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Jean-Claude Schmitt est médiéviste et directeur d’études à l’École des Hautes études en Sciences Sociales, où il enseigne l’histoire des images et des représentations dans l’Occident médiéval. Parmi ses nombreux ouvrages, nous pouvons citer La raison des gestes dans l’Occident médiéval (Gallimard, 1990), Les Revenants. Les vivants et les morts dans la société médiévale (Gallimard, 1994), Le corps, les rites, les rêves, le temps. Essais d’anthropologie médiévale (Gallimard, 2001), Le Corps des...

Well-documented shade adaptations include physiological and morphological traits of shoots and leaves. Belowground shade adaptations (roots or other buried structures) are rarely mentioned in the literature and have never been studied in tree seedlings. This study evaluates the functional role of adventitious roots developed by most balsam fir (Abies balsamea) seedlings under a closed canopy. Our goal was to describe the relationships between growth, biomass allocation, and adventitious root development in balsam fir seedlings (5–26 cm tall, 9 to 33 y old) excavated under a closed canopy (< 8% full sunlight). Seedling height, branch number and crown width increased linearly with stem diameter measured at ground level. The dry mass of stems and roots increased exponentially and tree vigour (photosynthetic/non-photosynthetic biomass ratio) decreased exponentially as stem diameter increased. Results indicate that shade tolerance is limited by size and concurrent radial increment at the stem base. Re...

The percentage of above-canopy Photosynthetic Photon Flux Density (%PPFD) was measured at 0, 50 and 100 cm above the forest floor and above the main understory vegetation in stands of (1) pure Betula papyrifera (White birch), (2) pure Populus tremuloides (Trembling aspen), (3) mixed broad-leaf-conifer, (4) shade-tolerant conifer and (5) pure Pinus banksiana (Jack pine) occurring on both clay and till soil types. %PPFD was measured instantaneously under overcast sky conditions (nine locations within each of 29 stands) and continuously for a full day under clear sky conditions (five locations within each of eight stands). The percentage cover of the understory layer was estimated at the same locations as light measurements. Mean %PPFD varied from 2% at the forest floor under Populus forests to 15% above the understory vegetation cover under Betula forests. Percent PPFD above the understory vegetation cover was significantly higher under shade intolerant tree species such as Populus, Betula and Pinus than under shade tolerant conifers. No significant differences were found in %PPFD above the understory vegetation cover under similar tree species between clay and till soil types. The coefficient of variation in %PPFD measured in the nine locations within each stand was significantly lower under deciduous dominated forests (mean of 19%) than under coniferous dominated forests (mean of 40%). %PPFD measured at the forest floor was positively correlated with %PPFD measured above the understory vegetation and negatively correlated with cumulative total percent cover of the understory vegetation (R2 = 0.852). The proportion of sunflecks above 250 and 500 I¼mol m-2 s-1 was much lower and %PPFD in shade much higher under Populus and Betula forests than under the other forests. Differences in the mean, variability and nature of the light environment found among forest and soil types are discussed in relation to their possible influences on tree succession.

A l’exception de rares temoins encore bien conserves, comme la torre delle Milizie ou la torre dei Conti, aux abords des forums imperiaux, et de quelques eglises qui gardent dans leurs murs et leurs decorations le souvenir de cette periode, le Moyen Âge n’imprime que tres furtivement sa marque dans la trame urbaine contemporaine de Rome. La quasi-totalite des traces de cet urbanisme medieval a en effet ete emportee par l’« ouragan baroque » (J.-C. Maire Vigueur), qui a modifie en profondeur l...

International audience

International audience

International audience

The Impact of Papal Justice in the Diocese of Uzès under John XXII. In the 1320’s, Pope John XXII (1316-1334) carried out a series of trials for heresy against his own political enemies across the north and the centre of Italy. Among them were not only members of powerful noble families (the Viscontis, Estes, Montefeltros etc.), many minor lords as well as communities such as Recanati, Osimo or Spoleto, but also Emperor Ludwig IV from Bavaria. After their conviction as heretics, John XXII planned massive publications of the sentences in many dioceses across the west, in order to organize the crusade. The diocese of Uzès is particularly emblematic of the way theses publications were spread, from the bishopric to the most remote places of the diocese. It also shows the various actors of the preaching and the concrete organization of the publications., L’impact de la justice pontificale dans ie diocèse d’Uzès au temps de Jean XXII. Le pape Jean XXII (1316-1334) engagea dans les années 1320 une longue série de procès pour hérésie contre ses ennemis politiques dans toute l’Italie du Nord et du Centre. Parmi les accusés figuraient non seulement des membres des familles seigneuriales les plus puissantes (Les Visconti, les Este, les Montefeltro etc), de nombreux petits seigneurs locaux et des communautés comme Recanati, Osimo ou Spolète, mais aussi l’empereur Louis IV de Bavière. Après leur condamnation comme hérétiques, Jean XXII organisa une publication massive des sentences de condamnation dans de nombreux diocèses d’Occident, afin d’organiser la croisade. Le diocèse d’Uzès est particulièrement emblématique de la manière dont cette publication fut effectuée, depuis l’évêché jusque dans les endroits les plus reculés du diocèse. Il met aussi en lumière les différents acteurs qui ont contribué à ces prédications et le déroulement des publications., Parent Sylvain. L’impact de la justice pontificale dans le diocèse d’Uzès au temps de Jean XXII : la publication des procès contre les fils de Matteo Visconti et Louis de Bavière. In: Les Justices d'Église. Toulouse : Éditions Privat, 2007. pp. 287-316. (Cahiers de Fanjeaux, 42)