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Introduction Les recherches sur la productivité planctonique des réservoirs visent à en améliorer la production piscicole (Mc Queen et al., 1992). En Côte d'Ivoire, les petits barrages agropastoraux font l'objet d'une exploitation croissante et incontrôlée (Idessa, 1992), mais jusqu'ici, les études étaient surtout focalisées sur les barrages hydroélectriques (Yte, 1982 ; N'Douba et al., 1985 ; Noba, 1998 ; Ouattara, 1998). Notre travail, réalisé lors d'une vaste prospection spatiale conduite ...

Spatial and temporal variabilities in species composition, abundance, distribution, and bioeroding activity of euendolithic microorganisms were investigated in experimental blocks of the massive coral Porites along an inshore-offshore transect across the northern Great Barrier Reef (Australia) over a 3-year period. Inshore reefs showed turbid and eutrophic waters, whereas the offshore reefs were characterized by oligotrophic waters. The euendolithic microorganisms and their ecological characteristics were studied using techniques of microscopy, petrographic sections, and image analysis. Results showed that euendolithic communities found in blocks of coral were mature. These communities were dominated by the chlorophyte Ostreobium quekettii, the cyanobacterium Plectonema terebrans, and fungi. O. quekettii was found to be the principal agent of microbioerosion, responsible for 70-90% of carbonate removal. In the offshore reefs, this oligophotic chlorophyte showed extensive systems of filaments that penetrated deep inside coral skeletons (up to 4.1 mm) eroding as much as 1 kg CaCO3 eroded m(-2) year(-1). The percentage of colonization by euendolithic filaments at the surface of blocks did not vary significantly among sites, while their depths of penetration, especially that of O. quekettii (0.6-4.1 mm), increased significantly and gradually with the distance from the shore. Rates of microbioerosion (0.1-1.4 kg m(-2) after 1 year and 0.2-1.3 kg m(-2) after 3 years of exposure) showed a pattern similar to the one found for the depth of penetration of O. quekettii filaments. Accordingly, oligotrophic reefs had the highest rates ofmicrobioerosion ofup to 1.3 kg m(-2) year(-1), whereas the development of euendolithic communities in inshore reefs appeared to be limited by turbidity, high sedimentation rates, and low grazing pressure (rates0.5 kg m(-2) after 3 years). Those results suggest that boring microorganisms, including O. quekettii, have a significant impact on the overall calcium carbonate budget of coral reef ecosystems, which varies according to environmental conditions.

indexedcc; International audience; The Gambia Estuary, a “normal” estuary with a decreasing salinity gradient from the mouth towards the head, is moderately exploited by small-scale fisheries and does not receive any severe pollution from either agriculture or industrial activities. Neither the Gambia River nor its estuary are artificially impounded. As the last large West African estuary free of major human disturbance, it is of considerable interest for comparative studies on the effect of major environmental perturbations in West African estuarine ecosystems. The aquatic environment and fish communities of the Gambia Estuary (about 250 km long) were studied by purse seine sampling at different periods in the river cycle, covering all hydro-climatic seasons that are characteristic of West African estuaries. Emphasis was placed on the diversity, composition, structure and distribution of fish assemblages in relation to fluctuations in physico-chemical factors such as water temperature, salinity and turbidity. Results on the aquatic environment, mainly the salinity range (from freshwater to 39) and dissolved oxygen (never a limiting factor for fish in the estuary) and on the main characteristics of the fish fauna (high diversity of life cycles, all the ecological categories represented) indicated that the Gambia Estuary was free of major climatic perturbation and reinforced the choice of this system as a reference for the study of the effects of major perturbations on estuarine tropical fish communities.

