Succession secondaire et perte de diversité végétale après réduction du broutage dans un paturage boisé des Alpes centrales suisses

Freléchoux F., Meisser M. and Gillet F. 2007. Secondary succession and loss in plant diversity following a grazing decrease in a wooded pasture of the central Swiss Alps. Bot. Helv. 117: 37 – 56. Reduced cattle grazing pressure in the Alps has caused the reforestation of many subalpine pastures during the last decades. To understand the dynamics of natural reforestation and to evaluate how this change affects plant species diversity, we described the vegetation of a wooded pasture in the central Swiss Alps (Sembrancher, Valais) using the integrated synusial method. Based on stratified vegetation relevés in 27 plots,we defined 11 community types at the synusial level (two tree-layer, five shrub-layer, and four herb-layer synusiae), and four community types at the phytocoenosis level (pasture, tall forbs and scrub, wooded pasture and forest). The spatial distribution of these four phytocoenoses suggests that they represent successional stages after abandonment, and that the pathway of vegetation succession depends on the aspect. We suppose that on northern oriented, cool and shady locations, abandoned pastures first develop towards tall-forb meadows and scrub with Alnus viridis, and then to a preforested stage with Picea abies and Larix decidua. In contrast, on western oriented, warm and sunny location, Larix decidua (mainly) and Picea abies directly colonize the abandoned pastures, but further succession finally leads to the same pre-forested stage as on northern slopes. Plant species richness was highest in open areas and decreased by 25% as tree cover increased from 6% to 65%. According to our successional model, plant species diversity is lost more rapidly on northern slopes (with species-poor green alder scrub) than on western slopes (with species-rich young larch forests), suggesting that northern slopes most urgently need an appropriate grazing management. Manuscrit accepté le 28 mars 2007     

Le Paléolithique supérieur dans la péninsule coréenne et l’archipel du Japon

There is one decisive gate between the Asian continent and the archipelago of Japan which is the strait of Tsushima that exists between the Korean peninsula and the archipelago. The strait is very narrow; however, the depth is relatively deep. If the sea level did not fall down to at least 130 meters below the present level, the terrestrial bridge would not be formed there. We know the former case concerning the first human population of which crossed this maritime gate of human groups 50,000 years ago. One supposes that the men did not have any means to cross there without the terrestrial bridge previous to 50,000 years. According to the studies of the abyssal drills of the Sea of Japan that one noted several lowering of the sea level according to the marine isotopic stages (MIS): 2, 6, 10, 12, 16, 18 and 20. With regard to the marine isotopic stage 2 that correspond to the Maximum-coldness of the last glacial when the sea dropped in below 125 meters in relation to the present level. According to study of the seismic stratigraphy and according to the obtained ages of seabed sediments by the method of carbon 14 that one concluded the concerned strait remained always like a marine channel and narrow during the last glacial (Park et al., 2000). We notice the typological common points between the lithic industry of the Korean peninsula and the one of the Kyushu island during the marine isotopic stage 2 (MIS-2) which are the tanged point (flake point), the bifacial point to triangular section (point to three retouched faces), etc. However, there are some differences in the composition of tools and the fabrication technique. Regarding the cultural origin and the big human migration, we cannot prove them for now. Such situation showed that some obstacles existed between such two regions. There are no common features on the flaking technique and the typology before 50,000 years in these two regions since we do not have any affirmative overdraft.     

Site du Paléolithique inférieur de Bogatyri/Sinyaya Balka dans la péninsule de Taman,Kraï de Krasnodar,Russie

The paper aims to present new multidisciplinary results obtained from the study of the Lower Palaeolithic Bogatyri/Sinyaya Balka site (the Taman peninsula), organized after 2010. The particular attention is given to the estimation of the age of the site and to the unique way of adaptation of the Homo erectus to the special environmental conditions of the Taman peninsula.     

Dosage du fer et de l'aluminium échangeable dans les minéraux argileux et dans les sols

Résumé Une méthode est proposée pour le dosage du fer et de l'aluminium échangeable dans les minéraux argileux et dans les sols. La méthode est basée sur l'extraction successive des oxinates de fer et d'aluminium en fonction du pH.Les conditions optimales et l'influence des divers facteurs déterminant l'extraction quantitative et sélective de ces deux éléments ont été préalablement étudiées.Publication du Centre de Chimie Biologique et Colloïdale du sol subsidié par I'I.R.S.I.A.     

