Proton exchange membrane fuel cell operation and degradation in short-circuit.

International audienceThis paper presents an experimental study dealing with operation and degradation during an electrical short circuit of a proton exchange membrane fuel cell stack. The physical quantities in the fuel cell (electrical voltage and current, gas stoichiometry, pressures, temperatures and gas humidity) are studied before, during and after the failure. After a short circuit occurs, a high peak of current appears but decreases to stabilize in a much lower value. The voltage drops in all the cells and even some cells presents reversal potentials. The degradation is quantified by using electrochemical impedance spectroscopy

Demografía y crecimiento primario durante la regeneración de tres especies de pino a lo largo de gradientes climáticos

13 páginas, 4 figuras y 3 tablasLa regeneración es un proceso crítico en la dinámica de los bosques, que presenta una marcada heterogeneidad temporal y espacial. En este trabajo se pretende avanzar en el conocimiento de las variables bióticas y abióticas que determinan a escala local la presencia, abundancia y crecimiento primario de plántulas de tres especies de pino: Pinus sylvestris, P. nigra y P. uncinata, y determinar el efecto relativo del clima. Para ello se muestrearon 216 parcelas distribuidas a lo largo de gradientes climáticos en siete localidades montañosas. Se censaron las plántulas recién emergidas y el resto de juveniles, y se midieron los crecimientos anuales. Los resultados mostraron diferencias significativas entre especies con efectos directos e indirectos del clima sobre la demografía y el estado de los juveniles. En las tres especies se apreció que la supervivencia de los juveniles aparecía desplazada hacia altitudes mayores respecto donde se producía el óptimo de la emergencia. Las relaciones locales de competencia y facilitación ejercieron efectos importantes sobre la regeneración de las tres especies, siendo éstos modulados por el clima.Ministerio Español de Innovación y Ciencia Consolider-Montes (CSD2008_00040), Los autores agradecen a toda la gente que hizo posible el trabajo de campo: R. Freire, B. Santamaría, J. Martínez, D. López, R. Ruíz-Puche, E. Molina, L. Ivorra, S. Martín, B. Ros y C. Boubekeur. También el apoyo estadístico de R. Manson.Proyecto europeo BACCARA (CE: FP7-226299, 7FP)Peer reviewe

What EU policy framework do we need to sustain High Nature Value (HNV) farming and biodiversity? Policy Paper prepared in the framework of HNV-Link (project funded by the H2020 Research and Innovation Programme under Grant Agreement no 696391)

This policy paper builds upon the work carried out in the framework of HNV-Link (H2020 Project, 2016-2019, www.hnvlink.eu), a thematic multi-actor network on High Nature Value (HNV) Farming involving 13 partners from 10 European countries. The goal of this network is to support HNV farming systems by inspiring and sharing innovations/practices that improve their socio-economic viability while preserving their ecological value and the public services they provide. HNV-Link informs policymakers and authorities at the European and national levels of the main policy stakes around HNV farming, and to recommend adjustments of the Common Agricultural Policy (CAP) and other policies in order to adequately support HNV farming, the territories in which they are embedded, and the communities that depend on them. In Europe, farmers operate within a complex and constraining environment and policy/regulatory framework, including income support and rural development measures of the CAP, but also the numerous regulations related to agriculture, food hygiene/safety, animal health/welfare, environment protection, and climate change. This framework can provide farms with incentives or on the contrary, hinder their development, and it has consequently a major influence on their economic viability and the survival of the communities depending on farming. This institutional framework was designed to deal mainly with the problems that intensive farms face. Far less weight has been placed on designing and implementing policies adapted to the needs of HNV farms, i.e. those low-intensity farms which rely on and safeguard a rich biodiversity and associated ecosystem services made up of a variety of habitats and landscapes elements. Hence, there is a need for a creative yet thoughtful design and implementation of adapted policy measures

Recruitment patterns of four tree species along elevation gradients in Mediterranean mountains : not only climate matters

Evidence of tree regeneration failure of some species in the Iberian Peninsula forests warns us about the impact that the global change may exert on the preservation of Mediterranean forests, such as we know them. Predictions agree about an exacerbation of the summer drought there, acknowledged as the main limiting factor for the recruits' survival. On the other hand, many studies have also proved the relevant role that local heterogeneity has over the spatial distribution of forest species recruitment by providing safe sites. Therefore, to unravel how climate interacts with local factors over juveniles' performance seems crucial for the design of successful management strategies that allow facing the global warming. Here, we surveyed the natural recruitment of four dominant tree species in seven mountainous regions in the Iberian Peninsula, along entire elevational ranges as surrogates of their climatic ranges. Two of them have alpine and temperate distributions with populations at their rear edge in the Spanish mountains: Fagus sylvatica and Pinus uncinata; and the other two have a genuine Mediterranean distribution: Quercus ilex and Pinus nigra. Our main goal was to analyze for each species the effect of climate, local factors (i.e. light availability, stand structure and ground cover) and the interactions among them to identify the main drivers leading the regeneration process, assessed in terms of presence, abundance and mean annual growth of juveniles. The results showed different environmental factors determining the recruitment patterns of each species. Nevertheless, they highlighted the pervasive role exerted by both climate and fine scale factors, particularly the co-occurring vegetation on recruits' abundance, and the light availability on their growth. Moreover, we found some interactions among annual mean temperature and local factors, suggesting that climate and local heterogeneity act hierarchically, i.e. the local conditions may mitigate or exacerbate the impact of climate on juveniles. These results advocate for further research to increase our knowledge on the complex net of interactions among factors involved in recruitment at different scales, which in turn should be taken into account and incorporated in forthcoming management strategies

Participation: a pillar of sustainable forest management in the Mediterranean

Partie III - Mediterranean forest-based solutions. Chapter 12International audienc

Participation: a pillar of sustainable forest management in the Mediterranean

Partie III - Mediterranean forest-based solutions. Chapter 12International audienc

Participation: a pillar of sustainable forest management in the Mediterranean

Partie III - Mediterranean forest-based solutions. Chapter 12International audienc