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Forest areas, somewhat neglected during the period of the "Trente Glorieuses", are experiencing renewed interest in favor with the ecological and energy transition, and social mobilization. Thus, they are at the heart the development of many conflicts and regarded as able to reconcile economic growth and ecological contribution, notably through mitigation plans to climate change. The maritime pine is a privileged specie in New Aquitaine. Benefiting from strong institutional support, a strong industrial fabric and several decades of research, the exploitation of this softwood tends to become a model at the expense of other silvicultural crops such as chestnut. The third French species after oak and beech, the chestnut is ubiquitous in the Dordogne and its fruits have long been the staple diet of the Périgourdins. But for several decades, observers seem to insist on the decline of this tree and predict an uncertain future. Deceiving, it is gradually replaced by the maritime pine. However, since the 1990s, some people have noted the emergence of a semblance of reorganization and modernization of the sectors. Through a dual temporal approach, this thesis analyses the past and present dynamics of the chestnut tree in Dordogne, details the strategies and actions carried out by the actors and the assets and pressures that impact the development of this resource, in order to evaluate prospects of this controversial object.; Les espaces forestiers, quelque peu délaissés pendant la période des « Trente Glorieuses », connaissent un regain d’intérêt à la faveur de la transition écologique et énergétique et des mobilisations sociales. Ceux-ci sont ainsi au coeur de nombreux conflits d’aménagements et ils sont considérés comme capables de concilier croissance économique et contribution écologique via notamment les stratégies d’atténuation au changement climatique. Le pin maritime constitue une essence privilégiée en Nouvelle-Aquitaine. Bénéficiant d’un fort soutien institutionnel, d’un puissant tissu industriel et de plusieurs décennies de travaux de recherche, l’exploitation de ce résineux tend à devenir un modèle aux dépends d’autres cultures sylvicoles comme le châtaignier. Troisième essence française après le chêne et le hêtre, le châtaignier est omniprésent en Dordogne et son fruit a constitué pendant longtemps l’alimentation de base des Périgourdins. Mais depuis plusieurs décennies, les observateurs semblent insister sur le déclin de cet arbre et lui prédisent un avenir incertain. Dépérissant, il est peu à peu remplacé par le pin maritime. Cependant, à partir des années 90, certains relèvent l’émergence d’un semblant de réorganisation et de modernisation des filières. À travers une double approche temporelle, ce mémoire analyse les dynamiques passées et présentes du châtaignier en Dordogne, détaille les stratégies et actions menées par les acteurs et les atouts et pressions qui impactent le développement de cette ressource, afin d’évaluer des perspectives pour cet objet controversé.

Our objective was to evaluate the relative contribution of physicochemical (diffusion) and biological (mineralization) processes to the supply of ionic P (iP) in solution and potential P availability to plants in a low P sorbing forest soil. To this end, we quantified the gross amount of diffusive iP (ionic P species that can be transferred from the solid phase to the soil solution due to a gradient of concentration, F DIFF ), P remineralization (gross mineralization of microbial P, F REM ), and gross mineralization of P in dead soil organic matter (F MDSOM ) using isotopic dilution techniques during a long-term (154 d) incubation experiment. Initial pools of P in dead soil organic matter and of microbial P represented high proportions (77 and 17%, respectively) of total P (31 μg g ―1 ). The F MDSOM value (1.0 μg g ―1 ) was lower than the F DIFF value (1.2 μg g ―1 ) during the 154-d period of incubation. The F MDSOM and F DIFF values were quantitatively very low compared with F REM (13.7 μg g ―1 ). The F REM value contributed largely to the total pool of isotopically exchangeable iP (89%), suggesting that microorganisms play a crucial role in P availability and cycling. Net organic P mineralization (F MDSOM + F REM - P immobilization by microorganisms) caused a large increase (340%) in readily available P (iP in solution). Extrapolated to longer time scales (1 yr or more), F MDSOM appeared to be higher than F DIFF since F DIFF rapidly reaches its theoretical maximum value. We conclude that, in our low P sorbing sandy forest soil, inorganic P sorbed to the solid phase represented a small but rapidly available pool, and P in dead soil organic matter a larger but slowly available pool. Our work showed that the relative contribution of physicochemical or biological processes to plant available P depends on the length of the observation period. Limits of the isotopic dilution approaches to quantify gross or net organic P mineralization are discussed.

The models about plant growth developped until date generally take into account the light availability, nutrients and water as the main factors affecting this metabolic function. Numerous studies since the 70s suggests that the wind can also have significant effects on growth. This phenomenon is called thigmomorphogenesis and is an acclimation mechanism of the plant to the wind it undergoes during its life. This study is a first approach for a better understanding of thigmomorphogenesis in maritime pine, in order to integrate the wind factor in growth modelling of this species, which has a special economic importance in Aquitaine. Initially, we wanted to test the hypothesis that individuals submitted to strong wind would respond with an increase in the radial growth of their trunks compared to the less exposed individuals. In parallel, we decided to explore the response in trunk flexion to wind stress. The results have failed to show a clear effect of wind on the radial growth of the maritime pine trunk, but the maintenance of the experience on the longer term is expected to bring satisfactory results. About the trunk flexion, we put in relation the deformations of the trunks with the wind speeds measured in parallel to better understand how the trunk flexion varies with the dimensions of the tree.; Les modèles de croissance des végétaux développés jusqu’à présent prennent généralement en compte la disponibilité en lumière, nutriments et eau comme les principaux facteurs ayant une incidence sur cette fonction métabolique. De nombreuses études menées depuis les années 70 tendent à montrer que le vent peut lui aussi avoir des effets non négligeables sur la croissance. Ce phénomène est appelé thigmomorphogenèse et constitue un mécanisme d’acclimatation de la plante au régime de vent qu’elle subit au cours de sa vie. Cette étude constitue une première approche pour mieux connaitre la thigmomorphogenèse chez le Pin maritime afin d’intégrer le facteur vent dans les modèles de croissance de cette essence, qui a une importance économique particulière en Aquitaine. Dans un premier temps, nous avons voulu tester l’hypothèse selon laquelle des individus fortement exposés au vent auraient une croissance radiale du tronc supérieure à celle d’individus moins exposés. En parallèle, nous avons voulu explorer la réponse en flexion du tronc à la contrainte de vent. Les résultats n’ont pas permis de mettre en évidence un effet clair du vent sur la croissance radiale du tronc de Pin maritime, mais le maintien de l’expérience sur plus long terme devrait permettre d’obtenir des résultats satisfaisants. En ce qui concerne la flexion du tronc, nous avons mis en relation les déformations des troncs avec les vitesses de vents mesurées en parallèle afin de mieux appréhender la manière dont la flexion du tronc varie avec les dimensions de l’arbre.

