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Large ungulate populations are known to cause economic damage to agriculture and forestry. Bark damage is particularly detrimental to the timber production of certain species, including Picea abies (L.) Karst (Norway spruce): after bark is wounded, rot often spreads in the trunk base, damaging the most valuable log section. Numerous studies have provided valuable information on various aspects of this process, for example identifying factors governing tree sensitivity to bark-stripping or estimating the rate of decay spread in the trunk. The financial consequences over a full timber production cycle have nevertheless remained poorly quantified and uncertain. Coupling a forest dynamics model (GYMNOS) with models of damage occurrence and decay spread, we simulated the effect of ranging levels of bark-stripping damage on financial losses. The simulations were repeated for sites of ranging fertility and with different protection measures (fences or individual protections). The net present values of these different simulations were estimated and compared to estimate the cost of the damage and the cost-effectiveness of the damage protections. Protecting plantations against bark-stripping damage with fences was found unlikely to be worthwhile. By contrast, individual protections placed on crop trees could be helpful, particularly in the most fertile stands. Loss of revenue depended greatly on the factors tested: we estimated that the average damage cost could be about 53 €/ha/year, reducing timber yield by 19% in the study area, in Southern Belgium.

International audience; New silvicultural practices to meet the requirements of ecosystem-based forest management are being adopted operationally, even if the long-term outcomes remain unknown. In eastern Quebec, Canada, the conversion of plantations from even-aged to irregular or uneven-aged stands is being carried out in 10% of commercial thinning operations. Existing growth and yield simulators cannot be used to forecast stand development. Here we apply a novel individual tree-level simulator to plantations characterized by high levels of natural regeneration ingrowth, such as those observed in Quebec. The simulator user can either choose distance-dependent or distance-independent competition indices, depending on user preference or simulation needs. Calibration statistics and validation results indicate that both versions perform very well. When applied to operational silvicultural scenarios, the simulator shows that thinning does not influence total stand yield; however, tree spatial aggregation does change. Moreover, the variability among the different simulation runs is greater for spatial statistics than for stand yield. Overall, thinning from below has the greatest effect on stand structure, whereas the smallest is from early crop tree release, used as the initial conversion step. This pattern implies that the first and second thinnings of the conversion process towards irregular or uneven-aged stands may not have a major effect on stand structure. In the case of the conversion process, the consequences for stand structure must thus be viewed as a longer-term issue. More importantly, the conversion process does not reduce stand yield, thereby reducing one of the key concerns of forest managers.

Given the multiple abiotic and biotic stressors resulting from global changes, management systems and practices must be adapted in order to maintain and reinforce the resilience of forests. Among others, the transformation of monocultures into uneven-aged and mixed stands is an avenue to improve forest resilience. To explore the forest response to these new silvicultural practices under a changing environment, one needs models combining a process-based approach with a detailed spatial representation, which is quite rare. We therefore decided to develop our own model (HETEROFOR for HETEROgeneous FORest) according to a spatially explicit approach, describing individual tree growth based on resource sharing (light, water and nutrients). HETEROFOR was progressively elaborated within Capsis (Computer-Aided Projection for Strategies in Silviculture), a collaborative modelling platform devoted to tree growth and stand dynamics. This paper describes the carbon-related processes of HETEROFOR (photosynthesis, respiration, carbon allocation and tree dimensional growth) and evaluates the model performances for three broadleaved stands with different species compositions (Wallonia, Belgium). This first evaluation showed that HETEROFOR predicts well individual radial growth (Pearson's correlation of 0.83 and 0.63 for the European beech and sessile oak, respectively) and is able to reproduce size–growth relationships. We also noticed that the net to gross primary production (npp to gpp) ratio option for describing maintenance respiration provides better results than the temperature-dependent routine, while the process-based (Farquhar model) and empirical (radiation use efficiency) approaches perform similarly for photosynthesis. To illustrate how the model can be used to predict climate change impacts on forest ecosystems, we simulated the growth dynamics of the mixed stand driven by three IPCC climate scenarios. According to these simulations, the tree growth trends will be governed by the CO2 fertilization effect, with the increase in vegetation period length and the increase in water stress also playing a role but offsetting each other.

