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Introduction: Climate change will have a differential impact on mountain forest growth linked to elevation. Objective: To evaluate the interrelationships of growth ring components at altitudinal gradient limits of Pinus hartwegii Lindl. in three mountains of east-central Mexico. Materials and methods: We analyzed 295 tree samples from Cofre de Perote, Pico de Orizaba and Monte Tláloc corresponding to the period 1960-2017 with a total of 17 700 observations per variable (ring width and density [TRW, TRD], earlywood [EWW, EWD], latewood [LWW, LWD] and minimum and maximum density [MID, MAD]). Results and discussion: Growth parameters were higher at the lower limit (≈3 500 m). The correlation of TRW with EWW (r ≥ 0.95) and LWW (r ≥ 0.78) was significant (P < 0.05). TRD correlated with EWD (r ≥ 0.83) and MID (r ≥ 0.72), as well as EWD with MID (r ≥ 0.92) and LWD with MAD (r ≥ 0.92). At the upper limit (≈4 000 m), correlations of TRW, EWW and LWW with TRD, EWD and MID were negative (-0.3 ≥ r ≥ -0.8). This may be explained by lower temperatures and growth periods reducing the relative importance of latewood in ring width. Conclusions: The information provided contributes to understand the dynamics of P. h ar t we g ii xylogenesis in response to climate and possible implications for radial growth facing climate change.

19 Pág., Microgeographical adaptation occurs when the effects of directional selection persist despite gene flow. Traits and genetic loci under selection can then show adaptive divergence, against the backdrop of little differentiation at other traits or loci. How common such events are and how strong the selection is that underlies them remain open questions. Here, we discovered and analysed microgeographical patterns of genomic divergence in four European and Mediterranean conifers with widely differing life-history traits and ecological requirements (Abies alba MIll., Cedrus atlantica [Endl.] Manetti, Pinus halepensis Mill. and Pinus pinaster Aiton) by screening pairs from geographically close forest stands sampled along steep ecological gradients. We inferred patterns of genomic divergence by applying a combination of divergence outlier detection methods, demographic modelling, Approximate Bayesian Computation inferences and genomic annotation to genomic data. Surprisingly for such small geographical scales, we showed that selection is strong in all species but generally affects different loci in each. A clear signature of selection was systematically detected on a fraction of the genome, of the order of 0.1%-1% of the loci depending on the species. The novel modelling method we designed for estimating selection coefficients showed that the microgeographical selection coefficient scaled by population size (Ns) was 2-30. Our results convincingly suggest that selection maintains within-population diversity at microgeographical scales in spatially heterogeneous environments. Such genetic diversity is likely to be a major reservoir of adaptive potential, helping populations to adapt under fluctuating environmental conditions., Agence Nationale de la Recherche, Grant/ Award Number: FLAG project (ANR-12- ADAP-0007-01); European Commission, Grant/Award Number: TOPWOOD project (MSCA-RISE-2014-645654- TOPWOOD) and grant agreement No. 676876 (GenTree); Ministère de l'Écologie, du Développement Durable et de l'Énergie, Grant/Award Number: GRAAL project (10-MCGOT-GICC-8-CVS-139)

Tree breeding programs and wood industries require simple, time- and cost-effective techniques to process large volumes of samples. In recent decades, near-infrared spectroscopy (NIRS) has been acknowledged as one of the most powerful techniques for wood analysis, making it the most used tool for high-throughput phenotyping. Previous studies have shown that a significant number of anatomical, physical, chemical and mechanical wood properties can be estimated through NIRS, both for angiosperm and gymnosperm species. However, the ability of this technique to predict functional traits related to drought resistance has been poorly explored, especially in angiosperm species. This is particularly relevant since determining xylem hydraulic properties by conventional techniques is complex and time-consuming, clearly limiting its use in studies and applications that demand large amounts of samples. In this study, we measured several wood anatomical and hydraulic traits and collected NIR spectra in branches of two Eucalyptus L'Hér species. We developed NIRS calibration models and discussed their ability to accurately predict the studied traits. The models generated allowed us to adequately calibrate the reference traits, with high R2 (≥0.75) for traits such as P12, P88, the slope of the vulnerability curves to xylem embolism or the fiber wall fraction, and with lower R2 (0.39–0.52) for P50, maximum hydraulic conductivity or frequency of ray parenchyma. We found that certain wavenumbers improve models’ calibration, with those in the range of 4000–5500 cm−1 predicting the highest number of both anatomical and functional traits. We concluded that the use of NIRS allows calibrating models with potential predictive value not only for wood structural and chemical variables but also for anatomical and functional traits related to drought resistance in wood types with complex structure as eucalypts. These results are promising in light of the required knowledge about species and genotypes adaptability to global climatic change.

In the long term, defoliation strongly decreases tree growth and survival. Insect outbreaks are a typical cause of severe defoliation. Eastern spruce budworm (Choristoneura fumiferana Clem.) outbreaks are one of the most significant disturbances of Picea and Abies boreal forests. Nevertheless, in boreal conifers, a 2-year defoliation has been shown to quickly improve tree water status, protect the foliage and decrease growth loss. It suggests that defoliation effects are time-dependent and could switch from favorable in the short term to unfavorable when defoliation duration exceeds 5–10 years. A better understanding of the effect of defoliation on stem radius variation during the needle flushing time-window could help to elucidate the relationships between water use and tree growth during an outbreak in the medium term. This study aims to assess the effects of eastern spruce budworm (Choristoneura fumiferana Clem.) defoliation and bud phenology on stem radius variation in black spruce [Picea mariana (Mill.) B.S.P.] and balsam fir [Abies balsamea (L.) Mill.] in a natural stand in Quebec, Canada. We monitored host and insect phenology, new shoot defoliation, seasonal stem radius variation and daytime radius phases (contraction and expansion) from 2016 to 2019. We found that defoliation significantly increased stem growth at the beginning of needle flushing. Needles flushing influenced the amplitude and duration of daily stem expansion and contraction, except the amplitude of stem contraction. Over the whole growing season, defoliation increased the duration of stem contraction, which in turn decreased the duration of stem expansion. However, the change (increase/decrease) of the duration of contraction/expansion reflects a reduced ability of the potential recovery from defoliation. Black spruce showed significantly larger 24-h cycles of stem amplitude compared to balsam fir. However, both species showed similar physiological adjustments during mild stress, preventing water loss from stem storage zones to support the remaining needles’ transpiration. Finally, conifers react to defoliation during a 4-year period, modulating stem radius variation phases according to the severity of the defoliation.

International audience; Establishing drying-limits for mortality of different tree species and understanding the anatomical and physiological traits involved is crucial to predict forests' responses to climate change. The xylem of Eucalyptus camaldulensis presents a complex of solitary vessels surrounded by different imperforate tracheary elements and parenchyma that influence, in a poorly known way, its hydraulic functioning. We aimed at describing the dynamics of embolism propagation in this type of xylem, seeking any vessel-size pattern, and unraveling the threshold of xylem embolism leading to nonrecovery after drought in E. camaldulensis. We assigned potted saplings to a protracted water-stress for 70 days. We relied on colorimetric and hydraulic methods to test for links between xylem anatomy and embolism propagation in the main stem. On average, the occurrence of embolism was randomly distributed in the stem xylem, but the probability of embolized vessels was higher than predicted by chance in the narrowest vessels of individuals that experienced low to moderate water-stress. The saplings could recover from severe water-stress if their percentage loss of conductance (PLC) was

Background: Mountain forest soils (≥2,500 m a.s.l.[1]), where elevation is crucial in the ecosystem dynamic, have a great capacity to capture and preserve carbon for a long time. The aim of this research was to determine the role of elevation combined with soil, climate, and vegetation variables on soil organic carbon (SOC) stocks distribution under P. hartwegii in the Nevado de Toluca Volcano, a protected area in Mexico. Topsoil samples (0-15 cm depth) collected every 100 m in elevation (3,400-4,000 m) were chemically and physically examined in statistical analysis together with vegetation structure and climate variables. Derived from field forest conditions, elevation plots were additional analyzed as logged (3,400-3,800 m) vs no-logged (3,900-4,000 m). Results: SOC stocks followed a significant linear trend (r2= 0.70; p= 0.02) along the elevation gradient, being highest at 4,000 m (173.1 ± 5.2 Mg C ha-1) and lowest at 3,700 m (146.8 Mg C ha-1). Multiple regression analyses showed that SOM, BD, and mean annual temperature (MAT) were the main abiotic drivers of SOC stocks variability (94.5 %) along the elevation gradient. Meanwhile, from the logistic multiple regression, higher tree shrubs and herbs density, in addition to lower tree height and grass cover at lower elevations, indicate a significant effect of logging on soil traits and vegetation structure, depending on the elevation plot. Conclusions: This research evaluated the SOC stocks and the potential effect of current warming over mountain soils, using the elevation as a proxy for both environmental and human drivers of SOC stocks in mountain forest ecosystems. Higher SOM and grass cover, larger-diameter trees together with low temperatures and logging restrictions in the high elevation range suggest a slower decomposition rate and SOC long-term stability. Despite the fact that we do not know about the intensity and cutting cycle, nor the size of the clearings derived from the trees removed, results from this research show how logging could exacerbate these effects and diminish SOC stocks, as well as the capacity of mountain soils to mitigate the effects of climate change.

