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Fast track microfluidic screening of the antibody repertoires of 12 convalescent COVID-19 donors comprising 2.8mio antibodies yielded MTX-COVAB, a human-derived monoclonal antibody with low picomolar neutralization IC50 of SARS-CoV-2. COVAB neutralization potency is on par with the Regeneron cocktail as demonstrated in a comparative neutralization assay. MTX-COVAB shows strong efficacy in vivo and binds to all currently identified clinically relevant variants of SARS-CoV-2. MTX-COVAB completes GMP manufacturing by the end of this year and will be tested in the clinic in March 2021.

Plentering with pines – results from the United States Until now, scientifically reliable data on plentering of light-demanding tree species in Europe have been lacking. This gap is filled with long-term trials from the USA, among others with southern yellow pines. In the southern state of Arkansas, two plots of 16 hectares were installed in 1936, in the context of a large-scale trial of mixed loblolly pine (Pinus taeda L.) and shortleaf pine (Pinus echinata Miller) stands, in which plentering has been applied using single-tree harvest of predominantly sawtimber-sized trees (dbh >30 cm) with natural regeneration. The aim of the experiment is to investigate the possibilities and limits of uneven-aged silviculture with shade-intolerant tree species, and whether this can be applied in cutover southern yellow pine stands in order to improve the stand structure, to increase growth, and to make periodic harvests possible. The two plots were in different initial states – one more or less fully stocked, the other with poor initial stocking. Since 1936, 18 complete surveys have been conducted where all trees 10 cm and larger were tallied by diameter. During that same time period, 14 plenter harvests have been carried out using the Volume Control-Guiding Diameter Limit method in both plots. In order to check the variability of stand structure within the 16-hectare stands, each was subdivided into four quarters, and the diameter distributions were compared within each quarter. The uneven- aged structure was checked by a sample of tree-ring counts. Both stands retained continuous canopy cover throughout the observation period. The initial differences in the number of stems, the basal area, the standing volume, the proportion of sawtimber, the average basal area and the mean quadratic diameter dg became alike in the course of time, which shows the flexibility of plentering and the tendency to develop stands where the harvest of growth appears to be sustainable. The dg of the harvest was initially slightly more than 20 cm, but is today more than 50 cm. The average total growth is 6 m3/ha and year. The results show that these stands are uneven-aged stands in an advanced stage of the transformation to plentering. We suspect that in the absence of a major natural disturbance event, the plentering approach in southern yellow pines will continue to be promising in the future.

Climate-induced tree mortality became a global phenomenon during the last century and it is expected to increase in many regions in the future along with a further increase in the frequency of drought and heat events. However, tree mortality at the ecosystem level remains challenging to quantify since long-term, tree-individual, reliable observations are scarce. Here, we present a unique data set of monitoring records from 276 permanent plots located in 95 forest stands across Switzerland, which include five major European tree species (Norway spruce, Scots pine, silver fir, European beech, and sessile and common oak) and cover a time span of over one century (1898–2013), with inventory periods of 5–10 years. The long-term average annual mortality rate of the investigated forest stands was 1.5%. In general, species-specific annual mortality rates did not consistently increase over the last decades, except for Scots pine forests at lower altitudes, which exhibited a clear increase of mortality since the 1960s. Temporal trends of tree mortality varied also depending on diameter at breast height (DBH), with large trees generally experiencing an increase in mortality, while mortality of small trees tended to decrease. Normalized mortality rates were remarkably similar between species and a modest, but a consistent and steady increasing trend was apparent throughout the study period. Mixed effects models revealed that gradually changing stand parameters (stand basal area and stand age) had the strongest impact on mortality rates, modulated by climate, which had increasing importance during the last decades. Hereby, recent climatic changes had highly variable effects on tree mortality rates, depending on the species in combination with abiotic and biotic stand and site conditions. This suggests that forest species composition and species ranges may change under future climate conditions. Our data set highlights the complexity of forest dynamical processes such as long-term, gradual changes of forest structure, demography and species composition, which together with climate determine mortality rates., Frontiers in Plant Science, 10, ISSN:1664-462X

