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International audience; Forested landscapes often exhibit large spatial variability in vertical and horizontal foliage distributions. This variability may impact canopy-atmosphere ex- changes through its action on the development of turbulent structures. Here we inves- tigate in neutral stratification the turbulent structures encountered in a maritime pine forest characterised by a high, dense foliated layer associated with a deep and sparse trunk space. Both stand and edge regions are considered. In situ measurements and the outputs of large-eddy simulations are used and analysed together. In stand conditions, far from the edge, canopy-top structures appear stronlgy damped by the dense crown layer. Turbulent wind fluctuations within the trunk space, where the momentum flux vanishes, are closely related to these canopy-top structures through pressure diffusion. Consequently, auto-correlation and spectral analyses are not quite appropriate to characterise the vertical scale of coherent structures in this type of canopy, as pressure diffusion enhances the actual scale of structures. At frequencies higher than those associated with canopy-top structures, wind fluctuations related to wake structures developing behind tree stems are observed within the trunk space. They manifest themselves in wind velocity spectra as secondary peaks in the inertial subrange re- gion, confirming the hypothesis of spectral short-cuts in vegetation canopies. In the edge region specific turbulent structures develop just below the crown layer, in addi- tion to canopy-top structures. They are generated by the wind shear induced by the sub-canopy wind jet that forms at the edge. These structures provide a momentum exchange mechanism similar to that observed at the canopy top but in the opposite di- rection and with a lower magnitude. They may develop as in plane mixing-layer flows, with some perturbations induced by canopy-top structures. Wake structures are also observed within the trunk space in the edge region.

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.

International audience; L- and P-band airborne polarimetric synthetic aperture radar (SAR) data acquired by the RAMSES system over different height maritime pine (Pinus Pinaster Ait.) stands of the Nezer forest (Landes, France) have been evaluated for forest biophysical parameter estimation. A pseudolinear correlation has been brought to evidence at P-band between polarimetric anisotropy and mean tree height, which is also linked to other biophysical parameters in the Nezer forest, meaning that SAR polarimetry constitutes a promising tool for forest parameter retrieval at low frequency. The spatial conditions have been evaluated through the quantification of the impact of signal-to-noise ratio diminution and resolution degradation on the forest height inversion. It has been shown that the inversion accuracy remains acceptable for N Esigma0, representing the noise level of the SAR image, which is lower than -15 dB, and for spatial resolution increasing up to 15 m.

International audience; Bark beetles are notorious pests of natural and planted forests causing extensive damage. These insects depend on dead or weakened trees but can switch to healthy trees during an outbreak as mass-attacks allow the beetle to overwhelm tree defences. Climatic events like windstorms are known to favour bark beetle outbreaks because they create a large number of breeding sites, i.e., weakened trees and for this reason, windthrown timber is generally preventively harvested and removed. In December 1999, the southwest of France was struck by a devastating windstorm that felled more that 27 million m3of timber. This event offered the opportunity to study large-scale spatial pattern of trees attacked by the bark beetle Ips sexdentatus and its relationship with the spatial location of pine logs that were temporally stored in piles along stand edges during the post-storm process of fallen tree removal. The study was undertaken in a pure maritime pine forest of 1300 ha in 2001 and 2002. We developed a landscape approach based on a GIS and a complete inventory of attacked trees. During this study more than 70% of the investigated stands had at least one tree attacked by I. sexdentatus. Spatial aggregation prevailed in stands with n≥15 attacked trees. Patches of attacked trees were identified using a kernel estimation procedure coupled with randomization tests. Attacked trees formed patches of 500–700 m2 on average which displayed a clumped spatial distribution. Log piles stemming from the sanitation removals were mainly distributed along the large access roads and showed an aggregated spatial pattern as well. The spatial relationship between patches of attacked trees and log pile storage areas was analyzed by means of the Ripley’s statistic that revealed a strong association at the scale of the studied forest. Our results indicated that bark beetle attacks were facilitated in the vicinity of areas where pine logs were stored. The spatial extent of this relationship was >1000 m. Similar results were obtained in 2001 and 2002 despite differences in the number and spatial distribution of attacked trees. The presence of a strong “facilitation effect” suggests that log piles should be removed quickly in order to prevent outbreaks of bark beetles.