Sur les transports de réserves et les transports de couvain dans la ruche

Résumé Dans cet exposé, nous avons montré que les Abeilles sont capables de changer de place les réserves sucrées et le couvain. Ces comportements ne correspondent pas à des conditions de vie normales de la colonie.Cependant, le transport des réserves indique la possibilité, pour les Abeilles, de réagir à une perturbation importante selon un ordre que nous avions déjà établi dans l'élevage des larves (Montagner, 1962). C'est ainsi qu'en cas de nourrissement brutal et pendant une période de disette, elles tendent à grouper la majeure partie des réserves près de la reine, tout en laissant une place sur un cadre pour la ponte. La reine représenterait donc bien, dans la ruche, le potentiel survie à partir duquel les ouvrières auraient tendance à répartir leurs activités de façon décroissante.Par contre, les transports de couvain ne semblent répondre à aucun plan d'organisation comme chez les Fourmis. Nous avons montré qu'ils étaient associés à de profondes perturbations, telles que le manque de nourriture ou la perte de la reine.

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Summary The results of these studies indicate that bees are able to remove sugary stores and brood.We have established that bees remove their stores according to a certain order that we also made evident when studying brood rearing (Montagner, 1962). So, the bees hoarded the most part of their stores in the side of the hive where the queen stood, when we fed them suddenly during a dearth time.Then, the queen would be in beehive the attractive center from which the workers would share theirs activities in a decreasing way.On the contrary, it never seemed to us that the removals of brood were connected to any right order as for ants. We have established that they were associated to great troubles in beehive such as a want of food or the death of the queen.

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Zusammenfassung In diesem Bericht haben wir bewiesen, dass die Bienen die Zuckervorräte und die Brut an andere Plätze zu bringen vermögen. Dieses Verhalten entspricht nich den normalen Lebenszuständen der Kolonie.Soch bezeugt der Transport der Vorräte die Möglichkeit für die Bienen, gegen eine erhebliche Störung, nach einer bestimmten Regel zu reagieren, die wir schon bei der Aufzucht der Larven festgestellt haben (Montagner, 1962).Also, im Falle einer plötzlich verstärkten Zufuhr und während einer Mangelperiode haben sie die Neigung, den grössten Teil der Vorräte um die Königin zu sammeln, indem sie aber einen Platz für das Eierlegen auf einem Rahmen frei lassen. Die Königin würde also im Bienenstock die Möglichkeit der Fortdauer darstellen. Von dieser Tatsache ausgehend würden die Arbeiterinnen also ihre Tätigkeit in abnehmender Weise ausüben.Im Gegenteil scheinen die Brutversetzungen keinem Organisationsplan zu entsprechen, wie es bei den Ameisen der Fall ist. Wir haben gezeigt, dass sie mit schwerwiegenden Störungen, wie z. B. dem Nahrungsmangel oder dem Tod der Königin, in Verbindung stehen.

     

Etude preliminaire de stades de la méiose humaine dans les spermatocytes et les ovocytes

Summary Human meiotic chromosomes, from spermatocytes and ovocytes, are described after observations of whole mount preparations under E.M. Small testicular and ovarian fragments are put in distillated water, then macerated; the cell suspension is spread on the surface of sheet copper grids covered with formvar plus collodion films. After dehydratation interesting stages are selected under L.M. before observations under E.M.Zygotene and pachytene are the most common stages. During pachytene the chromomeres are well individualized; the synaptonemal complex may be observed; chromatin fibers connect the chromosomes to nuclear pores, interchromosomal fibers joint the bivalents. Zygotene and pachytene bivalents are very similar in the male and the feminine germ cells.     

Place de la scintigraphie et de la radiothérapie dans les évacuations sanitaires hors du Bénin de 2006 à 2010

Because of the insufficiency of technical tray in Benin hospitals, medical practitioners have recourse to medical evacuation abroad for better taking care of patients. This study presents statistics of medical evacuations made outside Benin, for scintigraphy and radiotherapy, funded by the government from January 2006 to December 2010. For a total of 769 patients from 2- to 80-years-old, 229 patients (29.8%) were concerned by these two indications. Urology, cardiology, and gynecology were the most important specialties, which provide medical evacuations in 24%, 23.6% and 13.15% of cases respectively. The pathologies involved were essentially malignant tumors in 66.8% of cases and heart diseases in 16.2% of cases. The strengthening of medical instrument and staff through nuclear medicine and radiotherapy center should contribute to improve the performance of Benin sanitary system and to reduce the medical evacuations abroad.     