New forest edges are continuously being created by forest management. In the Swiss Alps, silvicultural treatments have partly changed from the selection cutting widespread two decades ago to a more intensive strip cutting. However, little is known about the impact of such harvesting on tree growth and on the structural development of Alpine forest stands dominated by Norway spruce (Picea abies (L.) Karst.), which have high economic and protective value. We therefore investigated the effect of strip cutting in four Alpine spruce stands differing in site and stand conditions through a dendrochronological analysis of 134 tree stems. The change in growth rate was assessed for the 10-year period before and after the cutting year, and rate changes in edge and non-edge trees were compared. The relative change in Hegyi’s competition index before and after the cut was used as a proxy for the change in space and related resources. A linear model was developed to assess the effects of biotic and abiotic variables on changes in growth after strip cutting. Radial growth responses varied greatly between the stands, with a significant increase only in edge trees in the two north-facing sites, i.e. 12% and 60%. Changes in tree competition had the strongest impact on tree growth, followed by site effects. With the same relative change in competition index, the radial growth of edge trees increased more strongly in reaction to cutting than that of non-edge trees. Additionally, small-diameter trees growing near edges benefited more from the strip cutting than larger trees. Our results suggest that strip cutting on north-facing slopes can boost the growth of trees on the east and north-east-facing forest edges. Small spruce trees growing along newly created forest edges can be kept to enhance stand yield. As cutting often leads to long forest edges and may thus affect the growth of a significant proportion of the forest area, such effects should be considered in planning cutting layouts.

The optimization of forest management under climate change uncertainty requires a comparison of many alternative management options under different climate scenarios and the use of stochastic and adaptive approaches. Empirical growth and yield models are highly suitable for this, provided they include sensitivity to environmental influences. Here, we present a climate-sensitive empirical growth and yield model that is based on the direct integration of environmental effects in dynamic growth and survival functions, which allows for the evaluation of changing site conditions over time. Individual-tree diameter and height growth and the probability of a tree to survive any 5-year period were modelled for even-aged beech (Fagus sylvatica) stands in Switzerland using a distance-independent approach. Changing site conditions were based on a drought index (locally adjusted water balance) and sum of degree-days. The data for fitting the model were taken from 30 permanent yield plots repeatedly measured from 1930 to 2010. Reasonable results were obtained in the model evaluation: (1) validation against independent National Forest Inventory data indicated that the incorporation of drought and sum of degree-days in the model was appropriate; (2) accurate simulations over around 50 years of past stand development were achieved (for changes in basal area over 5-year measurements in all plots, the bias was 3 % and the root mean square error 32 %); and (3) the impact of climate change may vary considerably along the range of current site conditions. We thus conclude that the model can be used in management planning under climate change uncertainty.

High-throughput sequencing of immunoglobulin (Ig) repertoires (Ig-seq) is a powerful method for quantitatively interrogating B cell receptor sequence diversity. When applied to human repertoires, Ig-seq provides insight into fundamental immunological questions, and can be implemented in diagnostic and drug discovery projects. However, a major challenge in Ig-seq is ensuring accuracy, as library preparation protocols and sequencing platforms can introduce substantial errors and bias that compromise immunological interpretation. Here, we have established an approach for performing highly accurate human Ig-seq by combining synthetic standards with a comprehensive error and bias correction pipeline. First, we designed a set of 85 synthetic antibody heavy-chain standards (in vitro transcribed RNA) to assess correction workflow fidelity. Next, we adapted a library preparation protocol that incorporates unique molecular identifiers (UIDs) for error and bias correction which, when applied to the synthetic standards, resulted in highly accurate data. Finally, we performed Ig-seq on purified human circulating B cell subsets (naïve and memory), combined with a cellular replicate sampling strategy. This strategy enabled robust and reliable estimation of key repertoire features such as clonotype diversity, germline segment, and isotype subclass usage, and somatic hypermutation. We anticipate that our standards and error and bias correction pipeline will become a valuable tool for researchers to validate and improve accuracy in human Ig-seq studies, thus leading to potentially new insights and applications in human antibody repertoire profiling., Frontiers in Immunology, 9, ISSN:1664-3224