International audience; The effect of drought on forest water use is often estimated with models, but comprehensive models require many parameters, and simple models may not be sufficiently flexible. Many tree species, Pinus species in particular, have been shown to maintain a constant minimum leaf water potential above the critical threshold for xylem embolism during drought. In such cases, prediction of the relative decline in daily maximum transpiration rate with decreasing soil water content is relatively straightforward. We constructed a soil-plant water flow model assuming constant plant conductance and daily minimum leaf water potential, but variable conductance from soil to root. We tested this model against independent data from two sites: automatic shoot chamber data and sap flow measurements from a boreal Scots pine (Pinus sylvestris L.) stand; and sap flow measurements from a maritime pine (Pinus pinaster Ait.) stand. To focus on soil limitations to water uptake, we expressed daily maximum transpiration rate relative to the rate that would be obtained in wet soil with similar environmental variables. The comparison was successful, although the maritime pine stand showed carry-over effects of the drought that we could not explain. For the boreal Scots pine stand, daily maximum transpiration was best predicted by water content of soil deeper than 5 cm. A sensitivity analysis revealed that model predictions were relatively insensitive to the minimum leaf water potential, which can be accounted for by the importance of soil resistance of drying soil. We conclude that a model with constant plant conductance and minimum leaf water potential can accurately predict the decline in daily maximum transpiration rate during drought for these two pine stands, and that including further detail about plant compartments would add little predictive power, except in predicting recovery from severe drought.

International audience; Maritime pine (Pinus pinaster) is the main tree cropping species in the Landes of Gascogne forest range in south western France. Soils are nutrient poor, sandy podzosols and site fertility is determined essentially by organic matter content and depth of water table, which is known to limit root growth. We hypothesised, with an ultimate goal of constructing a nutrient uptake model applicable to this region, that the organic top horizons together with the depth of the water table should be the most important parameters related to fine root distribution and presence of associated mycorrhiza. To test this hypothesis, we compared two adult Pinus pinaster stands, contrasting in depth of water table and soil fertility and evaluated fine roots (diameter < 2 mm) of understory species and fine roots and ectomycorrhizal morphotypes of Pinus pinaster down to 1.2 m, using a soil corer approach. Total fine root biomass of Pinus pinaster was not significantly different between both sites (3.6 and 4.5 t ha(-1) for the humid, respectively, dry site), but root distribution was significantly shallower and root diameter increased more with depth at the humid site, presumably due to more adverse soil conditions as related to the presence of a hardpan, higher amount of aluminium oxides and/or anoxia. Fine roots of Pinus pinaster represented only about 30% of total fine root biomass and 15% of total fine root length, suggesting that the understory species cannot be ignored with regards to competition for mineral nutrients and water. A comparison of the ectomycorrhizal morphotypes showed that the humid site could be characterised by a very large proportion of contact exploration types, thought to be more relevant in accessing organic nutrient sources, whereas the dry site had a significantly higher proportion of both long-distance and short-distance exploration types, the latter of which was thought to be more resistant to short-term drought periods. These results partly confirm our hypothesis on root distribution as related to the presence of soil mineral nutrients (i.e. in organic matter), point out the potential role of understory plant species and ectomycorrhizal symbiosis and are a valuable step in building a site-specific nutrient uptake model.

A finite element model was developed to study the influence of aerial architecture on the structural dynamics of trees. The model combines a complete description of the axes of the aerial architecture of the plant with numerical techniques suitable for dynamic nonlinear analyses. Trees were modeled on the basis of morphological measurements that were previously made on three 4-year-old Pinus pinaster Ait. saplings originating from even-aged stands. Calculated and measured oscillations were compared to evaluate model behavior. The computations allowed the characteristics of the fundamental mode of vibration to be estimated with satisfactory accuracy. Inclusion of a topological description of the aerial system in a mechanical model provided insight into the effect of tree architecture on tree dynamic behavior. Simplifications of the branching pattern in the model led to overestimations of the natural swaying frequency of saplings by 10 to 20%. Inadequate values of stem and root anchorage stiffness resulted in errors of 10 to 20%. Modeling results indicated that aerodynamic drag of needles is responsible for 80% of the damping in the studied trees. Additionally, damping of stem movement is reduced by one half when branch oscillations are not considered. It appears that the efficiency of the dissipative mechanisms depends directly on crown topology.