International audience; Context: Douglas-fir, a fast growing conifer from western North America, recently suffered diebacks following drought in France. We investigated the link between native-source climate and provenance drought resistance in a common garden in France. We compared the adaptive potential of provenances from different parts of the natural area. Methods: We collected branches from a 25-year-old provenance trial replicated in two test sites in southern France. We estimated provenance variation of cavitation resistance traits, survival and circumference. We compared Washington-Oregon provenances to coastal and interior Californian provenances. Results: In the common gardens, the hydraulic traits were significantly variable between provenances, with a strong site x provenance interaction, and significantly related to the climate of the natural area and survival. The relationships were different between variables and test-sites. The two test-sites and their particular climatic selective pressure revealed different geographical adaptive structures in the natural area. Conclusions: Douglas-fir evolutionary adaptation to drought results from natural selection to summer climate and shapes populations for cavitation resistance. In the dryer site only, the Interior California provenances seem more drought resistant. The strong within-provenance variations suggest that there is also a certain withinprovenance adaptation potential to drought at the cost of variable mortality rates.

Wood density is the product of carbon allocation for structural growth and reflects the trade-off between mechanical support and water conductivity. We tested a conceptual framework based on the assumption that micro-density depends on direct and indirect relationships with endogenous and exogenous factors. The dynamics of wood formation, including timings and rates of cell division, cell enlargement, and secondary wall deposition, were assessed from microcores collected weekly between 2002 and 2016 from five black spruce stands located along a latitudinal gradient in Quebec, Canada. Cell anatomy and micro-density were recorded by anatomical analyses and X-ray measurements. Our structural equation model explained 80% of micro-density variation within the tree-ring with direct effects of wall thickness (σ = 0.61), cell diameter (σ = -0.51), and photoperiod (σ = -0.26). Wood formation dynamics had an indirect effect on micro-density. Micro-density increased under longer periods of cell-wall deposition and shorter durations of enlargement. Our results fill a critical gap in understanding the relationships underlying micro-density variation in conifers. We demonstrated that short-term responses to environmental variations could be overridden by plastic responses that modulate cell differentiation. Our results point to wood formation dynamics as a reliable predictor of carbon allocation in trees.

Tree death is not always preceded by a visible decline in vigor (canopy dieback) or a progressive loss in crown volume. Identifying early-warning signals of incipient decline can help to implement the necessary measures to prevent tree death. The aim of this work is to understand what functional alterations preceded the massive drought-induced death of adult Pinus canariensis trees in an arid stand, located in the Canary Islands. To this aim, we analyzed interannual variations in earlywood and latewood width, wood density and anatomy, and carbon isotope composition, and the relationships among these variables, in dead and living trees from 1980 to 2013. Dead trees grew less since the 1990′s, produced fewer parenchyma rays and resin canals, and exhibited a trend of decreasing latewood density and a marked shift in carbon isotope discrimination over the last 34 years that were reversed in living trees. Higher wood density in living trees resulted from thicker tracheid cell walls rather than narrower lumens. The intrinsic water use efficiency shifted from higher to lower values in dead trees after the 2000s. These results suggest a carbon limitation to maintain hydraulic safety under xylem tension, as well as to maintain storage and defense capacity, which can render trees more vulnerable to severe drought episodes. A long-term trend of decreasing tree-ring density and a reduced intrinsic water use efficiency in the short-term can be early-warning signals of carbon limitation and tree decline in drought-stressed P. canariensis. The analysis of these variables can be used to assess tree decline risks in similarly vulnerable conifer populations inhabiting drought-prone regions.

International audience; One factor that determines a tree’s resilience capacity to drought is its level of interaction with aggravating biotic factors, such as bark beetles, which in turn depends on whether insect populations are at an endemic or epidemic stage. In a Mediterranean natural forest ecosystem, we investigated the ecophysiological characteristics of trees which (i) predispose Pinus halepensis to attacks of endemic populations of bark beetles (Tomicus destruens) and (ii) that arise as a result of these attacks. The annual life cycle of Tomicus destruens features an initial dispersal phase of sexually mature adults towards pine trunks for the purposes of brood production, and a second dispersal phase of callow adults from trunks to pine shoots for sexual maturation. During a three-year survey of endemic bark beetle attacks in a stand of 178 trees, we found that trees targeted for trunk attacks showed a more aggregated distribution pattern than those targeted for shoot attacks. Moreover, shoot-attacked trees were clearly larger and taller, had lower wood density, and were less exposed to competition than non-attacked trees. No differences were found between the characteristics of trunk-attacked trees and non-attacked ones. We found crown defoliation, lower primary growth and alteration of trunk non-structural carbon in phloem in the year following trunk attacks, although this did not affect vulnerability to cavitation of the vascular system, secondary growth, wood density, and xylem starch. Conversely, the health status and physiological variables of the shoot-attacked trees were not altered, which may be explained by their initial vigor. We conclude that the distribution of Tomicus destruens attacks at the plot level was independent of the ecophysiological traits of the host trees. It was mainly determined by the dispersal strategy of the endemic bark beetle population especially during brood production as only trunk attacks significantly weakened the trees.

Ongoing climate variability strongly affects high-elevation forests, influencing the wood formation process (e.g., xylogenesis). Furthermore, spatio-temporal studies to establish links of wood properties and tree performance are needed. Using linear mixed-effects models, empirical cumulative distribution functions, and spatial analysis, we explore time trends and space connections of wood density of Pinus hartwegii Lindl. to remotely sensed variables (Moderate Resolution Imaging Spectro-radiometer MODIS-derived) in two high-elevation forests in M&eacute, xico, Tl&aacute, loc (TLA) and Jocotitl&aacute, n (JOC) Mountains. Results indicated that elevation and cambial age effects are important factors explaining wood density variation. Minimum earlywood&mdash, MID, average&mdash, AVE, and maximum latewood density&mdash, MXD were statistically similar between mountains (p &gt, 0.05), but TLA showed a significant increase in MID over time with higher values after 1950. Wood density values and spatial correlations were site-dependent with TLA exhibiting the highest correlations between MXD and the Normalized Difference Vegetation Index (NDVI) of the spring season (r = 0.59, p &lt, 0.05). Overall, correlations to remotely sensed information were positive with MXD, negative for MID and divergent for AVE. Historical temperature defines MID along the elevation gradient, while MXD was related to soil moisture only at low-elevation sites where soils are deeper. We found that two high-elevation forests, 115 km away from each other, with similar climate, soil, and vegetation, behaved differently regarding their xylogenesis, indicating the potential of using the link between wood micro-density and remotely sensed information to understand forest response to climate change effects.

Until recently, the roles of plant MADS-box genes have mainly been characterized during inflorescence and flower differentiation. In order to precise the roles of AGAMOUS-LIKE 12, one of the few MADS-box genes preferentially expressed in roots, we placed its cDNA under the control of the double 35S CaMV promoter to produce transgenic walnut tree and Arabidopsis plants. In Juglans sp., transgenic somatic embryos showed significantly higher germination rates but abnormal development of their shoot apex prevented their conversion into plants. In addition, a wide range of developmental abnormalities corresponding to ectopic root-like structures affected the transgenic lines suggesting partial reorientations of the embryonic program toward root differentiation. In Arabidopsis, AtAGL12 overexpression lead to the production of faster growing plants presenting dramatically wider and shorter root phenotypes linked to increased meristematic cell numbers within the root apex. In the upper part of the roots, abnormal cell divisions patterns within the pericycle layer generated large ectopic cell masses that did not prevent plants to grow. Taken together, our results confirm in both species that AGL12 positively regulates root meristem cell division and promotes overall root vascular tissue formation. Genetic engineering of AGL12 expression levels could be useful to modulate root architecture and development.