From the perspective of academic and small research laboratories, the most common and practical strategy for recombinant expression of full-length monoclonal antibodies is to perform transient plasmid transfection of mammalian cells, resulting in small-scale and limited protein production. The generation of stable antibody producing mammalian cell lines enables larger-scale and consistent expression, however this approach is rarely pursued due to the time-consuming and expensive process of single colony screening and characterization. In order to bridge the gap between the simplicity of transient transfection and consistent production by stable cell lines, we describe a method to stably integrate antibody genes into the endogenous immunogenomic loci of hybridoma cells using CRISPR/Cas9 genome editing. Initially, the antibody variable light (VL) chain is deleted by multiplexed Cas9 cleavage; subsequently, the variable heavy (VH) chain is replaced by a fluorescent reporter gene (mRuby) by Cas9-assisted homology-directed repair (HDR). This cell line is customized by replacing mRuby with a synthetic antibody (consisting of a VL, light constant region and VH) by once again using Cas9-assisted HDR. Due to hybridomas' inherent ability to surface display and secrete antibodies, they provide a suitable host for both the selection and the production process, substantially streamlining the process for stable cell line generation, and thus we refer to this platform as plug-and-(dis)play (PnP) hybridomas.

In this contribution we present the results of a Swiss-Italian joint sylvicultural experiment to verify if and how the single-tree-oriented silviculture can be applied to chestnut coppices to enhance timber production for industry and structural timber. The study was carried out in five 7 to 17 years old, pure chestnut coppice stands growing on sites of medium to good fertility in central Italy and southern Switzerland. The single-tree-oriented silviculture (option A, 100-150 target trees per hectare) was compared to the stand-oriented silviculture (option B) and to the natural evolution (option C) in terms of growth performance (i.e. individual annual radial increment), stand stability and efficiency (namely leaf area index [LAI], incidence of game and gall wasp attacks, harvesting damages). Suitability of the different treatments has been evaluated on effective (Option A) and theoretical (Options B and C) target trees as selected at time of the first thinning. First results show a significant higher increment response of the target trees in option A compared to the two other silvicultural systems, and a general fast and dynamic recovery of canopy cover after the thinnings in both silvicultural treatments, but even more in the single-tree-oriented silviculture, where two thinnings were necessary within few years. Due to the short time since the arrival of the gall wasp at the experimental sites, no clear impact patterns have been detected. Nevertheless, the attack severity seems to be higher in the target trees of the A option. Damages caused at the stem base by red deer or harvesting operations were clearly higher in the option A, which may reduce the positive outcome of this slvicultural option.

In Valais, a dry Inner-Alpine valley in Switzerland, increasing tree mortality has been related to drought and reduced forest management, which have led to increased competition between trees. Since increasing drought and reduced forest management were co-occurring during the last decades, it is not clear if forest management alone could increase tree resistance to drought. To test whether thinning of Scots pine (Pinus sylvestris L.) stands could be used to mitigate the effects of drought, we analyzed a long-term thinning trial set up in xeric Pfynwald forest in 1965. The trial featured one control (unmanaged plots; basal area 40m2ha−1) and three thinning intensities; light (33m2ha−1), medium (22m2ha−1) and heavy (11m2ha−1). Thinning was repeated in 1971, 1978 and 2010. Individual tree radial growth responses and tree leaf area to sapwood area ratio were assessed and compared among treatment. Additionally, stand-level growth, tree mortality and the relationship between stand density and tree diameter (allometric slope r) were analyzed and compared between two periods (1978–1990; 1991–2009) where the last period was drier. Individual tree basal area increment increased significantly for up to three decades after heavy thinning and mortality rates decreased with decreasing basal area while stand-level growth did not significantly differ. The higher mortality rate and the more negative allometric slope r in the second period suggests that site conditions have become hotter and drier and can partially explain a decrease in the basal area in the control plots and in the light thinning treatment. Leaf area to sapwood area ratio increased with lower basal area and suggests that competition for water was reduced. Taken together, our results suggest that a reduction in basal area of 40–60% to ca. 15–25m2ha−1 could mitigate drought effects on Scots pine on xeric sites for the coming decades prolonging the provision of important ecosystem services. After this time, sustainability of Scots pine forests at xeric sites will depend on the intensity of anticipated climate change, so that in the worst case, thinning might be applied to convert Scots pine forests to mixed forests with more drought-resistant species.

