A volume equation for predicting individual tree volume, and a taper function for describing a stem profile were developed for a little known species, Styrax tonkinensis (Siam benzoin) in northern Laos. The species has high potential commercial value and can make an important contribution to the local economy. It can provide two different types of products, a non-wood product (benzoin resin) and timber. In Laos, the most important product is currently resin, and the use of timber for commercial purposes is rare. One reason is that information about the timber is not available. In Vietnam, on the other hand, the species is an import pulpwood species. Data used in this study came from 73 trees. Trees were purposely selected to ensure coverage of a full range of tree sizes. Measurement was undertaken only on over-bark diameters due to some constraints, limitations and problems during the field data collection. However, due to the importance of under-bark volume for this species, a small available dataset was used to build a bark model as an interim guide to the errors associated with using over-bark models for estimating under-bark volumes. From this bark model, errors in estimating under-bark volumes of trees with diameters at breast height between 10cm and 17 cm were approximately 18%. Nineteen individual volume models, and 7 individual taper functions were compared for bias and precision. Collective names for the volume equations tested include single-entry, double-entry, logarithmic, combined variables. Most volume models had similar bias but a few were clearly biased. The models with similar bias were further evaluated by four common statistics including bias, standard error of estimates, standard deviation of residuals and mean absolute deviation. The results showed that a five parameter model was ranked first, and was the most precise model. However, the magnitudes of difference in prediction errors between this model and other models, particularly the three parameter model were not significant. For practical purposes, the simpler model was preferred. Seven taper functions tested here belong to three different groups including single taper equations, compatible taper equations and segmented taper equations. Evaluation of taper equations used the same residual analysis procedures and criteria as those applied with volume equations. Graphical residual analysis showed that most taper models had similar precision with their errors in diameter predictions being similar in range. However, some models showed obvious bias. The most highly ranked taper model was a compatible taper model of polynomial form. It was the least biased model. The second ranked model was a single, simple model. This latter model is relatively simple to apply, but it is not compatible with the volume model, yielding slightly different estimates of volume if it is integrated and rotated around the longitudinal axis of a tree. However, if the sole purpose is to describe tree taper, it is the best model to use.

Ces travaux d'archéométrie concernent l’étude moléculaire par GC-MS de marqueurs lipidiques (biomarqueurs) préservés au sein de sols archéologiques et de substances végétales impliquées en tant qu'ingrédients dans la confection d’artefacts. Des analyses complémentaires en isotopie du carbone de composés individuels et des mesures de datation au 14C (AMS MICADAS) de la matière organique totale des sols, d'extraits lipidiques et d'un composé individuel (miliacine) ont également été effectuées. Cette approche a permis:- de montrer l’existence de la culture de millet dès l’âge du Bronze en Alsace, les sols associés à cette culture et leur contenu organique ayant été piégés et préservés dans des silos à grains enterrés datés de l’âge du Fer.- d'identifier la nature de structures archéologiques comme étant d'anciennes latrines et une aire de stabulation de bétail via l'identification de stéroïdes fécaux.- d'établir des critères chimiotaxonomiques fiables basés sur l'analyse des lipides pour l’authentification de résines de styrax et de liquidambars.- d'identifier la nature d'une résine issue de Styrax officinalis ayant été incorporée dans l’enduit organique ornant un crâne décoré (IXème millénaire av. J.-C., site de Nahal Hemar, Israël).- de mettre en évidence l’emploi de brai de bouleau comme agent collant lors de la confection d’un bijou daté du Premier âge du Fer. / In this archaeometric study, lipid biomarkers from archaeological soils and organic substances originating from plants found on artefacts were investigated by GC-MS. In addition, the stable carbon isotopic composition of individual lipids and the 14C age (AMS MICADAS) of soil organic matter, lipid extracts and one isolated compound (miliacin) were determined. Such an archaeometric approach allowed:- the existence of a millet cultivation during the Bronze Age in Alsace to be unveiled for the first time based on preserved molecular remains of this cereal in agricultural soils trapped within grain silos dated from the Iron Age.- the function of uncharacterized archaeological structures to be identified as ancient latrines and a stall area based on the identification of faecal steroidal markers.- reliable chemotaxonomic criteria for the authentication of styrax resins and liquidambar gums to be established using specific organic markers (triterpenoids, notably).- the vegetal component of an organic coating decorating a skull from the 9th millennium BC (Nahal Hemar site, Israel) to be identified as a resin from Styrax officinalis.- the use of birch bark tar as adhesive for the making of a jewellery dated from the Iron Age to be discovered.