Large wild ungulates are a major biotic factor shaping plant communities. They influence species abundance and occurrence directly by herbivory and plant dispersal, or indirectly by modifying plant-plant interactions and through soil disturbance. In forest ecosystems, researchers' attention has been mainly focused on deer overabundance. Far less is known about the effects on understory plant dynamics and diversity of wild ungulates where their abundance is maintained at lower levels to mitigate impacts on tree regeneration. We used vegetation data collected over 10 years on 82 pairs of exclosure (excluding ungulates) and control plots located in a nation-wide forest monitoring network (Renecofor). We report the effects of ungulate exclusion on (i) plant species richness and ecological characteristics, (ii) and cover percentage of herbaceous and shrub layers. We also analyzed the response of these variables along gradients of ungulate abundance, based on hunting statistics, for wild boar (Sus scrofa), red deer (Cervus elaphus) and roe deer (Capreolus capreolus). Outside the exclosures, forest ungulates maintained higher species richness in the herbaceous layer (+15%), while the shrub layer was 17% less rich, and the plant communities became more light-demanding. Inside the exclosures, shrub cover increased, often to the benefit of bramble (Rubus fruticosus agg.). Ungulates tend to favour ruderal, hemerobic, epizoochorous and non-forest species. Among plots, the magnitude of vegetation changes was proportional to deer abundance. We conclude that ungulates, through the control of the shrub layer, indirectly increase herbaceous plant species richness by increasing light reaching the ground. However, this increase is detrimental to the peculiarity of forest plant communities and contributes to a landscape-level biotic homogenization. Even at population density levels considered to be harmless for overall plant species richness, ungulates remain a conservation issue for plant community composition.

-Litterfall is the first phase of the biogeochemical cycle and returns nutrients to the soil. This paper demonstrates the quantitative distribution of the different components throughout the year in four stands of a beech time sequence. Litterfall increases as the forest evolves and as basal area increases: from 2.1 t/ha/an in the thicket to 4.7 t/ha/an in the mature high forest. Leaves represent 90% of the total litterfall in the young stand and 70% in the oldest stand. The proportion of leaves decreases during forest rotation. Most of the categories are related to the age and basal area, because of the architecture and maturity of the trees. Other factors could explain litterfall dynamics, e.g. human management or animals. Climate is a preponderant factor for the litterfall production and plays a role in the species phenology. The litterfall dynamics during the time sequence, and the observed shifts in phenology give rise to different pedogenetic processes.litter production / beech / time sequence / dry matter Résumé -Production de litière dans une chronoséquence d'une hêtraie (Fagus sylvatica) atlantique. Les retombées de litière sont à la base des cycles biogéochimiques et assurent le retour au sol des nutriments. Cet article présente la répartition quantitative, par compartiment, au cours de deux ans de suivi et dans quatre peuplements de hêtre d'une chronoséquence. Les retombées totales de litière augmentent avec l'âge de la parcelle et la surface terrière : de 2,1 t/ha/an dans le fourré à 4,7 t/ha/an dans la vieille futaie. Les feuilles représentent 90 % des retombées totales dans le jeune peuplement et 70 % dans la parcelle âgée. La proportion de feuilles diminue au cours de la chronoséquence. La plupart des catégories sont reliées à l'âge et à la surface terrière, par l'intermédiaire de l'architecture et de la maturité du peuplement. D'autres facteurs peuvent expliquer la dynamique des retombées: la sylviculture, les animaux. Le climat est un facteur prépondérant dans la production de litière et a un rôle également sur la phénologie des espèces. La dynamique des retombées de litière au cours de la chronoséquence ainsi que les décalages phénologiques observés sont à la base de processus pédogénétiques diffé-rents.hêtre / retour litière / chronoséquence / matière sèche Ann. For. Sci. 58 (2001) [755][756][757][758][759][760][761][762][763][764][765][766][767][768] 755

