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Two newly discovered species of fungi in the genus Corinectria, referred to as Corinectria sp. X and Corinectria sp. Y was found in Central Siberia in 2006 and sequenced 2020. This thesis aims to broaden the knowledge of the host range of these species in inoculation tests done on cuttings and saplings of Abies alba. The two new species are thought to be vectored by the bark beetle Polygraphus proximus. Their close relative Corinectria fuckeliana is a common wound inhabiting fungi on Picea abies in northern Europe but is known to infect a wide range of hosts. The inoculation test on saplings gave a positive result for pathogenicity on A. alba and re-isolation of fungi was somewhat successful, barely completing Koch’s postulate. An eventual outbreak of the two Corinectria spp. on A. alba in Europe is most likely going to happen in association with P. proximus or another insect vector., Två nyligen upptäckta svamparter i släktet Corinectria, nämnda som Corinectria sp. X och Corinectria sp. Y upptäcktes i centrala Sibirien år 2006, och sekvenserades 2020. Det här arbetet ämnar bredda kunskapen om möjliga värdarter för dessa arter genom inokulationstest på sticklingar och ungträd av Abies alba. De två nya arterna tros spridas med hjälp av barkborren Polygraphus proximus. Den närbesläktade svampen Corinectria fuckeliana är vanligt förekommande i sår på Picea abies i norra Europa men är känd för att infektera ett brett sortiment av värdträd. Inokulationstestet på ungträden gav ett positivt resultat för patogenicitet på A. alba och återisolering av svampen var någorlunda lyckat, vilket till viss del färdigställde Kochs postulat. Ett eventuellt utbrott av de två Corinectria-arterna på A. alba i Europa sker med största sannolikhet i association med P. proximus eller någon annan insektsvektor.

Here, we present a detailed study of the diversity, species composition, ecology and phytosociological characterization of the Habitat of Community Interest (priority type) at a European level Bog woodland (HIC 91D0*) in the Pyrenees, carried out through 23 inventories taken according to the Braun-Blanquet methodology, from the Benasque valley (central Pyrenees) to the Cerdanya region (eastern Pyrenees). The results show a clear separation of communities according to the dominant tree and to hydrology. We recognize a birch wooded mire of Betula pubescens Ehrh. as a new association: Blechno spicanti-Betuletum pubescentis ass. nov. within the alliance Betulion pubescentis Lohmeyer et Tüxen ex Scamoni et H. Passarge 1959. We also include in this alliance the Abies alba Mill wooded mires. The mires with open pine populations of Pinus uncinata Ramond ex DC. subsp. uncinata have been differentiated into two new associations characterized mainly by bryophytes: Sphagno papillosi-Pinetum uncinatae ass. nov., within the Betulion pubescentis alliance Lohmeyer et Tüxen ex Scamoni et H. Passarge 1959, and Sphagno capillifolii-Pinetum uncinatae ass. nov., within the Eriophoro vaginati–Piceion abietis H. Passarge 1968 alliance. These communities always occupy small areas and have no direct threats, but they are influenced by the forest dynamics of the adjacent forests and by livestock activity, both with notable changes in recent decades. The particularities of these forests and the presence of some bryophytes included in the Spanish red list or rare in Catalonia (Sphagnum squarrosum Crome, S. centrale C.E.O. Jensen, S. fallax H. Klinggr., S. flexuosum Dozy & Molk., S. medium Limpr.) demand protection and monitoring to guarantee their conservation., Este trabajo da cuenta de un estudio detallado de la diversidad, composición florística, ecología y caracterización fitosociológica del hábitat de interés comunitario prioritario a nivel europeo (HIC) 91D0* en los Pirineos. Se ha realizado a partir de 23 inventarios tomados según la metodología fitosociológica de Braun-Blanquet, desde el valle de Benasque (Pirineo central) hasta la comarca de la Cerdaña (Pirineo oriental). Los resultados muestran una separación clara de comunidades según el árbol dominante y la hidrología. Reconocemos un bosque turboso de Betula pubescens Ehrh. como una nueva asociación: Blechno spicanti-Betuletum pubescentis ass. nov. dentro de la alianza Betulion pubescentis Lohmeyer et Tüxen ex Scamoni et H. Passarge 1959. Incluimos también en esta alianza un bosque turboso de Abies alba Mill. Los bosques turbosos de Pinus uncinata Ramond ex DC. subsp. uncinata han sido diferenciados en dos nuevas asociaciones caracterizadas fundamentalmente por briófitos: Sphagno papillosi-Pinetum uncinatae ass. nov., de la alianza Betulion pubescentis Lohmeyer et Tüxen ex Scamoni et H. Passarge 1959, y Sphagno capillifolii-Pinetum uncinatae ass. nov., de la alianza Eriophoro vaginati–Piceion abietis H. Passarge 1968. Estas comunidades ocupan siempre superficies pequeñas y no tienen amenazas directas, pero están influidas tanto por el cambio climático como por la dinámica forestal de los bosques adyacentes y por la actividad ganadera, ambas sujetas a cambios notables en los últimos decenios. Las características particulares de estos bosques y la presencia en ellos de algunos briófitos incluidos en la lista roja española o raros en los pirineos (Sphagnum squarrosum Crome, S. centrale C.E.O. Jensen, S. fallax H. Klinggr., S. flexuosum Dozy & Molk., S. medium Limpr.) demandan protección y seguimiento para garantizar su conservación.