International audience; To assess the possibility of restoring the original plant community of grey dune from a pine plantation, a synchronic study of the seed banks of three habitats, the grey dune, the pine plantation, and a clearing, was conducted at Quiberon (France). Five stations were selected: a Grey dune, Pine plantation 1, Pine plantation 2, Clearing 1, and Clearing 2. In contrast to the pine plantations, clearing 1, subject to heavy human disturbance, had a great similarity between its seed banks and its established vegetation. The larger clearing (C2) tend to resemble the grey dune, whereas the other was dominated by ruderal species. The analysis of the seed banks demonstrated differences between the clearings and the pine plantations from which they were derived. The potential vegetation of the clearings was closer to that of the grey dune and had a larger number of species with a short life cycle than the pine plantations. The seed banks of the pine plantations were not similar to that of the grey dune, but also differed from that of closed vegetation. This study suggested that it may not be possible to obtain a short term restoration of a grey dune after just clear felling only with the help of seed banks. On the other hand, seed dissemination could facilitate a restoration in a larger time scale as for clearings.

International audience; During germination and post-germinative growth of Pinus pinaster Ait. seeds, triglycerides are hydrolysed and concurrently the embryo accumulates starch. In this study, the spatio-temporal variation of starch accumulation was described in zygotic embryos associated (ZE+) or not (ZE−) to their megagametophyte and in somatic embryos (SE). In germinating ZE+, starch was accumulated in the growing tissues, following closely the spatio-temporal pattern of triglycerides depletion. In contrast, in ZE− and SE, starch was only found in cortical cells close to the culture medium. In germinating ZE+, the spatio-temporal variations of starch accumulation can be thus interpreted as the result of the changing contact between the megagametophyte and the growing tissues and also of the existing interactions between triglyceride hydrolysis and the allocation of sucrose exported from the megagametophyte.

The color change of wood after exposure to UV light may produce aesthetical damages. The stability of the color to light exposure is an important issue. This study describes experiments of testing the color stability of heat-treated wood samples. Heat treatment was done at 240°C during 2 hours, under nitrogen. Heat-treated samples of ash, beech, maritime pine and poplar heartwood were exposed to UV-light (QUV equipped with fluorescent lamps UVA-340) during 835 hours. Color measurements during accelerated weathering were made at intervals throughout the test period. The results are presented in ΔE and L* a* b* coordinates according to the CIELab system. The experiments show that the color stability for heat-treated wood is better during the 835 hours of exposure when compared to untreated wood. The properties of heat treated wood (lignin modifications, and monomers of phenolic compounds) are probably involved in the retified wood resistance against UV light under experimental conditions.

Considering the key role of Monochamus galloprovincialis (Olivier) (Coleoptera: Cerambycidae) in the dispersion of the pine wood nematode, Bursaphelenchus xylophilus (Steiner & Bührer) Nickle (Nematoda: Aphelenchoidea), in Europe, defining the host spectrum and preference of M. galloprovincialis is of primary importance for forest management. Therefore, comparative studies under laboratory conditions were performed in order to define the feeding and oviposition preferences of M. galloprovincialis adults as well as the larval development on Pinus sylvestris and Pinus pinaster. Both nutrition and oviposition were significantly higher on P. sylvestris. However, no difference was found when comparing larval survival on the two Pinus species even though larvae attended the fourth instar earlier when reared on P. sylvestris than on P. pinaster. The results of this study reinforce the suspicions of a future rapid propagation of the nematode, by M. galloprovincialis, into the Pine forests all over Europe., Θεωρώντας τον ρόλο του Monochamus galloprovincialis κλειδί στην εξάπλωση του νηματώδη του πεύκου στην Ευρώπη, η διαλεύκανση του εύρους των ξενιστών και των προτιμήσεων του Μ. galloprovincialis σε αυτούς είναι πρωτεύουσας σημασίας για την προστασία του δάσους.Συγκριτικές μελέτες σε συνθήκες εργαστηρίου διεξήχθησαν με σκοπό την διευκρίνηση των διατροφικών και ωοθετικών προτιμήσεων των ενηλίκων αυτού του εντόμου καθώς και της ανάπτυξης των προνυμφών του στα P. sylvestris και P. pinaster. Η διατροφή και η ωοτοκία βρέθηκαν στατιστικά πιο σημαντικές στο P. sylvestris αλλά καμία διαφορά δεν βρέθηκε στην επιβίωση των προνυμφών στα δύο είδη πεύκου. Οι προνύμφες έφτασαν στην 4η ηλικία νωρίτερα στο P. sylvestris από ότι στο P. pinaster. Τα αποτελέσματα της παρούσης μελέτης ισχυροποιούν τις υποψίες για μια γρήγορη μελλοντική εξάπλωση του νηματώδη σε ολόκληρη την Ευρώπη.