International audience; In the subalpine forest ecosystems of the French Alps, European larch trees (Larix decidua Mill.) are periodically affected by outbreaks of a defoliating insect, the larch budmoth (Zeiraphera griseana (Hubner, 1799); LBM). To assess the long-term dynamics of LBM populations, we propose a spatiotemporal analysis of a long outbreak chronology reconstruction for the entire French Alps covering the period 1414-2009. This chronology was obtained by analyzing tree ring width (TRW) chronologies collected from 44 larch populations. The evidence of a latitudinal gradient in LBM is an original result that we have related to the "travelling waves" and "epicenter" theory. Wavelet analyses revealed a strong explicit continuous signal for periodicities of 4, 8, and 16 years throughout the entire 1500-2003 time series, except for a loss of power from 1690 to 1790 and since the early 1980s. We hypothesize that these abrupt changes could reflect a physiological response of LBM to past climatic variations. The spatial and temporal variability of LBM outbreaks and the propagation phenomenon in the French Alps highlighted by this study raises questions regarding its future dynamics in response to the expected climate change.; Dans les écosystèmes forestiers subalpins des Alpes françaises, le mélèze (Larix decidua Mill.) subit périodiquement les épidémies d’un insecte défoliateur, la tordeuse du mélèze (Zeiraphera griseana (Hübner, 1799); LBM). Afin de mieux comprendre les dynamiques à long terme des populations de tordeuse, nous proposons dans cet article une analyse spatio-temporelle d’une très longue reconstruction des épidémies pour la période 1414–2009 sur l’ensemble des Alpes françaises. Cette chronologie a pu être reconstruite à partir des cernes de croissance de 44 populations de mélèze. Les résultats ont permis de mettre en évidence le rôle d’un gradient latitudinal que nous avons attribué au phénomène théorique des « épicentres » et « vagues de dissémination ». D’autre part, les analyses temporelles, réalisées à l’aide de la méthode des ondelettes, ont révélé l’existence d’un fort signal continu pour des fréquences périodiques de 4, 8 et 16 ans sur l’ensemble de la chronologie à l’exception d’une perte d’énergie entre 1690 et 1790 et depuis le début des années 1980. Ces changements pourraient refléter une réponse physiologique de la tordeuse à des variations climatiques passées. La variabilité temporelle et spatiale des épidémies de tordeuse ainsi que le mode de propagation à travers les Alpes françaises nous ont conduits à nous interroger sur les dynamiques futures de l’insecte et de son hôte en réponse au réchauffement climatique rapide dans les écosystèmes de haute élévation.

Until recently, the roles of plant MADS-box genes have mainly been characterized during inflorescence and flower differentiation. In order to precise the roles of AGAMOUS-LIKE 12, one of the few MADS-box genes preferentially expressed in roots, we placed its cDNA under the control of the double 35S CaMV promoter to produce transgenic walnut tree and Arabidopsis plants. In Juglans sp., transgenic somatic embryos showed significantly higher germination rates but abnormal development of their shoot apex prevented their conversion into plants. In addition, a wide range of developmental abnormalities corresponding to ectopic root-like structures affected the transgenic lines suggesting partial reorientations of the embryonic program toward root differentiation. In Arabidopsis, AtAGL12 overexpression lead to the production of faster growing plants presenting dramatically wider and shorter root phenotypes linked to increased meristematic cell numbers within the root apex. In the upper part of the roots, abnormal cell divisions patterns within the pericycle layer generated large ectopic cell masses that did not prevent plants to grow. Taken together, our results confirm in both species that AGL12 positively regulates root meristem cell division and promotes overall root vascular tissue formation. Genetic engineering of AGL12 expression levels could be useful to modulate root architecture and development.

The ongoing climate warming affects most tree species across their biogeographic distribution range. The bottom and the top of an elevational gradient are appropriate environments to observe the effect of climate warming in contrasted temperature conditions.AimsTo retrospectively study the effect of the ongoing climate warming on Larix decidua trees located in warm and cold conditions, i.e., at the bottom (1200 m) and the top (2300 m) of an elevational gradient, respectively.MethodsDendroecological analysis of two groups of Larix decidua trees located at very low (1200 m) and very high (2300 m) elevations. Construction of climatic response curves for annual ring variables. Decomposition of the variance of the response models into their high and low frequency components.ResultsAt Briançon, in the French Alps, the increase of the daily maximum temperature during the last 50 years is already almost 3 °C for the March?October period. The results reveal contrasted behaviors at both ends of the investigated elevational gradient. Basal area increment, ring width, and their earlywood and latewood components increase or level off at the top of the gradient, while they all strongly decrease at the bottom. At the bottom, the low frequency warming effect explains the recent ring width decrease, with no influence of the high frequency temperature variation. At the top, both the low frequency warming effect and the high frequency temperature effect explain each about half of the ring width variation encompassed by the model. Latewood density displays the same trend as ring width, while earlywood density decreases at both ends of the gradient.ConclusionSuch opposed trends of the radial growth time trends between the top (2300 m) and the bottom (1200 m) of the gradient reflects the respectively favorable and unfavorable effects of climate warming at such ends of this Larix decidua elevational gradient. We propose that the strong ring width decrease observed at the warmer bottom announces a coming dieback. The corresponding wood density decrease will affect wood hydraulic properties in a way that is unclear. Fil: Rozenberg, Philippe. Institut National de la Recherche Agronomique; Francia Fil: Chauvin, Thibaud. Institut National de la Recherche Agronomique; Francia Fil: Escobar Sandoval, Margarita. Institut National de la Recherche Agronomique; Francia Fil: Huard, Frédéric. Institut National de la Recherche Agronomique; Francia Fil: Shishov, Vladimir. Siberian Federal University; Rusia Fil: Charpentier, Jean Paul. Institut National de la Recherche Agronomique; Francia Fil: Sergent, Anne Sophie. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche. Instituto de Investigaciones Forestales y Agropecuarias Bariloche. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones Forestales y Agropecuarias Bariloche; Argentina Fil: Vargas Hernandez, J. Jesus. No especifíca; Fil: Martinez Meier, Alejandro. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche. Instituto de Investigaciones Forestales y Agropecuarias Bariloche. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones Forestales y Agropecuarias Bariloche; Argentina Fil: Pâques, Luc. Institut National de la Recherche Agronomique; Francia

Until recently, the roles of plant MADS-box genes have mainly been characterized during inflorescence and flower differentiation. In order to precise the roles of AGAMOUS-LIKE 12, one of the few MADS-box genes preferentially expressed in roots, we placed its cDNA under the control of the double 35S CaMV promoter to produce transgenic walnut tree and Arabidopsis plants. In Juglans sp., transgenic somatic embryos showed significantly higher germination rates but abnormal development of their shoot apex prevented their conversion into plants. In addition, a wide range of developmental abnormalities corresponding to ectopic root-like structures affected the transgenic lines suggesting partial reorientations of the embryonic program toward root differentiation. In Arabidopsis, AtAGL12 overexpression lead to the production of faster growing plants presenting dramatically wider and shorter root phenotypes linked to increased meristematic cell numbers within the root apex. In the upper part of the roots, abnormal cell divisions patterns within the pericycle layer generated large ectopic cell masses that did not prevent plants to grow. Taken together, our results confirm in both species that AGL12 positively regulates root meristem cell division and promotes overall root vascular tissue formation. Genetic engineering of AGL12 expression levels could be useful to modulate root architecture and development.

International audience; The spatial and temporal distributions of plant hormones during tree-ring formation are beginning to be elucidated. Plant hormones play specific roles in tree-ring formation depending on the developmental zone in which they operate. Tree rings are the result of the seasonal activity of the vascular cambium, the secondary meristem of woody angiosperms and gymnosperms. During tree-ring formation, a combination of endogenous and environmental factors affects cambial division, cell differentiation and maturation; this, in turn, affects wood quantity and quality. Among the endogenous factors affecting tree-ring formation, plant hormones are recognized as determinant players in regulating many aspects of the features and fate of each xylem cell. Most of our knowledge regarding the roles of plant hormones on tree-ring formation comes from herbaceous plants, although an increasing interest involves the analysis of the hormonal patterns in tree-species. This paper reviews the state of knowledge of the role of plant hormones during tree-ring formation by focusing on experiments performed on woody species. An overview of the main plant hormones and their main activities during radial tree growth will be followed by discussion of their role in each tree-ring developmental stage and in the overall tree-ring seasonal pattern.

With the ongoing climate change, water stress is prone to become a commonplace event leading plant growth and productivity worldwilde under threat because of the disruption of their water status. Forests are highly sensitive to climate change due to the lack of sufficient knowledge related to tree adaptive responses to environmental fluctuations. Structural and physiological adaptations to drought require complex interactions between anatomy, physiology and biochemistry. Thus, long term maintenance of hydraulic integrity is crucial for survival of tree, including important forestry species that are widely distributed worldwide such as Eucalyptus camaldulensis. Xylem, the main pathway for water transport over long distances of this species, is made of solitary vessels surrounded by different imperforate tracheary elements and parenchyma that may influence in a poorly known way their xylem safety and hydraulic efficiency.

International audience; center dot Key message Spring temperature increase is the main driver of larch tree wood formation onset along a 1000-m elevation gradient in the Southern Alps, while its cessation is more probably controlled by water stress at the lowest elevation and photoperiod at higher ones. center dot Context The survival of perennial plants depends on their adaptation to changing environment and specially temperature, which in trees is notably implemented through wood formation process. center dot Aims Our main objective is to understand how the phenology of wood formation is related to environmental factors and to temperature in particular. center dot Methods We monitored the xylogenesis of 60 larch trees, distributed in four stands along an elevation gradient of 1000 m in the French Southern Alps. center dot Results Cambial activity started around mid-May at the lowest site (1350 m) and around mid-June at the highest one (2300 m), showing a delay of 5.4 days per degrees C. The onset of wall-thickening and mature phenophases followed the same linear trend with a delay of 5.2 and 3 days per degrees C, respectively. Phenophase cessations followed a parabolic trend with trees from the lowest site finishing their growth the first, while those from 1700 m finished the last. Our results show that the onset of xylem formation is mainly driven by spring temperature increase, while its cessation is more related to photoperiod, with water shortage being able to hasten it. center dot Conclusion Future climatic changes will most probably increase growing season length (but not necessarily wood production) and shift upwards the optimal elevation for larch growth in the Southern Alps.