Ongoing climatic change is threatening the survival of drought-sensitive tree species, such as silver fir (Abies alba). Drought-induced dieback had been previously explored in this conifer, although the role played by tree-level genetic diversity and its relationship with growth patterns and soil microsite conditions remained elusive. We used double digest restriction-site-associated DNA sequencing (ddRADseq) to describe different genetic characteristics of five silver fir forests in the Spanish Pyrenees, including declining and non-declining trees. Single nucleotide polymorphisms (SNPs) were used to investigate the relationships between genetics, dieback, intraspecific trait variation (functional dendrophenotypic traits and leaf traits), local bioclimatic conditions, and rhizosphere soil properties. While there were no noticeable genetic differences between declining and non-declining trees, genome–environment associations with selection signatures were abundant, suggesting a strong influence of climate, soil physicochemical properties, and soil microbial diversity on local adaptation. These results provide novel insights into how genetics and diverse environmental factors are interrelated and highlight the need to incorporate genetic data into silver fir forest dieback studies to gain a better understanding of local adaptation.

This dataset is a valuable component of the article titled "Monitoring Montane-Subalpine Forest Ecotone in the Pyrenees: Integrating Sequential Forest Inventories and Landsat Imagery." The dataset provides comprehensive information necessary for implementing the analysis and models described. These analyses encompass studying the variations in Abies alba Mill. and Pinus uncinata Ramond. basal area and Replacement Index over three reference years (1991, 2002, and 2015). Additionally, the study applies linear mixed-effects models, considering altitude, aspect, total basal area, year, and protection level (National Park vs. protection buffer zone) as fixed effects, and plot as a random effect. By utilizing the reflectance values from the Landsat composites of 1991, 2002, and 2015, a Support Vector Machine binary classifier can be trained using presence/absence indicators for A. alba and P. uncinata, enabling the prediction of species’ distribution throughout the entire study area. All methods are thoroughly described in the manuscript.