article présenté lors du colloque ‘Innovations Sylvicoles’ qui s’est tenu à Pierroton le 3 décembre 2014; National audience; Plant material for reforestation or afforestation is of first importance to ensure adaptation of stands to local environmental conditions and to reach goals of wood productivity and quality. Generally the first step focuses on an exploration of between species diversity; then a breeding programme is set up to produce improved genetic material. Maritime pine was chosen for afforestation in the Landes forest (south west of France) during the XIXth century. Later on, a breeding programme was established during the 60’ies based on the local provenance. Development of improved material made it possible to increase stand productivity and quality. Genetic gains of current varieties reach more than 30% for growth and stem straightness. Exploration of diversity between and within species becomes again a key issue in the new context of Landes forest where sustainable intensification is required. Maritime pine will stay the main species in the Landes forest. Nevertheless, strategies are under development to implement new genetic diversity in the breeding programme for adapting futures varieties to environmental and economic changes.; Le choix du matériel végétal pour le reboisement ou l’afforestation est essentiel pour assurer une bonne adaptation du peuplement aux conditions pédo-climatiques locales et atteindre un niveau de production et une qualité correspondants aux objectifs fixés. La première étape consiste généralement à explorer la diversité interspécifique avant de mettre en place un programme de sélection génétique dont l’objectif est de fournir régulièrement du matériel amélioré. Dans les landes de Gascogne, le choix s’est porté, au cours du XIXème siècle, sur le pin maritime puis un programme d’amélioration a été initié dans les années soixante à partir de la provenance locale. L’utilisation de matériel amélioré a permis d’augmenter sensiblement la productivité et la qualité des peuplements. Aujourd’hui, les variétés permettent un gain génétique supérieur à 30% pour la croissance et la rectitude du tronc. Le contexte nouveau de la forêt landaise, où une intensification durable de la production est demandée, a relancé les travaux d’exploration de la variabilité inter- et intra- spécifique. Le pin maritime restera l’espèce de choix dans le massif landais. Toutefois, des stratégies pour infuser de la variabilité intraspécifique dans le programme d’amélioration sont en cours de développement afin que les futures variétés soient adaptées aux évolutions économiques et environnementales.

Summary Polyacrylamide isoelectric focusing with specific staining for laccase activity was used to characterize laccase from European Armillaria species (Armillaria ostoyae, Armillaria mellea, Armillaria gallica, Armillaria cepistipes). The enzyme was extracted from culture media either supplemented, or not, with pine sawdust, and also from Pinus pinaster naturally infected by A. ostoyae, or artificially inoculated with A. mellea and A. ostoyae. Some differences in banding patterns were found for Armillana isolates according to the species and the culture media, but a common band at pI = 3.4 was found in all the extracts tested, independently of their origin (culture filtrate or wood).

Infestation rate of Dioryctria sylvestrella was studied for the following three categories of maritime pine: (i) those trees that had been selected for pruning and pruned; (ii) those trees that had been selected for pruning but not pruned; and those trees that had neither been selected nor pruned. In comparing 10 diameter classes and 4 dates of pruning, the percentage of trees attacked was recorded. In both pruned and unpruned trees, the level of attack increased with tree diameter, according to a logistic curve. Pruned trees were significantly more infested than unpruned trees. Selection for pruning did not result in a significant higher rate of attack in unpruned trees. The percentage of pruned trees attacked did not differ significantly according to the date of pruning. The interaction between tree diameter and tree type did not induce any significant difference in infestation rate. The model of tree infestation, involving primary attraction for the female moth, was strengthened. Volatile attractants, originating in the constitutive oleoresin, might allow the selection of susceptible trees. Tree pruning, creating bark wounds, and tree vigour, increasing bark cracking, could similarly, though independently, increase constitutive resin flow, thus enhancing tree attractiveness.

320 ref. *INRA Orléans, Documentation, Ardon 45166 Olivet Diffusion du document : INRA Orléans, Documentation, Ardon 45166 Olivet Diplôme : Diplôme d'Ingénieur Agronome; The present work is intended as a step toward a description of the maritime pine genome (Pinus pinaster Ait.). It initiates a study of quantitative traits variation using this description,The growth performances of the trees composing the breeding population of maritime pine are known thanks to general combining abilities measured in progeny tests. Eighteen trees representing the range of performances were sampled in this population. The variability of the proteins contained in the haploid endosperms (or megagametophytes) of these pines was studied by two-dimensional electrophoresis, An average of 12 endosperms per tree were analysed and compared.After a systematic analysis of the variation observed, 84 loci were described, responsible for position or amount modifications or presence/absence of proteins, Human genetics techniques were used to build a map. Seventeen linkage groups were detected, which included 65 loci and covered 530 centimorgans, The methods used to estimate and to test for linkage between loci are discussed. The linkage data allowed us to estimate the genome length of maritime pine, It was found to be around 2000 centimorgans, Pines contain one of the greatest quantity of DNA per cell. Some considerations about the relationship between physical and genetic maps in angiosperms and gymnosperms are thus proposed.The relationship between the weight of megagametophytes and the alleles expressed in these haploid organs was studied for every locus. The effect of three loci was detected. The diploid genotype of 18 pines for the 84 loci was compared to their growth performances thanks to different statistical techniques, The results suggest that protein amount variation could be related to quantitative traits, the usefulness and limits of quantitative trait loci (QTL), particularly for forest tree breeding, are discussed.; Ce travail suggère une description du génome du Pin maritime (Pinus pinasier Ait.) et envisage l'utilisation de cette description pour l'étude de la variabilité de caractères quantitatifs.Les performances de croissance des arbres constituant la population de base du programme d'amélioration du pin maritime sont connues grâce à leurs aptitudes générales à la combinaison, évaluées en tests de descendances. Cette étude concerne 18 arbres de cette population, choisis pour couvrir la gamme de variation des performances. La variabilité des protéines contenues dans les endospermes haploïdes (ou mégagamétophytes) de ces pins a été étudiée grâce à l'électrophorèse bidimensionnelle. Une douzaine d'endospermes par arbre ont été analysés et comparés.À la suite d'une analyse systématique des variations observées, 84 locus sont décrits, impliqués dans des variations de position, de quantité ou de présence/absence des protéines. Des techniques de génétique humaine ont permis de construire une carte qui localise 65 locus sur 17 groupes de liaison et couvre 530 centimorgans au total. Les méthodes d'estimation et de test de la liaison entre deux locus sont discutées. À partir des données de liaison obtenues, la taille du génome du Pin maritime a pu être estimée à environ 2000 centimorgans. Sachant que les pins possèdent de grandes quantités d'ADN, une réflexion sur les différentes descriptions du génome, en terme de cartographie et de quantité d'ADN, est proposée.La relation entre le poids des mégagamétophytes et les allèles exprimés dans ces organes haploïdes a été étudiée pour chaque locus. L'effet de certains locus a pu être mis en évidence. Le génotype diploïde des pins aux 84 locus a été confronté à leurs performances de croissance grâce à différentes techniques statistiques. Les résultats suggèrent que la variabilité des quantités de protéines pourrait être liée à la variation de caractères quantitatifs. Une réflexion sur l'étude des bases génétiques des caractères quantitatifs, sur l'intérêt et sur les limites de la recherche et de l'utilisation de locus à effets quantitatifs (QTL), notamment dans le cadre particulier de l'amélioration des arbres forestiers, est suggérée.