To determine if trees respond to dynamic and static loading in the same manner, 2-year-old maritime pine (Pinus pinaster Ait.) trees were subjected to different types of mechanical loading in the field. One block of trees (the control) were kept in pots and planted in the field at an angle of 0 or 45 degrees to the vertical. A similar block of leaning potted trees was planted nearby and subjected to frequent, unilateral wind loading for a period of 1 s every 2 min. Half the leaning trees were oriented toward the direction of wind loading and half were oriented along the axis of wind loading. The stem profile was measured three times during the growing season to quantify the rate of stem straightening. Compression wood formation and stem shape were measured in all plants. No differences in mean height or diameter were observed between blocks and all leaning trees straightened, but not at the same rate. Although no difference in the rate of apical straightening occurred between control and wind-treated trees, the righting response of the basal part of the stem of leaning trees subjected to wind was four times greater than that of leaning trees without wind. No differences in the righting response were observed between leaning trees growing toward and trees growing away from the source of wind. No significant differences in compression wood formation were found between control trees and wind-treated trees, indicating that other factors must determine the reorientation rate of leaning trees. Results are discussed with reference to the quality of compression wood in conifers and the mechanotransductive pathway in plants.

We examined the response of early growth of maritime pine seedlings to combined levels of light and phosphorus. Seedlings were grown under three levels of phosphorous availability, i.e., two relative addition rates (RAR = 2 and 4 g P (100 g-1)P d-1) and a free-access to P, crossed with two light levels (photosynthetic photon flux densities of 150 and 450 mmol m-2 s-1, respectively). Relative growth rate (RGR) and relative uptake rate of phosphorus (RUR) were computed, as well as the amount of light absorbed per seedling. We found that phosphorus and light acted as limiting factors with a complex interaction. Under low light and at the lowest P level, P and light were co-limiting, i.e., growth was enhanced only when P and light were increased together. Light was the limiting factor for growth under low light conditions at all other levels of P availability. P was the limiting factor at a RAR of 2% under high light. Enhancing P from 4% to free access did not significantly improve growth under high light. RUR was controlled systematically by P availability at 2 and 4% RAR. RGR values were close to RUR values except under free access to P. Therefore, growth-independent accumulation of P was observed under high P conditions. The differences in biomass production among P treatments were explained primarily by the reduced amount of radiation intercepted by the seedlings as a consequence of their reduced leaf area. No effect of P treatments were observed on the calculated radiation-use efficiency (RUE), which was found to be larger under low light. This confirms that pine seedlings adjust to moderate phosphorus deficiency mainly by changing their morphology (leaf area, dry-mass partitioning) while biochemical and photochemical limitations of photosynthesis play only a very secondary role., Interaction des effets de la disponibilité en phosphore et en lumière sur la croissance de jeunes plants de pin maritime. La croissance de jeunes plants de pin maritime a été suivie en chambre de culture à deux niveaux d'éclairement et trois de disponibilité en phosphore. Deux taux d'addition relatifs en P (RAR = 2 et 4 g P (100 g-1 P j-1) et un libre accès au P ont été appliqués en combinaison avec deux niveaux d'éclairement (150 et 450 mmol m-2 s-1). Le taux de croissance relatif (RGR) et le taux d'absorption relatif de P (RUR) ont été calculés. La surface foliaire, la quantité de rayonnement absorbé et l'efficience d'utilisation du rayonnement (RUE) ont aussi été estimés. Les disponibilités en phosphore et en lumière ont limité la croissance suivant un schéma d'interaction complexe. Au plus faible niveau d'éclairement et d'ajout en phosphore, les deux facteurs étaient co-limitants et la croissance n'était augmentée que lorsque les deux facteurs augmentaient simultanément. La lumière était le facteur limitant pour les traitements sous faible éclairement à tous les autres niveaux de disponibilité en P. Le phosphore était limitant pour des RAR de 2% sous fort éclairement. Le taux de prélèvement relatif en P (RUR) était contrôlé par la disponibilité en P aux taux d'addition relatifs (RAR) de 2 et 4%. Les valeurs de RGR étaient proches des valeurs de RUR sauf au plus fort niveau de disponibilité en P où une accumulation de P indépendante de la croissance a été observée. La réduction de la croissance sous limitation en P est explicable par la réduction de la quantité de rayonnement absorbé par les plants, par suite d'une expansion limitée et plus lente de leur surface foliaire. Il n'y a pas eu d'effet de la disponibilité en P sur le RUE. Le RUE était par contre plus élevé sous faible éclairement. En conclusion, nos résultats confirment que les jeunes plants de pin maritime soumis à une déficience modérée en P ajustent leur croissance (réduction de l'expansion de la surface foliaire) sans effet majeur sur le RUE.