Climate change affects forest growth in numerous and sometimes opposite ways, and the resulting trend is often difficult to predict for a given site. Integrating and structuring the knowledge gained from the monitoring and experimental studies into process-based models is an interesting approach to predict the response of forest ecosystems to climate change. While the first generation of models operates at stand level, one now needs spatially explicit individual-based approaches in order to account for individual variability, local environment modification and tree adaptive behaviour in mixed and uneven-aged forests that are supposed to be more resilient under stressful conditions. The local environment of a tree is strongly influenced by the neighbouring trees, which modify the resource level through positive and negative interactions with the target tree. Among other things, drought stress and vegetation period length vary with tree size and crown position within the canopy. In this paper, we describe the phenology and water balance modules integrated in the tree growth model HETEROFOR (HETEROgenous FORest) and evaluate them on six heterogeneous sessile oak and European beech stands with different levels of mixing and development stages and installed on various soil types. More precisely, we assess the ability of the model to reproduce key phenological processes (budburst, leaf development, yellowing and fall) as well as water fluxes. Two two-phase models differing regarding their response function to temperature during the chilling period (optimum and sigmoid functions) and a simplified one-phase model are used to predict budburst date. The two-phase model with the optimum function is the least biased (overestimation of 2.46 d), while the one-phase model best accounts for the interannual variability (Pearson's r=0.68). For the leaf development, yellowing and fall, predictions and observations are in accordance. Regarding the water balance module, the predicted throughfall is also in close agreement with the measurements (Pearson's r=0.856; bias =-1.3 %), and the soil water dynamics across the year are well reproduced for all the study sites (Pearson's r was between 0.893 and 0.950, and bias was between −1.81 and −9.33 %). The model also reproduced well the individual transpiration for sessile oak and European beech, with similar performances at the tree and stand scale (Pearson's r of 0.84–0.85 for sessile oak and 0.88–0.89 for European beech). The good results of the model assessment will allow us to use it reliably in projection studies to evaluate the impact of climate change on tree growth in structurally complex stands and test various management strategies to improve forest resilience.

International audience; Abstract• Key messageThe best options to parametrize a radiative transfer model change according to the response variable used for fitting. To predict transmitted radiation, the turbid medium approach performs much better than the porous envelop, especially when accounting for the intra-specific variations in leaf area density but crown shape has limited effects. When fitting with tree growth data, the porous envelop approach combined with the more complex crown shape provides better results. When using a joint optimization with both variables, the better options are the turbid medium and the more detailed approach for describing crown shape and leaf area density.• ContextSolar radiation transfer is a key process of tree growth dynamics in forest.• AimsDetermining the best options to parametrize a forest radiative transfer model in heterogeneous oak and beech stands from Belgium.• MethodsCalibration and evaluation of a forest radiative transfer module coupled to a spatially explicit tree growth model were repeated for different configuration options (i.e., turbid medium vs porous envelope to calculate light interception by trees, crown shapes of contrasting complexity to account for their asymmetry) and response variables used for fitting (transmitted radiation and/or tree growth data).• ResultsThe turbid medium outperformed the porous envelope approach. The more complex crown shapes enabling to account for crown asymmetry improved performances when including growth data in the calibration.• ConclusionOur results provide insights on the options to select when parametrizing a forest radiative 3D-crown transfer model depending on the research or application objectives.

International audience; Climate change affects forest ecosystem processes and related services due to climate variability. These might affect ecosystem functioning, especially productivity. Regarding management issues, mixed stands are considered a relevant option to maintain forest cover and ecosystem services under climate change. However, the possibility to maintain these mixed stands with management actions with positive effects on forest functioning under climate change remains uncertain and deserves further investigations. Relying on a simulation-based study with a forest gap model (ForCEEPS), we thus addressed the following questions: (1) Are monospecific stands vulnerable to climate change? (2) Would mixed stands significantly mitigate climate change effects on forest productivity and wood production under climate change? (3) Would conversion to mixed stand management affect significantly forest productivity and wood production under climate change compare to monospecific management? In this study, we quantified potential climate change effect (using RCP 8.5 and present climate) and management’s effect in the French Alps, focusing on five species (Fagus sylvatica, Abies alba, Picea abies, Pinus sylvestris, and Quercus pubescens). We tested different scenarios, with various composition, structure, or environmental conditions, under climate change. These simulations showed that monospecific stands currently growing in stressful conditions would be vulnerable to climate change. Managing mixed stands or conversion from pure to mixed stands would make it possible to maintain higher productivity in the long term than monospecific stands, depending on the species and the sites considered. Our results will feed into discussion on forest management in the context of climate change.