International audience

Diplôme : Dr. d'Université

International audience; 1/ The disruption of host-finding cues has been proposed as a key mechanism underlying the lower damage caused by phytophagous insects in mixed forests. We tested this hypothesis by investigating the distribution of pine processionary moth Thaumetopoea pityocampa (Denis & Schiffer-Müller) (Lepidoptera) infestation at the edges of pure stands of Pinus pinaster (AÏton) at some distance from nonhost trees (Experiment 1) or bordered in part by a broadleaved hedgerow (Experiment 2). 2/An ‘edge effect' was demonstrated, with trees at the edge of the stand being more heavily infested than those at the interior of the stand. 3/ The presence of a nonhost broadleaved hedgerow in front of the edge of the pine stand resulted in lower T. pityocampa infestation. There were significantly fewer T. pityocampa nests behind the hedgerow than on the exposed part of the edge. The presence of the hedgerow did not dilute or repel T. pityocampa infestation further into the pine stand, although it decreased the infestation of T. pityocampa throughout the pine stand. The decrease in T. pityocampa infestation behind the hedgerow was greater when the broadleaved hedgerow was taller than the pine trees. 4/These results highlight the benefits of using nonhost tree species on the edge of monospecific forest stands to reduce insect damage. This approach could be promoted as an innovative forest pest management method.

Situées dans le Sud-Ouest de la France, les Landes de Gascogne s’étendent sur environ 1,5 million d’hectares. L’activité forestière y est spatialement dominante, et l’agriculture présente sous forme d’ilots, le plus souvent irrigués. Déjà mis à l’épreuve sur la période récente par deux tempêtes majeures (Martin en 1999 et Klaus en 2009), le massif forestier de pin maritime est également confronté à des attaques sanitaires récurrentes et à la menace permanente des incendies. Parallèlement, depuis une vingtaine d’années, cet espace à dominante rurale, localisé à proximité de zones métropolitaines au Nord et au Sud, et bordé à l’Ouest par une façade littorale attractive, connait une forte croissance démographique et une diversification de ses activités économiques. Au regard des enjeux présents, les incertitudes concernant le devenir des Landes de Gascogne sont grandes. Elles le sont d’autant plus lorsqu’on envisage les enjeux de long terme : conséquences du changement climatique, dynamiques d’urbanisation, effet de la demande énergétique sur les industries du bois et la sylviculture… Les évolutions en cours et à venir questionnent le devenir de la filière forêt-bois, son insertion dans les dynamiques territoriales et, plus largement, le devenir de ce territoire dans l’espace régional mais aussi national, européen, et mondial. La prospective Massif des Landes de Gascogne lancée conjointement par le Conseil Régional d’Aquitaine et l’INRA a élaboré des scénarios d’évolution du Massif des Landes de Gascogne à l’horizon 2050 où les futurs possibles de la forêt et de la filière prennent place dans des devenirs territoriaux contrastés.

Single Nucleotide Polymorphisms (SNPs) are the most abundant form of genetic variation in the genome. In this poster, we reviewed what has been achieved in terms of highly-multiplexed SNP genotyping assay construction in maritime pine (Pinus pinaster Ait.), the main conifer used for commercial plantation in southwestern Europe. Seven custom SNP-assays (384 and 1536-plex), oriented towards broad applications, have been designed. We illustrated here the usefulness of this genotyping technology to address specific questions related to i/ genetic diversity and population structure analysis, ii/ linkage and QTL mapping and iii/ association mapping. With respect to genetic diversity and differentiation, a custom VeraCode assay for 384 SNPs mostly based on a larger array designed for linkage mapping (see below) allowed to obtain less blurred, albeit similar, breeding zone boundaries than a set of 12 nuSSRs screened on the same individuals. Levels of diversity were also more accurately estimated, showing clear differences among gene pools. Interestingly, a relatively small subset of SNPs would be enough to develop an application tool for origin certification, which could have a notable impact on current operational practices. In terms of linkage mapping, a custom GoldenGate assay for 1,536 SNPs detected through the resequencing of gene fragments (in vitro SNPs) and from Sanger-derived Expressed Sequenced Tags (in silico SNPs) was established. Offspring from two mapping pedigrees were genotyped. A consensus map comprising 357 SNPs from 292 different loci was constructed and the analysis of sequence homology between mapped markers and their orthologs in a Pinus taeda linkage map, made it possible to align the 12 linkage groups of both species. Moreover, QTL detection for different traits is underway. In terms of association mapping, a custom GoldenGate assay with 384 SNPs was built and used to genotype 160 unrelated plus-trees from a half-sib experimental design for which breeding values (for height growth, circumference, stem straightness at 8 years, lignin content and extractives at 31 years) were available. Taking into account multiple testing, one single SNP in a gene encoding a putative fasciclin-like arabinogalactan protein was found to be associated with growth traits. We conclude that the VeraCode/GoldenGate assays can be used successfully for high-throughput SNP genotyping in maritime pine, a conifer species that has a genome seven times the size of the human genome. This first generation of SNP-arrays has been recently upgraded to an Infinium-array (containing 10.5k SNPs) thanks to deep sequencing based on new generation sequencing technologies. The Infinium-array also includes SNPs from comparative orthologous sequences with other major conifer species, providing a wider collection of anchor points for comparative genomics among these major groups of forest trees.

