Modelling water uptake provides a new perspective on grass and tree coexistence

Root biomass distributions have long been used to infer patterns of resource uptake. These patterns are used to understand plant growth, plant coexistence and water budgets. Root biomass, however, may be a poor indicator of resource uptake because large roots typically do not absorb water, fine roots do not absorb water from dry soils and roots of different species can be difficult to differentiate. In a sub-tropical savanna, Kruger Park, South Africa, we used a hydrologic tracer experiment to describe the abundance of active grass and tree roots across the soil profile. We then used this tracer data to parameterize a water movement model (Hydrus 1D). The model accounted for water availability and estimated grass and tree water uptake by depth over a growing season. Most root biomass was found in shallow soils (0-20 cm) and tracer data revealed that, within these shallow depths, half of active grass roots were in the top 12 cm while half of active tree roots were in the top 21 cm. However, because shallow soils provided roots with less water than deep soils (20-90 cm), the water movement model indicated that grass and tree water uptake was twice as deep as would be predicted from root biomass or tracer data alone: half of grass and tree water uptake occurred in the top 23 and 43 cm, respectively. Niche partitioning was also greater when estimated from water uptake rather than tracer uptake. Contrary to long-standing assumptions, shallow grass root distributions absorbed 32% less water than slightly deeper tree root distributions when grasses and trees were assumed to have equal water demands. Quantifying water uptake revealed deeper soil water uptake, greater niche partitioning and greater benefits of deep roots than would be estimated from root biomass or tracer uptake data alone. © 2015 Mazzacavallo, Kulmatiski. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Sylvain FÉREZ, Mensonge et vérité des corps en mouvement, Paris, L’Harmattan, 2005, 189 pages.

 « Dans le monde de l’Éducation physique, le nom de Claude Pujade-Renaud est associé à l’expression corporelle et à la critique du sport ». Avec Mensonge et vérité, Sylvain Férez nous offre une biographie riche et complexe d’une femme, Claude Pujade-Renaud, au parcours atypique (de l’éducation physique à la littérature, de l’homosexualité à l’hétérosexualité, du langage du corps au langage des mots) et aux réflexions intenses sur le sens des langages. La première étape de ce parcours de vie e..

Des femmes à la conquête des sommets : Genre et Alpinisme (1874-1919)

À partir des publications officielles du Club Alpin Français, d’archives publiques et privées et de la presse sportive et féministe, ce travail analyse l’influence du genre sur la pratique de l’alpinisme et, à l’inverse, les conséquences de son évolution sur les mutations du genre. Présentes dans l’activité en même temps que les hommes, les femmes alpinistes parviennent progressivement à sortir du modèle conformiste de l’excursionnisme féminin pour découvrir des nouveaux espaces et de nouvelles difficultés. Avec modération et sens du compromis, elles revendiquent et conquièrent de nouveaux droits mais sans remettre en cause les hiérarchies entre les sexes et la spécificité de l’identité féminine. Grâce à cette soumission, elles sont tolérées et initiées par les hommes et l’institution alpine. Sous leur contrôle, elles sont officiellement invitées à devenir de bonnes mères et de parfaites épouses. Mais à long terme, grâce aux vertus de l’entraînement, elles découvrent de nouvelles possibilités corporelles, de nouveaux plaisirs et pour certaines une nouvelle destinée.Based on official materials published by the « CAF », on public and private archives, and on sports and feminist articles, this work questions the effects of gender on mountaineering and, whereas, the consequences of his evolution on the gender’changes. Present in the activity at the same time that men, the women mountaineering slowly free oneself of excursionism’s model to discover new frontiers and new difficulties. With moderation and compromise, they claim and obtain new rights but without ever questioning hierarchy between genders and the female specificity. This submissive attitude allows women to be tolerated and at the same time initiated by men and the alpine institution. Under their control women are officially encouraged to become good mothers and perfect spouses. Long term though, thanks to training, they discover new physical capabilities, new enjoyments and, for some, new destinies

Sylvain FÉREZ, Mensonge et vérité des corps en mouvement, Paris, L’Harmattan, 2005, 189 pages.

 « Dans le monde de l’Éducation physique, le nom de Claude Pujade-Renaud est associé à l’expression corporelle et à la critique du sport ». Avec Mensonge et vérité, Sylvain Férez nous offre une biographie riche et complexe d’une femme, Claude Pujade-Renaud, au parcours atypique (de l’éducation physique à la littérature, de l’homosexualité à l’hétérosexualité, du langage du corps au langage des mots) et aux réflexions intenses sur le sens des langages. La première étape de ce parcours de vie e..