Growth and nutrition of hydroponically cultivated pine seedlings (Pinus pinaster Ait.) were investigated at various phosphorus (P) availabilities. P was added either with free access or at a relative addition rate of 0.02 and 0.04 day−1. Laboratory observations were compared with adult growth performances in the field in two sets of experiments: the first with three contrasting populations, the second with seven full-sib families within a population. Significant differences in P productivity (growth rate per unit P in the plant) and in maximal relative growth rate were observed in both experiments, but correlation with adult performances was restricted to populations. Selection for nutrient-related traits would thus be possible, but understanding of the relationship between growth and nutrition needs further evaluation. The minimum P concentration in the seedlings supporting maximum growth ([P]optimum) varied from 2.2 to 3.8 mg g−1 DM, which is in agreement with values obtained in other species. The root/...

Nitrogen (N2) fixation by Ulex species was studied in a range of mature maritime pine (Pinus pinaster Ait.) stands as well as in a phosphorus (P) fertilization trial in a young (6-year-old) open pine stand. The biomass was estimated by allometric relationships, and the percentage of N derived from atmosphere was calculated according to the natural 15N abundance method. Ulex stand biomass was lower in the mature pine stand than in the young open pine stand. In the latter pine stand, Ulex mean annual biomass increment ranged from 1 to 5 Mg·ha–1·year–1, increasing with P fertilization dose, as did the Ulex stand biomass, ranging from 5.4 to 31.1 Mg·ha–1 after six growing seasons in the most highly fertilized treatment. For the sites where the natural 15N abundance method was applicable, the calculated percentage of N in the Ulex europaeus L. tissues derived from atmosphere was very high (mean = 82%; range = 59%–100%). At the other sites, the N2 fixation was probably also very important but could not be calculated with confidence. Here, the mean fixation rate of the former sites was used to calculate the N2 fixation flux. The estimated annual N2 fixation flux ranged from 0.5 to 5.1 kg N·ha–1·year–1 in the mature pine stands. In the young open pine stand, the Ulex understory fixation ranged from 8.1 to 57.4 kg N·ha–1·year–1, increasing with P fertilization dose. Considering the low levels of N fluxes in theses ecosystems, these figures are very high.

International audience; We investigated the radial variation of sap flow within sapwood below the live crown in relation to tree size in 10-, 32-, 54- and 91-year-old maritime pine stands (Pinus pinaster Ait.). Radial variations were determined with two thermal dissipation sensors; one measured sap flux in the outer 20 mm of the xylem (J(ref)), whereas the other was moved radially across the sapwood in 20-mm increments to measure sap flux at multiple depths (J(i)). For all tree sizes, sap flow ratios (R-i = J(i)J(ref)(-1))declined with increasing sapwood depth, but the decrease was steeper in trees with large diameters. Correction factors (C) were calculated to extrapolate J(ref) for an estimate of whole-tree sap flux. A negative linear relationship was established between stem diameter and C, the latter ranging from 0.6 to 1.0. We found that neglecting these radial corrections in 10-, 32-, 54- and 91-year-old trees would lead to overestimation of stand transpiration by 4, 14, 26 and 47%, respectively. Therefore, it is necessary to account for the differential radial profiles of sap flow in relation to tree size when comparing tree transpiration and hydraulic properties among trees differing in size

International audience; Two unigene datasets of Pinus taeda and Pinus pinaster were screened to detect di-, tri- and tetranucleotide repeated motifs using the SSRIT script. A total of 419 simple sequence repeats (SSRs) were identified, from which only 12.8% overlapped between the two sets. The position of the SSRs within their coding sequences were predicted using FrameD. Trinucleotides appeared to be the most abundant repeated motif (63 and 51% in P. taeda and P. pinaster, respectively) and tended to be found within translated regions (76% in both species), whereas dinucleotide repeats were preferentially found within the 5'- and 3'-untranslated regions (75 and 65%, respectively). Fifty-three primer pairs amplifying a single PCR fragment in the source species (mainly P. taeda), were tested for amplification in six other pine species. The amplification rate with other pine species was high and corresponded with the phylogenetic distance between species, varying from 64.6% in P. canariensis to 94.2% in P. radiata. Genomic SSRs were found to be less transferable; 58 of the 107 primer pairs (i.e., 54%) derived from P. radiata amplified a single fragment in P. pinaster. Nine cDNA-SSRs were located to their chromosomes in two P. pinaster linkage maps. The level of polymorphism of these cDNA-SSRs was compared to that of previously and newly developed genomic-SSRs. Overall, genomic SSRs tend to perform better in terms of heterozygosity and number of alleles. This study suggests that useful SSR markers can be developed from pine ESTs

