The effects of population density and summer drought were analysed by means of diameter and height growth in sessile oaks (Quercus petraea) on the stand and individual tree scales. Dendrometric ...inventory data collected from two networks of silvicultural experimentation were used (LERFOB and GIS Coop networks, 9 sites, 31 plots, 99 inventories, ages from 10 to 120 years). These networks study the effects of a broad range of densities, from freely growing trees (relative density index, or RDI, close to 0) to maximum density situations where self-thinning occurs (RDI equal to or in excess of 1). Climate conditions vary from 660 to 850 mm per year with a heat gradient of 9.5 to 11.5 °C (average 1990-2010). Generally speaking, density very strongly affects tree and stand growth, with drought playing a secondary role that is nonetheless significant. Overtopped trees contribute very little to the growth of the stand, particularly when the stand is dense. Drought reduces growth, particularly that of non-dominant trees. Density and drought therefore have the same effect: they accentuate growth differences between trees when stresses are greater. By allocating more resources to diameter growth as compared to height growth, trees in open stands are more “stocky”. In contrast, in densely populated stands, there is “a race for light” making for greater height growth, especially that of overtopped trees. In all cases, drought has a greater effect in reducing height growth than in reducing diameter growth. Finally, following a particularly severe drought (1976), trees recovered most quickly at the drier sites (recovery in 2 years) while the overtopped trees in the higher density stands recovered very little (still no recovery 7 years later). These results suggest that sessile oak adapts better in drier conditions.
Les effets de la densité du peuplement et de la sécheresse estivale ont été analysés sur la croissance en diamètre et en hauteur du Chêne sessile (Quercus petraea) à l’échelle du peuplement et de l’arbre. Les données des inventaires dendrométriques issues de deux réseaux d’expérimentations sylvicoles ont été utilisées (réseaux LERFOB et GIS Coop, 9 sites, 31 placettes, 99 inventaires, âges de 10 à 120 ans). Ces réseaux étudient les effets de larges gradients de densité, depuis des arbres en croissance libre (relative density index, ou RDI, proche de 0) jusqu’à des situations de densité maximale avec des phénomènes d’autoéclaircie (RDI supérieur ou égal à 1). Les conditions climatiques varient de 660 à 850 mm par an pour un gradient thermique de 9,5 à 11,5 °C (moyenne 1990-2010). D’une façon générale, la densité module très fortement la croissance des arbres et du peuplement, la sécheresse jouant un rôle secondaire mais néanmoins significatif. Les arbres dominés participent peu à la croissance du peuplement et ceci est d’autant plus vrai que le peuplement est dense. La sécheresse réduit la croissance et ceci particulièrement pour les arbres non dominants. Ainsi densité et sécheresse ont le même effet, c’est-à-dire qu’elles accentuent les différences de croissance entre arbres quand les contraintes augmentent. En allouant davantage de ressources à leur croissance en diamètre par rapport à leur croissance en hauteur, les arbres dans les peuplements ouverts sont « trapus ». Au contraire, dans les peuplements denses, c’est la « course à la lumière » avec une croissance en hauteur accrue et ceci d’autant plus que l’arbre est dominé. Dans tous les cas, la sécheresse réduit davantage la croissance en hauteur que la croissance en diamètre. Enfin, après une sécheresse exceptionnelle (1976), la récupération des arbres a été la plus rapide sur les sites les plus secs (récupération après 2 ans) et elle fut très faible pour les arbres dominés dans les peuplements les plus denses (toujours pas de récupération après 7 ans). Ces résultats suggèrent une meilleure adaptation des chênes sessiles dans les conditions plus sèches.
