Philippe Dreyfus

Capsis: an open software framework and community for forest growth modelling

ContextForest 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.AimsOur objective was to encourage software reuse and simplify model implementation.MethodsThe 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.ResultsCapsis 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.ConclusionThe Capsis framework facilitates collaborative and shared software development. Moreover, it is a powerful way to support scientific animation in the frame of forest science.

Joint simulation of stand dynamics and landscape evolution using a tree-level model for mixed uneven-aged forests

Abstract• ContextA century and more after a major reforestation program, large areas in the French Southern Alps have moved to a landscape mosaic of old pine plantations and new, heterogeneous and uneven-aged, mixed stands. These conditions are challenging foresters in silvicultural practices and management choices.• AimsThe aims of this study are to understand, analyze, model, and simulate the ongoing phenomena, and to propose a decision-making tool.• MethodsAn individual-based forest dynamics model considering recruitment, growth, and mortality (as related to the spatial arrangement of stands and species, to site conditions and competition) and a simulation system including spatial sampling are designed and calibrated to allow simulation of both silviculture treatments at the stand level and management strategies at the forest or landscape level.• ResultsBy keeping track of the trees while simulating at the forest level, they offer an alternative to upscaling strategies and a suitable tool for prediction of stand and forest characteristics in situations influenced by strong driving forces such as colonization and forest maturation.• ConclusionThis approach is a straightforward means for adjusting forest management to trends such as expansion of shade-tolerant species; as spatial and temporal variation in site conditions are accounted for, it is also a promising way towards predicting their warming-induced upward shift.

Connecting an architectural plant model to a forest stand dynamics model—application to Austrian black pine stand visualization

Abstract• ContextForest stand dynamics models simulate the growth of trees in stands; based on field measurements and system knowledge, they provide a relatively precise representation of forest growth and are well adapted for forest management purposes. Architectural models describe the structure of plants according to ontogenetic development processes; as a support of biomass production and partitioning at organ scale, they simulate individual tree development.• AimsThe aim of this study was to link a stand dynamics model and an architectural model to simulate stand dynamics, in which the ecological or silvicultural modelling from the stand model and the architecture representation could be integrated, to provide individual tree details at the stand level.• MethodsStand-level simulations of Austrian black pine dynamics provided global results on tree growth from the empirical forest growth model PNN, and branching details for individual trees were provided by the functional–structural plant model (FSPM) GreenLab.• ResultsIndividual tree dynamics were computed, and the simulated trees were integrated at the stand level for visualizing two different management scenarios.• ConclusionBy combining a stand dynamics model adapted to forest management with an FSPM with detailed tree architecture, it is possible to simulate individual tree structure with consistent dimensions, adapted to ecological and silvicultural modelling for decision support in forest management.

Gestion des peuplements en forêt publique : nouvelles pistes de recherche, développement et innovation

NDLR : La première version de cet article est parue dans Innovations agronomiques, 56, 2016. Nous remercions la rédaction de Innovations Agronomiques de nous avoir autorisés à en publier une deuxième version dans la Revue forestière française. L’objet de cet article était de rendre compte de la démarche d’appropriation des travaux de recherche par les gestionnaires et notamment par le département Recherche, Développement et Innovation de l’ONF. Les auteurs de ce département tiennent à remercier les laboratoires associés à ces travaux et qui sont cités tout le long du texte : INRA, Irstea, FCBA, IRD, CIRAD...

Réponse au climat et à ses variations au cours du XXe siècle du Sapin pectiné, du Hêtre, des Pins noir, sylvestre et à crochets en contexte méditerranéen montagnard

Temporal instability of climate signal in tree-ring width of the five dominant species (Pinus nigra ssp. nigra, P. sylvestris, P. uncinata, Abies alba, Fagus sylvatica) growing under Mediterranean mountainous climate was studied over the last century (1910-2004). To disentangle the tree–climate–site complex, the effects of both soil water availability (dry, mesic and humid sites) and altitude (from 430 to 1690 m) were investigated on the response patterns. Responses to climate were analysed using bootstrapped correlation coefficients from 17 ring-width chronologies built from 293 trees sampled in 64 stands in South-Eastern France. Temporal analyses were performed considering fourthy-six 50-years intervals (from 1910-1959 to 1955-2004). May-June drought was the primary limiting factor. For Pinus sylvestris, summer precipitation played also a key role. Fagus sylvatica was the less responding species with no clear common pattern. Low soil water availability led to an increasing correlation with precipitation in May for Pinus nigra and Abies alba. Precipitation from May to August prevailed on the driest conditions for Pinus sylvestris. Correlation analyses suggested that warm autumn or winter enhanced growth, except for Fagus sylvatica. For Pinus nigra, the importance of April temperature increased with increasing altitude. Temporal analyses revealed a stability of sensitivity for the highest contexts (Pinus uncinata and Fagus sylvatica). At lower altitudes, the correlation with minimum temperature in April increased while temperature more often exceeded the threshold of 0°C over the last decades. For precipitation, a decrease in the strength of correlation was observed without close relationships with local xericity.

Quelles dimensions et quels indices d’hétérogénéité privilégier pour l’expérimentationdans les peuplements forestiers mélangés ou irréguliers ?

Although there is much debate about the relevance of mixed or uneven-aged forests to resilience (1) and to the productivity of ecosystems in a context of global climate change, there are still no recommendations as to the various dimensions of heterogeneity to be monitored and the associated indices to describe and quantify them. In this article, the authors present the main dimensions of heterogeneity that should be considered, on the scale of a stand, for the purposes of experimental study of relations between heterogeneity, dynamics and function of stands: species diversity, diversity of tree size and age, heterogeneity of their spatial distribution and finally, site-factor heterogeneity. They provide a brief overview of the indices conventionally used to characterize those dimensions. The indices are then examined with a view to conducting experiments in established stands where certain dimensions of heterogeneity are to be controlled, monitored or simply followed over time. (1) The capacity of an ecosystem […] to return to its original state by means of various processes of slow dynamics, after being totally or partially destroyed by a natural hazard or by a disruption. (Bastien et Gauberville, 2011, translation from French).