International audience; Characterizing drought resistance of forest trees is an important aim in the worldwide context of increasing forest decline and dieback. Furthermore, wood demand is increasing all around the world, urging the need for the domestication of native species and the selection of the most resistant individuals. While near-infrared spectroscopy is now recognized as an efficient tool to predict wood physical and chemical properties involves in wood quality, its ability to predict wood hydraulic function remains anecdotic, although it has recently gained interest. In this study, we tested near-infrared spectroscopy as a high-throughput method for quantifying both resistance to cavitation and basic wood density in the South American conifer Austrocedrus chilensis. Models were obtained in two laboratories using the same sample set. To assess resistance to cavitation, vulnerability curves were obtained using the air-injection method. Basic wood density was measured in the same samples as used for resistance to cavitation. Partial least squares regression models with cross-validation were used to establish relationships between the NIRS spectra and wood traits. The accuracy of the models strongly depended on the traits being used for calibration. Models obtained in both laboratories were similar, demonstrating the genericity of the approach whatever equipment used. Promising results were obtained for two cavitation parameters (water potential at 12% and 50% of hydraulic conductivity loss) and basic wood density. Prediction errors for these traits were low. In contrast to studies at the interspecific level, basic wood density and resistance to cavitation were negatively correlated at the intraspecific level in the studied species, but our calibration models shown than basic wood density cannot be used as a good predictor of functional traits. The NIRS has high potential to be put into practice as a rapid, reliable, and non-destructive method to determine, resistance to xylem cavitation, a trait involved in drought resistance.

Key message[br/] Despite variable dynamics of genetic diversification at the different altitudinal levels, strong gene flow tends to standardize larch genetic diversity: the larch forest distributed along the altitudinal gradient can be regarded as a single population.[br/] [br/] Context[br/] While in forest tree species many studies focus on the structure of the genetic diversity at the natural range and at the forest stand levels, few studies have worked at intermediate levels like the landscape level.[br/] [br/] Aims[br/] We tried to determine to what degree altitude variation can affect the genetic diversity and the local structure of the genetic diversity of European larch (Larix decidua Miller) at the landscape level.[br/] [br/] Methods[br/] Using microsatellite markers, we determined the between- and within-plot genetic structure and the spatial genetic structure (SGS) of four altitudinal plots distributed between 1,350 and 2,300 m a.s.l. in a European larch forest located in the French Alps.[br/] [br/] Results[br/] A homogenous neutral genetic structure was detected along this gradient. The intensity of the SGS was found to be stronger at 2,300 m and decreased at the 2,000-m plot. It was low or non-existent at the 1,700- and 1,350-m altitudinal levels.[br/] [br/] Conclusion[br/] Our results suggest that the genetic structure observed at the landscape level in this European larch forest was only slightly affected by climatic variation, human activities, or historical events. However, the variation of intensity of the SGS within the altitudinal plots indicates the existence of variable genetic dynamics, despite the globally uniform genetic structure along the altitudinal gradient.

Wood density, considered a heritable trait, is often associated with drought tolerance and can be a useful trait for tree breeders to select drought-tolerant provenances. Provenance trials are a useful tool to disentangle genetic variation from plasticity of adaptive traits among populations within the same species. If wood density is a strongly heritable trait selected by climatic conditions, we hypothesize that its variation in provenance trials should be shaped by the provenance climatic variables. To test our hypothesis we collected wood density data of provenance trials from the literature. We used thirty publications published between 1966 and 2015 including 25 species (13 angiosperms and 12 gymnosperms). At the intraspecific level, eight species showed significant positive correlations between wood density and drought conditions of the provenance, two species showed the opposite trend and the remaining 15 species showed no correlation with the climatic conditions of the provenances. For the 10 species with wood density strongly linked to the climatic conditions of the provenance, such relationship reflects a strong genetic determinism and a theoretical fitness optimum. For the other 15 species, wood density does not seem to be the main selection target of drought. This information is critical in the frame of breeding programs for selecting provenances more adaptable to different climate change scenarios.

International audience; Key message Separating the internal (ontogenetic) and external (environmental) components of maritime pine development during controlled soil water deficit helps to highlight the plastic response. The adjusted measurements reveal significant differences between families for their plastic response for several physiology and growth traits. Context Soil water deficit is and will be a growing problem in some regions. Pinus pinaster Ait. is a species of commercial interest and is recognized as a drought-avoiding species. It is thus of interest to evaluate the adaptation potential of P. pinaster to soil water deficit. Aims This paper aims to estimate the plastic response to the variation of water availability at the family level (half-sibs). Methods Two-year-old P. pinaster cuttings from four families were submitted during 6 weeks to two contrasting watering regimes. The experiment started in April 2011 shortly after sprouting. The photosynthesis and stomatal conductance to water vapor were measured on 1-year-old needles. Intrinsic water-use efficiency was calculated as the ratio of photosynthesis to stomatal conductance. Radial growth, length of terminal shoot, and total height were also measured. The ontogenetic component of tree development was estimated on the well-watered trees for all the traits. Then, this development effect was eliminated from the data collected on the trees submitted to the soil water deficit in order to keep only the effect of this soil water deficit. Results After 6 weeks of reduced watering, the value of all adjusted traits decreased. An average plastic response to the variation of water availability was found to be significant and variable at the family level for the six adjusted variables. Conclusion These results suggest that there is genetic variation of phenotypic plasticity to drought in P. pinaster for several traits, including stomatal conductance, which appears to be a promising variable for future selection for resistance to drought.

International audience; Deciphering climatic factors limiting cambial activity is critical to forecast the potential of trees to respond to ongoing climatic change. We explored multiple xylem traits, including tree-ring width, inter-annual micro-density variation and intra-annual density fluctuations (IADF), to unveil the climatic factors constraining cambial activity of a Mediterranean conifer (Pinus pinaster) along a continental-aridity gradient. Secondary growth responded mainly to water availability, explaining as much as 64.7% of earlywood growth variance for earlywood growth. The continuous and non-overlapping timing of the climatic signals of earlywood and late wood growth reflected a continuous water limitation of secondary growth along the growing season. Drought also had an extraordinary impact on minimum (D-min) and maximum (D-max) density, with maximal explained variances reaching 47.4% and 39.1%, respectively. D-min was negatively associated to water availability during the initiation of earlywood formation, whereas D-max responded positively to water availability during two distinct periods: previous winter and the initiation of latewood formation. IADFs in the latewood were quite common along the gradient, occurred in 21-51% of the rings, and responded to episodes of high rainfall and elevated temperature at different phases of latewood formation. Xylem traits identity outperformed site as a driver of climatic signal, revealing the potential of a multi-proxy approach to unveil multiple facets of the xylogenetic cycle. Cambial plasticity, i.e. the ability to adjust the xylogenesis rate and to arrest and resume cambial activity to exploit favorable climatic windows, was critical for Pinus pinaster to thrive within wide climatic envelopes. Nevertheless, the pervasive effect of water availability on all analyzed traits indicates that forthcoming reduced precipitation and increased evapotranspiration, as predicted by climate change models, will negatively impact P. pinaster secondary growth along its whole environmental range.

International audience; The correlation between tree ring width and density and short-term climate fluctuations may be a useful tool for predicting response of wood formation process to long-term climate change. This study examined these correlations for different radiata pine genotypes and aimed at detecting potential genotype by climate interactions. Four data sets comprising ring width and density of half- and full-sib radiata pine families were used. Correlations with climate variables were examined, after the extraction of the effect of cambial age. Cambial age explained the highest proportion of the ring to ring variation in all variables. Calendar year and year by family interaction explained a smaller but significant proportion of the variation. Rainfall had a positive correlation with ring width and, depending on test site, either a negative or positive correlation with ring density. Correlations between temperature during growing season and ring density were generally negative. Climate variables that influence ring width and wood density can be identified from ring profiles, after removing the cambial age effect. Families can be selected that consistently show desirable response to climate features expected to become prevalent as a result of climate change.