International audience; Climate change impacts forest functioning and dynamics, and large uncertainties remain regarding the interactions between species composition, demographic processes and environmental drivers. There are few robust tools available to link these processes, which precludes accurate projections and recommendations for long-term forest management. Forest gap models present a balance between complexity and generality and are widely used in predictive forest ecology. However, their relevance to tackle questions about the links between species composition, climate and forest functioning is unclear. In this regard, demonstrating the ability of gap models to predict the growth of forest stands at the annual parameterization scale resolution—representing a sensitive and integrated signal of tree functioning and mortality risk—appears as a fundamental step. In this study, we aimed at assessing the ability of a gap model to accurately predict forest growth in the short term and potential community composition in the long term, across a wide range of species and environmental conditions. To do so, we present the gap model ForCEEPS, calibrated using an original parameterization procedure for the main tree species in France. ForCEEPS was shown to satisfactorily predict forest annual growth (averaged over a few years) at the plot level from mountain to Mediterranean climates, regardless of the species. Such an accuracy was not gained at the cost of losing precision for long-term predictions, as the model showed a strong ability to predict potential community compositions. The mechanistic relevance of ForCEEPS parameterization was explored by showing the congruence between the values of key model parameter and species functional traits. We further showed that accounting for the spatial configuration of crowns within forest stands, the effects of climatic constraints and the variability of shade tolerances in the species community are all crucial to better predict short-term productivity with gap models. Synthesis. The dual ability of predicting short-term functioning and long-term community composition, as well as the balance between generality and realism (i.e. predicting accuracy) of the new generation of gap models may open great perspectives for the exploration of the biodiversity–ecosystem functioning relationships, species coexistence mechanisms and the impacts of climate change on forest ecosystems. A free Plain Language Summary can be found within the Supporting Information of this article.

Climate change affects forest ecosystem processes and related services due to increasing temperature and increasing extreme drought event frequency. This effect can be direct through the alteration of the physiological responses of trees, but also indirect, by modifying interactions between trees and thus changing communities’ composition. Such changes might affect species richness with high impacts on ecosystem functioning, especially productivity.Regarding management issues, mixed stands are usually considered a good option to maintain forest cover and ecosystem services under climate change. However, the possibility to maintain these mixed stands with management actions with positive effects on forest functioning under climate change remains uncertain and deserves further investigations. Relying on a simulation-based study with a forest gap model, we thus addressed the following questions: (1) Are monospecific stands vulnerable to climate change? (2) Would mixed stands significantly mitigate climate change effects on forest productivity and wood production under climate change? (3) Would conversion to mixed stand management affect significantly forest productivity and wood production under climate change compare to monospecific management?With a 150 years simulation approach, we quantified potential climate change effect (using RCP 8.5) compared to present climate and managements effect in the French Alps, focusing on five tree species. The gap-model we used included a management module, which allowed testing six silvicultural scenarios on different stands, with various composition, structure or environmental conditions, under climate change.These simulations showed that monospecific stands currently growing in stressful conditions would be too vulnerable to climate change to be maintained. Managing mixed stands or conversion from pure to mixed stands would make it possible to maintain higher productivity in the long-term than monospecific stands, even under severe climate change. This pattern depends to species and sites considered. Our results will feed into discussion on forest management in the context of climate change.

A preprint peer-reviewed and recommended by Peer Community In Evolutionary Biologyhttps://evolbiol.peercommunityin.org/; Sexual selection has long been known to favor the evolution of mating behaviors such as mate preference and competitiveness, and to affect their genetic architecture, for instance by favoring genetic correlation between some traits. Reciprocally, genetic architecture can affect the expression and the evolvability of traits and mating behaviors. But sexual selection is highly context-dependent, making interactions between individuals a central process in evolution, governing the transmission of genotypes to the next generation. This loop between the genetic structure conditioning the expression and evolution of traits and behaviour, and the feedback of this phenotypic evolution on the architecture of the genome in the dynamic context of sexual selection, has yet to be thoroughly investigated. We argue that demogenetic agent-based models (DG-ABM) are especially suited to tackle such a challenge because they allow explicit modelling of both the genetic architecture of traits and the behavioural interactions in a dynamic population context. We here present a DG-ABM able to simultaneously track individual variation in traits (such as gametic investment, preference, competitiveness), fitness and genetic architecture throughout evolution. Using two simulation experiments, we compare various mating systems and show that behavioral interactions during mating triggered some complex feedback in our model, between fitness, population demography, and genetic architecture, placing interactions between individuals at the core of evolution through sexual selection. DG-ABMs can, therefore, relate to theoretical patterns expected at the population level from simpler analytical models in evolutionary biology, and at the same time provide a more comprehensive framework regarding individual trait and behaviour variation, that is usually envisioned separately from genome architecture in behavioural ecology