Key message: Abies alba Mill.–Pinus uncinata Ramond. ecotone dynamics are examined along both altitudinal and protection level gradients by combining field inventories and Landsat data. An upward expansion of A. alba to the subalpine belt is observed in the last decades as a result of stand maturation after logging cessation. Context: High-mountain forests constitute sensitive locations to monitor the impacts of global change on tree-species composition and ecotone dynamics. In this study, we focus on the Spanish Pyrenees where silver fir (Abies alba Mill.) coexists with mountain pine (Pinus uncinata Ramond.) forming montane-subalpine ecotones. Aims: The main goal of this study is to assess the spatiotemporal dynamics of the silver fir–mountain pine ecotone and its underlying driving factors. Methods: We reconstructed the spatial distribution and dynamics of the species by combining remote sensing imagery and field plot data from 1989 to 2015, employing support vector machine techniques for image classification. Using variance analysis and mixed effects models, we then analyzed the evolution of basal area and replacement index, a measure of relative change in species composition, over time and altitude range. Additionally, we explored their relationship with site factors and protection level (National Park vs. protection buffer zone). Results: Silver fir has expanded its distribution in both the National Park and the protection buffer zone, whereas mountain pine has remained stable. Both species exhibit increased basal area associated with stand maturation and a higher level of protection. The replacement index indicates a rise in silver fir in the understory on North-facing slopes, attributed to stand densification. These findings are particularly noticeable in the area with the highest level of protection. Conclusion: The cessation of traditional land uses has led to ongoing stand densification, promoting succession and favoring the increased abundance of silver f

We reconstructed vegetation, fire and watershed history during the Late Roman-Early Middle Ages and in the last three centuries in a mixed conifer forest forming the middle mountain elevational belt in the inner Alpine region, analyzing co-registered micro-botanical data, charcoal particles, sediment lithology, nutrients, and modern pollen deposition from a high-resolution peat record in Valmalenco (Italian Alps). During Late Roman Age the site hosted a dump mixed conifer forest dominated by Picea abies and Abies alba on peaty forest soil, locally affected by fires which also triggered episodes of hillslope denudation. Fire frequency increases during Early Middle Ages dry and warm phases, favoring Alnus viridis and Larix, while Abies alba and Alnus glutinosa type maintained a main role in the pre- and post-fire. Specifically, Abies alba, nowadays eradicated from the Valmalenco watershed, withstood the local regime of low intensity surface fires for more than a millennium, from the Late Roman throughout the Early Middle Ages. Larix, Alnus viridis and Fraxinus excelsior abundance in modern vegetation is ascribed to effects of intensified disturbance in the Early Modern Age, and to further woodland thickening triggered by fire suppression and abandonment after the Second World War.

Recent drought-induced dieback alters forest dynamics, which are also shaped by past management. In western Pyrenean silver fir (Abies alba) stands, dieback concurs in space and time with the legacies of past management, but the impacts on forest growth, structure and composition are unknown. We aim to disentangle how dieback interacts with the legacies of past human use and modulates the recent dynamics of silver fir forests. To this end, we sampled eleven silver fir forests across wide climatic gradients and included declining and non-declining sites. We measured radial growth, structure, composition, understory cover and type and amount of deadwood. Silver fir growth declines in response to late-summer drought. In declining sites, most defoliated stands showed the lowest silver fir density and were those where growth depended more on water availability. Tree death enhanced the cover of dominant understory plants such as Buxus sempervirens. Past management activities leave an imprint in the growth of silver fir, such as releases due to past logging, but also affect the number of stumps and snags and the current tree density. A more extensive monitoring will be required to fully disentangle the multiple influences of past management legacies and current climate change on forest dynamics.

