Abstract: Amerindian populations have been experiencing major socio-economic changes for several decades, in a context of rapid demographic growth. This article addresses the ways in which the Amerindian populations of French Guiana have adapted their land use and natural resource management systems to cope with the pressures exerted on their lands and lifestyles. The aim was to investigate the resilience of their systems for land and natural resource use. The concentration of Amerindian habitats around the town of Camopi, which is linked to the availability of health and school infrastructure and to efforts to promote a sedentary lifestyle, is a factor of increasing natural resource scarcity and social alienation. The system is adapting by fragmenting the Amerindian habitat into peripheral villages and extending farmlands along rivers to access to more space. These villages replicate patterns of spatial organisation that are similar to those found in traditional Wayãpi and Teko villages, except that habitation is sedentary, as families hope to have their villages equipped with at lEast drinking water and electrification. Habitat fragmentation is spatially limited by the time taken for daily journeys to school, and therefore by school bus services (dugout), which means that land use is effectively conditioned by services and infrasrtucture. Other living quarters are maintained at a distance from the village, so that the habitat is bi-local: families have a main home where services and infrastructure are available, and a secondary itinerant home further away, which is chosen according to the quality of farmland, the hunting yield of hunting resources, the history of the location and family networks. These distant homes are kept up by spending income from social assistance on transport. It's thus shown that these Amerindian systems for land and natural resource uses are highly adaptable, in that their sustainability is guaranteed by the reconstruction of a circular pattern of mobility in accordance with the intensity of resource use.

Abstract: This article reviews an experimental system set up in French Guiana to test different selective thinning methods that started ten to fifteen years after logging in order to reconstitute commercially viable stands within the shortest time. The thinning methods tested involve a combination of selective intervention within a radius of 10 metres around crop trees and systematic intervention applied uniformly to the entire forest parcel. The resulting thinning intensity produces an 8% to 45% reduction in basal area. While the growth of the residual stand is strongly boosted in all species and for all diameters, there is little change in basal area because of high mortality and lower recruitment of commercial species. Standing commercial capital, however, is strongly affected by the thinning operations as defined. In effect, these thinning methods that benefit crop stems do not meet the objective of shorter rotations in Guiana's tropical logging forests. On the other hand, the measurements made in under-treatment stands agree with those obtained at the Paracou experimental station and confirm the need to adopt long cutting cycles of more than fifty years to ensure that the extraction of valuable species is sustainable in the current logging context in French Guiana.

Abstract: The rich ecology of tropical forests is intimately tied to their moisture status. Multi-site syntheses can provide a macro-scale view of these linkages and their susceptibility to changing climates. Here, we report pan-tropical and regional-scale analyses of tree vulnerability to drought. We assembled available data on tropical forest tree stem mortality before, during, and after recent drought events, from 119 monitoring plots in 10 countries concentrated in Amazonia and Borneo. In most sites, larger trees are disproportionately at risk. At least within Amazonia, low wood density trees are also at greater risk of drought-associated mortality, independent of size. For comparable drought intensities, trees in Borneo are more vulnerable than trees in the Amazon. There is some evidence for lagged impacts of drought, with mortality rates remaining elevated 2 yr after the meteorological event is over. These findings indicate that repeated droughts would shift the functional composition of tropical forests toward smaller, denser-wooded trees. At very high drought intensities, the linear relationship between tree mortality and moisture stress apparently breaks down, suggesting the existence of moisture stress thresholds beyond which some tropical forests would suffer catastrophic tree mortality.

Abstract: 1. Leaf-litter ants represent a major component of biodiversity and are excellent bioindicators reflecting the health of terrestrial ecosystems. This study, conducted in an unspoiled forest near the Nouragues Research Station, represents the first inventory of leaf-litter ant diversity conducted in French Guiana, and so can be considered as the baseline dataset for ants in this country. 2. Ants were extracted from the leaf-litter using the Ants of the Leaf Litter Protocol, along an altitudinal gradient at four forest sites, including an inselberg. 3. A total of 196 ant species representing 46 genera distributed over eight subfamilies were collected. Four distinct communities spread over a gradient of diversity were thus identified: the liana forest was the most species-rich (140 species) followed by the forested plateau (102 species), the transition forest (87 species) and the forest at the top of the inselberg (71 species). 4. The discovery of species new to science plus several species recorded for the first time in French Guiana, coupled with the particular context of this area, suggests that the Nouragues Research Station might represent a centre of endemism. Once completed, this leaf-litter ant dataset will contribute greatly to the knowledge of ant biodiversity in French Guiana, and has the potential to progressively become an indispensable tool for country-wide conservation planning programmes.