Evolution and transitions in complexity: the science of hierarchical organization in nature. By Gerard A. J. M. Jagers op Akkerhuis

International audienceThis book, written with 12 collaborators (biologists, physicists, and philosophers from various countries), is the result of a long-standing endeavor to find a law in the “organization of nature,” according to the expression used in an enlightening foreword. From 1994 on, Jagers op Akkerhuis has developed a conceptual system called the operator hierarchy allowing us to view nature (a concept encompassing all scales of the whole universe) as a ladder, with rungs of increasing complexity, from quarks to neural networks, which he considers “increasing perfection.

Humus: dark side of life or intractable 'aether'?

Does humus exist or is it just a view of the mind as some authors claimed it? I suggest, based on the observation of the activity of soil organisms, that humus should be considered as the 'dark side' of life and not as an intractable chemical component of soil organic matter. Most properties humus confers to the soil ecosystem are linked to high surface area for nutrient exchange and water retention and strong affinity to mineral particles. Comminution and transport of organic matter along the soil profile, together with intimate blending with mineral particles, take a prominent part in ecosystem services provided by humus. Microscopy, coupled with thorough examination of humus profiles, may help to reveal the biological origin of humus and the chain of processes by which living matter is transformed and recycled within the soil ecosystem

Dynamics of Vaccinium myrtillus patches in mountain spruce forest

International audienceThe dynamics of Vaccinium myrtillus (bilberry) patches were studied in spruce (Picea abies) forest at the higher montane and lower subalpine level in the Tarentaise valley (Savoy, France). Although aerial parts of the shrub may give some indication of age and density of the patches, the annual growth and death of rhizomes are better indicators of patch dynamics. In some cases, dead and young rhizomes may occur simultaneously in the same patch, indicating that growth and death proceed continuously on the inside of dense patches. At mountain sites, slope position of plants significantly influences rhizome growth. A theoretical model of growth of bilberry patches is proposed which takes into account the anisotropic influence of slope and the postulated independence of different rhizome units belonging to the same individual

Comparative study of soil organic layers in two bilberry-spruce forest stands (Vaccinio-Piceetea): relation to forest dynamics

International audienceMorphological features of twelve humus profiles demonstrating the diversity of vegetation types present in subalpine forests were compared, together with soil fauna. Two forest stands of spruce [Picea abies (L,.) Karat.] in association with bilberry (Vaccinium myrtillus L,.), located at 1630 and 1880 m altitude (Macot-La Plagne, Tarentaise valley, Savoy, France), were studied. Morphological observations of small soil volumes were made on disturbed samples by the method of Ponge, but here transformed into quantitative data. Analysis of the data gave evidence of a large degree of heterogeneity of the form of humus in a given forest stand, but most of the observed variation might be explained by differences in vegetation, due to phases of the forest cycle and sylvicultural practices. Regeneration sites are characterized by the development of a herbaceous cover under which a mull humus is built through the activity of burrowing earthworm species. During the phase of intense growth of spruce organic matter accumulates in the top few centimeters. At this stage, the Al horizon previously formed under the action of endogeous earthworms becomes inactive but its crumby structure remains stable. Anecic worms (earthworms with a high amplitude of vertical movements) appear again under adult trees. As a result, changes in the form of humus are observed, with seemingly mull formation (burying of litter) but without true incorporation of organic matter to mineral matter. This humus was named dysmull. Thus soil conditions that prevail in the regeneration sites were developed to some extent under pre-existing adult trees. A parallel evolution of soil fauna, form. of humus and vegetation may thus be described. The above mentioned sequence is not the only one possible. When small gaps in the canopy are created by unsuitable sylvicultural practices such as selection thinning, the development of ericaceous species (bilberry at the higher montane and subalpine levels) may impede the natural forest cycle. Under bilberry, dramatic changes in the form of humus occur: disappearance of the Al horizon previously formed under spruce, accumulation of undecomposed organic matter and, at the subalpine level, podzolization. Accumulation of organic matter under bilberry is mainly due to mosses

Position morphologique du crâne des Lémuriens dans l'ensemble des Primates

La variation cranio-faciale de tous les Primates est décrite ici par l'analyse factorielle des mensurations prises sur 764 crânes d'individus de tous âges et des deux sexes, appartenant à toutes les familles de l'Ordre. La plupart des espèces actuelles y sont représentées, bien que l'échantillonnage soit irrégulier et assez restreint en crânes infantiles. En dépit de ces imperfections, les résultats du «tri factoriel» effectué sont bons et montrent que notre échantillon était représentatif

Primate cranium morphology through ontogenesis and phylogenesis: factorial analysis of global variation

International audienceFactorial analysis of Primate cranial morphology describes variation of the Order in postnatal growth, and shows the positions of some fossil specimens relative to present species

Metal immobilization and soil amendment efficiency at a contaminated sediment landfill site: a field study focusing on plants, springtails, and bacteria

International audienceMetal immobilization may contribute to the environmental management strategy of dredged sediment landfill sites contaminated by metals. In a field experiment, amendment effects and efficiency were investigated, focusing on plants, springtails and bacteria colonisation, metal extractability and sediment ecotoxicity. Conversely to hydroxylapatite (HA, 3% DW), the addition of Thomas Basic Slag (TBS, 5% DW) to a 5-yr deposited sediment contaminated with Zn, Cd, Cu, Pb and As resulted in a decrease in the 0.01 M Ca(NO(3))(2)-extractable concentrations of Cd and Zn. Shoot Cd and Zn concentration in Calamagrostis epigejos, the dominant plant species, also decreased in the presence of TBS. The addition of TBS and HA reduced sediment ecotoxicity and improved the growth of the total bacterial population. Hydroxylapatite improved plant species richness and diversity and decreased antioxidant enzymes in C. Epigejos and Urtica dïoica. Collembolan communities did not differ in abundance and diversity between the different treatments

Morphogenèse du crâne des Primates: analyse factorielle, implications taxinomiques, place et redéfinition du genre Homo

International audienceUne analyse factorielle de crânes de Primates décrit la variation totale de l'ordre à partir de la croissance post-natale et la position de quelques spécimens fossiles par rapport à la morphologie crânienne d'espèces actuelles