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.

     

Etudé de l'incorporation du 5-fluorouracile dans les acides ribonucléiques de transfert et ribosomiques de levure

5-Fluorouracil incorporation into ribosomal and transfer RNA's of yeast5-Fluorouracil is incorporated into ribosomal and transfer RNA's of Saccharomyces cerevisiae. The effects of this incorporation on the base composition and on the physicochemical properties of rRNA's and tRNA's have been studied.5-Fluorouracil causes an inhibition of the growth of yeast and induces a decrease in the rRNA content of the yeast cells. The analogue is incorporated into rRNA in place of uracil. The molecular integrity of the polynucleotide chains is not altered.As far as tRNA's are concerned, 5-fluorouracil is also incorporated in place of uracil and of some uracil derivatives (pseudouridine, ribothymidine) but to a higher extent than into rRNA's. The amount of 5-6-saturated pyrimidine derivatives is unchanged. Preparations of tRNA, where up to 65 % of uracil were replaced by 5-fluorouracil, have been obtained.The secondary structure of 5-fluorouridine (FU)-containing tRNA's as judged from the melting curves is only slightly modified. It was possible to separate by chromatography on hydroxyapatite three FU-containing aminoacyl-tRNA's (glycyl-, lysyl- and phenylalanyl-tRNA's) from the corresponding normal aminoacyl-tRNA's.     

Recherches sur l'hérédité de la dilution et du blanchiment du pelage dans le genre cavia

Sans résuméTravail exécuté grâce à une subvention de la DonationGeorges etAntoine Claraz, instituta et curataJohannis Schinz professoris auspiciis Série zoologie n^o 66     

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.     

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.