1AbstractMany studies have predicted large changes in forest dynamics during the next century because of global warming. Although empirical approaches and studies based on species distribution models provide valuable information about future changes, they do not take into account biotic interactions and stand-level demographic variations. The objective of this study was to quantify the local and regional variability of the growth and regeneration of three important forest species growing often in mixed stands in Europe (Picea abies (L.) Karst., Abies alba Mill., Fagus sylvatica), and to assess the climatic drivers of this variability. For that purpose, we collected a large forestry data set compiling the long-term (up to 100 years) evolution of species and size distributions for 163 stands across Europe, in the mesic distribution area of these forests. We used an inverse modeling approach, Approximate Bayesian Computation, to calibrate an individual-based model of forest dynamics on these data. Our study revealed that the variability of the demographic processes was of the same order of magnitude between stands of a same forest as between different forests. Out of the three species and two demographic processes studied, only the fir growth strongly varied with temperature. Water availability did not explain any demographic variation over stands. For these forests experiencing mesic conditions, local unmeasured factors seem therefore to have an influence at least as important as macro-environmental factors on demographic variations. Efforts to include these important factors in projection scenarios should therefore be prioritized. Besides, our study demonstrates that inverse modelling methods make possible the analysis of long-term forestry data. Such data should therefore be more widely compiled and used for ecological and global change research.

The impact of climate change on the soil microbiome potentially alters the biogeochemical cycle of terrestrial ecosystems. In semi-arid environments, water availability is a major constraint on biogeochemical cycles due to the combination of high summer temperatures and low rainfall. Here, we explored how ten years of irrigation of a water-limited pine forest in the central European Alps altered the soil microbiome and associated ecosystem functioning. A decade of irrigation stimulated tree growth, resulting in higher crown cover, larger yearly increments of tree biomass, increased litter fall, and greater root biomass. Greater amounts of plant-derived inputs associated with increased primary production in the irrigated forest stands stimulated soil microbial activity coupled to pronounced shifts in the microbiome from largely oligotrophic to more copiotrophic lifestyles. Microbial groups benefitting from increased resource availabilities (litter, rhizodeposits) thrived under irrigation, leading to enhanced soil organic matter mineralization and carbon respired from irrigated soils. This unique long-term study provides new insights into the impact of precipitation changes on the soil microbiome and associated ecosystem functioning in a water-limited pine forest ecosystem and improves our understanding of the persistency of long-term soil carbon stocks in a changing climate. This article is protected by copyright. All rights reserved.

The mixture of beech (Fagus sylvatica L.) and oak (sessile oak, Quercus petraea (Matt.) Liebl., and pedunculate oak, Q. robur L.) is of considerable importance in Europe and will probably become even more important under climate change. Therefore, the performance of oak and beech in mixture was compared with the species’ growth in pure stands. Data from 37 long-term mixing experiments in Poland, Germany and Switzerland were pooled for analysis of mixing effects on stand productivity and possible interrelationships with mixing portions or site conditions. We found that on average, mixed stands of oak and beech exceeded biomass productivity in pure stands by 30 % or 1.7 t ha−1 year−1, as the growth of both species was benefitted by the mixture. However, that the interaction actually ranged from facilitation and overyielding on poor sites to underyielding on fertile sites triggered by competition. An empirically derived interaction model showed volume and dry mass growth changing in mixed stands from gains of 50 % to losses of 10 % depending on site conditions. It is concluded that the analysed mixture grows in accordance with the stress-gradient hypothesis and that our results suggest a site-specific relationship between species mixture and biomass productivity. As a consequence, an adequate species mix should result in increased productivity under steady state as well as climate change.