International audience

Diplôme : Dr. d'Université

As forest edges are a major source of heterogeneity in fragmented landscapes, the atmospheric flow over forested areas is often under their influence. Understanding how far the upstream edge has an impact on the turbulent wind flow in a forest canopy is important, in particular for scalar flux measurement. In this study, edge and stand flows over a maritime pine forest characterized by a dense crown layer located above a deep and sparse trunk space are analysed in detail from in situ measurements and large-eddy simulations (LES). The LES model used here appears to simulate remarkably well most characteristics of the turbulent wind flow for this particular canopy structure. It is shown that the main characteristics of the edge flow in this case differ from those usually observed in forests with a more uniform vertical foliage distribution. The main differences are (i) the development of turbulence above the canopy occurring closer to the edge, (ii) the absence of a well-defined enhanced gust zone around the top of the canopy, (iii) the presence of a large secondary wind maximum within the trunk space, and (iv) the development of a positive momentum flux layer below the crown layer. Most of these differences are related to the presence of a substantial sub-canopy wind jet induced by the wind flow through the trunk space at the edge. The secondary velocity maximum induced by this wind jet differs from that observed in homogeneous stand conditions, where it seems to be related to the mesoscale pressure gradient. The wind jet appears to decrease very slowly with distance from the edge, so that edge effects are still significant at 9 h from the edge (where h is the mean canopy height). The length of the adjustment region is shown to be greater than 10–15 h , and to depend on the depth of the trunk space. In very fragmented forested areas with deep and sparse trunk space, within-canopy flow may always be under the influence of edges.

International audience

International audience; The longevity of a generalist (Ooencyrtus pityocampae) and a specialist (Baryscapus servadeii) egg parasitoid of the pine processionary moth (Thau-metopoea pityocampa) was compared under laboratory feeding conditions including water and honeydew from aphid species growing on maritime pine (Pinus pinaster) or pedunculate oak (Quercus robur). The longevity of both parasitoid species increased when specimens were fed with honeydew. This increase was larger for the generalist (3.7, 32.0 and 38.0 days) than for the specialist (3.0, 23.3 and 21.5 days) parasitoid species when fed with water, oak and pine aphid honeydew respectively. The phenology of the specialist species B. servadeii is well-adapted with its host availability with or without food supply. The generalist species O. pityocampae could overlap its host emergence curve during 14.0–20.0 days when fed with oak and pine aphid honeydew respectively, vs. no overlap when no supplementary food was provided. Analysis of honeydew composition indicated that sugars and amino acids may have distinct effects on parasitoid longevity.

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International audience

International audience; In order to further our understanding of surface fluxes at the regional scale, it is necessary to use satellite and numerical model data. However such data must be validated by ground measurements. For this eddy correlation measurement systems are traditionally used. These measurements are rather limited in their footprint (surface of influence) compared with typical pixel surfaces and model grid sizes (several kms). One promising method, at least for sensible and latent heat surface fluxes measurements, is the use of scintillometry. In recent years this method has been shown to be robust for the estimation of sensible heat flues using optical (0.93µm) Large Aperture Scintillometers (Lagouarde et al 2002, DeBruin 2002) over scales ranging from several hundreds of meters to several kilometers (compatible with the aforementioned satellite and numerical data). On the other hand, the use of scintillometry for the estimation of latent heat fluxes (prototype microwave scintillometers ,27 GHz) is rather more difficult and results related to measurements over vegetation in the literature remain limited (Green 2001, Meijninger 2002). In order to evaluate the scintillometer method for latent heat fluxes we setup a dual scintillometer experiment, one optical (Univ. of Wageningen) and the other microwave (prototype Univ. of Eindhoven), over a young homogenous maritime pine forest (height 2-3m), installing the instruments at 8.5m with a trajectory of 550m in the southwest of France. The homogeneous short trajectory was chosen, as it is both compatible with reference eddy correlation measurements on site (Gill R3, Licor 7500) and microwave propagation constraints. Results from the 2009 measurement campaign, several months, will be presented, where preliminary results confirm the robustness of the method for sensible heat fluxes. As for the estimation of latent heat fluxes, the flux estimation would appear to be more complicated. Both sensible and latent heat fluxes will be presented with a particular attention to the latent heat fluxes and the role of the temperature-humidity correlation in the estimation by scintillometry.

International audience; Forest edges are a major source of heterogeneity in fragmented landscapes. Consequently, the atmospheric flow over forested areas is often under their influence. Understanding how far a forest edge may influence turbulent wind flow within the canopy is important, in particular for scalar flux measurement. In this study, the edge flow over a maritime pine forest characterized by a high and dense crown layer associated with a large and sparse trunk space is analyzed in detail from in situ measurements and large-eddy simulation (LES). The LES model appears to simulate remarkably well most characteristics of the turbulent wind flow in this particular case of canopy foliage distribution. It is shown that the main characteristics of the edge flow differ from those usually observed in forests with a more uniform vertical foliage distribution. The main differences are (i) the presence of a large secondary wind maximum within the trunk space, (ii) the development of the turbulent region above the canopy occurring closest to the edge, (iii) the absence of a well-defined enhanced gust zone and (iv) the development of a positive momentum flux layer below the crown layer. Most of these differences are related to the presence of a strong sub-canopy wind jet induced by the wind flow through the trunk space at the edge. This wind jet decreases very slowly with distance from the edge, so that edge effects are still significant at 9 h from the edge (where h is the mean canopy height). This implies that the length of the adjustment region is probably more than 10-15 h, and therefore that in very fragmented forested areas with large and sparse trunk space, within-canopy flow may always be under the influence of edges.