Stem taper curves, volume tables and volume yield compartments in Sessile Oak. Since the 1970ies, efficient volume tables are available for the main broadleaved species. Nevertheless, estimates of ...volumes obtained this way for Sessile Oak are still considered too high by some forest managers. We address this question by analysing the volume yield of Oak stands. The analysis is done by modelling the distribution of volume between stem and branches and the geometrical shape of stems (taper curves). The robustness of the method was tested by use of several, large size samples, covering the main sources of variability (age and silviculture). The coherence with former volume tables was favourably tested. Simulations based on a growth model were done in order 1) to explore the variability of volume yield with respect to site quality and silvicultural scenarios; 2) to dispatch total yield according to different criteria (stem-branches, crown-log, bark-sapwood-heartwood); 3) to evaluate the percentage of losses during industrial processing of Oak timber. Results indicate that the disagreement between practicians and scientists on volume simply refers to the nature of the volume (commercial log vs. total volume).
Bien que des tarifs de cubage à double entrée existent depuis 20 ans pour les principales essences feuillues françaises, les volumes ainsi estimés pour le Chêne sessile apparaissent parfois trop forts aux gestionnaires forestiers. Nous abordons cette question en analysant la production en volume des chênaies. L'analyse est conduite en modélisant d'une part la répartition du volume entre tige et branches, d'autre part la forme géométrique de la tige. La robustesse de la méthode est testée grâce à plusieurs jeux de données de grande taille, couvrant les principales sources de variabilité (âge, sylviculture). La cohérence avec les tarifs de cubage existants est évaluée favorablement. Des simulations basées sur un modèle de croissance permettent d'explorer les variations de la production selon la fertilité de la station et la sylviculture, mais aussi de décomposer cette production selon divers critères (tige-branches, houppier-grume, écorce-aubier-duramen) et finalement d'évaluer le rendement du Chêne lors de la transformation industrielle. Les résultats indiquent que le désaccord entre praticiens et chercheurs sur les volumes porte tout simplement sur l'objet cubé (volume commercial vs. total).
• Studies on wood density variations are necessary for estimating the forest carbon pool. Further, they can help predict the technological properties of wooden end-products. While there have been ...frequent reports on the relationships between wood density, cambial age, and ring width, there is little information about the historical trend in wood density for the last century, particularly in the context of global climate change.
• In this study, different sources of variations in mean ring density (site, tree, ring age, ring width, and calendar date) were studied using an original sampling design. A total of 105 Norway spruce (
Picea abies
Karst.) trees were sampled in north-eastern France, from thirteen sites with trees of different ages growing at the same site and in similar conditions. X-ray densitometry measurements were performed on samples taken at breast height. The chronology of the mean ring density over the 20th century was estimated by using a statistical modelling approach based on linear mixed-effects models after accounting for the effect on the mean ring density introduced by different ring widths, cambial ages, sites, and trees.
• The mean ring density of Norway spruce was seen to decrease by about 18 kg m
−3
relative to the year 1900. The chronology showed no evolution between 1900 and 1950, a steep decline from 1950 to 1980 (reaching a maximum decrease of 30 kg m
−3
), followed by an increase from 1980 to 2000.
• The observed decrease was consistent with the results of previous works and supports the hypothesis that this could indicate a global trend and that this trend is independent of the wood structure. Moreover, high inter-annual density variations were found. In future studies, the influence of climate on the wood density and within-ring properties must be clarified to identify the anatomic causes for wood density variations.
Results are presented from an ongoing research study of the productivity of forest trees in France. The results provided here are from studies on the height growth of beech Fagus sylvatica in ...northern France, and focus on the growth patterns that have been delineated (over the period 1870 to 2000), and the contrasts that have been found between the NE and NW regions. The study method adopted, and the growth model that has been derived, are described in detail. Different scenarios were simulated for the development of mature beech by the year 2100 in order to clarify the management options that are available; these consider age of exploitation, aspect and storm risk. The findings are discussed and conclusions drawn.
Les résultats présentés ici sont issus d'études sur la croissance en hauteur du hêtre dans le nord de la France, et portent sur les schémas de croissance qui ont été délimités (sur la période 1870 à 2000), et les contrastes constatés entre le Nord-Est et le Nord-Ouest. La méthode d'étude adoptée et le modèle de croissance qui en a été dérivé sont décrits en détail. Différents scénarios ont été simulés pour le développement du hêtre mature d'ici 2100 afin de clarifier les options de gestion disponibles ; ceux-ci prennent en compte l'âge d'exploitation, l'exposition et le risque de tempête. Les résultats sont discutés et des conclusions tirées.
