Plaidoyer pour une sylviculture du Pin d'Alep par les techniciens de terrain

Constatant qu'ils gèrent une forêt où le Pin d'Alep tient une place prédominante, les auteurs proposent d'en améliorer la sylviculture. Ils évoquent les modes de traitement qu'impose l'état des peuplements : la futaie régulière devant être traitée en priorité, la futaie d'aspect jardiné et les peuplements mélangés qui sont les plus délicats à aménager. Après avoir examiné les difficultés rencontrées dans ces aménagements, les auteurs concluent que le mode de sylviculture le plus approprié est la futaie régulière par parquets de 0,5 à 4 ha

Mobility of trace metals in freshwater sediments by coupling solid-liquid exchanges, biogeochemical reactions and interstitial diffusion

Sediments may act as a sink for nutrients and trace metals after deposition. It may pose a risk for surface water quality and ecosystem health when environmental changes lead to release nutrients and trace metals stored in these sedimentary stocks. The management of the quality of freshwater systems needs to understand the processes of remobilisation of these stocks. This mobility is dependent on the erosion, on the interstitial diffusion of the mobile phases and on the bioturbation. These mechanisms depend on early diagenetic processes that condition the physical and biogeochemical properties of the sedimentary column. These properties are mainly influenced by the redox transformations resulting from oxidation of the organic matter by the microbial activity. These reactions generate vertical profiles of nutrient and metals concentrations along the sedimentary column. This paper aims to propose a modelling and an experimental protocol to determine vertical profiles of nutrients and trace metals in saturated sedimentary columns of freshwater systems. The modelling approach is based on a coupling between bio-geochemical processes [1], interstitial diffusion [2, 3] and solid-liquid exchanges. The main originality of the model is the pH determination that is directly calculated from the pore water concentrations of the ionic species. As illustration, this paper presents an application to natural sediment cores collected in the Durance Rivers

Abhandlungen von Friedrich Wilhelm Bessel : in drei Bänden

Bd. 1 : Bewegungen der Körper im Sonnensystem, Sphärische AstronomieBd. 2 : Theorie der Instrumente, Stellarastronomie, MathematikBd. 3 : Geodäsie, Physik, Verschiedenes, Literaturhrsg. von Rudolf Engelman