Diplôme : Dr. d'Université; The forest cultivation techniques of maritime pine in the South Western France deeply changed in the 1970’s. In particular the reforestation method shifted from assisted natural regeneration to intensive techniques including soil ploughing, phosphoric fertilization and seeding, then plantation with improved material in the 1980’s. As the proportion of “intensively cultivated” stands in final cut will increase drastically in the next decades, it is now necessary to anticipate the impact of these reforestation methods on the wood properties for the wood industry, from the analysis of the oldest.Trees were sampled from 14 stands in the South Western France covering a wide range of mean volume. On each stand, 4 trees were selected for physical properties measurement. Within ring wood density, latewood content, heartwood diameter and spiral grain angle were measured on wood disks collected at different heights within each tree. At the same time 8 trees were harvested and bucked into 2.2 m long logs. After drying, visual aspect and mechanical properties of the sawn boards were assessed.Based on the data, deterministic models were developed to predict the variables based on selected stand and tree characteristics. The models for heartwood content in cross section explain quite well the variation with height (more than 70% of the variation). The heights of green and dead branches were identified as important variables in the models for nature of knot in trees. The developed models, for spiral grain angle, radial variations of wood density and mechanical properties, have a relatively low level of prediction, but it has highlighted the effect of cambial age and ring width on these properties. The growth rate has so a negative impact on the mechanical properties of wood of maritime pine. Based on the mixed model analysis with repeated measurements structure, the trees and stand effect on the residual variation were estimated. Applied on silvicultural scenarios, these models have been used in a simplified approach to estimate the strength of timber that can potentially be obtained from the resource. The transfer of these models with forest managers could allow a better estimate of the quality of wood, and thus a better allocation in a post-storm context where the resource is scarce.; Les techniques de culture du pin maritime dans les Landes de Gascogne ont connu des changements importants à partir des années 1960. A côté de peuplements de sylviculture traditionnelle basée sur la régénération naturelle assistée, se sont succédés de nouveaux types de peuplements sous le vocable de « ligniculture ». La proportion de ces peuplements menés intensivement, dans la récolte des coupes rases en Aquitaine, va augmenter rapidement dans les dix prochaines années. Les données technologiques faisant actuellement défaut sur cette ressource, il est nécessaire d’anticiper dès aujourd’hui l’impact de ces pratiques sylvicoles sur les propriétés du bois.Des arbres ont été échantillonnés dans 14 parcelles réparties dans les Landes de Gascogne. Sur chaque parcelle, 4 arbres ont été sélectionnés pour les mesures des propriétés physiques. Les variations radiales de densité intra-cerne, de proportion de bois final, de duramen et d’angle du fil ont été mesurées. Parallèlement 8 arbres ont été exploités. Après sciage puis séchage, l’aspect visuel et les propriétés mécaniques des avivés obtenus ont été mesurés. Sur la base des données recueillies et de données d’études précédentes, des modèles déterministes ont été développés pour prédire les variations des caractéristiques étudiées. Ces modèles de la famille des modèles mixtes, sont constitués d’une partie « fixe » commune à l’ensemble des arbres et d’une partie aléatoire qui quantifie les écarts propres à la parcelle et aux arbres (appelés effet « parcelle » et effet « arbre »). Un modèle décrivant les variations avec la hauteur dans l’arbre du taux de duramen, basé sur l’âge des arbres a été développé, il explique plus de 70% de la variation. Les modèles décrivant les variations radiales de l’angle du fil, de la densité, et des propriétés mécaniques du bois ont un niveau de prédiction plus faible, mais un effet significatif de l'âge cambial et de la largeur de cerne sur ses propriétés a été mis en évidence. La vitesse de croissance a un impact négatif sur les propriétés mécaniques du bois de pin maritime.Appliqué à des scénarios sylvicoles ces modèles ont permis d'estimer le classement mécanique des sciages pouvant potentiellement être obtenus à partir de la ressource.Le transfert de ces modèles auprès des gestionnaires forestier pourrait permettre une meilleure estimation de la qualité des bois et donc leur meilleure allocation dans un contexte post tempête où la ressource en pin maritime en Aquitaine se fait rare.

Mixed forests are less prone to insect damage than pure forests because ofreduced host accessibility and/or improved control by natural enemies. To test thesehypotheses, we have studied the ecology of the pine processionary moth (PPM)(Thaumetopoea pityocampa) and its parasitoid, in a monoculture of maritime pine(Pinus pinaster) plantations, the Landes de Gascogne forest. There, open areas(firebreaks, clear cuts) and patches of broadleaved woodlands (hedgerows, riparianforest, natural forest remnants) still persist locally. In this study we have shown that:(1) Pine stand colonization by PPM was limited by the presence ofbroadleaved hedgerows at stand edge. Broadleaved trees formed physical barriersdisrupting the visual detection of pine trees by PPM females when searching for anoviposition site.(2) The longevity of the two main PPM egg parasitoids increased whenspecimen were fed with honeydew produced by oak aphids. The generalist species,which emerges two months before PPM, could benefit from this longer lifespan tooverlap its host emergence.(3) PPM pupae survived better in the soil of open areas than under forestcovers (pine or broadleaved trees), because of higher temperature and humidity. Theassociation between pine stands and open areas benefits PPM through habitatcomplementation, whereas the presence of broadleaved trees may act as anecological trap for PPM caterpillars.(4) Maritime pine stands within heterogeneous landscapes exhibited lowerPPM infestations than similar stands within pine monocultures. PPM infestation levelsdecreased with increasing percent broadleaved area in the surrounding landscape.These results are discussed according to the ecological mechanisms whichmay explain the relationship between insect herbivory and tree species diversity.Perspectives for improved PPM management in the Landes de Gascogne forest, andfor further scientific research are proposed., Les peuplements forestiers mélangés subissent moins de dégâts d’insectes herbivores que les peuplements purs, du fait d’une diminution de l’accessibilité à la ressource ou/et d’une amélioration des conditions de survie de leurs ennemis naturels. Pour vérifier ces hypothèses, nous avons étudié un insecte ravageur, la processionnaire du pin (Thaumetopoea pityocampa), et ses insectes parasitoïdes dans le contexte de monoculture de pin maritime (Pinus pinaster) de la forêt des Landes de Gascogne, où persistent localement des zones de milieu ouvert (parefeux, coupes rases) et des boisements d’essences feuillues (haies en bordure de peuplement de pin, ripisylves, îlots). Nous avons pu démontrer que :(1) La colonisation des parcelles de pin par la processionnaire est limitée parla présence de haies de feuillus en lisière de parcelle. En effet, les feuillus jouent un rôle de barrière physique, entravant la détection visuelle des pins par la femelle de processionnaire lorsqu’elle recherche un site d’oviposition.(2) La longévité des principaux parasitoïdes, spécialiste et généraliste, des œufs de processionnaire est favorisée par la consommation de miel lat produit par des pucerons du chêne. Cela permet notamment à l’espèce généraliste, qui émerge deux mois avant la processionnaire, de prolonger sa présence dans le milieu et donc d’augmenter sa probabilité de parasiter des pontes de processionnaire.(3) Les chrysalides de processionnaire du pin survivent mieux dans le sol des milieux ouverts que sous couvert forestier (de pin ou de feuillus), du fait d’une température et d’une humidité plus élevées. L’association de pins et de milieux ouverts favorise la processionnaire par complémentation des habitats, tandis que la présence de feuillus peut représenter un piège écologique pour les chenilles au moment de l’enfouissement.(4) À l’échelle du paysage, les peuplements de pin maritime au centre de paysages hétérogènes sont moins infestés que dans les paysages de monoculture.De plus, les niveaux d’infestation de la processionnaire diminuent lorsque la proportion de feuillus dans le paysage environnant augmente.Ces résultats sont interprétés en fonction des mécanismes écologiques expliquant la relation entre diversité et herbivorie. Des possibilités de transfert vers la gestion forestière de la forêt des Landes de Gascogne sont proposées, ainsi que des perspectives en termes de recherche scientifique.

