fue toda una revolución en el diseño de automóviles y estilo de su carrocería. Se han modelizado los elementos móviles, así como, las suspensiones, la dirección, los neumáticos y los frenos y como parte rígida, el chasis y la carrocería. Con lo cual, permite simular el comportamiento del automóvil en distintas pruebas.
Para llevar a cabo esta modelización, el primer paso ha sido la toma de medidas sobre un archivo de SolidWorks fielmente reproducido, lo que ha servido para definir la geometría y posición de todos los elementos móviles. Con estos datos se ha pasado a la modelización de cada uno de estos elementos como cuerpos en el programa Adams/Car de MSC Software.
Finalmente, se han simulado diferentes maniobras para comprobar el funcionamiento del modelo en diferentes situaciones, como; pruebas de suspensión, tanto delantera como trasera, pruebas de aceleración, deceleración…
De esta manera se puede prever el comportamiento del coche al realizar modificaciones como el cambio de elementos, variación en los reglajes, etc.[EN] This project consists of a mechanical modelization Austin MINI Cooper 1964, which was a
revolution in automotive design and style of bodywork. The movile elements have been
modelized, as suspension, steering, tires and brakes also the direction part, the chassis
and bodywork. Whereupon, to simulate the behavior of the car in different tests.
To perform this modeling, the first step has been taking action on a SolidWorks file
faithfully reproduced, which has served to define the geometry and position of all the
moving parts. With these data we have gone to the modelization of each of these
elements as bodies in Adams/Car MSC Software program.
Finally, we have simulated various maneuvers to test the operation of the model in
different situations, like; test suspension, both front and back, testing acceleration,
deceleration...
This way you can predict the behavior of the car in different maneuvers and possible
settings.Espinosa Brotons, A. (2014). Modelización y simulación dinámica de un automóvil utilitario de tracción delantera. https://riunet.upv.es/handle/10251/173612Archivo delegad
Addressing the challenge of photovoltaic growth: Integrating multiple objectives towards sustainable green energy development
No full textPhotovoltaic production is growing globally thanks to climate change mitigation efforts. However, this growth is seldom planned which can lead to conflicts with other land uses, mostly agriculture and biodiversity conservation. There is, therefore, urgent need for adequate planning to minimise potential conflicts. We demonstrate how to identify priority areas for photovoltaic development to meet projected targets for 2050, as well as critical areas for the maintenance of different types of agriculture and biodiversity conservation, using Catalonia (NE Spain) as a case study. We tested three planning scenarios simulating alternative photovoltaic development models: setting targets at the whole regional scale or splitting those targets across counties distributing them equitably by county energy demand or area available for photovoltaic development. Photovoltaic targets could only be achieved when setting targets at the whole of Catalonia scale, although leading to heterogeneous distribution of development efforts and associated impacts on agriculture and biodiversity across counties. Setting targets for each county based on energy demand was far from achieving the regional photovoltaic development target, driven by the limited land available in some highly urbanised counties, where energy demand concentrates. On the other hand, setting targets based on area available within each led to the most equitable distribution of potential impacts of photovoltaic development, while also approaching the regional photovoltaic development target. Adequate planning of photovoltaic development will be key to ensure that photovoltaic development does not flourish at the expenses of other land uses, like maintenance of agricultural production or biodiversity.Full Tex
Habitat selection by Ortolan Buntings Emberiza hortulana in post-fire succession in Catalonia: implications for the conservation of farmland populations
No full textThe Ortolan Bunting Emberiza hortulana is a long-distance migrant that has suffered major population declines across much of its European breeding range. While northern populations are bound largely to farmland, Mediterranean populations are largely confined to habitats subject to recurrent wildfires. Habitat selection of the Ortolan Bunting was assessed in a recently burnt area in Catalonia at landscape and habitat scales. A Zero-inflated Poisson procedure was used to model the abundance of birds in relation to landscape and habitat variables. The most parsimonious landscape model predicted the highest abundance on south-facing slopes, with a gradient above 10°. The most parsimonious habitat model showed a positive quadratic effect of bare ground and regenerating oak Quercus spp., with predicted optima for abundance around 20-30% and 20% cover, respectively. There was a clear relationship between predicted abundance of the Ortolan Bunting and post-fire regenerating oak shrubs. South-facing, moderately sloping areas were favoured and bare ground was a key feature of the species' habitat. A matrix combining patches of sparse oak shrubs and patches of bare ground appears to be the optimal breeding habitat in the Mediterranean. The maintenance or provision of similar habitat features, especially patches of bare ground, may prove crucial for the conservation of rapidly declining Ortolan Bunting populations on farmland across temperate Europe
Are Fragments Islands? Landscape Context and Density‐Area Relationships in Boreal Forest Birds
No full textInternational audienc
Assessing the role of Natura 2000 at maintaining dynamic landscapes in Europe over the last two decades: implications for conservation
No full textContext
The Natura 2000 aims to promote the persistence of biodiversity and traditional uses. European landscapes have, however, undergone large transformations in the past decades, mainly associated with the abandonment of less productive lands concentration of intensive agriculture. These changes could pose management challenges and new opportunities to the achievement of the network´s goals.