International audience; The genetic composition of forest stands dynamically evolves driven by the combination of natural processes and management practices. Evolution-oriented forest management consists in understanding and stewarding these combined processes to enhance short-term adaptation and productivity while maintaining long-term evolvability.Silviculture is a sequence of practices, each having multiple possible genetic impacts, depending one on the other. Moreover, silvicultural practices interact with demographic changes due to other natural causes like environment changes. All these dependencies and interactions make an analytical approach of the resulting evolutionary dynamics, based on quantitative genetics, very complex. Here, we developed a demo-genetic simulation approach of this issue.Previous demo-genetic models in forest systems mainly focused on the possible impacts of silviculture on the overall (neutral) gene diversity. Here we focus on the selection effects on growth. We coupled a quantitative genetics model to a growth dynamics model calibrated for Cedrus atlantica, and simulated various scenarios of silviculture, using the CAPSIS simulation platform (http://capsis.cirad.fr/capsis/help_en/luberon2).We compared the effect of various management practices on (i) the growth, (ii) the genetic quality and (iii) the evolutionary potential of the stand. We show that different silviculture sequences may result in very different levels of selection intensity for growth, which have different impacts on the dynamics of genetic means and variances from one generation of trees to the next. We also show the importance of all stages of interventions, including those in the juvenile stage, on the final genetic impacts. Finally, we show that the effective genetic impacts of a given silviculture guideline are highly influenced by pragmatic choices in the forest and by local disturbance regimes.This work should be considered as a “proof of concept” showing that demo-genetic models coupling forest dynamics, quantitative genetics, silviculture practices and natural disturbances are feasible. Such models provide a powerful approach to investigate the potential genetic impacts of silviculture and guide evolution-oriented forest management. We are currently extending this approach to other species and other contexts.

Given the multiple abiotic and biotic stressors resulting from global changes, management systems and practices must be adapted in order to maintain and reinforce the resilience of forests. Among others, the transformation of monocultures into uneven-aged and mixed stands is an avenue to improve forest resilience. To explore the forest response to these new silvicultural practices under a changing environment, one need models combining a process-based approach with a detailed spatial representation, which is very rare. We therefore decided to develop our own model (HETEROFOR) according to a spatially explicit approach describing individual tree growth based on resource sharing (light, water and nutrients). HETEROFOR was progressively elaborated through the integration of various modules (light interception, phenology, water cycling, photosynthesis and respiration, carbon allocation, mineral nutrition and nutrient cycling) within CAPSIS, a collaborative modelling platform devoted to tree growth and stand dynamics. The advantage of using such a platform is to use common development environment, model execution system, user- interface and visualization tools and to share data structures, objects, methods and libraries. This paper describes the carbon-related processes of HETEROFOR (photosynthesis, respiration, carbon allocation and tree dimensional growth) and evaluates the model performances for a mixed oak and beech stand in Wallonia (Belgium). This first evaluation showed that HETEROFOR predicts well individual radial growth and is able to reproduce size-growth relationships. We also noticed that the more empirical options for describing maintenance respiration and crown extension provide the best results while the process-based approach best performs for photosynthesis. To illustrate how the model can be used to predict climate change impacts on forest ecosystems, the growth dynamics in this stand was simulated according to four IPCC climate scenarios. According to these simulations, the tree growth trends will be governed by the CO2 fertilization effect with the increase in vegetation period length and in water stress also playing a role but offsetting each other.

Climate change affects forest growth in numerous and sometimes opposite ways and the resulting trend is often difficult to predict for a given site. Integrating and structuring the knowledge gained from the monitoring and experimental studies into process-based models is an interesting approach to predict the response of forest ecosystems to climate change. While the first generation of such models operates at stand level, we need now individual-based and spatially-explicit approaches in order to account for structurally complex stands whose importance is increasingly recognized in the changing environment context. Among the climate-sensitive drivers of forest growth, phenology and water availability are often cited as crucial elements. They influence, for example, the length of the vegetation period during which photosynthesis takes place and the stomata opening, which determines the photosynthesis rate. In this paper, we describe the phenology and water balance modules integrated in the tree growth model HETEROFOR and evaluate them on six Belgian sites. More precisely, we assess the ability of the model to reproduce key phenological processes (budburst, leaf development, yellowing and fall) as well as water fluxes. Three variants are used to predict budburst (Uniforc, Unichill and Sequential), which differ regarding the inclusion of chilling and/or forcing periods and the calculation of the coldness or heat accumulation. Among the three, the Sequential approach is the least biased (overestimation of 2.46 days) while Uniforc (chilling not considered) best accounts for the interannual variability (Pearson’s R = 0.68). For the leaf development, yellowing and fall, predictions and observation are in accordance. Regarding the water balance module, the predicted throughfall is also in close agreement with the measurements (Pearson’s R = 0.856, bias = −1.3 %) and the soil water dynamics across the year is well-reproduced for all the study sites (Pearson’s R comprised between 0.893 and 0.950, and bias between −1.81 and −9.33 %). The positive results from the model assessment will allow us to use it reliably in projection studies to evaluate the impact of climate change on tree growth and test how diverse forestry practices can adapt forests to these changes.