Phytoplankton biomass, productivity and assemblages were studied during the main hydrological seasons in two shallow reservoirs in Ivory Coast (West Africa). In this area, the hydrological pattern begins with the flood from July to October, that is the main change in environmental condition. The flood is followed by a dry period from November to March; then the rainy season resumes from April with numerous and intense storms. Chlorophyll-α concentrations ranged from 5.0 to 27.4 μg l -1 in mesotrophic Brobo reservoir and from 15.1 to 123.0 μg l -1 in eutrophic Nambengue reservoir. Despite their different trophic states phytoplankton production varied between 0.2 and 1.8 g C m -2 d -1 in both reservoirs. Both Chlorophyceae and Cyanobacteria largely dominated the phytoplankton communities. Opportunist species (mainly Chlorophyceae), with medium sized cells (10-15 μm equivalent spherical diameter, ESD), were observed during the flood. Slow growing/slow sinking species, with relatively large cells (> 15 μm ESD, mainly Cyanobacteria and Chlorophyceae), were present during the dry season. Small species (< 10 μm ESD), dominated by Chlorophyceae and Cyanobacteria were abundant during the rainy season. At this late stage of the hydrological year, N 2 fixing Cyanobacteria like Anabaena and Anabaenopsis were also present. Eight functional associations (H I, J, K, L M , N, P, S 1, X 1) from the thirty-one proposed by REYNOLDS et al. (2002) were outlined in the two systems surveyed; these functional groups were representative of warm, shallow, turbid, nutrient-enriched and frequently mixed habitats. A large part of the biomass was composed of cells hardly matching the needs of superior consumers, in size as well as in shape. These conditions could explain the inefficient transfer of biomass within the pelagic food web. resulting in trophic dead end and contributing to the eutrophication of the sites.

Gilberto Righi together with other taxonomists described the earthworm fauna of Amazonia in what is still a very limited number of sites. The Guayana Shield, North of the Amazon river and East of the Orinoco, comprises the largest extent of pristine forest on earth. One hundred and five species distributed among 36 genera have been recorded in this area. Eighty seven species were found in only one of the five large areas where some sampling had occurred which led us to estimate that the earthworm fauna of Amazonia probably comprises over 2000 species. Only 10 peregrine species, all exotic except for Pontoscolex corethrurus, were found in most regions where they colonise disturbed areas and tend to eliminate native species. Tentative estimates of the local-to-regional values of species richness for a few invertebrate groups show that earthworms have by far the lowest rates. It is, therefore, likely that deforestation of large areas results in the elimination of many species since the rate of endemism is extremely high in earthworms.

International audience; The shallow submarine hydrothermal field of the Prony Bay (New Caledonia) discharges hydrogen- and methane-rich fluids with low salinity, temperature (

International audience; 1. Spatial patterns of freshwater fish species at regional and local scales were investigated to explore the possible role of interspecific interactions in influencing distribution and abundance within communities occupying coastal streams of North-Western France. 2. Nine sites from nine streams situated in the same biogeographical region were sampled annually over the 6-year period from 1990 to 1995. 3. Similar habitats (sites) with richer regional colonization pools exhibited proportionally richer local communities in terms of number of species, total density and total biomass of individuals. Furthermore, no negative relationships were found between density and biomass of each of the most common species and local species richness. 4. Results of dynamic regression models (applied to the above-mentioned species) suggest an absence of strong competition between all pairs of species. 5. The evidence on lack of density compensation for species-poor communities and absence of perceptible interspecific competition between species suggest that the communities studied are non-interactive. 6. Two main explanations can be advanced. First, the local abundance of species in the communities studied could be determined through differential responses to unpredictable environmental changes, rather than through biological interactions. Second, as a result of historical events, the communities studied are reduced in congeneric species which can limit, in turn, the influence of interspecific competition in structuring these communities. 7. These results underline the strong influence of regional processes in shaping local riverine fish communities and minimize the possible influence of species interactions in governing these communities.

Large-scale studies focused on the diversity of continental slope ecosystems are still rare, usually restricted to a limited number of diversity indices and mainly based on the empirical comparison of heterogeneous local data sets. In contrast, we investigate large-scale fish diversity on the basis of multiple diversity indices and using 1454 standardized trawl hauls collected throughout the upper and middle slope of the whole northern Mediterranean Sea (36 degrees 3' - 45 degrees 7' N; 5 degrees 3'W - 28 degrees E). We have analyzed (1) the empirical relationships between a set of 11 diversity indices in order to assess their degree of complementarity/redundancy and (2) the consistency of spatial patterns exhibited by each of the complementary groups of indices. Regarding species richness, our results contrasted both the traditional view based on the hump-shaped theory for bathymetric pattern and the commonly-admitted hypothesis of a large-scale decreasing trend correlated with a similar gradient of primary production in the Mediterranean Sea. More generally, we found that the components of slope fish diversity we analyzed did not always show a consistent pattern of distribution according either to depth or to spatial areas, suggesting that they are not driven by the same factors. These results, which stress the need to extend the number of indices traditionally considered in diversity monitoring networks, could provide a basis for rethinking not only the methodological approach used in monitoring systems, but also the definition of priority zones for protection. Finally, our results call into question the feasibility of properly investigating large-scale diversity patterns using a widespread approach in ecology, which is based on the compilation of pre-existing heterogeneous and disparate data sets, in particular when focusing on indices that are very sensitive to sampling design standardization, such as species richness.