In the south-west of France the protected butterfly Euphydryas aurinia occurs mainly in two habitat types: humid herbaceous vegetations and dry grasslands, where it is supposed to use Succisa pratensis and Scabiosa columbaria respectively as larval host-plants. Our observations from 2005 to 2009 in the western part of the Gironde department showed the frequent use of another host-plant: Lonicera periclymenum. This part of the Gironde is covered by evenaged maritime pine stands. Larval nests were mainly observed in Molinia caerulea dominated clearcuttings and firebreaks, and at pine stand edges., Dans le Sud-Ouest de la France, Euphydryas aurinia, un papillon de jour protégé, colonise principalement deux types d’habitats : des milieux herbacés humides et des pelouses sèches. Les plantes-hôtes généralement admises pour les chenilles sont respectivement Succisa pratensis pour le premier type d’habitat et Scabiosa columbaria pour le second. Nos observations, réalisées entre 2005 et 2009 dans la partie ouest du département de la Gironde, ont montré l’utilisation fréquente d’une autre plante-hôte : Lonicera periclymenum. Cette partie de la Gironde est principalement occupée par des plantations de pins maritimes et les nids de chenilles ont été observés dans des coupes rases et des pare-feux dominés par la Molinie et en bordure des peuplements de pins.

Après décembre 1999, le massif de pin maritime des Landes de Gascogne a de nouveau été sévèrement frappé par la tempête Klaus du 24 janvier 2009. Les acteurs forêt-bois s’interrogent sur les disponibilités en bois du massif à moyen terme. Une telle analyse prospective requiert des informations sur l’état de la ressource au lendemain de la tempête. Les données collectées par l’IFN sur le massif landais depuis 2005, et l’inventaire IFN des dégâts de tempête, ont permis d’actualiser la ressource à une date postérieure à la tempête, et donc de quantifier le capital en production après celle-ci. Ce travail de modélisation conjointe IFN / INRA a aussi permis de faire progresser les outils de simulation de la ressource. Les résultats obtenus dans la présente étude permettent désormais d’envisager une étude de la ressource forestière et des disponibilités en bois après la tempête.

Chapitre 12; International audience

International audience; To test for different stem reorientation strategies in leaning seedlings of maritime pine (Paws master Art) and loblolly pine (Anus taeda L), we inclined dormant plants at 0 degrees,45 degrees and 9 degrees for 35 days in optimal growth conditions Stem angle to the vertical was measured at regular intervals After 22 and 35 days, bending tests were earned out to determine stem elasticity and stiffness The quantity of compression wood (CW) formed was also measured Results showed that after 24 h, the apices of leaning maritime pine stems had completely reoriented to the vertical, whereas no such primary tropic response was observed in loblolly pine After 22 days, the significantly stiffer loblolly pines had begun straightening up from the stem base, but not maritime pine After 35 days, the overall secondary reorientation process was more efficient in loblolly pine, with significantly more CW produced In both species, CW had formed immediately on tilting stems, i e no early wood cells had formed As maritime pine originates from a dry to semi-arid region, having less CW will mean that water uptake will be greater for the same xylem area compared to loblolly pine which possesses more CW In establishing maritime pine seedlings, rapid apical orientation with regard to light and gravity will compensate for a slower straightening up mechanism in the more lignified parts of the stem Therefore, juvenile needle exposure to patches of light will be maximised at all times

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International audience

European gorse (Ulex europaeusL.) is a spiny shrub that grows spontaneously in the understorey of forests and heathlands in western Europe. Gorse is a pioneer species and forms large seed banks that can persist for a long time while buried deeply in the soil. Although many studies have been conducted on gorse seed banks in invasive contexts and in scrubland ecosystems, few data are available on forests in a native context. The aim of the present study was thus to report on the variability of seed-bank density in ‘critical’ stages in the forest management of pine stands (five stands) in south-western France. We examined variations in the number of gorse seeds as a function of soil depth but also of the presence and abundance of adult gorse in the understorey. Seed-bank density did not show a clear decrease in seed number with pine stand age, principally because gorse also appears to be able to establish itself in mature pine stands, probably thanks to local disturbances. In the pine stands in our study, the presence and abundance of seeds in the soil appeared to depend mostly on the presence of adult gorse as seeders in the understorey. Finally, we observed that, contrary to what has generally been found in scrubland ecosystems, most gorse seeds were located in the 5–10 cm soil layer rather than in the 0–5 cm soil layer. This depletion of the first 5 cm may be linked to seed germination that was not compensated for by the production of new seeds.

International audience

National audience

National audience

International audience

International audience; The fate of carbon in the soil plant system was followed by using pulse-labelling of 10 m tall trees in the field with 13 CO2 for a short period of time. The study is conducted on three tree species (beech, oak and pine) that are among the major species in European forests. Trees are labelled at three distinct phenological phases during the growing season. The assimilated 13 C by plants during the pulse labelling was then tracked in soil CO2 efflux with a high temporal resolution using tuneable diode laser absorption spectrometry and in the microbial compartment from soil cores (root + mycorrhiza transfer) and in mesh cores that permit the ingrowth of mycorrhiza hyphae but exclude roots (no-root cores).

