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

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Balandier et al., Bramble development relative to light, 2/25 Summary 17 Bramble (Rubus fruticosus L.) is a common weed in temperate forest and also in other world 18 ecosystems where it is recorded as an invasive plant. Although it has been described to 19 efficiently compete for water and nutrients, little is known on its competitive ability for light. 20We described bramble canopy architecture, cover relative to light availability and light 21 interception ability in 60 areas of bramble thicket at 18 sites in France and England with 22 contrasting soils and climates. Leaf area and leaf number can be predicted by the cane length. 23Leaf inclination distribution was planophile. There was a good relationship between light 24 interception and LAI of the different bramble thickets, with no significant site influence, 25meaning that a single model can be used to predict light interception by bramble in different 26 conditions. Bramble LAI and cover increased logarithmically with light availability to reach 27 30% cover at only 5 to 7 % light. Consequently bramble is able to tolerate deep shade, which 28 is not in accordance with its reputed moderate to high light requirement reported in the 29 literature and suggests that it will difficult to control this species by manipulating tree canopy. 30This would have adverse consequences on tree regeneration.

-Forest regeneration can be inhibited by competition for environmental resources (water, nutrients, light) between tree seedlings and some competitive species that are generally light-demanding species developing in gaps. The study's aim was to quantify the development of two competitive species (Rubus idaeus and Cytisus scoparius) present in the chaîne des Puys, France, relatively to light in gaps inside Picea abies stands. On 29 transects linking the stand to the gap centre (223 points), light intensity was measured (0-80% of relative light) and floristic measurements (cover and height of the different species) were done. Development of both competitive species is positively connected to light, with a bell-shaped curve with a maximum of 40-50% for R. idaeus and a quite constant increase to 80% (maximum of light recorded in the experimentation) for C. scoparius. These results are discussed relatively to understorey vegetation management in order to favour forest regeneration.regeneration / light / understorey vegetation / competition Résumé -Croissance de deux espèces compétitrices (Rubus idaeus, Cytisus scoparius) colonisatrices des trouées en forêt tempérée selon la disponibilité en lumière. En forêt, la compétition pour la captation des ressources (eau, nutriments, lumière) entre certaines plantes très colonisatrices et les jeunes arbres peut mettre en péril la régénération forestière. Ces espèces sont généralement héliophiles et se développent donc dans les trouées, environnements également favorables aux semis. Le but de l'étude était de quantifier le développement de deux espèces colonisatrices (Rubus idaeus et Cytisus scoparius) de la chaîne des Puys (France) en fonction de l'intensité lumineuse dans des trouées situées en forêt d'épicéas. Des mesures de lumière ont été réalisées sur 29 transects reliant l'intérieur du peuplement au centre d'une trouée (223 points au total, 0-80 % d'éclairement relatif) en parallèle à des mesures floristiques (taux de recouvrement et hauteur des différentes espèces). Les deux espèces répondent à la lumière, selon une courbe en cloche avec un maximum à 40-50 % pour R. idaeus et une augmentation quasi linéaire jusqu'à 80 % (maximum mesuré dans l'expérimentation) pour C. scoparius. Ces résultats sont discutés en terme de gestion de la végétation forestière pour favoriser la régénération. régénération / lumière / végétation de sous-bois / compétition

2/35Abstract 21We developed a double-digitizing method combining a hand-held electromagnetic digitizer 22 and a non-contact three-dimensional (3D) laser scanner. The former was used to record the 23 positions of all leaves in a tree and orientation angles of their lamina. The latter served to 24 obtain the morphology of leaves sampled in the tree. As the scanner outputs a cloud of points, 25 software was developed to reconstruct non-planar (NP) leaves composed of triangles, and to 26 compute numerical shape parameters: midrib curvature, torsion and transversal curvature of 27 the lamina. Combination of both methods allowed building 3D virtual trees with NP leaves. 28The method was applied to young beech trees (Fagus sylvatica) selected in different sunlight 29 environments (from 1 to 100% of incident light) in forest of central France. Leaf morphology 30 responded to light availability, with more bent shape in well lit leaves. Light interception at 31 the leaf scale by NP leaves was decreased from 4 to 10%, for shaded and sunlit leaves 32 compared to planar leaves. At the tree scale, light interception by trees made of NP leaves was 33 decreased by 1 to 3% for 100% to 1% light, respectively. 34 35