Study of the ichthyofauna diet in the Ichkeul Lake (Tunisia)

In order to define the structure of trophic network of Ichkeul Lake in Tunisia, diet of main teleost fish species was determined during two seasons, wet and dry. A total of 491 stomachs from 16 teleost species was analyzed. The analysis revealed spatial variability (East under marine influence and West with more continental effect) and temporal one (wet and dry seasons). Based on stomach contents, nine trophic groups were revealed, including eight monospecific groups. The main prey are mudflat snails (Hydrobia ventrosa, H. acuta), bivalves (Abra alba, Cerastoderma glaucum), amphipods and isopods, as well as seagrass (Potamogeton pectinatus, Ruppia cirrhosa) and water brackish algae (Ulva spp. and Chaetomorpha spp., Cladophora sp., Polysiphonia sp.)

An hybrid approach of low frequency room equalization: Notch filters based on common acoustical pole modeling

International audienceIn this paper, a new method of low frequency multiple-point equalization for room acoustics is presented. This approach is theoretically based on Common Acoustical Pole (CAP) modeling of the room transfer functions developed previously by Haneda et al. [1]. With the hybrid approach, the multiple-point equalizer is made up with cascaded notch filters which coefficients are directly determined from the CAP model. This new method reduces the complexity of the equalizing structure in addition to an automatisation of notch filters design which should be very attractive to many applications such as home theater systems by intelligently controlling room modes

Iterative equalization of room transfer function using biquadratic filters

International audienc

The Mediterranean in check: Biological invasions in a changing sea

In recent decades, the high introduction rate of alien species (AS) has been mainly due to the increasingly widespread human movements, which often compromise natural barriers, facilitating the invasion of new geographic areas and environments. Being completely new in the recipient habitat, alien invasive species can often have strongly negative impacts on native communities, sometimes causing substantial and irreversible ecological and economic damage. Thus, AS have been branded as “negative” and are often targeted for eradication. However, an accurate assessment of ecological and economic impacts of alien taxa is still lacking in many species, and this is particularly true in marine environments. We focused on the Mediterranean Sea, a very important marine biodiversity “hot spot,” which is among the areas that have been most influenced by the arrival of non-native species, a process also linked to global warming, leading to a deep transformation of this basin. We describe both negative and positive aspects of some well-known introductions, assuming a different view of conservation. Biological invasions are, in fact, a fundamental and integral aspect of nature that has always been present in the history of life on Earth. Imagining that nature is static and needs to be restored to a particular state is not a reasonable way of looking at the processes of life. With this in mind, we argue that defining priorities in management and conservation is a prerogative that should not be based on the containment/eradication of one or another species, but on the conservation of those environmental conditions that are essential for the proper functioning of ecosystems. In other words, native versus non-native species distinction cannot be the main guiding principle in conservation and restoration. For this reason, great attention must be paid to the containment of those human activities that cause greater pollution and rapid changes, and therefore threaten the habitats and biodiversity that we care about most

Effects of mixing tree species and water availability on soil organic carbon stocks are depth dependent in a temperate podzol

Mixing tree species is a forest management strategy put forward to increase and stabilize primary productivity. Yet, little is known about soil organic carbon (SOC) storage in mixed species forests, particularly under water shortage. In this study, we used a tree diversity experiment in southwestern France to assess the interactive effects of water availability (via irrigation) and mixing tree species (monocultures of pine (Pinus pinaster) and birch (Betula pendula) versus mixed plots of pine-birch and pine-birch-oak (Quercus robur)) on SOC stocks in the forest floor and across five mineral soil layers (0-5, 5-15, 15-30, 30-60 and 60-90 cm deep). We found that SOC stocks were negatively affected by irrigation in the forest floor due to an increase in decomposition rates. However, SOC stocks were positively influenced by both the mixing of tree species and irrigation in the mineral soil, particularly at the 15-30-cm soil depth. This is because root niche partitioning in mixed plots and an increase in tree biomass in irrigated plots may have resulted in greater organic matter inputs through rhizodeposition and the incorporation of microbially-derived compounds. These preliminary results indicate that SOC dynamics and its response to biotic and abiotic factors are strongly dependent on soil depth. Our data further highlight that the positive effect of mixing trees on SOC stocks was higher in irrigated plots, thereby contradicting the idea that tree mixture effects are expected to be greater when environmental conditions are harsher. We conclude that mixing tree species can increase SOC stocks in the short term in temperate forests, even if the exact mechanisms remain to be identified.Diversité et Productivité des forêTs impactées par le Changement ClimatiqueCARbone, Traits fonctionnels associés, et leur Optimisatio

Associational resistance to a pest insect fades with time

Tree diversity is one of the drivers of forest resistance to herbivores. Most of the current understanding of the diversity resistance relationship comes primarily from short-term studies. Knowing whether tree diversity effects on herbivores are maintained over time is important for perennial ecosystems like forests. We addressed the temporal dynamics of the diversity resistance relationship by conducting a 6-year survey of pine attacks by the pine processionary moth Thaumetopoea pityocampa (PPM) in a tree diversity experiment where we could disentangle tree composition from host density effects. During the first years after planting the trees, PPM attacks on maritime pine Pinus pinaster were reduced in the presence of birch Betula pendula, a fast-growing non-host tree (i.e. associational resistance). This effect was maintained but faded with time as the pines eventually grew taller than neighbouring birches. The number of repeated attacks on individual pine trees also decreased in mixed pine-birch stands. Pine density had a positive effect on stand colonisation by PPM and a negative effect on the proportion of trees that were attacked. Pines were less likely to be repeatedly attacked as pine density increased, with attacks being spread over a larger number of host trees. Collectively, these results unravel the independent contribution of tree species composition and host density to tree resistance to herbivores. Both processes had directional changes over time. These results indicate that the resistance of planted forests to herbivores can be improved by carefully choosing the composition of mixed forests and the timing of species planting