Key message In this exploratory study, we show how combining the strength of tree diversity experiment with the long-term perspective offered by forest gap models allows testing the mixture yielding behavior across a full rotation period. Our results on a SW France example illustrate how mixing maritime pine with birch may produce an overyielding (i.e., a positive net biodiversity effect). Context Understanding the link between tree diversity and stand productivity is a key issue at a time when new forest management methods are investigated to improve carbon sequestration and climate change mitigation. Well-controlled tree diversity experiments have been set up over the last decades, but they are still too young to yield relevant results from a long-term perspective. Alternatively, forest gap models appear as appropriate tools to study the link between diversity and productivity as they can simulate mixed forest growth over an entire forestry cycle. Aims We aimed at testing whether a forest gap model could first reproduce the results from a tree diversity experiment, using its plantation design as input, and then predict the species mixing effect on productivity and biomass in the long term. Methods Here, we used data from different forest experimental networks to calibrate the gap model ForCEEPS for young pine (Pinus pinaster) and birch (Betula pendula) stands. Then, we used the refined model to compare the productivity of pure and mixed pine and birch stands over a 50-year cycle. The mixing effect was tested for two plantation designs, i.e., species substitution and species addition, and at two tree densities. Results Regarding the comparison with the experiment ORPHEE (thus on the short term), the model well reproduced the species interactions observed in the mixed stands. Simulations showed an overyielding (i.e., a positive net biodiversity effect) in pine-birch mixtures in all cases and during the full rotation period. A transgressive overyielding was detected in mixtures resulting from birch addition to pine stands at low density. These results were mainly due to a positive mixing effect on pine growth being larger than the negative effect on birch growth. Conclusion Although this study remains explorative, calibrating gap models with data from monospecific stands and validating with data from the manipulative tree diversity experiment (ORPHEE) offers a powerful tool for further investigation of the productivity of forest mixtures. Improving our understanding of how abiotic and biotic factors, including diversity, influence the functioning of forest ecosystems should help to reconsider new forest managements optimizing ecosystem services.

La diversité des capacités d'adaptation est no seulement importante entre essences forestières mais aussi au sein de chaque espèce. La diversité génétique intra-spécifique observée à un instant donné est une "prise de vue" dans une évolution continue. Cette diversité est aussi le carburant nécessaire pour l'évolution des espèces. Pour mieux comprendre les impacts des pratiques de gestion sur la diversité génétique et construire des stratégies d'adaptation à long terme, nous intégrons information génétique et perturbations accidentelles dans des outils existants de simulation d'itinéraires sylvicoles.

A growing body of research suggests mixed-species stands are generally more productive than pure stands as well as less sensitive to disturbances. However, these effects of mixture depend on species assemblages and environmental conditions. Here, we present the Salem simulator, a tool that can help forest managers assess the potential benefit of shifting from pure to mixed stands from a productivity perspective. Salem predicts the dynamics of pure and mixed even-aged stands and makes it possible to simulate management operations. Its purpose is to be a decision support tool for forest managers and stakeholders as well as for policy makers. It is also designed to conduct virtual experiments and help answer research questions. In Salem, we parameterised the growth in pure stand of 12 common tree species of Europe and we assessed the effect of mixture on species growth for 24 species pairs (made up of the 12 species mentioned above). Thus, Salem makes it possible to compare the productivity of 36 different pure and mixed stands depending on environmental conditions and user-defined management strategies. Salem is essentially based on the analysis of National Forest Inventory data. A major outcome of this analysis is that we found species mixture most often increases species growth, in particular at the poorest sites. Independently from the simulator, foresters and researchers can also consider using the species-specific models that constitute Salem: the growth models including or excluding mixture effect, the bark models, the diameter distribution models, the circumference-height relationship models, as well as the volume equations for the 12 parameterised species. Salem runs on Windows, Linux, or Mac. Its user-friendly graphical user interface makes it easy to use for non-modellers. Finally, it is distributed under a LGPL license and is therefore free and open source.