Assessing tree growth patterns and deviations from expected climate baselines across wide environmental gradients is fundamental to determine forest vulnerability to drought. This need is particularly compelling for the southernmost limit of the tree species distribution where hot droughts often trigger forest dieback processes. This is the case of some silver fir (Abies alba) populations located in southwestern Europe (Spanish Pyrenees) which present ongoing dieback processes since the 1980s. We sampled 21 silver fir stands showing different dieback intensity, assessed using defoliation levels, quantified their growth patterns and characterized their responses to climate. Then, we assessed growth deviations from climatic predictions using the process-based Vaganov-Shashkin (VS) growth model. The forests showing most intense dieback, i.e. highest defoliation levels, were mainly located in low-elevation sites of the western Pyrenees. Trees in these stands displayed the lowest growth rates and the highest year-to-year variability in growth and their growth was limited by late-summer evaporative demand. In eastern and central Pyrenees, we detected a mild growth limitation by low soil moisture during the late growing season and positive growth recovery in recent years with respect to a climate baseline. Decreasing growth trajectories were the most common pattern, while rising trends were common in stands with low dieback in eastern and central Pyrenees. Our results portend systematic spatial variability of growth trends across the Pyrenean silver fir populations forming the south-western distribution limit of the species in Europe. Decoupling of growth between eastern and western populations observed in the recent decades suggests contrasting vulnerability to climate change, and more importantly, the decoupling of growth patterns in western clusters could be used as an early-warning signal of impending dieback. Consequently, we foresee future dieback events to have more

L’avet és un arbre molt singular al Montseny, de gran rellevància paisatgística i científica, malgrat la seva escassa distribució al massís. És un dels arbres que forma part del corpus mental amb que popularment s’associa el Montseny però, a més, havia tingut històricament importància econòmica per la construcció de vaixells, específicament per a arbres de les naus. La seva explotació silvícola va ser molt important al segle XX, sobretot amb la demanda de fusta per la Primera Guerra Mundial, en que s’instal·là una serradora a l’àrea de Passavets, Objectius de Desenvolupament Sostenible::15 - Vida d'Ecosistemes Terrestres, Objectius de Desenvolupament Sostenible::4 - Educació de Qualitat, Postprint (published version)

Probability and uncertainty maps showing the potential and realized distribution for the silver fir (Abies alba, Mill.) for Europe from the dataset prepared by Bonannella et al. (2022) and predicted using Ensemble Machine Learning (EML). Potential distribution map cover the period 2018 - 2020; realized distribution cover the period 2000 - 2020.

There is large uncertainty on the future of European silver fir (Abies alba) forests and how they will respond to climate warming. Many studies, such as Walder et al. (2021), suggest they will show positive growth trends and a larger distribution area in response to warmer conditions whenever summer drought is not severe and long. This contradicts localized dieback events in continental, drought-prone Mediterranean sites mainly located in the southwestern margin of the current species distribution range. We discuss these disagreements and propose compound climate extremes and elevated atmospheric drought as drivers of dieback in similar marginal silver fir populations.

Legacies of past climate conditions and historical management govern forest productivity and tree growth. Understanding how these processes interact and the timescales over which they influence tree growth is critical to assess forest vulnerability to climate change. Yet, few studies address this issue, likely because integrated long-term records of both growth and forest management are uncommon. We applied the stochastic antecedent modelling (SAM) framework to annual tree-ring widths from mixed forests to recover the ecological memory of tree growth. We quantified the effects of antecedent temperature and precipitation up to 4 years preceding the year of ring formation and integrated management effects with records of harvesting intensity from historical forest management archives. The SAM approach uncovered important time periods most influential to growth, typically the warmer and drier months or seasons, but variation among species and sites emerged. Silver fir responded primarily to past climate conditions (25–50 months prior to the year of ring formation), while European beech and Scots pine responded mostly to climate conditions during the year of ring formation and the previous year, although these responses varied among sites. Past management and climate interacted in such a way that harvesting promoted growth in young silver fir under wet and warm conditions and in old European beech under drier and cooler conditions. Our study shows that the ecological memory associated with climate legacies and historical forest management is species-specific and context-dependent, suggesting that both aspects are needed to properly evaluate forest functioning under climate change.