The aim of this work was to investigate the quantitative relationships between the rates of fungal soil exploration and their effects on plant growth and phosphorus (P) nutrition in soil with varying P availability. Ectomycorrhizal associations were established between Pinus pinaster and the basidiomycete Hebeloma cylindrosporum. Plants were grown for 4 and 6 months in mini-rhizoboxes filled with a 0.5 mm soil layer with two contrasting P levels ()P and +P soils), containing 3 or 50 mg of bicarbonate extractable P per kg of dry soil, respectively. Surface areas of the soil layers colonised by the roots and the hyphae were estimated using image analysis. High P availability decreased the rates of fungal soil colonisation, calculated as 0.92 � 0.19 cm 2 day � 1 plant � 1 in the )P soil and 0.42 � 0.1 cm 2 day � 1 plant � 1 in the +P soil over the 4–6 months period. Four-month old mycorrhizal plants accumulated lower amounts of biomass and total P than non-mycorrhizal plants, regardless the level of P availability. By contrast, 6-month old mycorrhizal plants were larger and contained more P than non-mycorrhizal plants, especially in the +P soil. However, mycorrhizal plants were always different from non-mycorrhizal P-deficient plants, which had an increased root surface and root P allocation. To explain these contradictory results, we propose that P accumulation by mycorrhizal plants derives mainly from fungal P uptake. The net P transfer from the fungus to the plant was estimated as 0.36 and 0.66 lmol of P per cm 2 of mycelium in )P and +P soil, respectively. Our data demonstrated that, despite the inhibitory effect of the high soil P availability on the rates of fungal soil colonisation, the ectomycorrhizal symbiosis was more efficient to improve host plant P nutrition in these conditions. 2004 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.

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.

International audience; Maritime pine (Pinus pinaster) stands in the Aquitaine region are of great economic importance but subject to Atlantic storms. In the Bordeaux region, two experimental sites located near each other, aged 20 and 51 years, made it possible to study the effects of different types of silviculture on wind-firmness during the 1999 storm. Stand density has a major influence on tree growth. When density increases, height increases and circumference decreases appreciably. In the dense stands, windthrown trees were less abundant and there were more leaning pines. With respect to other silvicultural factors in stands planted at typical densities: (i) genetic breeding did not increase damage intensity at the 20-year-old experimental site and phosphorus fertilisation decreased the windthrow at the 51-year-old experimental site; (ii) compared to the undamaged trees, the circumference of windthrown trees was 3.6 cm smaller, the relative crown length was 10% shorter and the stem taper coefficient was higher. This research has shown that wind-firmness is better in stands where the height, circumference and crown length are homogeneous. A more closed canopy seems to improve wind resistance by increasing the damping effect of swaying as a result of the crowns being in contact with each other and provides a more favourable ratio between the aerial parts and the roots.; Résistance au vent de peuplements de pin maritime dans le sud-ouest de la France. Influence de la densité, de la fertilisation et de l'amélioration génétique sur deux dispositifs endommagés lors de la tempête du 27 décembre 1999. Les peuplements de Pinus pinaster en Aquitaine sont économiquement très importants mais exposés aux tempêtes océaniques. Dans la région de Bordeaux, deux dispositifs de 20 et 51 ans peu éloignés ont permis d'étudier l'influence de la sylviculture sur la résistance au vent lors de la tempête de 1999. La densité est le facteur sylvicole le plus influent sur les caractéristiques des peuplements. Quand la densité augmente, la circonférence moyenne diminue notablement et la hauteur moyenne a tendance à augmenter. Les chablis étaient moins abondants et les pins penchés plus nombreux dans les peuplements denses. Pour les densités pratiquées en forêt de production : (i) l'amélioration génétique n'a pas augmenté l'intensité des dégâts dans l'essai de 20 ans, et la fertilisation au phosphore a réduit le taux de chablis sur l'essai de 51 ans ; (ii) par rapport aux pins intacts, les chablis ont une circonférence inférieure de 3,6 cm, une longueur relative de houppier plus courte de 10 % et un coefficient d'élancement du tronc plus fort. Ces caractéristiques peuvent traduire la diminution des capacités d'amortissement du balancement des arbres lors des bourrasques. Ces recherches ont montré que la résistance au vent est meilleure dans les peuplements homogènes en hauteur, circonférence ou longueur de houppier. Un couvert plus fermé semble améliorer la résistance au vent en augmentant l'amortissement des oscillations des houppiers par contact entre houppiers, ainsi que le rapport entre les parties aériennes et les racines.