International audience; Correction to: Annals of Forest Science https://doi.org/10.1007/s13595-017-0686-2 In Table 2 in the original article, torching index (TI) and crowning index (CI) values were incorrectly expressed in km/s. The correct units are km/h. The original article has been corrected. The online version of the original article can be found at https://doi.org/10.1007/s13595-017-0686-2

Key message We describe a modeling system that enables detailed, 3D fire simulations in forest fuels. Using data from three sites, we analyze thinning fuel treatments on fire behavior and fire effects and compare outputs with a more commonly used model. Context Thinning is considered useful in altering fire behavior, reducing fire severity, and restoring resilient ecosystems. Yet, few tools currently exist that enable detailed analysis of such efforts. Aims The study aims to describe and demonstrate a new modeling system. A second goal is to put its capabilities in context of previous work through comparisons with established models. Methods The modeling system, built in Python and Java, uses data from a widely used forest model to develop spatially explicit fuel inputs to two 3D physics-based fire models. Using forest data from three sites in Montana, USA, we explore effects of thinning on fire behavior and fire effects and compare model outputs. Results The study demonstrates new capabilities in assessing fire behavior and fire effects changes from thinning. While both models showed some increases in fire behavior relating to higher winds within the stand following thinning, results were quite different in terms of tree mortality. These different outcomes illustrate the need for continuing refinement of decision support tools for forest management. Conclusion This system enables researchers and managers to use measured forest fuel data in dynamic, 3D fire simulations, improving capabilities for quantitative assessment of fuel treatments, and facilitating further refinement in physics-based fire modeling.

1. Calibration of local, regional or global allometric equations to estimate biomass at the tree level constitutes a significant burden on projects aiming at reducing Carbon emissions from forest degradation and deforestation. The objective of this contribution is to assess the precision and accuracy of Terrestrial Laser Scanning (TLS) for estimating volumes and above-ground biomass (AGB) of the woody parts of tropical trees, and for the calibration of allometric models. 2. We used a destructive dataset of 61 trees, with diameters and AGB of up to 186.6 cm and 60 Mg respectively, which were scanned, felled and weighed in the semi-deciduous forests of eastern Cameroon. We present an operational approach based on available software allowing the retrieving of TLS volume with low bias and high accuracy for large tropical trees. Edition of the obtained models proved necessary, mainly to account for the complexity of buttressed parts of tree trunks, which were separately modelled through a meshing approach, and to bring a few corrections in the topology and geometry of branches, thanks to the amapstudio-scan software. 3. Over the entire dataset, TLS-derived volumes proved highly reliable for branches larger than 5cm in diameter. The volumes of the remaining woody parts estimated for stumps, stems and crowns as well as for the whole tree proved very accurate (RMSE below 2.81% and R-2 above of .98) and unbiased. Once converted into AGB using mean local-specific wood density values, TLS estimates allowed calibrating a biomass allometric model with coefficients statistically undistinguishable from those of a model based on destructive data. The Unedited Quantitative Structure Model (QSM) however leads to systematic overestimations of woody volumes and subsequently to significantly different allometric parameters. 4. We can therefore conclude that a non-destructive TLS approach can now be used as an operational alternative to traditional destructive sampling to build the allometric equations, although attention must be paid to the quality of QSM model adjustments to avoid systematic bias.

[Departement_IRSTEA]Territoires [TR1_IRSTEA]SEDYVIN; International audience; Context : Distribution of removed trees among species and diameter classes is usually used to characterize selection harvesting. This information is, however, rarely available when analysing past time series. The challenge is then to determine the minimal level of information required to characterize harvests. Aims: We tested in this work whether an algorithm based on the total number of trees and volume to be removed enabled the reconstruction of harvesting diameter distributions, when combined with stand diameter distribution before harvest. Methods: We tested the algorithm against empirical data in the case of selection system, comparing distributions by χ² tests, and extended its evaluation to more diversified theoretical situations. Results: Observed harvesting distributions were well-reconstructed in most empirical cases, with better results when considering mean simulated distributions. The algorithm was also effective for other thinning and harvesting strategies: low thinning, thinning of dominants, and mechanical thinning, whatever the structure of the stand before being cut. Conclusion: Total number of trees and volume harvested appeared thus sufficient to reconstruct DBH distribution of removed trees in diverse situations, provided that the distribution before harvest was known. This algorithm, therefore, enables the simulation of complex harvesting operations with minimal information.