Between 1995 and 2008 the granting of the Binding Forest Award led to fresh cooperation between forest owners and research on silviculture, growth and yield at the Swiss Federal Institute for Forest, Snow and Landscape Research. Various topics were treated: a study of the beech coppices in Rothenfluh rapidly made it clear that very little was known about this formerly widespread type of forest management and its consequences. The same was true to a lesser extent for the conversion of rather uniform high forest into selection forest (in Plasselb), and for the selective management of light demanding tree species, such as the oak, in Rheinau. In Boudry, cooperation between practice and research already existed: the prize award here led to new approaches in the production of high quality oak, whilst taking ecological values into account. All these new projects are still in their earliest stages and will call for a great deal of “sustainability”, in both senses of the word, from all those involved. Considering the long periods of time required for the development of forest ecosystems, this is in fact self-evident.

Adequate management practices to attain the profiles specified in the Swiss guidelines for the management of mountain protection forests are not always unequivocally clear. This applies among others for beech forests that have a protective function against rockfall. We defined two management scenarios, one of which aims at harvesting trees starting with a minimum diameter at breast height of 40 cm, whereas the other one is focused on the creation of small gaps (area of 500 m2) over a maximum of 10% of the total stand area. These scenarios along with a control scenario characterized by no management were studied using the forest growth model BWINPro. In the control scenario, number of trees, basal area and standing volume were highest. The developments simulated under the two management scenarios were similar, when in scenario thinning harvesting levels corresponded to the growth over a 10-year period. In the other cases, number of trees, basal area and standing volume are lower under scenario gap because harvesting interventions occur more regularly. If the rocks have a volume exceeding 0.2 m3, the requirements of the profiles are attained more quickly under scenario gap, because in scenario thinning the larger trees are preferentially harvested. Because tree regeneration was not simulated, it is difficult to realistically predict the development of the number of trees. However, management interventions are needed in such forests, particularly if the profile for rocks with a volume below 0.2 m3 is to be attained and maintained.

Drought during the vegetation period has en effect on tree growth. Using daily precipitation data and growth records from long-term research plots, we investigated what can be defined as “drought” and how strong its effect is. Dry or humid periods are defined as the deviation from the long-term daily mean of precipitation. Such periods must last at least 60 days to be considered as being decisive for tree growth. The drought values are used together with other site and stand parameters as explaining variables in a model for the basal area increment for Norway spruce (Picea abies [L] H. Karst.), silver fir (Abies alba Mill.), European beech (Fagus sylvatica L.) and oak (Quercus L), based on data from long-term growth and yield plots which are located in the neighbourhood of precipitation measurement stations. These models explain 55 to 89% of the variance. In drought situations basal area increment drops clearly for spruce and beech, for fir only weakly and oak shows no reaction. Furthermore, we checked if there happened additional or compulsory felling after drought periods and if the basal area growth changed significantly compared to the growth in the period before. For both it is not the case, despite distinct drought periods in the last century, especially in the 40s with the extreme year of 1947. Therefore we do not expect dramatic changes for the investigated species in similar drought situations under the prerequisite that the other conditions do not change essentially.

Studies on the production and yield of forests in Switzerland depend entirely on collaboration between owners and forestry services. Not a single square meter of trial area on which to conduct experiments or studies actually belongs to the research institute. The trial areas are spread across the country and their location owes nothing to chance; there are relatively few such areas in Canton Neuchâtel. The present article traces the history and the current situation regarding yield studies in this canton and presents some conclusions. Populations of spruce and beech served only to produce yield tables for FLURY (1907). Plenter forest areas still exist that serve to illustrate long term growth development, the balance of the situation and total growth performance. The oak stands at Boudry are representative of older oak populations.

Une etude sur la capacite a rejeter de souche du châtaignier (Castanea sativa Mill.) a ete effectuee dans un taillis d'environ 60 ans d'âge en Suisse au sud des Alpes. La coupe de taillis s'est faite par l'elimination de tous les arbres vivants et morts. Un inventaire des rejets de souche a ete realise apres deux, respectivement quatre ans afin d'analyser la croissance et la mortalite du nouveau peuplement et de verifier les facteurs influencant la capacite a rejeter de souche. La mortalite des souches est de 4 %, le nombre de rejets par souche (48) est eleve et la croissance des rejets remarquable. La structure du peuplement, la densite des souches et la dimension des vieilles souches n'ont pas d'influence negative sur la capacite de production des rejets ou sur la croissance en diametre et en hauteur de ceux-ci. Par contre on observe que la qualite de la coupe de la souche a un effet positif. En conclusion, la mesure de la hauteur du rejet dominant peut servir comme un indicateur valable de la vigueur de la regeneration dans un taillis de châtaignier.