The number of species (species richness) is certainly the most widely used descriptor of plant diversity. However, estimating richness is a difficult task because plant censuses are prone to overlooking and identification errors that may lead to spurious interpretations. We used calibration data from the French ICP-level II plots (RENECOFOR) to assess the magnitude of the two kinds of errors in large forest plots. Eleven teams of professional botanists recorded all plants on the same eight 100-m 2 plots in 2004 (four plots, eights teams) and 2005 (four plots, nine teams including six from 2004), first independently and then consensually. On average, 15.5% of the shrubs and trees above 2 m were overlooked and 2.3% not identified at the species level or misidentified. On average, 19.2% of the plant species below 2 m in Electronic supplementary material The online version of this article (height were overlooked and 5.3% were misidentified and 1.3% were misidentified at the genus level (especially bryophytes). The overlooking rate also varied with plant species, morphological type, plot and team. It was higher when only one botanist made the census. It rapidly decreased with species cover and increased with plot species richness, the recording time of the census in the tree layer and the number of the censuses carried out during the day in the ground layer. Familiarity of the team with the local flora reduced the risk of overlooking and identification errors, whereas training had little impact. Differences in species richness (over space or time) in large plots should be cautiously interpreted, especially when several botanists participate in the survey. In particular, the quality of the data needs to be evaluated using calibration training and, if necessary, may be improved by involving more experienced botanists working in teams and by fixing a minimum recording time.

-The Kyoto Conference identified the need to establish an accurate inventory of carbon stocks in forests. Carbon stocks were estimated in a beech forest (Fougères forest -France) using a combination of in situ field samples with existing soil and vegetation maps. Soil, humus and vegetation stocks were measured at 100 sampling points distributed throughout representative classes within the entire forest massif. Carbon levels in the soil and humus were determined in the laboratory; models predicting the biomass were used to estimate the stocks in the vegetation. From the statistical analyses and existing maps these point data were extrapolated to the whole forest using two changes of scale. The total carbon stock was estimated to lie in a range between 442 200 and 505 105 tC (a difference of 15%). Half of the carbon stock was found in the soil, 45% in the vegetation and 5% in the humus. To evaluate the accuracy of this estimate, possible sources of error were examined and quantified. The carbon stocks in the vegetation were the most variable. Nevertheless, the results are likely to be integrated into future forest management plans and generalised in other contexts to evaluate carbon stocks at a regional scale.carbon stocks / forests / Fagus sylvatica / scale change / soil / humus / vegetation Résumé -Estimation du stock de carbone dans une hêtraie (forêt de Fougères, Ouest de la France) : extrapolation de la parcelle au massif. La conférence de Kyoto a révélé le besoin d'établir un inventaire précis des stocks de carbone en milieux forestiers. Les stocks de carbone ont été estimés dans une hêtraie (forêt de Fougères, France) en combinant un échantillonnage sur le terrain avec des cartes existantes du sol et de la végétation. Les stocks de carbone dans le sol, les humus et la végétation ont été mesurés sur 100 points distribués dans les classes représentatives de l'ensemble du massif forestier. Les teneurs en carbone dans le sol et les humus ont été déterminées par analyses au laboratoire. Pour la végétation, des modèles de biomasse carbonée établis dans divers peuplements du massif ont ensuite été utilisés pour les autres peuplements. Après analyse statistique de la variabilité, et sur la base des cartes disponibles, les valeurs des stocks de carbone ont été extrapolées à l'ensemble du massif forestier en utilisant deux changements d'échelle. Le stock total de carbone a été estimé dans une fourchette entre 442 200 et 505 105 tC (un écart de 15 %). La moitié du stock de carbone se trouve dans le sol, 45 % dans la végétation et 5 % dans les humus. Pour évaluer la qualité de ces estimations, les sources d'erreurs ont été examinées et quantifiées. La variabilité est la plus élevée dans le compartiment de la végétation. Cette démarche devrait être généralisée à d'autre conditions écologiques afin d'améliorer l'estimation des stocks de carbone de la forêt française.