Woody plant resprouting has received considerable attention in the last two decades as human disturbances continue to encroach on terrestrial ecosystems globally. We examined the regeneration mechanisms of a Caatinga dry forest in the context of slash-and-burn agriculture and resprouting ability of the local flora. We excavated two old fields (from 32) experiencing early forest regeneration dominated by the tree Pityrocarpa moniliformis (Fabaceae) to map clonal propagation and, in parallel, submitted 260 seedlings from 13 woody plant species to experimental clipping. What seemed to be ‘seedlings’ popping up around P. moniliformis stumps and remaining adults actually were condensed sets of root suckers connected via complex networks of long, ramified shallow horizontal roots without taproots. We mapped respectively 39 and 783 connected root suckers, which summed 96 m and 910 m in root length. Regarding the seedlings, 33% resprouted across nine species with resprouting rates varying between 5–100%. Seedling height before clipping positively influenced resprouting vigour. Our preliminary results suggest that the Caatinga dry forest supports a relatively high proportion of resprouting species, some of them able to clonally propagate and playing an ecosystem-level role by responding to early forest regeneration and high abundance/biomass across both regenerating and old-growth forests.

In the last years, a growing number of studies have focused on the search for biological indicators of human impact in freshwater environments. Given their susceptibility to different types of impact, larval digeneans have been considered as useful tools for the study of temporal variations in parasite communities. However, few studies have been carried out in lotic environments. For that reason, the spatio-temporal variations of the larval digenean assemblages parasitizing the gastropod Heleobia parchappii were analysed in four human-impacted streams, located on the coast of Argentina. In total, 4800 specimens of H. parchappii were collected seasonally, and 12 digenean species belonging to eight families were registered. Three of the streams showed similar species presence but, during spring and summer, the streams located within the city presented lower species presence than the streams located in the urban periphery. By contrast, the spatial prevalence values evidenced a higher variation between the environments. Streams located in the urban periphery showed higher prevalence values throughout the year, compared to those calculated for streams located within the city. The spatio-temporal variations of larval digenean assemblages parasitizing H. parchappii seem to be mainly influenced by the diversity and vagility of definitive hosts, the types of digenean life cycles and habitat characteristics. However, environmental disturbances derived from anthropogenic activities are highlighted as the probable main factors that may affect the composition and dynamic of these parasite assemblages.

Face to the increasing anthropogenic disturbances that affect coral reef ecosystems, it becomes urgent to define appropriate ecological indicators for monitoring purposes. One useful approach is to search for a simplified description of the structure of biological communities that are highly diverse and complex on coral reefs. To this end, we propose to represent the trophic structure of coral reef fish assemblages by using fractional trophic levels assigned to each fish species. Fish abundance trophic spectra (i.e., the distributions of fish abundance per trophic level) were established for the fringing reefs of two bays located in the city of Nouméa (New Caledonia). The comparison of these trophic spectra revealed a similar trophic structure in the two bays, in spite of contrasted levels of fish abundance due to habitat damages. The embayment degree was characterized by changes in the fish trophic structure, reflecting a decreasing influence of urban and industrial wastes discharged in the bottom of the bays. This case of study shows the interest of using fractional trophic levels for the description of highly diverse biological communities. The trophic level-based approach offers new prospects in the search for ecological indicators, by characterizing the structure of biological communities by trophic signatures which testify to the disturbance level affecting their environment.

Running waters are perhaps the most impacted ecosystem on the planet as they have been the focus for human settlement and are heavily exploited for water supplies, irrigation, electricity generation, and waste disposal. Lotic systems also have an intimate contact with their catchments and so land-use alterations affect them directly. Here long-term trends in the factors that currently impact running waters are reviewed with the aim of predicting what the main threats to rivers will be in the year 2025. The main ultimate factors forcing change in running waters (ecosystem destruction, physical habitat and water chemistry alteration, and the direct addition or removal of species) stem from proximate influences from urbanization, industry, land-use change and water-course alterations. Any one river is likely to be subjected to several types of impact, and the management of impacts on lotic systems is complicated by numerous links between different forms of anthropogenic effect. Long-term trends for different impacts vary. Concentrations of chemical pollutants such as toxins and nutrients have increased in rivers in developed countries over the past century, with recent reductions for some pollutants (e.g. metals, organic toxicants, acidification), and continued increases in others (e.g. nutrients); there are no long-term chemical data for developing countries. Dam construction increased rapidly during the twentieth century, peaking in the 1970s, and the number of reservoirs has stabilized since this time, whereas the transfer of exotic species between lotic systems continues to increase. Hence, there have been some success stories in the attempts to reduce the impacts from anthropogenic impacts in developed nations. Improvements in the pH status of running waters should continue with lower sulphurous emissions, although emissions of nitrous oxides are set to continue under current legislation and will continue to contribute to acidification and nutrient loadings. Climate change also will impact running waters through alterations in hydrology and thermal regimes, although precise predictions are problematic; effects are likely to vary between regions and to operate alongside rather than override those from other impacts. Effects from climate change may be more extreme over longer time scales (>50 years). The overriding pressure on running water ecosystems up to 2025 will stem from the predicted increase in the human population, with concomitant increases in urban development, industry, agricultural activities and water abstraction, diversion and damming. Future degradation could be substantial and rapid (c. 10 years) and will be concentrated in those areas of the world where resources for conservation are most limited and knowledge of lotic ecosystems most incomplete; damage will centre on lowland rivers, which are also relatively poorly studied. Changes in management practices and public awareness do appear to be benefiting running water ecosystems in developed countries, and could underpin conservation strategies in developing countries if they were implemented in a relevant way.

Dans le but d'étudier la composition de l'ichtyofaune et les grandes tendances des relations poissons-habitats dans les milieux anthropisés, 4 secteurs d'un tronçon de 50 km de la Garonne ont été suivis en hiver 1994 et été 1995. Les écoulements sont lotiques et correspondent à la Zone à Barbeau pour les secteurs amont et aval de Toulouse. Dans la traversée de l'agglomération, la Garonne est divisée en bras supérieur et bras inférieur et les écoulements des deux secteurs correspondent à la Zone à Brême. Le secteur du bras inférieur et le secteur aval Toulouse sont soumis à de fortes pressions anthropiques. Les techniques d'échantillonnages utilisées sont les pêches électriques (méthode EPA) dans les secteurs lotiques et les pêches aux filets (EPF) dans les secteurs artificialisés à écoulement lentique. 27 espèces appartenant à 10 familles, à dominance de Cyprinidae, ont été recensées. Le peuplement est dominé par le barbeau (Barbus barbus L.), le goujon (Gobio gobio L.) et le chevaine (Leuciscus cephalus L.), en milieu lotique et par le gardon (Rutilus rutilus L.), la brême (Abramis brama L.) et l'ablette (Alburnus alburnus L.), en milieu lentique. Pour les 2 secteurs les plus soumis aux actions humaines, les différences par rapport aux secteurs moins anthropisés portent sur des espèces occasionnelles ou accidentelles. Ces différences sont plus marquées en milieu lentique. En effet, la richesse spécifique et l'abondance sont nettement plus élevées dans le bras inférieur (malgré les fortes actions humaines) que dans le bras supérieur où l'eau est pourtant de meilleure qualité. Les relations poissons-habitats en milieu lotique sont peu évidentes pour la majorité des espèces. En milieu lentique, la préférence d'habitat dans le bras supérieur est orientée vers les enrochements et la végétation aquatique. Les relations poissons-habitats sont perturbées dans le bras inférieur, morphodynamiquement comparable au bras supérieur, mais soumis à de fortes actions anthropiques.