The forests of the Schlagl-Monastery in the north-eastern corner of Austria are managed according to Reininger’s [Osterreichischer Agraverlag, Vienna, Austria, 163] idea of target diameter harvesting. Twenty years of observations in a 3.5 ha Norway spruce stand in Schlagl and the first re-observation of a permanent inventory in the nearly 500 ha forest management district (FMD) Sonnenwald are investigated and reveal that indeed small trees make efficient use of the area they gain from the removal of their larger neighbours and that the growth per hectare is not decreased by target diameter harvesting. It seems that over a rather long period in the investigated stand and in all stands above 80 years the number of larger trees removed will be replaced by the growth of smaller ones. Comparing the stem number distribution with Schutz’s [Schweiz. Z. Forstwes. 126 (9) Romandes, 178] equilibrium model shows that the steady state is not yet achieved but is fast approached by target diameter harvesting. Probably the equilibrium stocking volume is somewhat below the current average stocking of 450 m3 ha−1.

Producing quality chestnut timber from chestnut coppices by defining silvicultural approaches sustainable from the economic, ecological and socio-environmental point of view is a promising option for the future. Enhancing local silvicultural activities may turn in an improved quality timber production, in ecological benefits, in reducing of environmental loads related to timber import, and favouring direct and indirect (e.g., tourism) forestry industry in marginal areas. In our study we monitored the response of chestnut coppice stand to different silvicultural treatments: i) no treatment (control); ii) stand silviculture consisting in early and frequent low-thinning of moderate intensity; iii) single tree oriented silviculture consisting in early selection final target trees among the best phenotypes (up to 150 individuals per ha) and isolating their crown through free thinning in order to avoid any competition with neighbouring trees. Three experimental plots (1 in Canton Ticino, Switzerland and 2 in Toscana, Italy) were selected in homogeneous and fairly productive sites. First silvicultural interventions have been planned between January 2006 and February 2009 according to the development stage of the stand in each area. First results highlight the existence of both positive and negative aspects in all the considered options. A common trait among the thinned stands is the rapid recovery of the canopy within few years. Concerning the single tree silviculture, it allows producing a significantly higher increase in diameter of the target trees. But, it is disadvantageous in terms of extracting the harvested wood from the stand and it is highly susceptible to game damages. In the future we will carry on the research trials monitoring the considered silvicultural options also in terms of the overall economic balance.

International audience; This contribution presents a dynamic stand growth model for Beech (Fagus sylvatica L.) forests, based on a dataset provided by the Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf. The dataset includes 143 research plots, covering a wide range of growing sites and providing up to 16 interval measurements per research plot.* The objective of this research is to complement the range of existing beech growth models by bridging the gap between the historical yield tables and the single tree growth models. The specific aim is to develop transition functions which will project three state variables (dominant height, basal area and number of trees per hectare) at any particular time, in response to any arbitrary silvicultural treatment.* Two of the transition functions were derived using the generalized algebraic difference approach (GADA), the third one was derived with the algebraic difference approach (ADA). All the functions were fitted simultaneously using iterative seemingly unrelated regression and a base-age-invariant method. The influence of thinnings on basal area growth was included by fitting different transition functions for thinned and unthinned stands.* The overall model provides satisfactory predictions for time intervals up to 20 years. The new model is robust and its relatively simple structure makes it suitable for economic analysis and decision support.; Cette contribution présente un modèle dynamique de croissance des peuplements de hêtres (Fagus sylvatica L.), basé sur un ensemble de données fournies par l'Institut Fédéral Suisse de Recherche sur la Forêt, la Neige et le Paysage, WSL à Birmensdorf. L'ensemble des données comprend 143 parcelles de recherche, couvrant un large éventail de sites et fournissant jusqu'à 16 intervalles de mesures par parcelle de recherche.* L'objectif de cette recherche est de compléter la gamme de modèles de croissance du hêtre existants, en jetant un pont entre les tables de production historiques et les modèles de croissance d'arbre. L'objectif spécifique est de développer des fonctions de transition qui projeterons trois variables d'état (hauteur dominante, surface terrière et nombre d'arbres par hectare) à n'importe quel moment déterminé, en réponse à n'importe quel traitement sylvicole arbitraire.* Deux des fonctions de transition ont été calculées en utilisant l'approche différence algébrique généralisée (GADA), la troisième a été dérivée de l'approche différence algébrique (ADA). Toutes les fonctions ont été ajustées en utilisant simultanément une régression itérative sans lien apparent et une méthode basée sur l'invariance de l'âge. L'influence des éclaircies sur la croissance de la surface terrière a été inclue en ajustant différentes fonctions de transition pour les peuplements éclaircis et les peuplements non éclaircis.* Le modèle général fournit des prédictions satisfaisantes pour des intervalles de temps jusqu'à 20 ans. Le nouveau modèle est robuste et sa structure relativement simple fait qu'il est convient pour l'analyse économique et l'aide à la décision.