A central issue in plant evolutionary ecology is to understand how several coordinated suites of traits (i.e. traits syndrome) may be jointly selected within a single species. This study aims to describe patterns of variation and co-variation of functional traits in a water-stressed tree population and test their relationships with performance traits. Within a Mediterranean population of Fagus sylvatica experiencing recurrent summer droughts, we investigated the phenotypic variation of leaf unfolding phenology, leaf area (LA), leaf mass per area (LMA), leaf water content (LWC), water use efficiency (WUE) estimated by carbon isotopic discrimination (d13C), twig Huber- value (HV: the stem cross-section divided by the leaf area distal to the stem), wood density (WDens), and leaf nitrogen content (Nmass). First, a principal component analysis revealed that two main axes structured the phenotypic variability: the first axis opposed leaf unfolding earliness and LWC to LMA and WUE; the second axis opposed LA to HV. These two axes can be interpreted as the opposition of two strategies (water economy versus water uptake) at two distinct scales (leaf for the first axis and branches for the second axis). Second, we found that LMA, LA, leaf unfolding and LWC responded differently to competition intensity, while WUE, WDens and HV did not correlate with competition. Third, we found that all studied functional traits were related to growth and/or reproductive performance traits and that these relationships were frequently non-linear, showing strong interactions between traits. By highlighting phenotypic clustering of functional traits involved in response to water stress and by evidencing antagonistic selection favouring intermediate trait values as well as trait combinations, our study brought new insights on how natural selection operates on plant functional traits in a stressful environment.

International audience; Genetic variability of modulus of elasticity (MOE) was investigated in three genetic trials, including two progeny (16 years old) and one clonal (19 years old) trials of hybrid larch (Larix x eurolepis Henry). MOE was directly assessed on standing trees using the Rigidimeter, a bending device, and related to other traits including height, BH diameter and wood density. Mean MOE ranged from 5,183 to 9,228 MPa among families in the progeny trials and from 4,591 to 11,486 MPa in the clonal trial. Among traits studied, MOE was one of the most variable traits. It was strongly and positively related to wood density at both the individual and genotype mean levels. Interestingly too, wood stiffness did not seem, or only weakly, unfavourably linked to stem diameter at the phenotypical level, but it was negatively or not correlated to diameter at the genetic level. As well, MOE showed a high GxE stability over the two progeny trial sites. Narrow-sense heritabilities for MOE were moderate (around 0.36). In all three trials, they were lower than those for wood density or total height, and of the same level as for diameter. Improvement of wood stiffness of hybrid larch using the Rigidimeter seems possible and promising genetic gains are expected. Impacts of selection for growth traits on MOE are also discussed.

Microdensity profiles of Douglas-fir's clones and weather data were used to study phenotypic plasticity (dendroplasticity). Within-ring microdensity was interpreted as the variation of tree response to drought constraints during selected growing seasons. An original norm of reaction was obtained by pairing evident points of abrupt changes in tree-ring microdensity profiles and in weather indices. The coefficients of the non-linear models adjusted to the reaction norms were analysed as dendroplasticity variables. Dendroplasticity variables were significantly different between geographical locations, years and clones. Heritability of the dendroplasticity variables ranged from low to high and was similar to heritability values of microdensity variables such as mean ring density (MRD). Coefficients of genetic variation of dendroplasticity variables were intermediate between those of wood density and growth variables. Dendroplasticity variables were phenotypically and genetically related to ring microdensity variables, more strongly to latewood variables. Dendroplasticity provides retrospective, synthetic and easy-to-interpret information about tree response to the variation of the balance between water availability and water demand during the growing season. The proposed model of dendroplasticity is described by a number of parameters that are linked to a biological meaning. Our results suggest that there is a potential for adaptation to drought in Douglas-fir, with two mechanisms involved: at individual level, short-term plastic response during the growing season and, at population level, long-term, between-generation, evolution process.

In this work, we present a fast and promising method to evaluate the natural durability of wood based on X-ray microdensitometry. Tested on beech and Scots pine wood samples, our findings show that this methodology and the traditional EN standards methodology based on mass loss are strongly correlated. X-ray methodology is less time consuming (we can detect the effectiveness of the attack within 5-6 weeks) and less expensive (very cheap plastic Petri dishes instead of the expensive glass Kolle flasks); moreover, the proposed method allows to thoroughly examine the phases and the kinetics of the fungal attack, and to investigate the spatial repartition of the attack within the samples due to the low thickness of the sample.

National audience; Présentation d'un partie de la thèse de Maude Toigo portant sur l'étude de la densité et de la largeur de cerne de 108 chênes sessile et pin sylvestre en forêt d'Orléans

National audience

International audience; Wood can be seen as a record of cambial activity. Within a ring, density variation from earlywood to latewood is a consequence of the within growing season climate changes. We propose a method to synchronize the within-ring density profile with within-growing season climate variables. Thanks to this synchronization, we show that Douglas-fir cambium reaction to the variation of the withingrowing season minimum temperature is variable and quite strongly genetically controlled. Such variation has a direct consequence on wood density, and thus on wood quality.

International audience; Genetic parameters were estimated for wood and growth traits in two 19-yr-old clonal trials and a 40-yr-old full-sib progeny trial of Norway spruce [Picea abies (L.) Karst.]. In the clonal trials high (>0.4) broad-sense heritabilities were found for wood density traits, lignin content, number of internal cracks, growth traits, spiral grain and number of resin canals. Moderate (0.2-0.4) heritabilities were found for tracheid lumen diameter and cell wall thickness, microfibril angle and tracheid length, while low heritabilities (

The sampling design was based on the OPTMix experimental plots (Irstea Nogent-sur-Vernisson, France); OPTMix provided a part of the soil and dendrometric data as well. We thank Deki Fourcin, Sebastien Mace, Vincent Seigner and Yann Dumas for their help with data collection. We thank Frederic Miller from the INRA Orleans, Pierre Gelhaye and Frederic Mothe from the INRA Champenoux, and Frederic Lagane from the INRA Bordeaux for their help with sample preparations and microdensitometer analyses. We are thankful to Victoria Moore for correcting the English.; Mixing species has been proposed as a forest management option to mitigate the effects of the increase in summer drought episodes predicted by climate change models in temperate zones. Studying how the relationship between tree rings and summer drought episodes is modified by species mixture is of primary importance in this context. Based on a dendroclimatology study, we (i) qualified and quantified the relationship between ring width (RW) or mean ring density (MRD) and soil water deficit (SWD) in a ring-porous species, Quercus petraea, and a coniferous species, Pinus sylvestris, and (ii) determined if the relationships between tree ring characteristics and SWD are modified in mixtures. We found interspecific differences in RW patterns depending on the seasonality of the drought periods: RW in Q. petraea responded mainly to SWD from May to July, and RW in P. sylvestris to SWD from May to September. The ring-width of both species was strongly reduced by SWD; however, inter-specific differences in response to SWD seasonality triggered RW variations of opposite directions between the two species, for several years. In contrast, MRD for both species was dependent on the SWD from June to July. MRD in Q petraea increased slightly with SWD whereas MRD in P. sylvestris decreased strongly with SWD. The relationship between RW and SWD was not modified in mixtures compared to pure stands. We found that the effect of SWD on MRD was stronger in mixtures. The impact of SWD on species may be worsened in mixtures, but mixture of species with different growth sensitivities to the seasonality of the drought periods and to the drought intensity might help to buffer the effects of climatic fluctuations on the overall mixed stands productivity compared to pure stands. (C) 2015 Elsevier B.V. All rights reserved.

•We performed microdensity profiles in trees for which sapflow density data were available.•We studied the relationship between wood and sapflow density in these trees, growing in two different silvicultural treatments.•High wood density was found in the high-density stand for the first part of the tree-ring.•Lower sapflow density was found in trees from the high-density stand even when soil water availability was high.•We discuss the implications of our findings in the framework of ponderosa coordinated mechanism to cope drought.Abstract: Climate and stands management have an effect on the process of wood formation via resource availability. To improve knowledge of wood quantity and physical structure, increment cores of ponderosa pine were taken in high- and low-density stands growing in Patagonia, Argentina. Microdensity profiles were performed on trees for which sapflow density (Qs) data were available over two consecutive years (2004 and 2005, dry and wet years, respectively). Conventional and non-conventional microdensity variables were analyzed in the segment of the microdensity profile where Qs was measured. Trees in the low-density stand showed a greater capacity for water transport than trees in the high-density stand, even if no constraints in the soil water availability were confirmed, as was the case for the wet year. Minimum and earlywood density were significantly higher in the high-density stand in several analyzed years. These differences were not reflected in mean density of the whole radial profile. The structural changes in physical wood properties in relation to silvicultural treatments appear to affect plant water status, even in the wet growing season: greater wood density in the first part of the tree-ring may contribute to the observed Qs decrease found in the high-density stand. This fact may lead trees to lack the coordinated mechanisms of response to drought observed in more xeric sites. The increase of wood density in the first part of the tree-ring in ponderosa pine could be not conducive to acclimation, exposing trees to an increasing “dilemma” facing drought.