International audience; Mangroves are threatened ecosystems that provide numerous ecosystem services, especially through their wide biodiversity, and their bioremediation capacity is a challenging question in tropical areas. In a mangrove in Mayotte, we studied the potential role of microbial biofilm communities in removing nutrient loads from pre-treated wastewater. Microbial community samples were collected from tree roots, sediments, water, and from a colonization device, and their structure and dynamics were compared in two areas: one exposed to sewage and the other not. The samples from the colonization devices accurately reflected the natural communities in terms of diversity. Communities in the zone exposed to sewage were characterized by more green algae and diatoms, higher bacteria densities, as well as different compositions. In the area exposed to sewage, the higher cell densities associated with specific diversity patterns highlighted adapted communities that may play a significant role in the fate of nutrients.

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La variabilité à long terme de 18 peuplements de poissons a été étudiée dans des rivières françaises et ouest africaines. Les principaux résultats sont les suivants : 1) le coefficient de variation (CV) de la richesse spécifique, le CV de l'abondance totale et le CV moyen des espèces constitutives du peuplement augmentent avec la durée de l'étude; 2) selon la classification proposée par GROSSMAN et al. (1990) basée sur le CV moyen de l'abondance des espèces, tous les peuplements étudiés rentrent dans la catégorie des peuplements à fortes fluctuations interannuelles. Cependant certaines populations (les salmonidés en Bretagne par exemple) présentent une faible variabilité de leur densité; 3) dans le Rhône, les peuplements dont les populations manifestent une grande variabilité interannuelle sont ceux présentant le plus grand taux de renouvellement en espèces. Ce résultat est en accord avec l'hypothèse de HORWITZ (1978, "extermination hypothesis"). (Résumé d'auteur)

Spatio-temporal variability of prokaryotic water column communities inside and outside a Polynesian tropical lagoon subjected to pearl oysters farming was assessed in terms of abundance by quantitative PCR and diversity by DGGE. Communities and operational taxonomic units (OTUs) were analysed according to dry/rainy seasons and free-living/particle-attached state. Bacterial density was higher in the lagoon compared to ocean and a seasonal trend was observed. No influence of the localisation within lagoon or of the planktonic/attached states was noticed on bacterial abundance and diversity. The OTUs belonged to Cyanobacteria, to heterotrophic groups in Proteobacteria and Flavobacteria. Archaeal abundance showed seasonal tendency and particle-prevalence, but no effect of lagoon or oceanic location was observed. Lagoon and oceanic archaeal diversity were different and Euryarchaeota (MG-II, MBG, and Halobacteria) were detected. During the dry season, planktonic and particle-associated community differed, whereas at rainy season, both communities were similar and included members usually associated with coral.

Theories of species coexistence have played a central role in ecology and evolutionary studies of the origin and maintenance of biodiversity in highly diverse communities. The concept of niche and associated theories predict that competition for available ecological space leads to a ceiling in species richness that influences further diversification patterns. By contrast, the neutral theory supports that speciation is stochastic and diversity independent. We examined the phylogenetic community structure and diversification rates in three families and 14 sites within coral reef fish communities from the Indian and Pacific oceans. Using the phylogenetic relationships among 157 species estimated with 2300 bp of mitochondrial DNA, we tested predictions in terms of species coexistence from the neutral and niche theories. At the regional scale, our findings suggest that phylogenetic community structure shifts during community assembly to a pattern of dispersion as a consequence of allopatric speciation in recent times but overall, variations in diversification rates did not relate with sea level changes. At the local scale, the phylogenetic community structure is consistent with a neutral model of community assembly since no departure from a random sorting of species was observed. The present results support a neutral model of community assembly as a consequence of the stochastic and unpredictable nature of coral reefs favoring generalist and sedentary species competing for living space rather than trophic resources. As a consequence, the observed decrease in diversification rates may be seen as the result of a limited supply of living space as expected in a finite island model.