International audience; Lignification is an essential process in trees, playing a key role in sap conducting, mechanical support or biotic and abiotic stress resistance. Although structural genes coding for enzymes of the lignin biosynthetic pathway are well known, we are only beginning to understand the mechanisms that regulate this process. This study aimed at assessing the nucleotide diversity of 9 transcription factors which are thought to play key regulatory roles in conifer lignification, namely MYB1, 2, 4, 5, 8 and 14, HDZip31, LIM2 and SCL1. Individuals were sampled in Pinus pinaster natural populations from the French Atlantic coast. The “cisregulatory evolution” theory states that transcription factors possess little variation due to the large number of downstream target genes that would be affected, and are submitted to strong purifying selection. In line with this theory, nucleotide diversity observed in the 9 TFs was twice lower than for other structural genes from the lignin pathway. We then modelled a large range of bottleneck scenari and tested whether patterns of diversity at each gene departed from expectations. We will present the contrasting results across the different genes and discuss the consistency of the best fitting models with maritime pine species demographic history.

National audience; The oxygen isotope composition (d18O) of atmospheric CO2 is among a limited number of tools available to constrain estimates of biospheric gross CO2 fluxes at large scales. However, accuracy of the partitioning depends on the extent of isotopic disequilibrium between the signals carried by photosynthesis (dA) and soil CO2 exchange (dR) We coupled branch and soil chambers with TDL techniques to capture the d18O signals of these two gross fluxes within a Maritime pine forest. Our study revealed a strong and seasonally persistent isotopic disequilibrium between dA and dR that will be compared to preliminary model simulations in this presentation.

International audience; Methods for genetic transformation of maritime pine embryonal masses (EM) using Agrobacterium tumefaciens (At) have been independently established at 2 laboratories (FCBA and INRA) in France. The two procedures appeared roughly similar but technical differences were noticed during the decontamination and washing of co-cultivated EM, the subsequent reactivation culture step and the selection phase of transgenic lines. One major difference was the basal formulations of media used for At-mediated transformation development at FCBA (mDCR, modified Gupta and Durzan medium) and INRA (mLV, modified Litvay medium). Joined experiments were carried out in order to get insights on factors affecting the transformation rate based on a comparison of both procedures (one model genotype, C58pMP90 At strain, modified pCambia1301 binary vector harbouring the uidA-intron, hpt and bar genes). Our ultimate goal is to foster the transgenic approach as an efficient tool for establishing direct linkages between genes and phenotypes. We showed that the efficiency of the selected transformation procedures is tightly correlated with the basal medium formulation. Using mLV medium, currently recognized in both laboratories as a superior mineral base for maritime pine somatic embryogenesis, transformation yields were higher using the INRA procedure following either hygromycin or phosphinothricin selection. In contrast full advantage of the FCBA procedure could only be raised by using mDCR basal medium instead of mLV. In conjunction with strong phosphinothricin selection (1 mg l-1) the mDCR-based FCBA procedure was revealed as the best option to transform one model genotype of maritime pine (89.6 ± 18.4 phosphinothricin-resistant lines per g EM).

International audience; Initiation of somatic embryogenesis (SE) from immature excised zygotic embryos (IZE) in maritime pine was originally developed at FCBA using a modified DCR basal formulation (mDCR) with the 2,4-D auxin (13.5 μM) and the BA cytokinin (2.2 μM) as plant growth regulators (PGRs). In the frame of an international collaboration (initiation campaigns 2003-2004) we discovered that a modified Litvay basal medium (mLV) supplemented with the phenylurea cytokinin CPPU (4.04 μM) produced a significant increase in mean initiation rate (77 vs. 34%, Park et al. 2006, PCTOC 86: 87-101). This result was confirmed and strengthened during subsequent 2005-2008 initiation campaigns. Up to 92% mean initiation rate (2005 results) were obtained using the mLV/CPPU (4.04 μM) medium with quite moderate variation between years (62-92%, 4-5 families investigated per year, 200-300 IZE/family). The optimal CPPU concentration was studied and we concluded that up to a fourfold reduction of the original dose (1 μM) could be used without significant effect on initiation rate. Similar conclusions were drawn by reducing the initiation culture time of IZE on mLV/CPPU (4 μM) from 8 weeks to only one week. Interestingly initiation rates remained high (47-55%) when initiation media were deprived of CPPU, thus confirming the high interest of mLV for SE initiation in maritime pine. Substituting CPPU (4.04 μM) for the more conventional 2,4-D (9.04 μM) and BA (4.44 μM) PGRs in combination with 10 or 30 g/l sucrose significantly reduced initiation rates. mLV/CPPU (1 μM) was proposed as the optimal initiation medium at FCBA laboratory.

International audience; This study focuses on the effects of fuel structure and in particular its spatial heterogeneity in the context of fuel-break design. The coupled atmospherewildfire behaviour model HIGRAD/FIRETEC is used to simulate wind fields and fire propagation in a complex landscape including forest-to-break and breakto- forest transitions. Two different Mediterranean ecosystems are used here: a Pinus halepensis (light canopy) and a Pinus pinaster (dense canopy). In both ecosystems, two forest zones are separated by a 200 m break. The study is separated into two parts. First, the break-induced winds are simulated with FIRETEC. The impact of the break structure (cover fraction, clump size) on the mean wind and turbulence statistics are shown. A significant increase of wind velocity and turbulence amount is observed when the cover fraction is reduced within the break. In addition, at low cover fraction, the introduction of tree clumps also induces wind acceleration. In the second part of the study, a fire line is ignited in the area upwind of the break and the fire propagation is computed using the precomputed wind fields of the first part of the study. The fire propagates in the upwind forest area before crossing the break and propagating in the downwind forest area. A decrease of fire intensity occurs after several meters of propagation on the fuel-break. This intensity decrease is significant when the cover fraction is lower or equal to 25%, but negligible at 50%. In addition, in the Pinus pinaster canopy, the fuel structure and especially clump size affect the fire damage