Biomass equations are a helpful tool to estimate the tree and stand biomass production and standing stock. Such estimations are of great interest for science but also of great importance for global reports on the carbon cycle and the global climate system. Even though there are various collections and generic meta-analyses available with biomass equations for mature trees, reports on biomass equations for juvenile trees (seedlings and saplings) are mainly missing. Against the background of an increasing amount of reforestation and afforestation projects and forests in young successional stages, such equations are required. In this study we have collected data from various studies on the aboveground woody biomass of 19 common tree species growing in Europe. The aim of this paper was to calculate species-specific biomass equations for the aboveground woody biomass of single trees in dependence of root-collar-diameter (RCD), height (H) and the combination of the two (RCD2 H). Next to calculating species-specific biomass equations for the species available in the dataset, we also calculated generic biomass equations for all broadleaved species and all conifer species. The biomass equations should be a contribution to the pool of published biomass equations, whereas the novelty is here that the equations were exclusively derived for young trees

Ann. For. Sci. 65 (2008) Abstract -• The effect of two weeds (grasses and broom, Cytisus scoparius) competition on the growth and functional traits of European beech saplings (Fagus sylvatica) was investigated in an experimental plantation in the French Massif central.• We hypothesized that grasses would have a much more harmful effect than broom on beech growth through strong competition for soil water and nitrogen.• A randomized block design was used with three separate blocks, each possessing three types of vegetation; grasses (mainly Agrostis capillaris, Holcus mollis and H. lanatus), broom, and bare soil as a control.• Two years after plantation beech sapling growth was significantly greater in bare soil than with competition from grasses, and was intermediate on broom. Growth was positively correlated with beech leaf nitrogen content (N m ) and xylem water potential (Ψ x ). N and Ψ x were dependent, with nitrogen uptake probably decreasing with increasing drought. There was no clear correlation between growth and light transmitted 10 cm below the apex of the saplings.• Beech leaf mass on an area basis (LMA) was correlated with the three resource variables (water, nitrogen and light) and with growth, confirming that LMA is a sensitive functional trait integrating the degree of stress experienced by the saplings.• The results suggest that broom is less competitive than grasses and, if properly managed on a sufficiently well-watered site, can generate satisfactory conditions for beech establishment and growth.Fagus sylvatica / Cytisus scoparius / competition / nitrogen / water Résumé -Comparaison des effets de la compétition par les graminées (Graminoïdes) et le genêt (Cytisus scoparius) sur la croissance et les traits fonctionnels de plants de hêtre (Fagus sylvatica).• L'effet de la compétition de deux adventices (graminées et genêt, Cytisus scoparius) sur la croissance et les traits fonctionnels de plants de hêtre européen (Fagus sylvatica) a été expérimenté dans une plantation du Massif central.• Nous avons testé l'hypothèse selon laquelle les graminées ont un effet plus délétère que le genêt sur la croissance du hêtre à cause d'une très forte compétition pour l'eau du sol et l'azote.• Un plan d'expérience en trois blocs complets a été utilisé, chacun possédant trois types de végétation : des graminées (principalement Agrostis capillaris, Holcus mollis and H. lanatus), du genêt et un sol nu comme témoin.• Deux ans après la plantation, les plants de hêtre étaient significativement plus gros en sol nu par rapport à ceux subissant la compétition des graminées, ceux en présence du genêt étant intermédiaires. La croissance a été positivement reliée à la teneur en azote des feuilles (N m ) ainsi qu'au potentiel hydrique de xylème (Ψ x ). N m et Ψ x semblent dépendant, l'absorption d'azote diminuant avec l'augmentation de la sécheresse. Aucune corrélation significative n'a pu être mise en évidence entre la croissance des plants et la lumière transmise à 10 cm sous leur apex.• La masse foliaire rapportée à sa s...

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