La Forêt Tropicale Humide (FTH) est l'un des écosystèmes les plus riches et les plus complexes de la planète, que la disparition accélérée sous l'effet des activités humaines met au premier plan des préoccupations environnementales internationales. Dans le même temps, la relative méconnaissance de son fonctionnement en fait un enjeu prioritaire de la recherche fondamentale en écologie. Ce travail s'intéresse aux peuplements d'arbres des FTH et plus particulièrement à leur diversité spécifique et structurale, c'est-à-dire à la fois : à l'hétérogénéité de son mélange d'espèces qui renvoie à l'interaction entre processus évolutifs et écologiques présidant à l'apparition et la coexistence des espèces ; et à la variabilité de l'organisation tridimensionnelle des attributs physiques des arbres résultant des effets conjoints des processus biophysiques et de la dynamique forestière. Ces deux aspects sont étudiés de manière complémentaire par des méthodes d'analyse quantitatives adaptées aux spécificités des FTH. Les résultats obtenus conduisent à définir un cadre d'appréhension des phénomènes à une échelle intermédiaire dans le but d'évaluer la part relative des processus de colonisation-dispersion, de filtrage environnemental et d'interactions locales dans le maintien de la diversité des FTH.

El impacto de la estacionalidad de los ríos sobre las comunidades de macroinvertebrados fue estudiado en ríos de la zona Altoandina de Bolivia, durante la época de transición y época seca del año 2008. En nueve arroyos intermitentes y nueve permanentes se colectaron muestras de macroinvertebrados y parámetros ambientales. A traves de análisis multivariados, se determinaron relaciones entre variables biológicas (según riqueza, abundancia, composición trófica y rasgos biológicos) con las variables ambientales. La estacionalidad no tuvo efecto significativo sobre la riqueza ni densidad de macroinvertebrados, tampoco se encontraron efectos notorios sobre la composición trófica ni los rasgos biológicos (tipo de respiración), pero sí encontramos diferencias significativas en la composición taxonómica, especialmente en la proporción de Ephemeroptera, Plecoptera y Trichoptera (EPT); asimismo, encontramos que existen otras variables ambientales como la profundidad, solidos disueltos y pH que tienen mayor efecto que la intermitencia en la riqueza y densidad total. De acuerdo a datos climáticos de la región Andina de Bolivia se sabe que en el futuro habrá una disminución del agua, incluso la desecación temporal en varios ríos de la zona, esto debido a la disminución de los glaciares. De esta manera, el futuro cambio climático reflejado a través de la estacionalidad de los ríos, tendrá mayor efecto en los cambios de la estructura taxonómica que en la estructura funcional, lo que indica que probablemente tendrá implicaciones más fuertes en la conservación de taxa que en la composición de los rasgos de la comunidad de macroinvertebrados. The impact of hydrologic non-permanence (intermittent streams) on benthic macroinvertebrate communities was investigated in Bolivian head Andean streams. Samples of benthic macroinvertebrates and environmental variables were taken in nine intermittent and nine permanent streams during dry and transition to dry seasons during 2008. Using different multivariate analyses, we determined relationships between biological variables (richness, density, trophic composition and biological traits) and environmental variables. Hydrologic non-permanence had no significant effect on total species richness, total density, trophic composition or physiological traits (i.e. respiration). However, significant effects were found on taxonomic composition, specifically on taxonomic richness of Ephemeroptera, Plecoptera and Trichoptera. Likewise, we found that environmental variables such as profundity, total dissolved solids and pH have more important effects on total richness and density than hydrologic non-permanence itself. Thus, climate change would likely have stronger implications for taxa conservation than for the functional characteristics of stream macroinvertebrate communities. Fil: Moya, Nabor. Universidad Mayor de San Simón; Bolivia Fil: Gibon, François Marie. Muséum National d'Histoire Naturelle; Francia Fil: Oberdorff, Thierry. Muséum National d'Histoire Naturelle; Francia Fil: Rosales, Claudio. Universidad Mayor de San Andrés; Bolivia Fil: Dominguez, Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucuman. Instituto de Biodiversidad Neotropical. Universidad Nacional de Tucuman. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Biodiversidad Neotropical. Instituto de Biodiversidad Neotropical; Argentina