International audience; The Reineke Stand density rule relating stem numbers to the quadratic mean diameter is generally used as a reference for modelling maximal stand density.* The linearity of this relationship after double logarithmic transformation is generally assumed, but it must be questioned for untouched stands and stands with a conventional thinning regime. Curvilinearity is demonstrated for some spruce and beech stands in Switzerland and shown to be statistically representative. This relationship is independent of the site index. It can be interpreted as a change in mortality in young stages mainly due to competition and in older stages more to ageing. * A more accurate estimation of the maximal stand density needs to take into account the important variation around the mean course, known as the yield level. A simple method to assess the yield level of any stand regardless of whether it is thinned or not is presented, based on estimating the effect of a stand opening on the basal area.; La loi de Reineke reliant le nombre de tiges au diamètre quadratique moyen est généralement utilisée comme référence pour la modélisation de la densité maximale de peuplements.* On remet en question la linéarité d'une telle relation dans l'espace logarithmique, dans le cas des peuplements non traités aussi bien que pour ceux traités par des interventions conventionnelles. La curvilinéarité de cette relation est démontrée pour quelques peuplements purs d'épicéa et de hêtre en Suisse et dans sa représentativité statistique. La relation est indépendante de l'indice de fertilité et interprétée comme modification du type de mortalité au cours du développement, due pendant le jeune âge à la seule compétition, puis s'y ajoute celle due au vieillissement.* Une estimation appropriée de la densité maximale des peuplements doit tenir compte des variations importantes autour de la courbe moyenne connue comme niveau de production. Une méthode simple de détermination du niveau de production dans tous les cas de traitement antérieur est présentée, fondée sur une estimation de l'effet de l'ouverture du couvert sur la surface terrière.

International audience; Existing growth and yield plots of pure and mixed stands of Norway spruce (Picea abies (L.) H. Karst.) and European beech (Fagus sylvatica L.) were aggregated in order to unify the somewhat scattered sources of information currently available, as well as to develop a sound working hypothesis about mixing effects. The database contains information from 23 long-term plots, covering an ecological gradient from nutrient poor and dry to nutrient rich and moist sites throughout Central Europe.* An empirically formed interaction model showed, that depending on the site conditions, dry mass growth in mixed stands can range from − 46% to +138 % of the growth yielded by a scaled combination of pure stands at equal mixing proportions.* Drawing from the interaction model, overyielding of the mixed stands appears to be triggered by two separate mechanisms. On poor sites, where significant overyielding is commonly found, facilitation by beech offsets nutrient-related growth limitations in spruce. In contrast, overyielding of mixed stands occurs less frequently on rich sites, and appears to be based on an admixture effect, with spruce reducing the severe intra-specific competition common in pure beech stands.* It was concluded that silviculture can accelerate growth of spruce by beech admixtures on poor sites, while growth of beech can be promoted by admixture of spruce, particularly on excellent sites.