Cinétiques de la fixation du 18F-FDG dans les structures cérébrales : faisabilité et résultats préliminaires

ObjectDynamic positron emission tomography (dyn-PET) acquisitions using the radiotracer ¹⁸F-deoxyglucose (¹⁸F-FDG) are mainly developed in research studies of brain PET in kinetic modelling to determine the local glucose consumption rate. This procedure is difficult to establish, due to its requirement for blood sampling. Here, we propose a simple approach to constructing time–activity curves (TACs) for four different brain structures (the arterial & venous regions and grey & white matter) based on direct image measurements on chronologically reconstructed image volumes of regions of interest.Materials and methodsWe applied our processing on 14 control subjects to extract their physiological state. We defined the reference ¹⁸F-FDG kinetic curves as a “population averaged TAC” for four structures. To increase the curves accuracy, our method included the evaluation of two normalization based on the integral of the activity curve in the arteries and the veins.ResultsThe method showed discrimination between artery, venous, grey and white matters. The two normalization methods significantly reduce the dispersion for the grey and white matter curves and that venous normalization showed the best overall efficiency.ConclusionWe have designed and evaluated an approach for directly defining PopAv_TACs which are representative of given anatomical structures.     

L'excursion dans le Nord et l'Ouest de la France de la société internationale de phytosociologie

Sans résumé     

Territorialité et agressivité intra- et interspécifique dans les mosaïques de fourmis arboricoles

Tropical arboreal ants are distributed in a mosaic pattern in the canopy of forests and tree crop plantations each of them characterised by their status of dominance. One can distinguish ‘dominant’ species, characterised by extremely populous societies and highly developed interspecific as well as intraspecific territorial behaviour. They tolerate on their territory nonterritorial and less populous species classified as ‘non-dominants’. Nonetheless, many species do exist whose status is intermediary. Usually, they behave like non-dominant species but are able, under certain conditions, to defend a territory. They are cited as ‘sub-dominant’. According to the chemical trapping method employed by researchers, the structure of mosaics have most often been studied using an index of dominance, characterised by the number of negative or positive associations between one species and the others. This index only covers the relative presence or absence of the different species on the same trees. It only gives a punctual statement on the structure of the mosaic without any notion of evolution of the mosaic in time. It does not take into account the behavioural intra- and interspecific interactions. Aggressive interactions between species depend on genetic and environmental factors. Many studies have shown that aggressiveness is closely related to a mechanism of interindividual discrimination, permitting an individual to discriminate between nestmates and non-nestmates. This colonial recognition is based on the existence of a ‘colonial odour’ as a result of a blending of ‘individual odours’. Each individual odour is due to cuticular hydrocarbons which play the role of a contact pheromone. The colonial odour also depends on the environmental odour of the nest. Aggressiveness which results from this mechanism of recognition can be expressed through different mechanisms such as territorial behaviour, dominance hierarchy, and ritualised aggressive behaviour. Territorial behaviour is the expression of a strong intraspecific aggressiveness, by which workers of a colony defend an area of their vital domain against neighbouring conspecifics. In arboreal ant mosaics, dominance hierarchy can exist between dominant ants, and should explain the overturning of dominant ants in time. Ritualised behaviours were observed under intra- and interspecific low-aggressiveness conditions and allow to economise the loss of one or several workers during fights whose issue are uncertain. Their systematic study would greatly facilitate understanding of the evolution of arboreal mosaics.     

Technologie,typologie et analyses fonctionnelles de l’outillage lithique durant le néolithique ancien dans la Cueva de Murciélagos de Zuheros (Córdoba,Espagne) : réflexions sur la néolithisation du sud de la Péninsule Ibérique

The cave of Murciélagos de Zuheros (Cordoba, Spain) is one of the most important sites in Southern Iberian Peninsula. Its thick chronostratigraphic sequence includes occupations ranging from the Middle Palaeolithic to Roman times. Occupation levels corresponding to the earliest farming communities that established in modern-day Andalucia are remarkable due to its archaeological richness. This article focuses on the study of the lithic industry from these Early Neolithic levels, which is approached according to various tightly connected questions: raw material characterization, technical systems of production, and morphology and function of tools. Obtained results in their archaeological context are related to the questions on the origin of the Neolithic in Southern Iberian Peninsula.     

Matériel pour la récolte du microplancton dans les mares et étangs

Sans résuméCollège de France et Centre de Recherches Hydrobiologiques du C.N.R.S. à Gif.