Classical quantitative genetics and quantitative trait dissection analysis (QTL) approaches were used in order to investigate the genetic determinism of wood cellulose carbon isotope composition (δ 13 C, a time integrated estimate of water use efficiency) and of diameter growth and their relationship on adult trees (15 years) of a forest tree species (maritime pine). A half diallel experimental set-up was used to (1) estimate heritabilities for δ 13 C and ring width and (2) to decompose the phenotypic δ 13 C/growth correlation into its genetic and environmental components. Considerable variation was found for δ 13 C (range of over 3%‰) and for ring width (range of over 5 mm) and significant heritabilities (narrow sense 0.17/0.19 for δ 13 C and ring width, respectively, 100% additivity). The significant phenotypic correlation between δ 13 C and ring width was not determined by the genetic component, but was attributable to environmental components. Using a genetic linkage map of a full-sib family, four significant and four suggestive QTLs were detected for δ 13 C, the first for δ 13 C in a forest tree species, as far as known to the authors. Two significant and four suggestive QTLs were found for ring width. No co-location of QTLs was found between δ 13 C and growth.

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.

The objective of this work wa s to investigate the dynamics of embolism formation within a Douglas fir tree ring . Four resistant and four vulnerable 10 year old trees were selected among 50 trees, based on their P 50 . Stem s amples , taken next to those used to obtain the vulnerability to cavitation curves, were collected and submitted to increasing positive pressures, in order to simulate increasing tension caused by water stress in the xylem . Then the conductive surface of the samples was stained and s canned and the images were analyzed. X ray microdensity profiles were obtained on the same samples. The microdensity profiles of the 2011 ring were analyzed in three parts, earlywood, transition w ood and latewood. The dynamics of embolism propagation was observed separately in these three parts. O ur results showed that the initiation and the propagation of the cavitation follow a discrete trend, with at least two successive initiation events: first cavitation initiate s and propagate s rapidly in the latewood . Then, a second cavitation event begin s and spread s in the earlywood and eventually propagates to the transition wood, which remains the last conductive part in the ring before full embolism. W e observed that resistant to cavitation trees showed lower transition wood density than vulnerable to cavitation trees. Estación Experimental Agropecuaria Bariloche Fil: Dalla Salda, Guillermina. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche. Área de Recursos Forestales. Grupo de Ecología Forestal; Argentina Fil: Fernandez, Maria Elena. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce. Agencia de Extensión Rural Tandil. Consejo Nacional de Investigaciones Cientificas y Técnicas; Argentina Fil: Sergent, Anne Sophie. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Instituto de Investigaciones Forestales y Agropecuarias Bariloche; Argentina Fil: Rozenberg, Philippe. INRA. Biologie intégrée pour la valorisation de la diversité des arbres et de la forêt; Francia Fil: Badel, Eric. INRA. Biologie intégrée pour la valorisation de la diversité des arbres et de la forêt; Francia Fil: Martinez Meier, Alejandro. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche. Área de Recursos Forestales. Grupo de Ecología Forestal; Argentina

* Context[br/] Since the 2003 drought and heat wave, there have been many reports of Douglas-fir decline and dieback in France. Given the climate change that is predicted, more frequent drought episodes could induce recurrent decline processes. The nature and background of this threat requires a careful assessment.[br/] * Aims[br/] The objectives of this study were: (1) to test the hypothesis that the major climate hazard that accounts for the decline in Douglas-fir growth is drought, and (2) to identify the main vulnerability factors involved.[br/] * Methods[br/] Decline and recovery of radial growth were quantified of Douglas-fir in two particularly affected regions with a dendroecological approach; 899 trees were sampled on 58 plots. Mean climate data, ecological and dendrometric stand characteristics were tested in order to identify potential vulnerability factors[br/] * Results[br/] A clear relationship was evidenced between growth and soil water deficit. A severe decline of radial growth was induced by the 2003 drought and was maintained during subsequent years due to recurrent drought episodes. Growth recovery at the stand level was enhanced by soil nutrient fertility.[br/] * Conclusion[br/] Radial growth of Douglas-fir is clearly driven by the intensity of drought. In a context of climate change, an adaptive silvicultural strategy is required in order to cope with more frequent drought events. To mitigate the frequency and the intensity of water shortage episodes, site selection must take into account not only local climate characteristic but also soil properties like maximum extractable water content. Soil nitrogen fertility was found to play a key role for an efficient recovery of radial growth after drought episodes and thus must be preserved.

Fairly strong positive relationships between stiffness and density have often been reported. No stronger relationships have been found when using parameters of density profiles based on an earlywood-latewood boundary. In this study, we attempt to model the relationships among the stiffness of different samples and simple parameters derived from microdensity profiles, not established according to an earlywood-latewood boundary. Furthermore, we try to determine if there is a genetic variation for the relationship between stiffness and density. From the results, we find that the strongest relationship between a single density parameter and stiff- ness is r0.78, whereas it is r = 0.37 when involving a classical within-ring density parameter. At clone level, r 2 ranges from 0.88 to 0.95, while it is 0.51 for the bulked samples. The mathematical form of the models differ from one clone to another: there is a

Context: Since the 2003 drought and heat wave, Douglas-fir dieback has been reported in France in trees older than 30 years. Consequently, it is questioned whether selected Douglas-fir provenances are suited to the frequent and severe drought events which are forecast due to climate change. Aims: Our objective was to contribute to the screening of variability in productivity and growth response to soil-water deficit of mature trees from provenances not currently used for plantation in France. Methods: We sampled 22 provenances, including coastal and interior Douglas-fir, covering a wide part of its natural distribution, from Oregon to California for coastal provenances and from British Columbia to New Mexico for interior provenances. These provenances were planted at the mid 1970s in two provenance trials located in the south-west area of France. Variability of productivity, of wood density, and of radial growth in response to drought episodes among provenances was quantified and related to soil-water deficit computed by daily water balance calculations. Results: Whatever the provenance, annual radial growth is highly dependent on local soil-water deficit (Felines R 2 = 0.57, Le Treps R2 = 0.49). Radial growth and wood properties exhibit large differences between provenances at 30 years old. Variability between provenances for all wood characteristics studied is mainly structured geographically. Coastal provenances perform best for productivity at 30 years old (619 cm2 ± 59), and exhibit a small growth reduction in 2004, the second successive year of drought (−10.7 % ± 3.8). Surprisingly, the southern interior provenances from the driest environments in the natural range show a large growth reduction in 2004 (−30.5 % ± 5.2). Conclusions: The provenances tested exhibited significant differences in growth performance and growth reduction induced by the soil-water deficit. The approach coupling retrospective analysis of radial growth on mature trees and water balance modelling is relevant for evaluating provenance adaptation to more frequent or severe drought episodes. Fil: Sergent, Anne Sophie. Institut National de la Recherche Agronomique; Francia Fil: Bréda, Nathalie. Institut National de la Recherche Agronomique; Francia. Université de Lorraine; Francia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Sanchez, Leopoldo. Institut National de la Recherche Agronomique; Francia Fil: Bastien, Jean Charles. Institut National de la Recherche Agronomique; Francia Fil: Rozenberg, Philippe. Institut National de la Recherche Agronomique; Francia

Trees-Struct. Funct.ISI Document Delivery No.: AP9SQTimes Cited: 0Cited Reference Count: 52Diaz Britez, Manuela Ruiz Sergent, Anne-Sophie Martinez Meier, Alejandro Breda, Nathalie Rozenberg, PhilippeNational Research Agency (DRYADE project) [ANR-06-VULN-004]; Centre region Research Project Xylome [2009 0003 8263]; Regional Council of Burgundy region; Regional Council of Centre region, France; Parque Tecnologico Misiones; Universidad Nacional de Misiones, ArgentinaWe gratefully thank F. Geremia, Y. Lefevre, N. Metral, P. Behr, T. Paul and B. Issenut for their technical assistance during field data collection and F. Millier for fieldwork and laboratory measurements. The fieldwork was possible thanks to the help of agents from CRPF in the Midi-Pyrenees and Burgundy regions. We thank L. Sanchez and S. Marin for discussions during the preliminary steps of the study. We also thank all public and private forest owners for allowing tree coring. The research was funded by the National Research Agency (DRYADE project, ANR-06-VULN-004), the Centre region Research Project Xylome no 2009 0003 8263 and the Regional Council of Burgundy region. A.S. Sergent received a PhD grant from the Regional Council of Centre region, France, M. Ruiz-Diaz received fundings from the Parque Tecnologico Misiones and the Universidad Nacional de Misiones, Argentina.SpringerNew york; Proxies of adaptive traits for resistance to drought were discovered among original annual ring density variables in Douglas fir. A comparison of dead and surviving Douglas fir trees following the 2003 drought was made to define proxies of adaptive traits for resistance to drought. Increment cores were sampled from trees from three French regions: Centre, Midi-Pyr,n,es and Burgundy. Original tree-ring variables were calculated, based on a sliding density criterion dividing the microdensity profile into high- and low-density segments. Tree rings were analysed at each site in a number of consecutive annual rings before the 2003 drought event. Comparison between pairs of surviving and dead trees and between pairs of randomly selected trees (whether dead or alive) supports the evidence of systematic dissimilarities between surviving and dead trees in a number of original density variables. Correlation analysis between original and conventional ring density variables indicates a weak association. We found that the surviving trees were denser than the dead trees in all three sites, but that the denser part of the ring varied from region to region. We identified several original density variables intended to be used as proxies of adaptive traits in future studies of genetic determinism of Douglas fir resistance to drought.