Mixité et Éducation Physique et Sportive (1959-1975)

Dès les années 1960, la mixité s’instaure progressivement dans les établissements scolaires du secondaire sous l’effet de la réforme Berthoin. Pourtant l’Education Physique et Sportive échappe à l’impératif de cette mise en place. A partir d’une analyse de la revue Education Nationale de 1959 à 1975, cet article élucide les résistances de l’école à l’égard de la mixité et les représentations qu’elle véhicule sur l’éducation des filles et des garçons. Ainsi, le cas de l’EPS constitue un effet de loupe non seulement des résistances de l’école à l’égard d’une rencontre physique des corps, mais aussi de la conviction, unanimement partagée par les acteurs du système éducatif, d’une différenciation affective, physique et sociale naturelle entre les sexes.Coeducation was established gradually in French secondary schools during the 1960s in the wake of the Berthoin reform. Physical education escaped however these reforms. This article analyzes the journal Education Nationale between 1959 and 1975, in order to explain the schools’ resistance to coeducation as well as the dominant representations of its effect on the education of girls and boys. The study of physical education highlights the schools’ discomfort concerning bodily encounters as well as the widespread conviction among actors of the educational system that natural, emotional, physical and social differences existed between the sexes

Solubilizzazione isoterma della fase sigma in un acciaio superduplex UNS S32760

In questo lavoro si riportano i risultati delle prove di solubilizzazione isoterma della fase sigma eseguite su unacciaio inossidabile superduplex UNS S32760. Il materiale base è stato dapprima sottoposto a trattamentiisotermi a 1173 K e poi solubilizzato a 1323 K e a 1353 K. La cinetica di solubilizzazione è stata valutataprelevando i campioni dal forno a diversi intervalli di tempo e misurando la percentuale rimanente di precipitatomediante analisi di immagine. I risultati, riportati in termini di curve, mostrano, per le diverse temperature ditrattamento, la variazione di fase sigma in funzione del tempo e della percentuale iniziale di precipitato. Infine,è stato sviluppato un modello semiempirico che descrive con buona accuratezza i dati sperimentali

Most soil trophic guilds increase plant growth: a meta-analytical review

Trophic cascades are important drivers of plant and animal abundances in aquatic and aboveground systems, but in soils trophic cascades have been thought to be of limited importance due to omnivory and other factors. Here we use a meta-analysis of 215 studies with 1526 experiments that measured plant growth responses to additions or removals of soil organisms to test how different soil trophic levels affect plant growth. Consistent with the trophic cascade hypothesis, we found that herbivores and plant pathogens (henceforth pests) decreased plant growth and that predators of pests increased plant growth. The magnitude of this trophic cascade was similar to that reported for aboveground systems. In contrast, we did not find evidence for trophic cascades in decomposer- and symbiont-based (henceforth mutualist) food chains. In these food chains, mutualists increased plant growth and predators of mutualists also increased plant growth, presumably by increasing nutrient cycling rates. Therefore, mutualists, predators of mutualists and predators of pests all increased plant growth. Further, experiments that added multiple organisms from different trophic levels also increased plant growth. As a result, across the dataset, soil organisms increased plant growth 29% and non-pest soil organisms increased plant growth 46%. Omnivory has traditionally been thought to confound soil trophic dynamics, but here we suggest that omnivory allows for a simplified perspective of soil food webs – one in which most soil organisms increase plant growth by preying on pests or increasing nutrient cycling rates. An implication of this perspective is that processes that decrease soil organism abundance (e.g. soil tillage) are likely to decrease aboveground productivity. Synthesis Soil foodwebs have resisted generalizations due to their diversity and interconnectedness. Here we use results from a meta-analysis to inform a simplified perspective of soil foodwebs: one in which most soil trophic guilds increase plant growth. Our review also includes the first widespread support for the presence of trophic cascades in soils

Localization and role of the molecular scaffold testin during mitosis and in actin-based processes

The cytoskeleton is an important system in health and disease. Composed by three major classes of filaments, it ensures the maintaining of the cellular shape, it is involved in cell motility and cell division. The complex regulation of this system is mediated by a various number of proteins which often display multiple and differential functions. Testin is one of these cytoskeletal proteins described in important processes involving the actin cytoskeleton such as cell migration and cell spreading. This thesis is dedicated to the study of testin during the cell division process which is mainly regulated by the actin and microtubule cytoskeleton. Our results provided evidence that, during mitosis, testin is able to dynamically localize to mitotic structures like centrosome, midzone and midbody. Further investigations of this localization, particularly in cytokinesis, permit to conclude that testin is a midbody bulge protein capable to concentrate to this intercellular bridge through its LIM1 and LIM2 domains. Testin is involved in the regulation of the actin cytoskeleton through being part of a protein complex with amongst other zyxin and talin, also able to concentrate to the midbody. Therefore, using RNAi experiments, we showed that the localization of testin to the midbody is zyxin and talin independent. In order to understand the potential function of testin during the cell division process, we initiate the identification of the potential partners of testin during mitosis. Based on the known interactors of testin, themselves described to localize to the midbody, we performed pull down as well as knock-down experiments. We also started the screening of potential mitotic partners of testin using the BioID approach. Given these observations about the localization of testin during mitosis the question arose whether testin plays a role in this process of cell division. Indeed, modulating the expression of testin results in different phenotypes. Overexpression of testin leads in faulty spindle formation or in a lack of abscission thus ultimately to an increase in multinucleated cells. Conversely, down regulation of testin leads to a perturbation of the nuclear shape and the microtubule structure of the midbody. Taken together, these data suggest that, in addition to its important role in actin-based processes in interphase, testin, a novel midbody bulge protein is involved in mitosis where it appears required for the integrity of a microtubule structure

L'histoire des sportives : un déni de responsabilité ?

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