Omalizumab has been shown to reduce exacerbation rates in moderate to severe allergic asthma. Our aim was to evaluate omalizumab efficacy and safety in a real-life setting in severe asthmatic ...children. 104 children (aged 6-18 years), followed up in paediatric pulmonary tertiary care centres, were included at the beginning of omalizumab treatment. Asthma control levels, exacerbations, inhaled corticosteroid dose, lung function and adverse events were evaluated over 1 year. Children were characterised by allergic sensitisation to three or more allergens (66%), high IgE levels (mean 1125 kU · L(-1)), high rate of exacerbations (4.4 per year) and healthcare use during the previous year, and high inhaled corticosteroid dose (mean 703 μg equivalent fluticasone per day). Asthma control levels defined as good, partial or poor, improved from 0%, 18% and 82% at entry to 53%, 30% and 17% at week 20, and to 67%, 25% and 8% at week 52, respectively (p<0.0001). Exacerbation and hospitalisation rates dropped by 72% and 88.5%, respectively. At 12 months, forced expiratory volume in 1 s improved by 4.9% (p=0.023), and inhaled corticosteroid dose decreased by 30% (p<0.001). Six patients stopped omalizumab for related significant adverse events. Omalizumab improved asthma control in children with severe allergic asthma and was generally well tolerated. The observed benefit was greater than that reported in clinical trials.
We previously reported the French real-life experience of 1year of add-on treatment with omalizumab in 101 severe allergic asthmatic children (6-18years), 92 of whom were still receiving the ...treatment at the end of the first year 1. The study provided complementary data to the previous randomised trials 2-6. We showed a marked drop of 72% in the mean rate of severe exacerbations (from 4.4 per patient during the preceding year to 1.25 during the year of treatment) and of 88.5% for hospitalisations (44% of the patients during the preceding year to 6.7% during the year of treatment); a large improvement in asthma control (from 0% at initiation to 67% of well-controlled patients after 1year); a decrease of 30% of the mean inhaled corticosteroid (ICS) dose (from 703 at initiation to 488 mu g fluticasone equivalent per day after 1year); and a forced expiratory volume in 1s (FEV1) increase, from a mean of 88% to 92.1% of the predicted value. Treatment was discontinued in six patients due to serious adverse events attributed to omalizumab by the practitioner. Here we report the outcome of this cohort after 2years of omalizumab treatment.
Studies on wood density variations are necessary for estimating the forest carbon pool. Further, they can help predict the technological properties of wooden end-products. While there have been ...frequent reports on the relationships between wood density, cambial age, and ring width, there is little information about the historical trend in wood density for the last century, particularly in the context of global climate change. In this study, different sources of variations in mean ring density (site, tree, ring age, ring width, and calendar date) were studied using an original sampling design. A total of 105 Norway spruce (Picea abies Karst.) trees were sampled in north-eastern France, from thirteen sites with trees of different ages growing at the same site and in similar conditions. X-ray densitometry measurements were performed on samples taken at breast height. The chronology of the mean ring density over the 20th century was estimated by using a statistical modelling approach based on linear mixed-effects models after accounting for the effect on the mean ring density introduced by different ring widths, cambial ages, sites, and trees. The mean ring density of Norway spruce was seen to decrease by about 18 kg m(-3) relative to the year 1900. The chronology showed no evolution between 1900 and 1950, a steep decline from 1950 to 1980 (reaching a maximum decrease of 30 kg m(-3)), followed by an increase from 1980 to 2000. The observed decrease was consistent with the results of previous works and supports the hypothesis that this could indicate a global trend and that this trend is independent of the wood structure. Moreover, high inter-annual density variations were found. In future studies, the influence of climate on the wood density and within-ring properties must be clarified to identify the anatomic causes for wood density variations.
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