For a number of years in certain regions of France the Douglas-fir trees (Pseudotsuga menziesii [Mirb.] Franco) have presented symptoms of withering which have been attributed to drought. Our results show that the hydraulic function of the wood plays a part in the resistance of the Douglas-fir to dry conditions. Narrower cellular conduits, and therefore a greater wood density, contribute to the survival of trees confronted with a period of a marked water deficit. This idea is confirmed by the existence of significant relationships between wood density and hydraulic properties of wood in which the raw sap circulates, and also by the relationships found between the ecological preferences of specimens in their area of origin and the density of their wood in regions of France where they have been introduced. Those coming from dry regions have a tendency to develop wood with characteristics similar to that of trees which have survived drought. While the relationship between wood density and survival has been demonstrated, the differences in the nature of this relationship between different sites show that the mechanisms involved are complex and to a large extent still not understood. Le douglas (Pseudotsuga menziesii [Mirb.] Franco) présente depuis quelques années dans certaines régions de France des symptômes de dépérissement que nous attribuons à la sécheresse. Nos résultats montrent que le fonctionnement hydraulique du bois joue un rôle dans la résistance du douglas à la sécheresse: des conduits cellulaires plus étroits, c'est-à-dire une densité plus élevée, favoriseraient la survie d'arbres confrontés à un épisode de déficit en eau marqué. Cette idée est renforcée par l'existence de relations significatives entre densité du bois et propriétés hydrauliques du bois dans lequel circule la sève brute, et par les relations trouvées entre préférences écologiques de provenances dans leur aire d'origine et densité de leur bois dans les régions d'introduction en France: les provenances issues de régions sèches ont tendance à développer un bois possédant des caractéristiques proches de celles des survivants à la sécheresse. Si la relation densité du bois–survie a bien été mise en évidence, des différences entre sites dans la nature de cette relation montrent que les mécanismes impliqués sont complexes et encore largement incompris. Seit einigen Jahren zeigt die Douglasie (Pseudotsuga menziesii [Mirb.] Franco) in verschiedenen Regionen Frankreichs Absterbeerscheinungen, die wir der Trockenheit zuschreiben. Unsere Untersuchungen belegen, dass das Leitsystem des Holzes bei der Resistenz der Douglasie gegenüber Trockenheit eine Rolle spielt: Engere Gefässe, d.h. eine höhere Holzdichte, würden das Überleben der Bäume in Perioden mit ausgeprägtem Wassermangel begünstigen. Diese Idee wird durch signifikante Zusammenhänge zwischen der Holzdichte und den hydraulischen Eigenschaften des Splintholzes sowie durch die gefundenen Beziehungen zwischen den ökologischen Vorlieben der Provenienzen in ihrer Herkunftsregion und der Dichte ihres Holzes in den Regionen Frankreichs, in denen sie eingebracht wurden, belegt: Herkünfte aus trockenen Regionen haben die Tendenz, ein Holz zu entwickeln, das ähnliche Eigenschaften zeigt wie dasjenige von Bäumen, die Trockenperioden überlebten. Die Beziehung Holzdichte–Überleben konnte zwar klar herausgestellt werden, jedoch zeigen die Unterschiede zwischen den Standorten, dass die Wirkungsmechanismen komplex sind und grösstenteils noch nicht verstanden werden. Estación Experimental Agropecuaria Bariloche Fil: Rozenberg, Philippe. INRA. Biologie intégrée pour la valorisation de la diversité des arbres et de la forêt; Francia Fil: Sergent, Anne Sophie. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Instituto de Investigaciones Forestales y Agropecuarias Bariloche; Argentina Fil: Dalla Salda, Guillermina. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche. Área de Recursos Forestales. Grupo de Ecología Forestal; Argentina Fil: Martinez Meier, Alejandro. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche. Área de Recursos Forestales. Grupo de Ecología Forestal; Argentina Fil: Marin, Sara. INRA. Biologie intégrée pour la valorisation de la diversité des arbres et de la forêt; Francia Fil: Ruiz Diaz, Manuela. INRA. Biologie intégrée pour la valorisation de la diversité des arbres et de la forêt; Francia Fil: Bastien, Jean-Charles. INRA. Biologie intégrée pour la valorisation de la diversité des arbres et de la forêt; Francia Fil: Sanchez, Leopoldo. INRA. Biologie intégrée pour la valorisation de la diversité des arbres et de la forêt; Francia Fil: Bréda, Nathalie. INRA. Biologie intégrée pour la valorisation de la diversité des arbres et de la forêt; Francia

International audience; Introduction Relationships between wood density and hydraulic efficiency and safety (hydraulic specific conductivity and vulnerability to cavitation, respectively) could clarify the physiological process explaining the impact of density on fitness. We have used new, relatively high-throughput phenotyping methods to estimate genetic variation of wood hydraulic specific conductivity (k (s)) and vulnerability to cavitation (VC) as an important step toward demonstrating the adaptive value of wood density. Objective The first aim of this study is to test if, in Douglas-fir, there is a relationship between wood hydraulic properties (k (s) and VC) and wood density. The second objective is to estimate genetic variation of wood k (s) and VC. These results could aid understanding of the role of wood density in the hydraulic properties of xylem and may clarify the role of wood density in adaptation to drought. Results Many significant relationships were found between wood density and wood hydraulic properties at clone and tree level, as well as significant genetic variation for k (s) and VC. We have also found positive correlations between tree height, specific conductivity and vulnerability to cavitation, but no relation was found between radial growth and hydraulic variables. Conclusions Our results suggest that wood density has an adaptive value and that microdensity can be used to study adaptation to drought in Douglas-fir. The novel methods used to measure k (s) and VC proved to be interesting alternatives for localized measurement of wood hydraulic properties and were compatible with a robust estimation of genetic variation.

International audience; • Context : Teak (Tectona grandis L.f.) is a tropical timber which is appreciated worldwide and has been planted into many regions of the tropics. It is essential to obtain information about provenance variation of basic wood properties in order to preserve the wood quality of end-products derived from future plantations. Figuring is one of the wood characteristics valued for panelling and furniture and it is an important parameter to evaluate the quality of teak wood. The ring structure affects within-ring and between-ring colour variation and, therefore, the figure of wood and the related aesthetical aspects. • Methods : By means of microdensity profiles, we constructed a segmented linear model that depicts the anatomical structure of the rings. It effectively distinguished ring porous and diffuse porous rings, leading to the development of an efficient ring porosity index, further used to study the provenance variation of the ring structure. • Results : A significant provenance effect was detected for both wood density variables and ring anatomical structure. Although no correlation was detected between the ring structure and the precipitation level at the provenance origin, the two provenances from very wet climates were distinguished by low values of ring porosity index (diffuse porous ring). • Conclusion : The progenies in our study, collected from origins with various climates, planted in a new climate, seem to maintain to some extent the wood characteristics typical of their mother trees, suggesting that these ring characteristics may be inherited.

Background Eucalyptus is an important genus in industrial plantations throughout the world and is grown for use as timber, pulp, paper and charcoal. Several breeding programmes have been launched worldwide to concomitantly improve growth performance and wood properties (WPs). In this study, an interspecific cross between Eucalyptus urophylla and E. grandis was used to identify major genomic regions (Quantitative Trait Loci, QTL) controlling the variability of WPs. Results Linkage maps were generated for both parent species. A total of 117 QTLs were detected for a series of wood and end-use related traits, including chemical, technological, physical, mechanical and anatomical properties. The QTLs were mainly clustered into five linkage groups. In terms of distribution of QTL effects, our result agrees with the typical L-shape reported in most QTL studies, i.e. most WP QTLs had limited effects and only a few (13) had major effects (phenotypic variance explained > 15%). The co-locations of QTLs for different WPs as well as QTLs and candidate genes are discussed in terms of phenotypic correlations between traits, and of the function of the candidate genes. The major wood property QTL harbours a gene encoding a Cinnamoyl CoA reductase (CCR), a structural enzyme of the monolignol-specific biosynthesis pathway. Conclusions Given the number of traits analysed, this study provides a comprehensive understanding of the genetic architecture of wood properties in this Eucalyptus full-sib pedigree. At the dawn of Eucalyptus genome sequence, it will provide a framework to identify the nature of genes underlying these important quantitative traits.