Objective
Evaluate changes in land cover within Natura 2000 in the last two decades.
Methods
We use different Corine Land Cover datasets to construct transition matrices of land uses for measuring changes for each Natura 2000 site. We also explore the role of different drivers in observed changes and assess the impacts of these changes in the structure of landscape.
Results
Landscape has been highly dynamic within Natura 2000 in the last two decades with more than 20% undergoing land cover changes. The most systematic transitions involved both, succession processes towards naturalisation in older and more abrupt protected areas (PAs) and anthropization in less steep and more recently designated PAs. Changes across land cover categories had also significant effects on the landscape configuration towards a higher homogenisation.
Conclusions
Two different strategies would be needed to enhance the role of Natura 2000, (i) tighter control to ensure anthropization, mainly intensive agriculture, does not compromise conservation goals within PAs and (ii) tackle more effectively the ecological and socio-economic effects of abandonment in less productive areas to halt loss of key habitats. On the other hand, changes in composition and structure of landscape open new conservation opportunities derived from enhanced connectivity.Griffith Sciences, School of Environment and ScienceNo Full Tex
Community responses to extreme climatic conditions
No full textSpecies assemblages and natural communities are increasingly impacted by changes in the frequency and severity of extreme climatic events. Here we propose a brief overview of expected and demonstrated direct and indirect impacts of extreme events on animal communities. We show that differential impacts on basic biological parameters of individual species can lead to strong changes in community composition and structure with the potential to considerably modify the functional traits of the community. Sudden disequilibria have even been shown to induce irreversible shifts in marine ecosystems, while cascade effects on various taxonomic groups have been highlighted in Mediterranean forests. Indirect effects of extreme climatic events are expected when event-induced habitat changes (e.g. soil stability, vegetation composition, water flows altered by droughts, floods or hurricanes) have differential consequences on species assembled within the communities. Moreover, in increasing the amplitude of trophic mismatches, extreme events are likely to turn many systems into ecological traps under climate change. Finally, we propose a focus on the potential impacts of an extreme heat wave on local assemblages as an empirical case study, analysing monitoring data on breeding birds collected in France. In this example, we show that despite specific populations were differently affected by local temperature anomalies, communities seem to be unaffected by a sudden heat wave. These results suggest that communities are tracking climate change at the highest possible rate [Current Zoology 57 (3): 406–413, 2011]
Abandon des terres et avifaune (dynamiques spatiales et temporelles d un paysage méditerranéen)
No full textMONTPELLIER-SupAgro La Gaillarde (341722306) / SudocSudocFranceF
Forest connectivity percolation thresholds for fire spread under different weather conditions
No full textHow fuel influences fire spread at different spatial scales has been broadly studied but it is still under research. Although prior research has generally explored fuel effects at the stand scale, there is increasing recognition that forest structure and composition at the landscape scale can regulate fire size when weather conditions allow fire to have enough initial capacity to spread. Simulation models have usually been adopted to test forest landscape structure's effect on fire activity, but we still lack empirical evidence of these effects on a broad scale and using multiple fires. In this study, we use the graph theory and the percolation theory to test the relationship between forest functional connectivity and fire size in a Mediterranean region (Catalonia, NE Spain, similar to 32000 km(2)) and under different weather conditions. Using a total sample of 554 fires that occurred between 1987 and 2019, we relate fire size with forest connectivity inside the fire perimeter, which we describe with different interpretations of forest-land cover maps and at different fire dispersal distances (10-, 100- and 2000- meters spotting capacity). Previously, fires were classified according to the weather and drought conditions in which they occurred (windy, arid or regular days, and dry or non-dry conditions) with the hypothesis that the capacity of fire to "read" the forest landscape differs according to weather variables. We found that a forest percolation threshold existed for most types of fires: forest connectivity had a positive influence on fire size until a threshold at which the landscape becomes continuous and other processes to control fire cease to have effect. This percolation threshold is about 0.40 for fires occurring under arid conditions. Under regular weather conditions, the threshold is nonexistent and forest connectivity always exerts a positive effect on fire size. Notably, forest connectivity has no influence on fire size on windy- and dry-weather days. All these results are of paramount relevance for forest and landscape management aimed at reducing wildfire risk, since for fires driven by extreme weather conditions (more prone to happen in the future), landscape offers less opportunities to stop them. Researchers and managers need to identify the probability of experiencing each of the different weather types in a climate change context to boost the management of forests and landscapes in a cost-effective way.Spanish Government through the INMODESCERCA Programme from the Generalitat de CatalunyaEuropean Union's H2020 research and innovation program under the Marie Sklodowska-Curie gran
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