Este trabajo describe la estructura de la comunidad de macroinvertebrados acuáticos en un río altoandino de la cuenca amazónica boliviana. Se describe la variación anual y longitudinal en relación a factores ambientales. Este río libre de influencias antropogénicas, presenta una baja heterogeneidad longitudinal pero importantes variaciones de flujo. Además, como muchos ríos altoandinos, está alimentado y consecuentemente regulado por un glacial (Mururata). Este fenómeno decrece y está amenazado por la desaparición de los glaciales tropicales a causa del calentamiento global. Los efectos de la fauna podrían ser drásticos. Nuestros resultados muestran una baja riqueza de taxa de macroinvertebrados que sin embargo son abundantes, especialmente aquellas poblaciones que son permanentes: Baetidae (Andesiops peruvianus), Leptophlebiidae (Meridialaris tintinnabula), Gripopterygidae (Claudioperla tigrina), Simuliidae, Chironomidae y Oligochaeta. Mediante herramientas estadísticas de análisis multivariado, demostramos que la densidad y la riqueza de las poblaciones de macroinvertebrados están influenciadas por las variaciones de descarga hidráulica. This work describes the structure of a macro invertebrate community in a high Andean stream of the Bolivian Amazon basin. Annual and longitudinal variations in relation to environmental factors are described. This stream has a low longitudinal heterogeneity, high flow variations, and is free of anthropogenic influences. In addition, this river as many other high-Andean waterways, is fed and consequently regulated by a glacier (Mururata). This is a diminishing phenomenon, so the river is threatened by the disappearance of tropical glaciers due the global climatic warming. The effects on the aquatic fauna could be drastic. Our results show low taxa richness, which are nevertheless abundant, especially those macro invertebrates whose populations are permanent: Baetidae (Andesiops peruvianus), Leptophlebiidae (Meridialaris tintinnabula), Gripopterygidae (Claudioperla tigrina), Simuliidae, Chironomidae and Oligochaeta. Using Multivariate Analysis, we demonstrate that the densities and richness of the benthic populations are under the influence of hydrological discharge variations.

Dans le présent travail nous avons testé l'hypothèse de "convergence" selon laquelle les communautés soumises aux mêmes contraintes environnementales convergent vers une structure commune. Nous avons choisi comme modèle les poissons des cours d'eau tempérés et tropicaux de quatre régions zoogéographiques : Europe (France), Amérique du Nord (USA), Amérique du Sud (Bolivie) et Afrique (Gabon). Pour atteindre notre objectif, des comparaisons locales, régionales et intercontinentales des communautés de poissons ont été menées entre différents sites et entre différents cours d'eau en étudiant leurs caractéristiques ecomorphologiques et leur structure trophique. Les résultats montrent que l'organisation locale des communautés résulte de la combinaison de processus locaux et régionaux, abiotiques et biotiques, et s'inscrit par conséquent dans un contexte historique et biogéographique. A l'échelle locale nous avons pu montrer que certains guildes trophiques peuvent être prédites à partir de quelques attributs morphologiques. Par ailleurs, la richesse des communautés de poissons et leur structure trophique se sont avérées substantiellement convergentes d'une région à l'autre : le pourcentage des espèces invertivores (se nourrissant de façon exclusive d'invertébrés) tend à diminuer le long du gradient longitudinal des cours d'eau étudiés tandis que le pourcentage d'espèces omnivores augmente. Néanmoins, à position égale des sites sur le gradient longitudinal, les guildes herbivores/détritivores et piscivores, présentes dans les cours d'eau africains et sud-américains, sont pratiquement absentes des cours d'eau européens et nord-américains étudiés, peut-être en raison de différences en énergie disponible entre les systèmes tempérés et tropicaux. Ces résultats seront certainement utiles aux décideurs pour les aider à mettre en oeuvre des plans de conservation et de gestion des systèmes lotiques. (résumé d'auteur)