International audience; Wood is one of our most important natural resources and has been exploited for many hundreds of years as fuel, building material and a source of paper. Its composition is variable among and within species. The ability to monitor the intra-specific variability is a prerequisite to improve wood and end-products properties. This paper describes a study of the genetic control of a large set of wood properties, including growth, timber quality traits, wood chemical composition, kraft pulp production parameters and pulp properties, in a 12 $\times$ 12 half diallel of maritime pine (Pinus pinaster Ait.). While relatively high (h$^{2}_{\rm ns} > 0.3$) narrow-sense heritabilities were observed for density heterogeneity, lignin content, alpha-cellulose content and coarseness, no significant genetic effect was detected for hemi cellulose, water extractives, kraft pulp production parameters and pylodin. Slightly lower heritabilities ($0.15 < {\rm h}^{2}_{\rm ns} < 0.3$) were also obtained for wood density and fibre properties (length, width, curl, zero span). As a consequence and considering the phenotypic coefficient of variation obtained for these traits, improvement by selection of trees with outstanding wood quality is feasible. Nevertheless, it seems obvious that wood quality breeding can not be done without taking into account growth, and the only way to manage this constraint (negative correlation between growth and density) will be the constitution of elite "wood quality" populations in a already growth improved genetic population.; Déterminisme génétique des propriétés du bois impliquées dans la production papetière et la qualité du bois d'œuvre chez le Pin maritime (Pinus pinaster Ait.). Le bois, une des ressources naturelles les plus importantes, est exploité depuis des centaines d'années comme combustible, matériau de construction et source de papier. Sa composition est très variable, non seulement entre espèces mais aussi au niveau intra spécifique. La compréhension de cette variabilité intra spécifique est un pré-requis de l'amélioration des propriétés des produits à base de bois. L'objectif de l'étude présentée ici est la compréhension du déterminisme génétique de plusieurs caractères impliqués dans la composition chimique et les propriétés du bois (caractéristiques physiques, paramètres de production industrielle et propriétés de la pâte) grâce à l'étude d'un demi diallèle 12 $\times$ 12. Bien que des héritabilités au sens strict relativement élevées (h$^{2}_{\rm ns} >0,3$) aient été obtenues pour l'hétérogénéité de la densité, les contenus en lignine et en alpha-cellulose et la masse linéique, aucun effet génétique significatif n'a été mis en évidence pour le contenu en hémi-cellulose, les extractibles, les paramètres de production de pâtes kraft, et la densité estimée grâce au pilodyn. Des héritabilités plus faibles ($0.15 < {\rm h}^{2}_{\rm ns} < 0.3$) ont quant à elles été obtenues pour la densité du bois et les propriétés des fibres (longueur, largeur, courbure, rigidité). En conséquence, considérant les coefficients de variation phénotypiques obtenus pour ces caractères, des gains génétiques significatifs peuvent être attendus. Néanmoins, l'amélioration des propriétés du bois ne pourra pas se faire sans prendre en compte la croissance. Le seul moyen de gérer cette contrainte (induite par des corrélations négatives entre croissance et densité) sera la constitution de populations élites pour la qualité du bois au sein de bases génétiques déjà améliorées pour la croissance.

