Soil legacies of tree species richness in a young plantation do not modulate tree seedling response to watering regime.

Trees have a strong and species-specific influence on biotic and abiotic properties of the soil. Even after the vegetation is removed, the effect can persist to form so-called soil legacies. We investigated the effects of soil legacies of tree species richness on the emergence and growth of tree seedlings, and how these legacy effects modulate the seedling responses to irrigation frequency. We used a 9-year-old tree plantation on former agricultural land in Belgium, which is part of a biodiversity-ecosystem functioning experiment (FORBIO). Soil originating from monocultures and four-species plots, with different species combinations, was translocated to a greenhouse. Five tree species (Betula pendula, Fagus sylvatica, Pinus sylvestris, Quercus robur, and Tilia cordata) were sown and grown for one growing season in these soils. We performed a watering treatment (low and high irrigation frequency) to measure any potential interaction effects between the soil legacies and irrigation frequency. There was no evidence for soil legacy effects of species richness on plant performance or their response to the irrigation frequency. However, the effect of irrigation frequency was dependent on species identity of the tree seedlings. Despite the lack of clear legacy effects, performance measures did show correlated responses that are likely due to species composition effects. We ascribe these patterns to the young age of the forest and the agricultural past land use. At this early stage in forest development, the land-use history likely has a more important role in shaping soil characteristics that affect plant growth and their response to drought, than species diversity.

[Gas-liquid chromatographic determination of volatile compounds in spirits extracted by carbon disulfide]. / Dosage par CPG des composés volatils des eaux de vie extraits par le sulfure de carbone.

The quantitative analysis of potable spirits has for a long time been limited to overall determinations of different chemical classes of compounds. The application of GLC has for some years been developed along two different lines -- methods for determining the higher alcohols, and on the other hand qualitative analyses, making use of more sophisticated techniques, which have enabled several hundred different compounds to be identified in different types of spirits. It appeared to be of interest to develop a technique for routine quantitative analysis which would enable the maximum number of volatile compounds to be determined. The extraction of the volatile compounds of spirits with carbon disulphide can be carried out simply and reproducibly with a small sample size (10 ml). The experimental conditions for the extraction step and the GLC analysis (packed or capillary columns, manual or automatic injection, automatic processing of results, etc.) are discussed. A splitless injector using the "solvent effect" is required for analysis of the non-concentrated carbon disulphide extracts in the case of capillary columns.

[Use of the mass spectrometer as a specific detector in the analysis of alcoholic beverages by gas-liquid chromatography]. / Utilisation du spectromètre de masse comme détecteur spécifique dans l'analyse des boissons alcooliques par CPG.

The technique of selected ion monitoring (SIM) allows the mass spectrometer to be used as a selective detector when coupled to a gas chromatograph. The addition of a data acquisition system enables the selective quantitative determination of compounds to be made when present at low levels in a complex mixture. The detection limit of a compound may be lowered by 2 or 3 orders of magnitude, since the instrument is set to one or more ions which are specific for the compound(s) to be measured, for the maximum amount of time. This lowering of the detection limit and increase in selectivity makes it possible not only to determine compounds at ppb levels, but also to carry out rapid and selective determinations of compounds at the ppm level, using a smaller sample and a minimum of preliminary sample concentration. A fuller description of the principles of SIM is given. This technique has already found wide application in medical and environmental fields, and some examples of its application to alcoholic beverages are given: detection and determination of possible contaminants, such as phthalate, esters residual monomers from plastic materials (styrene, vinyl chloride), and traces of pesticides; determination of certain non-volatile compounds in wines; and the selective determination of certain compounds for which levels in finished products are limited such as the thujones, safrole, beta-asarone, and coumarine.