• Direct assessment of modulus of elasticity (MOE) on standing trees is attractive for breeders to evaluate genotypes prior to selection: this can be done using the Rigidimeter, a bending-based measurement device. • In this study, we tested its reliability to properly rank genotypes by relating trunk MOE with MOEs estimated with a vibrating analysis system (Bing) on different types of conditioned wood specimens from the same trees (boards and standardised 2$\times$2$\times$30 cm-clear-wood specimens). One hundred and ten trees from different genotypes of hybrid larch (Larix x eurolepis) were tested. • Mean trunk MOE was 7 300 MPa with a similar value obtained for sawn boards. Clear-wood specimens MOE increased from pith to bark from less than 6 000 MPa to nearly 9 000 MPa. Moderate correlations (r = 0.48-0.61) were found at the individual tree level between trunk MOE and MOE of wood samples. • Single specimen MOE was shown to be strongly related to a linear combination of trunk MOE and sample position. • At the genotype mean level, trunk MOE was highly correlated with wood samples MOE (r = 0.80-0.91). Ranking of genotypes based on trunk MOE was mostly consistent with that based on standardised specimens. • It was concluded that besides other operational advantages which are discussed, the Rigidimeter is a valuable tool for breeders to routinely evaluate and rank genotypes for stiffness prior to further selection., • L'évaluation directe du module d'élasticité (MOE) sur arbre debout intéresse les améliorateurs pour l'évaluation de la valeur des génotypes avant sélection : le Rigidimètre permet cette mesure sur arbre debout grâce à une mesure de la déviation du tronc sous l'effet d'une contrainte connue. • Dans cette étude, nous avons testé sa fiabilité en comparant ce module avec celui obtenu sur divers échantillons de bois séchés, grâce à un système d'analyse vibratoire (Bing). Cent dix arbres, issus d'un test de descendances de mélèze hybride (Larix x eurolepis), ont été analysés. Les pièces de bois comprenaient pour chaque arbre : (i) une planche centrale brute (4 cm d'épaisseur et 80 cm de longueur) tirée du billon de pied, (ii) la même planche délignée, et (iii) des éprouvettes standardisées (2$\times$2$\times$30 cm). • Le module de tronc sur pied atteignait en moyenne 7 300 MPa (2 180–12 174 MPa) avec une amplitude au niveau familial de 5 052 MPa à 8 948 MPa. Le MOE des planches était légèrement plus faible (7 256–7 182 MPa). Celui des éprouvettes normalisées variait de moins de 6 000 MPa au niveau de la moëlle à 9 000 MPa vers l'écorce. Des corrélations modérées (0,48–0,61) ont été trouvées au niveau individuel entre MOE sur arbre debout et MOE des échantillons de bois. • Cependant, il semble possible d'estimer le module des éprouvettes normalisées à partir entre autre du module des arbres sur pied et de la position de l'échantillon dans l'arbre. • Au niveau génotypique, le module de tronc était très fortement corrélé aux MOE des échantillons (0,80–0,91) et le classement des génotypes est apparu fiable. • Outre ses autres avantages (e.g. mise en place rapide, évaluation non destructive), le Rigidimètre est donc un outil bien adapté aux besoins des améliorateurs pour évaluer et classer leurs génotypes pour leur rigidité.

Drought response of three Douglas-fir clones (slow, intermediate and fast growing) inhabiting two different climatic regimes in France was examined. We used the hydraulic conductivity and the percent loss of conductivity due to embolism from stems and branches as well as wood microdensity measurements to determine the role of genetics in the control of embolism in this species. Conductivity and tree-ring's microdensity variables (ring width: RW, mean ring density: MRD, minimum ring density: MID and maximum ring density: MAD) were compared in growth rings in all three clones during a typical year (2002) vs. an extremely dry year (2003). A new method was developed in order to assess axial hydraulic specific conductivity (Ks) within tree rings. The results show that branches are more resistant to embolism than stems, and that there are significant differences in embolism resistance among the clones between the two sites. Ks varied between years, sites and clones but the site exerted the most significant effect. Lartimache (more humid site during 2003) trees showed substantially higher Ks than those inhabiting Chassenoix (strongly affected by the 2003 heat and drought wave site). Wood analysis showed a significant year effect for all ring variables and a significant clone effect for all ring variables except for MAD, while the site effect was significant for MRD and MAD. The existence of a genetic control for the study traits indicates that Douglas-fir populations introduced in France may have a selection potential to face extreme climate events like the 2003 heat and drought wave.

The genetic control of tree ring growth in Douglas-fir in response to the drought and heat-wave that occurred in 2003 in Europe was studied with microdensity profiles in three clonal experiments located in three different French regions. The drought and heat-wave significantly affected Douglas-fir wood formation. The Chassenoix site (Northeast of Massif-Central) was more severely affected that the other two: the 2003 year-ring was narrower and less dense than in the other sites and than the previous (2002) and following (2004) year-rings in the same site: ring growth stopped earlier and latewood did not develop completely. The year-rings 2004 and 2002 were very similar in this site. There was a significant genetic control for all ring parameters in the three sites and during the three years. The heritability was highly variable between years and among sites, without any clear pattern in this variability, except in Chassenoix where it was slightly lower in the 2003 year-ring. Variables measuring the response of trees to the 2003 event, i.e., the difference in ring width between 2002 and 2003, or between 2003 and 2004, showed a very variable degree of genetic control, from very low to relatively high. Douglas-fir seemed plastic enough to acclimate to the drought and heat-wave and then to recover during 2004. Furthermore the level of heritability estimated demonstrates that Douglas-fir has an adaptive potential that could be useful for multi-generation long-term response., La réponse du douglas à la canicule de 2003 en France a été étudiée à l'aide de profils microdensitométriques obtenus sur des arbres de 3 tests clonaux situés dans 3 régions différentes. La canicule a significativement affecté la formation du bois du douglas. Les arbres du site de Chassenoix, situé dans le Morvan, ont réagi plus fortement que ceux des 2 autres : le cerne de l'année de la canicule est plus étroit et moins dense que le même cerne dans les 2 autres sites et plus étroit et moins dense que les cernes immédiatement antérieur (2002) et postérieur (2004) dans le même site ; la formation du bois s'est arrêtée plus tôt et le bois final ne s'est pas complètement développé. À Chassenoix, le cerne de l'année 2004 ressemble plus au cerne 2002 qu'au cerne 2003, ce qui traduit une récupération. Nous mettons en évidence un contrôle génétique significatif pour toutes les variables intra-cernes dans les 3 sites, pour les 3 années 2002, 2003 et 2004. Les héritabilités sont très variables entre caractères, sites et années, sans structure particulière, sauf à Chassenoix où ces héritabilités sont légèrement plus faibles durant l'année de la canicule. Des variables décrivant la réponse des arbres entre 2002 et 2003 puis 2003 et 2004 sont très irrégulièrement contrôlées génétiquement, avec des héritabilités allant de 0 à près de 0,5. Le douglas semble avoir été suffisamment plastique pour s'acclimater à la sécheresse et canicule puis pour récupérer en 2004 une croissance proche de celle de 2002. De plus, son potentiel génétique démontré par le niveau d'héritabilité estimé lui donne également une capacité adaptative multi-génération à plus long terme.

International audience; Growth and form are the two main traits used for genetic improvement of maritime pine (Pinus pinaster Ait.) in the southwest of France. In this paper, wood density is studied to answer two main questions: Is there a general trend for density variability throughout tree development and has selection indirectly reduced wood density variability over breeding populations, owing to genetic unfavourable correlation with growth? Wood density and its components were studied in three polycross tests, each representative of one of the successive breeding populations. Wood density was measured with an X-ray densitometer in approximately 50 families per test with >1900 trees. A preliminary study showed that bark-to-pith ring indexing allows for a better estimation of genetic effects than does pith-to-bark indexing. Genetic variability of wood density appears to be highly dependent on the year considered and no general pattern can be detected over time. Whereas the variability of selected traits is known to have decreased over breeding populations, no significant change was found for variability of wood density.; La croissance et la rectitude sont les deux principaux critères utilisés pour l’amélioration génétique du Pin maritime (Pinus pinaster Ait.) dans le sud-ouest de la France. Dans cet article, la densité du bois a été étudiée pour répondre à deux questions principales : La variabilité de la densité du bois montre-t-elle une tendance générale au cours du développement de l’arbre et la variabilité de la densité a-t-elle été modifiée indirectement par la sélection en raison d’une corrélation défavorable entre la densité du bois et la croissance ? La densité du bois et ses composantes ont été analysées dans trois tests polycross représentant les populations d’amélioration successives. Au total environ 50 familles par test, soit plus de 1900 arbres, ont été mesurées par microdensitométrie. Une étude préliminaire a permis de montrer que l’annotation des cernes de l’écorce vers le cœur de l’arbre permet une meilleure estimation des effets génétiques par rapport à une annotation du cœur de l’arbre vers l’écorce. La variabilité génétique de la densité du bois apparaît fortement dépendante de l’année considérée mais notre étude ne révèle aucune tendance générale au cours des années. De plus, alors que la variabilité génétique des caractères sélectionnés a diminué au cours des populations d’amélioration, aucune évolution significative n’a été mise en évidence pour la variabilité de la densité du bois.