Cited Reference Count: many ref.Blackwell PublishingEnvironmental Sciences & Ecology; Marine & Freshwater Biology; Water Resources (provided by Thomson Reuters)http://www.blackwell-synergy.com/loi/lreraymond.lae@ird.fr; International audience; A comparative study of the fish communities in two lake ecosystems in Mali (Lakes Manantali and Selingue) was based on monitoring small-scale fishery landings for a 13-month period. The main difference between the two lakes is the fishing pressure, being higher in Lake Selingue and lower in Lake Manantali. The effects of fishing on the structure of the fish communities in the two lakes were analysed with the use of diversity indices, rank species abundance (RSA) and abundance-biomass comparative curve (ABC) methods. The diversity differed significantly between the lakes, being higher for Lake Selingue. Analysis of the community structure, using RSA curves, indicated a more regular distribution of the weights between fish species for Lake Selingue than for Lake Manantali. The two lakes exhibited different exploited fish community structures. For Lake Selingue, the fishery was based on smaller-sized species, compared to that for Lake Manantali. The indicators based on the species composition of exploited fish communities, in terms of abundance and life-history traits, seemed to be more relevant in this study. Indicators such as diversity indices and RSA curves depend strongly on the exploitation strategy, being unreliable for evaluating exploited fish communities from catch data.

Le Ministère chargé de l’environnement a lancé en 1999 le programme de recherche « écosystèmes tropicaux » avec l’appui du GIP ECOFOR. Ce programme vise à une meilleure connaissance des écosystèmes appliquée à la gestion et la conservation dans les départements, pays et les territoires d’outre-mer et leur environnement régional. Son objectif principal est de promouvoir une recherche finalisée sur le thème de la diversité biologique et de son utilisation dans le cadre des écosystèmes tropicaux dans les départements, pays et territoires d’outre-mer. Il s’agit de mettre au point les outils et les méthodes qui permettront aux pouvoirs publics d’optimiser les stratégies de préservation du patrimoine naturel et de sa biodiversité, en accord avec les usages des populations locales, dans une perspective de développement durable.

Con el propósito de determinar la composición y estructura de comunidades de macroinvertebrados bentónicos y su relación con factores ambientales en condiciones naturales alteradas, se tomaron muestras en 38 sitios de referencia y 29 sitios con perturbación antropogénica, distribuidos uniformemente a lo largo de la Cuenca Chipiriri, en la región del Piedemonte de Cochabamba. Encontramos mayor proporción en densidad y riqueza de grupos intolerantes como los efemerópteros, tricópteros y plecópteros en sitios de referencia respecto a los sitios perturbados. Por el contrario, los grupos tolerantes como los quironómidos (dípteros) dominaron significativamente en sitios perturbados. Los resultados obtenidos a través de análisis multivariados, nos muestran que la estructura y composición de las comunidades de macroinvertebrados pueden servir como bioindicadores de perturbación antropogénica. Sin embargo, estas comunidades responden también de manera significativa a factores ambientales bajo condiciones de referencia, lo cual nos sugiere que futuros trabajos de bio-evaluación de arroyos a través de índices bióticos deben excluir el efecto ambiental del efecto de la perturbación.

International audience; Soil macrofauna was surveyed in six sites characterised by different vegetation types on five occasions in the Western Ghats, India. Sampling sites included a primary forest, a weakly disturbed forest (slightly logged in the past), a highly disturbed forest (intensively logged), an Acacia auriculiformis plantation (8 years old), a pasture with high density of Phoenix humilis and a pasture without P. humilis. We showed that both land management and temporal variability induced significant changes in the soil macrofauna. Forest sites hosted larger densities of soil macroorganisms. The effect of seasons was apparent as some clear modifications in the fauna composition occurred. Some groups like earthwonns mainly exhibited temporal variability whereas others like millipedes were chiefly affected by land management options. The seasonal rhythms of soil macrofauna were poorly expressed in the pasture plots and the Acacia plantation, but were particularly clear in the forest sites. This interaction between land management and temporal patterns may be explained by some changes in the species composition associated with certain land-uses. Our approach was based on a between-within classes PCA that proved particularly useful by providing statistical tests and a hierarchy of land management and temporal rhythm effects