International audience; We constructed a high-density linkage map of maritime pine (Pinus pinaster Ait.) based on AFLP (Amplified Fragment Length Polymorphism) markers using a three-generation outbred pedigree. In a first step, male and female maps were established independently with test-cross markers segregating 1:1 (presence:absence of the amplified fragment in the full-sib progeny). In a second step, both maps were merged using intercross markers segregating 3:1 in the progeny. A combination of MAPMAKER and JOINMAP softwares was used for the mapping process. A consensus map was obtained and is available at URL http://www.pierroton.inra.fr/genetics/pinus/Map3/index.html. It covers 1441 cM and comprises a total of 620 AFLP markers on 12 linkage groups. The physical size of the maritime pine genome (51.5 pg/2C) was measured by flow cytometry, providing a physical/genetic size ratio of 13.78 Mb/cM. This map will be used to dissect the genetic architecture of economically (growth, wood quality) and ecologically (water-use efficiency) important traits into mendelian inherited components (QTLs: Quantitative Trait Loci). It will also provide a framework to localize more informative markers (ESTs: Expressed Sequence Tags) to be used as candidate genes in QTL detection experiments. The location of orthologous markers (ESTs and SSRs: Simple Sequence Repeats) will also allow the study of the genome structure of closely related conifer species using a comparative genome mapping approach.; Établissement d'une carte génétique à haute densité du pin maritime à partir de marqueurs AFLP. Nous avons construit une carte génétique du pin maritime (Pinus pinaster Ait.) en génotypant une famille de plein-frères appartenant à la troisième génération du programme d'amélioration, avec des marqueurs AFLP. Dans un premier temps, les cartes des parents mâle et femelle ont été établies indépendamment avec des marqueurs de type " test-cross " ségréguant dans les proportions 1:1 (présence:absence du fragment amplifié dans la famille de plein-frères). Dans un second temps ces deux cartes ont été fusionnées à l'aide de marqueurs de type " intercross ", ségréguant dans les proportions 3:1. La construction des cartes a été réalisée à l'aide des logiciels de cartographie génétique JOINMAP et MAPMAKER. Une carte génétique consensus des deux parents comprenant 12 groupes de liaison a finalement été obtenue et est accessible à l'URL suivante : http://www.pierroton.inra.fr/genetics/pinus/Map3/index.html. Elle couvre 1441 cM et comprend 620 marqueurs. Par ailleurs, la taille physique du génome du pin maritime a été estimée par cytométrie de flux à 51.5 pg/2C, donnant un rapport taille physique/taille génétique de 13.78 Mb/cM. Cette carte sera maintenant utilisée pour étudier l'architecture génétique de caractères d'intérêt économique (croissance, qualité du bois) et écologique (efficience d'utilisation de l'eau). Il s'agira de localiser les zones du génome (QTL, Quantitative Trait Loci) impliquées dans le contrôle génétique de ces caractères complexes. La carte génétique fournira aussi un support pour localiser d'autres types de marqueurs, tels que des gènes (EST, Expressed Sequence Tags) qui seront utilisés comme marqueurs candidats pouvant correspondre aux QTL. La localisation de marqueurs orthologues (EST et SSR, Simple Sequence Repeats) permettra d'étudier en outre la structure du génome des conifères en utilisant une approche par cartographie comparée.

Gráficos., The Mediterranean populations of maritime pine (Pinus pinaster Ait.) are typically small and have a scattered distribution, being threatened by human activities and forest fires. In the framework of the genetic-resources conservation program of this species, a native multi-age stand located in a Mediterranean area (central Spain) was studied using three highly polymorphic nuclear microsatellites (SSRs). Spatial autocorrelation analysis was conducted using Moran's index in order to detect fine-scale structure in both natural regeneration and mature trees. The spatial pattern of seed flow based on dispersed progeny was studied using a highly reliable subset of parent-offspring matches obtained by means of parentage analysis and simulation-based calculation of statistical confidence. Maritime pine showed a fine-scale structure at the seedling stage. In natural regeneration, the autocorrelograms indicated a patch size of approximately 10 m. The fine-scale structure seems to be produced by a restricted seed gene flow. In fact, there was an excess of parent-offspring matches in a radius of 15 m from the parent trees. Pines with a heavy seed, such as P. pinaster, are expected to have a short dispersal distance, thus producing a fine-scale structure. However, the fine-scale structure did not persist in the mature trees. Within-population genetic structure in Mediterranean pines may be affected by a number of post-dispersal events (e.g. mortality due to the severity of the Mediterranean climate and animal-mediated secondary dispersal during the summer period). Thus, great alteration in the pattern produced by the initial seed rain and differences in genetic structure between tree cohorts are expected., The study was funded by the Cooperation project DGCN-INIA CC95-0097 and the INIA project SC97-118. The first author was supported by a FPU scholarship from MECD (Ministerio de Educación, Cultura y Deporte).

