International audience

International audience

International audience

peer reviewed | Jaccard's distances between the aquatic bryophyte assemblages recorded in 1972-1973 and in 1997 in nine study sites along the Belgian course of the rivers Meuse and Sambre were correlated with the differences of concentrations of 13 physico-chemical factors (O2, N-NO2-. N-NH4+, N-NO3-, P-PO43-, K+, pH, Ca++, Fe, Cu, Pb, Zn and Mn) between 1972-1973 and 1996. The strong decrease in heavy metals pollution and the decrease of the trophic level are correlated with the recolonization of the most polluted sites in the 1970s by the pollution-sensitive species present in the valleys at the beginning of the century. Conversely, N-NO2-, N-N03" and K+ have increased between the two surveys. They currently reach much higher concentrations in the Sambre than in the Meuse, as well as N and micro-pollutants such as pyrene and anionic detergents. The different loads of these factors in the studied rivers might explain their different recolonization patterns. Although some species might have developed a tolerance to certain factors, an effort to improve the quality of the effluents coming from industrial areas still remains to be made, especially in the frame of the projects of river flooding of the riverine areas.

peer reviewed

peer reviewed | The effects of enhanced (NH4)(2)SO4 (NS) deposition on Norway spruce (Picea abies [L.] Karst) fine root biomass, vitality and chemistry were investigated using root-free in-growth cores reproducing native organic and mineral soil horizons. The cores were covered and watered every 2 weeks with native throughfall or throughfall supplemented with NS to increase deposition by 75 kg ha(-1) a(-1) NH4+-N (86 kg ha(-1) a(-1) SO42--S). The in-growth cores were sampled after 19 months and assessed for root biomass, necromass, length, tip number, tip vitality and fine root chemistry. Root biomass and fine root aluminium (Al) concentration were negatively correlated, but NS deposition had no effect on root growth or root tip vitality. NS deposition caused increased fine root nitrogen (N) concentrations in the organic horizon and increased Calcium (Ca) concentrations in the mineral horizon. Fine root biomass was higher in the organic horizon, where fine root Al and potassium (K) concentrations were lower and Ca concentrations higher than in the mineral horizon. Results highlighted the importance of soil stratification on fine root growth and chemical composition.

International audience | Integrated assessment of climate change implies the construction of models describing the very complex interactions among economic processes, geochemical or geophysical phenomena and ecological processes at the Earth level. This attempt is unprecedented in the history of science. To build models of a unique, very large and extremely complex object, the whole Earth, supposes the definition of concepts allowing the comparison of these models through their structures and not only comparisons of their numerical results. The purpose of this paper is to give some preliminary elements of such a structural comparison.

International audience

This paper presents some preliminary results on the implementation of a biodegradability batch test to fraction different types of wastewater samples to assess the variability of the WWTP influent composition.