Silvergran, Abies alba, är en ursprungligen odlad art som har fått snabb spridning i södra och mellersta Sverige de senaste 100 åren. Risk finns att denna art är invasiv och kan påverka vår inhemska flora och fauna negativt. I ett lövskogsområde norr om Uppsala finns en ungefär 70 år gammal plantering av silvergran som är nära 1200 kvadratmeter stor. I området kring planteringen har ett stort antal plantor av silvergran etablerat sig och syftet med denna studie är att kartlägga spridningen av arten i området. Studien kan bidra till att skapa ett generellt spridningsmönster för silvergran i liknande miljöer i Sverige. Att kartlägga spridningsmönstret kan vara fördelaktigt både för att kunna avgöra om arten måste klassas som invasiv, och om åtgärder behöver vidtas mot den möjligt invasiva ädelgranen. Skogsområdet är omgivet av åkermark och har inventerats genom transekter indelade i rutor. Från inventeringen är en generell spridning av silvergran kartlagd för skogsområdet. Granarna uppmättes i olika storlekskategorier, vilket är representerat i de framställda kartorna. På så sätt får man direkt en visuell överblick över spridningen av silvergran i skogsområdet från ursprungskällan. Tydligt är att silvergranen har stor möjlighet att på egen hand sprida sig i den sydliga, svenska lövskogen och hur spridningen av silvergran i framtiden kommer se ut är ett ämne för diskussion och studier.

The Barcode Index Numbers (BINs) are operational species units based on patterns of COI divergences that in most cases correspond to species. It has been repeatedly observed that more than one BIN can be found under the same species name particularly when large geographic scales are considered. One such case concerns Eupithecia conterminata, a species widespread in North European countries and restricted to mountainous regions in the rest of the continent, for which five BINs are found in Europe. In order to solve the question concerning the taxonomic status of these BINs and European populations, we employed an integrated approach by combining classical morphological traits (genitalia and wing markings) with those of molecular data, the latter involving both mitochondrial and nuclear genes. This approach allowed us to recognize two valid species in Europe, E. conterminata, currently known only in Fennoscandia, Baltic countries and Russia, and Eupithecia manniaria sp. rev., with distribution covering Central and South European countries. We furthermore synonymized Eupithecia pindosata syn. nov. from Greece with E. manniaria. The European range of these species and their mitochondrial diversity appear to be coherent with biogeographical histories of their foodplants Picea abies and Abies species.

Silvergran, Abies alba, är en ursprungligen odlad art som har fått snabb spridning i södra och mellersta Sverige de senaste 100 åren. Risk finns att denna art är invasiv och kan påverka vår inhemska flora och fauna negativt. I ett lövskogsområde norr om Uppsala finns en ungefär 70 år gammal plantering av silvergran som är nära 1200 kvadratmeter stor. I området kring planteringen har ett stort antal plantor av silvergran etablerat sig och syftet med denna studie är att kartlägga spridningen av arten i området. Studien kan bidra till att skapa ett generellt spridningsmönster för silvergran i liknande miljöer i Sverige. Att kartlägga spridningsmönstret kan vara fördelaktigt både för att kunna avgöra om arten måste klassas som invasiv, och om åtgärder behöver vidtas mot den möjligt invasiva ädelgranen. Skogsområdet är omgivet av åkermark och har inventerats genom transekter indelade i rutor. Från inventeringen är en generell spridning av silvergran kartlagd för skogsområdet. Granarna uppmättes i olika storlekskategorier, vilket är representerat i de framställda kartorna. På så sätt får man direkt en visuell överblick över spridningen av silvergran i skogsområdet från ursprungskällan. Tydligt är att silvergranen har stor möjlighet att på egen hand sprida sig i den sydliga, svenska lövskogen och hur spridningen av silvergran i framtiden kommer se ut är ett ämne för diskussion och studier.