International audience; This paper summarises the main characteristics of a new functional-structural ecophysiological model EMILION elaborated for pine species. It is based on the integration of the functioning of the tree aerial organs, shoots, buds and cones. It is founded on the modelling of carbon- and water- related processes at the organ level, and on the links that exist between the organs. The main processes described by EMILION are light distribution and interception, photosynthesis, respiration, stomatal conductance, transpiration, water transfer, phenology, and intra-annual growth. It uses an object-oriented approach. It has been parameterised and applied to adult Maritime pine (Pinus pinaster Ait.). The model simulates the distribution in the tree of carbon and water fluxes at a short time step. The principal inputs are stand and tree structure, and meteorological data. EMILION allows one to study the interaction of processes at the organ and tree level. An example application is presented, in which EMILION was used to simulate the carbon budget of existing branches, according to their age and location within the crown. This study was used to test one hypothesis of branch death, that death is a consequence of an imbalance between branch assimilate production and use. Our results show that the old branches of Pinus pinaster are autonomous for the carbon, but the ability of these branches to supply assimilates to rest of the tree appears very low. We conclude that this small carbon availability in the oldest branches is a cause of their limited development.; Principes du modèle structure-fonction Emilion et application à l'analyse de l'autonomie carbonée des branches dans le houppier. Un nouveau modèle écophysiologique EMILION de type structure-fonction est présenté. Ce modèle élaboré pour les espèces du genre Pinus, est basé sur l'intégration des connaissances relatives au fonctionnement des organes formant l'arbre, il est actuellement adapté au cas du Pin maritime (Pinus pinaster Ait.) adulte. Il s'appuie sur la modélisation des processus carbonés et hydriques à l'échelle de l'organe et sur les relations qu'établissent entre eux les organes qui sont liés. Différents types d'organes aériens sont distingués, les rameaux, les bourgeons et les cônes. Les principaux processus intégrés dans le fonctionnement des organes sont la distribution et l'interception du rayonnement, la photosynthèse, la respiration, la conductance stomatique, la transpiration, les transferts hydriques xylémiens, la phénologie et la croissance intra annuelle. Dans le modèle, chaque organe est représenté par un objet, et un arbre ou une branche par un objet Structure. Le modèle simule les flux de carbone et d'eau au sein de l'arbre à un pas de temps demi-horaire. EMILION permet d'étudier l'interaction des différents processus au sein des organes et au sein de l'arbre. Les entrées du modèle sont la structure du peuplement et de l'arbre modélisé, ainsi que les conditions climatiques. Une utilisation du modèle est présentée. EMILION est utilisé pour simuler, en fonction de leur âge et de leur position dans l'arbre, le bilan de carbone de branches réelles, afin d'analyser les hypothèses expliquant la mort des branches âgées, basées sur un déséquilibre entre production et consommation d'assimilats. Nos résultats montrent que les vieilles branches sont autonomes vis-à-vis du carbone, mais que la quantité d'assimilats quelles sont en mesure de fournir au reste de l'arbre devient relativement faible. Finalement nous supposons que cette faible disponibilité des assimilats, au sein des vieilles branches en peuplement, participe à la limitation de leur développement.

International audience; The bast scale Matsucoccus feytaudi is a specific pest of maritime pine that is endemic in the Iberian Peninsula and southwestern France, and invasive in southeastern France, Italy and Corsica where it causes heavy damages. We developed eight microsatellite polymorphic markers using an enrichment protocol in order to study the invasion pathways and infer the genetic diversity of the populations. All loci could be successfully amplified with no evidence of null alleles. Cross-species amplifications failed to amplify the congeneric Matsucoccus josephi

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.

An experimental field planted with Pinus pinaster mycorrhized under controlled conditions has been producing the two fungi for the past five years, but also various competitors. Fifteen mycorrhizal species appeared successively. Ecological conditions were studied for each species: temperature, humidity, distance trunk to fruiting area, … Interesting differences were noted in comparison with the ecology of the cultivated species.

International audience; We present here the results of a water and nutrient manipulation experiment in a five-year-old plantation of maritime pine in south-western France. Water and nutrient levels were manipulated in a factorial design with two levels of irrigation (control receiving only rainfall (C) and irrigated (I)) and three levels of fertilisation (control with no added nutrients (C), P-only (P) and annual addition of a complete nutrient mix (F)) in order to quantify growth limitations of plantation forest in this particular area. The treatments applied during five years increased above-ground biomass annual increment by 4% (I) to 58% (IF) with respect to the control (C). The fertilised plots had a slightly non-significant lower root-to-shoot ratio. The effect of irrigation was maximal in 2002, resulting in 6%, 7% and 12% higher growth rate on the F, C and P plots, respectively. A windstorm disturbed the experiment in 1999 and has affected preferentially the fertilised plots, with IF plots displaying 60% damage. The higher growth rate of fertilised and irrigated plots was attributed to both an increase (estimated at 5 to 15%) in the amount of light absorbed by the canopy, and an increase (estimated at 26% for IF plots) in the amount of above-ground biomass produced annually per unit leaf area.