Simulating the dynamics of heterogeneous forests calls for spatially explicit radiation transmission models at the scale of individual trees and requiring only a short computing time. Such a model was developed for spatially heterogeneous coniferous forest canopies. Based on the interception of light rays by parabolic crowns, it simultaneously calculates the radiation intercepted by each tree and the distribution of irradiance on the ground. For every sky direction, parallel rays aim at ground cell centres and are intercepted by tree crowns on their way. Slope and exposure are taken into account eliminating rays coming from above the slope. Optimisation in computing time is obtained by pre-selecting for each ray direction a rectangular cell neighbourhood around the target cell in such a way that potentially intercepting trees can only be found in this neighbourhood. Model evaluation was done by comparing hemispherical photographs with model predictions in a spatially heterogeneous Norway spruce (Picea abies, L. Karst) stand at the upper montane level in the Alps. Thanks to a satisfactory fit between model and data and a reasonably short computing time (about 2 min for 0.25 ha), the model can be considered for integration into a forest dynamics simulator. In the reference stand, 42% of incident radiation was intercepted by the highest trees (132 ha−1). Due to the clumped structure, 23% of incident radiation reached the soil. Interception by individual trees varied considerably as a function of tree size and location (from 0 to 60% of the potential interception of a tree growing in isolation). Irradiance at ground level was also extremely variable (between 0 and 50% of irradiance above the canopy), illustrating the need for spatial models in heterogeneous stands. The interception of radiation by trees was not affected by slope and exposure, unlike irradiance at ground level, which increased for southern exposures. Therefore, in terms of dynamics, regeneration should be the most sensitive to changes in these factors. Because the model produces precise radiation values at the ecosystem level, it allows analysis of the links between the structure of a forest stand and its energetic functioning synthetically.

AMAPstudio is a software suite dedicated to plants architecture modelling, designed for botanists and agronomists, providing features to edit, visualise, explore and simulate multi-scale plant descriptions. AMAPstudio is based on the multi-scale tree graph (MTG) data structure, which is commonly used to represent plant topology. The user can explore and edit the topology and the geometry of one or several plants. Specific data can be extracted with combinations of criteria and can be visualised in tables and graphs. Simple analysis functions can be run and data can be exported to external tools, e.g. R or any other statistical computing environment, for more specific analyses. AMAPstudio is also a framework in which modellers can integrate their own plant simulation models to build plant growth or scene dynamics scenarios and explore the results. Models can be of different kinds, they can address more or less functioning and interaction with other plants or with the environment, possibly enabling to run ecological studies. AMAPstudio is an open software built according to the Capsis methodology. It is scenario oriented and brings particularly interactive editors easing the daily work and knowledge transfer. It is a free open-source software (LGPL) available on all Java compatible operating systems and it can be downloaded on http://amapstudio.cirad.fr.

[Departement_IRSTEA]Territoires [TR1_IRSTEA]SEDYVIN; Spatial pattern has a key role in the interactions between species in plant communities. These interactions influence ecological processes involved in the species dynamics: growth, regeneration and mortality. In this study, we investigated the effect of spatial pattern on productivity in mature mixed forests of sessile oak and Scots pine. We simulated tree locations with point process models and tree growth with spatially explicit individual growth models. The point process models and growth models were fitted with field data from the same stands. We compared species productivity obtained in two types of mixture: a patchy mixture and an intimate mixture. Our results show that the productivity of both species is higher in an intimate mixture than in a patchy mixture. Productivity difference between the two types of mixture was 11.3% for pine and 14.7% for oak. Both species were favored in the intimate mixture because, for both, intraspecific competition was more severe than interspecific competition. Our results clearly support favoring intimate mixtures in mature oak-pine stands to optimize tree species productivity; oak is the species that benefits the most from this type of management. Our work also shows that models and simulations can provide interesting results for complex forests with mixtures, results that would be difficult to obtain through experimentation.

[Departement_IRSTEA]Territoires [TR1_IRSTEA]SEDYVIN; International audience; Context :Forest scientists build models to simulate stand growth and forests dynamics. Dedicated computer tools are often developed to implement these models in order to run silvicultural scenarios and explore simulation results. Aims Our objective was to encourage software reuse and simplify model implementation. Methods The scheme was to develop a framework and methodology allowing to simplify the implementation, integration, simulation and comparison of forest models by providing a set of common and standard tools. Results Capsis provides an open and modular software architecture based on various components, allowing to run forest growth simulations and display the results. The benefits of this framework are shown with the Samsara2 model, an individual-based and spatialised tree model. Capsis has been used successfully in many similar projects. In addition, the Capsis methodology defines how developers, modellers and end-users may interact. Conclusion The Capsis framework facilitates collaborative and shared software development. Moreover, it is a powerful way to support scientific animation in the frame of forest science.