As primary forest is cleared, pastures and secondary forest occupy an increasing space in the Amazonian landscape. We evaluated the effect of forest clearing on a soil macrofauna (invertebrate) community in a smallholder farming system of southeastern Amazonia. We sampled the soil macrofauna in 22 plots of forest, upland rice fields, pastures, and fallows of different ages. In total, we collected 10,728 invertebrates. In cleared plots the species richness per plot of the soil macrofauna fell from 76 to 30 species per plot immediately after forest clearance, and the composition of the new community was different. Ants, termites, and spiders were most affected by the disturbance. In plots deforested several years before, the effect of forest clearance highly depended on the type of land use (pasture or fallow). In fallows, the community was most similar to the initial state. The species richness per plot diversity in old fallows rose to 66 species per plot, and the composition was closer to the primary forests than to the other types of land use. On the contrary, in the pastures the species richness per plot diversity remained low, with 47 species per plot. In fallows, all the groups showed a species richness close to that in primary forest, whereas in the forest only the species richness of earthworms and coleoptera recovered. Our results suggest that forest clearing constitutes a major disturbance for the soil macrofauna and that the recovery potential of the soil macrofauna after 6 or 7 years is much higher in fallows than in pastures. Thus, fallows may play a crucial role in the conservation of soil macrofauna., Les communautés de macrofaune du sol en Amazonie du sud-est demeurent très peu décrites, malgré leur importance primordiale pour la compréhension du fonctionnement des sols, particulièrement ceux des milieux tropicaux. En effet, dans ces derniers, les conditions édaphiques sont souvent défavorables au cycle des nutriments, ce qui pose des problèmes de gestion dans les zones de déforestation.Parmi les facteurs potentiels structurant les communautés de la macrofaune du sol, la diversité de la végétation et la structure du paysage sont de plus en plus souvent proposées, mais peu d’études appuient ces hypothèses. Nous avons abordé ces questions par une étude multi échelle, avec un plan d’échantillonnage emboîté de 270 blocs TSFB, ce qui a permis d’étudier l’effet des différents facteurs selon l’échelle considérée. La zone géographique choisie est la localité de Benfica, une zone de déforestation par l’agriculture familiale, représentative de l’Amazonie du sud-est.Nos résultats montrent qu’au niveau du paysage, la richesse spécifique de macrofaune du sol peut être en bonne partie prédite par 3 variables, dont 2 paysagères : le type d’occupation du sol, la densité en lisière, et le nombre de type d’occupation du sol. La communauté de la macrofaune du sol est très appauvrie en rizière et en pâturage, alors qu’elle est plus élevée en forêt et jachère.Au niveau de la parcelle, le type de sol et la couverture végétale en pâturage influencent significativement la macrofaune du sol. En milieu arboré, la diversité de la macrofaune du sol est corrélée avec celle de la diversité de la litière, mais pas avec sa biomasse. D’autre part, la densité de la macrofaune de litière ne présente pas de structure spatiale significative sur des échelles de 2 à 10 m.Nous n’avons pas pu mettre évidence une relation entre le milieu de prédilection et les activités enzymatiques exprimées, mais cela peut être dû à une inadaptation du protocole.En testant plusieurs modèles statistiques, nous montrons que l’évaluation de la relation entre la structure du paysage et la richesse spécifique locale de la macrofaune peut être améliorée par l’utilisation d’un réseau de neurones (perceptron) au lieu de l’approche habituelle d’un modèle basé sur les GLM. Les 2 modèles s’avèrent performants, mais le perceptron apporte des résultats meilleurs en prenant en compte 10% de variance supplémentaire. D’un point de vue méthodologique, les analyses a posteriori que nous avons menées, montrent qu’une dizaine de points par type d’occupation du sol auraient été suffisant pour les analyses. Nous montrons également que les quadrats TSBF ont tendance à surestimer la densité réelle de la macrofaune de litière.Notre étude apporte donc des résultats inédits en montrant l’existence de relations entre la structure du paysage, la diversité de la litière, le type de sol, la structure du couvert végétal à fine échelle, et la communauté de la macrofaune du sol.Selon l’échelle considérée, nous avons identifié des facteurs différents qui influencent la macrofaune du sol, ce qui démontre l’intérêt de notre approche multi-scalaire. Afin d’approfondir ces résultats, il serait nécessaire de les conforter en étudiant ces relations dans d’autres systèmes pédologiques présents en Amazonie, d’approfondir les modalités de dispersion spatiale des organismes à l’échelle du paysage, et d’identifier les mécanismes conditionnant la relation entre la diversité de la macrofaune et celle de la litière.