Humusica 1, article 2 : Essential bases-Functional considerations

Humusica 1 and 2 Applied Soil Ecology Special issues are field guides for humipedon classification. Contrary to other similar manuals dedicated to soil, the objects that one can describe with these guides are living, dynamic, functional, and relatively independent soil units. This is the reason to why the authors dedicated the whole article number 2 to functional considerations even before readers could go in the field and face the matter to be classified. Experienced lectors can overstep many of the sections reported in this article. If the titles of sections "1 A functional classification", "2 What is a humus system?" and "3 Energetic considerations in terrestrial systems" stimulate the reader's curiosity, then we suggest to pass through them. Otherwise, only section "4 Climatic, plant litter, or nutritional constraints?" is crucial. Readers will understand how the soil works in terms of litter and Carbon accumulation, which one(s) among climatic, vegetational, or geological factors that intervene and strongly affect the formation processes of terrestrial (oxygenated) soils. The article concludes with a debate about a tergiversated question: can temperature influence humus decomposition? Preceding statements were used for explaining how the biological soil net can store in the soil a maximum of energy in the form of SOM, by raising a plateau partially independent of climatic conditions.Peer reviewe

L’état de changement de la lande à Erica scoparia L. sous l’effet du pâturage et de la colonisation par le chêne

Our aim was to ascertain whether changes in plant species richness and other vegetation features occur in heathland dominated by Erica scoparia L. (besom heath) through the impact of cattle grazing and oak colonization. Our study took place in the Brenne Regional Natural Park (center of France) where this ericaceous species, locally called ‘brande’, is now considered of patrimonial interest and protected at regional and European level. We selected 10 sites in a private property, covering a wide range of ecological conditions (shallow and deep soils, grazed and non-grazed besom heath, pure and oak-colonized besom heath). Vegetation (percent occupancy of plant species) was sampled in May-June 2006 (105 samples, 1m2 each) and the impact of shrub and tree vegetation on plant biodiversity was assessed by correspondence analysis (CA) and total and partial Mantel tests (Monte-Carlo procedure). An environmental gradient of decreasing light incidence from grazed heath to old heath to oak-wood was depicted, along which a number of ecological, morphological and physiological plant traits (growth habits, Ellenberg values, Grime strategies, Tolerance Index of the plant community) were observed to vary. Species richness decreases when ericaceous or, although to a lesser extent, oak cover increases and it increases under low to moderate cattle grazing. Consequences for the sustainable management of ‘brande’ are discussedL'état de changement de la lande à Erica scoparia L. sous l'effet du pâturage et de la colonisation par le chêne. - Le but de notre étude est de mettre en évidence les modifications de la richesse spécifique et d'autres caractères de la végétation qui surviennent sous l'influence du pâturage et de la colonisation par le chêne dans les landes dominées par Erica scoparia L. (brande). L'étude a été menée dans le Parc Naturel Régional de la Brenne (France, Région Centre) où cette Éricacée est aujourd'hui considérée comme patrimoniale et protégée au niveau régional et européen. Dix sites ont été choisis au sein d'une propriété privée, couvrant un large éventail de conditions écologiques (sols superficiels et profonds, brande pâturée et non pâturée, pure et envahie par le chêne). La végétation (pourcentage d'occupation de l'espace par les différentes espèces végétales) a été échantillonnée en mai et juin 2006 (105 relevés de 1 m ) et l'impact de la végétation arbustive et arborée sur la biodiversité végétale a été mis en évidence à l'aide de l'analyse des correspondances (AFC) et de tests de Mantel totaux et partiels (méthode de Monte-Carlo). Un gradient décroissant d'incidence de la lumière a été mis en évidence depuis la brande pâturée jusqu'à la brande âgée puis la chênaie, en rapport avec la variation de nombreux traits écologiques, morphologiques et physiologiques (types physionomiques, indices d'Ellenberg, stratégies de Grime, indice de tolérance de la communauté). La richesse spécifique décroît à mesure de l'extension des Éricacées ou, dans une moindre mesure, de celle du chêne et s'accroît sous pâturage faible à modéré. Les conséquences pour la gestion durable de la brande sont discutées

Données

Data used for structural ecological modellin

Microalgae starch-based bioplastics: Screening of ten strains and plasticization of unfractionated microalgae by extrusion

International audienceMicroalgae were considered in this work as a new resource for developing starch-based bioplastics. Ten green microalgae strains were screened at lab-scale for their ability to produce starch. A long run (800 h) two-stage accumulation strategy was designed with successive cultivation in sulfur-replete, then sulfur-depleted medium in autotrophic conditions. Starch content was assessed on cell lysate by enzymatic digestion of extracted starch into glucose. Chlamydomonas reinhardtii 11-32A strain was selected as it displayed a maximum starch-to-biomass ratio of 49% w/w, 460 h after being switched to a sulfur-deprived medium. Small-scale pilot production (30 L tubular photobioreactor) with C. reinhardtii 11-32A yielded sufficient biomass quantity to investigate its direct plasticization with glycerol in a twin-screw extruder. Microstructural characterization confirmed the ability for starch-enriched microalgae to be homogeneously plasticized, and hence the possibility to use microalgae as a new platform for the development of bioplastics

Changes in Collembola richness and diversity along a gradient of land-use intensity: A pan European study

Changes in Collembola richness and diversity along a land-use intensity gradient were studied in eight European countries (Portugal, Spain, France, Switzerland, Hungary, UK, Ireland and Finland). In each country a set of six 1 km2 land-use units (LUUs) were selected forming a gradient ranging from natural forest to agricultural dominated landscapes, passing through mixed-use ones. In addition to data on Collembola, detailed information regarding landscape diversity and structure was collected for each LUU. A total of 47,774 individuals were identified from 281 species. Collembola reacted not only to changes in the diversity of the landscape, but also to the composition of that diversity and the area occupied by each land-use type at each LUU. Although species richness patterns were not concordant among the different countries, the total number of species per LUU (landscape richness) was generally higher in natural forests and mixed-used landscapes, and lower in agricultural dominated landscapes. Moreover, high richness and diversity of Collembola at each LUU were associated with a diverse landscape structure, both in terms of number of patches and patch richness. Despite this comparable species richness between mixed-use landscapes and those dominated by natural forests, average species richness on forested areas (local richness) decreased along the gradient, showing that forest patches on mixed-use landscapes support a lower richness than in landscapes dominated by forest. This aspect is important when addressing the role of native forests in structuring biodiversity in disturbed and fragmented landscapes. Although a diverse landscape can support a high biodiversity, the results suggest that intensive fragmentation should be avoided with the risk of collapsing local species richness with the consequent result for regional biodiversit

Forets de montagne L'humus dans la dynamique des formations ligneuses

Projet de recherche Comite EGPN concernant uniquement la partie 'epicea tarentaise'SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : RP 185 (3367) / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Global distribution of earthworm diversity

Soil organisms, including earthworms, are a key component of terrestrial ecosystems. However, little is known about their diversity, their distribution, and the threats affecting them. We compiled a global dataset of sampled earthworm communities from 6928 sites in 57 countries as a basis for predicting patterns in earthworm diversity, abundance, and biomass. We found that local species richness and abundance typically peaked at higher latitudes, displaying patterns opposite to those observed in aboveground organisms. However, high species dissimilarity across tropical locations may cause diversity across the entirety of the tropics to be higher than elsewhere. Climate variables were found to be more important in shaping earthworm communities than soil properties or habitat cover. These findings suggest that climate change may have serious implications for earthworm communities and for the functions they provide.status: publishe