International audience; The objective of this paper is to study forest growth simulation based on functional-structural modelling and its potentials for forestry applications. The GreenLab model is used for this purpose owing to its computational performances, its calibration capacity on real plants and its extension to the stand level, by taking into account the competition between neighbouring plants and the interactions with the environment. We first propose a software design: 1) to manage the composition of forest scenes, 2) to simulate their growth based on parallel computing of individual trees with the GreenLab model, 3) to get the realistic and real-time 3D rendering of the simulation results. We then detail a test case to illustrate the potentialities of this new tool. Mono-specific stands of poplars and pines are simulated. We analyze the computation performances and illustrate the simulation results with 3D outputs. A very classical application in forest management, stand thinning, is also tested. Our tool provides new insights thanks to the detailed architectures of trees resulting from the functional-structural model.

To predict growth and yield of forests and plantations, forestry scientists often build models. In order to run simulations, these models are then implemented in computer programs. The resulting simulators can be used to run various scenarios, for instance to evaluate the effect of different initial situations (density, age, spatial structure...), to assess various management strategies (number, date and type of interventions) or to study the effect of natural disturbances (gaps, wind, fertility changes, etc.). The Capsis Platform accepts a great number of model types: from mono specific stand level or distanceindependent tree models to heterogeneous individual based models, spatially explicit or not. Such forestry growth and yield or dynamics models are integrated into Capsis by their authors in codevelopment with a computer developer after a short training and starting session together, according to the Capsis charter. This process quickly (days or weeks) results in a running simulator.

The Integrated Stand Growth Model (ISGM) is a prototype for pure even-aged stand which includes several nonlinear simultaneous equations: 1) basal area growth model; 2) self-thinning model; 3) dominant tree height growth model or site index curves; 4) relationship between average tree height and dominant tree height; 5) form height model and density index definition; basal area formula; stand volume formula. A new parameter estimation method of two-stage error-in-variable model (TSEM) for nonlinear simultaneous equations is used to estimate the parameters of ISGM to ensure the parameter estimation is unbiased and all the variables in the equations are compatible. The ISGM can be used to simulate pure even-aged stand growth with different values of site index, stand density, different thinning methods, and to draw a stand density control chart with the ForStat software (in Chinese) and in the Capsis platform (in English). The parameter estimation and simulation method are given in this paper.

Since the December 1999 storms, which caused extensive damage in Western Europe, the need for better forest management tools to calculate the risk of wind damage has been highlighted. Therefore, we constructed a computer model which simulates the mechanical stability of Maritime pine (Pinus pinaster Ait.) stands growing under the silvicultural conditions relevant to the Landes de Gascogne region, SW France. This study integrated (i) a tree growth model, PP3, as implemented in the software CAPSIS able to predict the development of Maritime pine stands over time under different silvicultural scenarios and (ii) a wind risk assessment model, geographical analysis of the losses and effects of storms (GALES), as implemented in the decision support system, ForestGALES. The GALES model predicts the critical mean wind speed required to break or overturn the mean tree in a stand. To adjust the species-dependent relationships for Maritime pine in the GALES model, we used data from winching tests. The effect of different spacings, thinning intensity, site fertility index and the effect of soil types on the critical wind speeds (CWS) were analysed for different silvicultural scenarios. The overturning CWS was usually lower than that for stem breakage, therefore overturning should occur more frequently than breakage in the Landes de Gascogne region. Simulations showed an increase in sensitivity to wind with height (age), whatever the silvicultural scenario. Two silvicultural scenarios with the same site index were simulated by contrasting the effect of initial density and intensity of thinning. Trees in the higher density stand showed a higher slenderness ratio and this stand was more resistant to wind up to an age of 45 years. Using the low-density silvicultural scenario, the effect of two different fertility indices was also tested. The highest site index resulted in a greater sensitivity to wind as tree top height was increased. To test different soil conditions, the empirical parameter determining anchorage resistance in GALES was changed and large differences in CWS were found. More studies are needed to improve the calibration of the aerodynamics model in GALES, taking into account the wide tree spacings and specific management practices used in the Landes de Gascogne region.