[EN] Assessment of the diversity of reproductive traits and genetic variation is of great relevance to the conservation of genetic resources and management of silver fir (Abies alba) populations. We have evaluated reproductive characteristics associated with female cones and seed morphology, as well as seed germination after subjecting seeds to five storage methods, in nine Romanian populations of A. alba. The genetic diversity of the populations was assessed with 12 polymorphic simple sequence repeat (SSR) markers. We detected significant differences between populations for all reproductive traits and considerable differences in seed germination and storage methods; seed storage in wet sand was the method resulting in the highest germination in all populations. Genomic SSRs (gSSRs) were more informative on average than expressed sequence tag SSRs (EST-SSRs) in the populations studied. The nine populations were genetically diverse, with an average number of alleles (N) per SSR locus between 3.50 and 4.83. The observed heterozygosity (Ho) in the nine populations was always lower than the expected heterozygosity (He), which resulted in values of the inbreeding coefficient (Fis) between 0.261 and 0.709. Genetic distances between populations ranged between 0.077 and 0.410. The cluster analysis based on genetic distances did not group accessions according to their geographical proximity, and despite a positive trend, the correlation between geographic and genetic distances was non-significant. The results of an analysis of molecular variance (AMOVA) revealed that only 9.1% of the total molecular variance is attributable to differences between populations. This low degree of genetic differentiation between populations is confirmed by the intermingling of individuals of different populations in a principal coordinate analysis (PCoA). We found evidence of a positive relationship between He and germination, as well as a negative one between Fis and germination, suggesting th

Silver fir (Abies alba Mill.) is a keystone conifer of European montane forest ecosystems that has experienced large fluctuations in population size during during the Quaternary and, more recently, due to land-use change. To forecast the species' future distribution and survival, it is important to investigate the genetic basis of adaptation to environmental change, notably to extreme events. For this purpose, we here provide a first draft genome assembly and annotation of the silver fir genome, established through a community-based initiative. DNA obtained from haploid megagametophyte and diploid needle tissue was used to construct and sequence Illumina paired-end and mate-pair libraries, respectively, to high depth. The assembled A. alba genome sequence accounted for over 37 million scaffolds corresponding to 18.16 Gb, with a scaffold N50 of 14,051 bp. Despite the fragmented nature of the assembly, a total of 50,757 full-length genes were functionally annotated in the nuclear genome. The chloroplast genome was also assembled into a single scaffold (120,908 bp) that shows a high collinearity with both the A. koreana and A. sibirica complete chloroplast genomes. This first genome assembly of silver fir is an important genomic resource that is now publicly available in support of a new generation of research. By genome-enabling this important conifer, this resource will open the gate for new research and more precise genetic monitoring of European silver fir forests.

Climate warming has lengthened the growing season by advancing leaf unfolding in many temperate tree species. However, an earlier leaf unfolding increases also the risk of frost damage in spring which may reduce tree radial growth. In equatorward populations of temperate tree species, both late frosts and summer droughts impose two constraints to tree growth, but their effects on growth are understudied. We used a tree-ring network of 71 forests to evaluate the potential influence of late frosts and summer droughts on growth in two tree species that reach their southern distribution limits in north-eastern Spain: the deciduous European beech (Fagus sylvatica L.) and the evergreen Silver fir (Abies alba Mill). The occurrence of late frost events and summer drought was quantified by using a high-resolution daily temperature and precipitation dataset considering the period 1950 2012. Late frosts were defined as days with average temperature below 0 °C in the site-specific frost-free period, whereas drought was quantified using the 18 month-long August Standardized Precipitation Evapotranspiration Index (SPEI). The growth of European beech and Silver fir was reduced by the occurrence of both late frost events and summer drought. However, we did not find a significant interaction on growth of these two climate extremes. Beech was more negatively impacted by late frosts, whereas Silver fir was more impacted by summer drought. Further studies could use remote-sensing information or in situ phenological records to refine our frost index and better elucidate how late frosts affect growth, whether they interact with drought to constrain growth, and how resilience mechanisms related to post-frost refoliation operate in beech. © 2019 Elsevier B.V.

Climate warming has lengthened the growing season by advancing leaf unfolding in many temperate tree species. However, an earlier leaf unfolding increases also the risk of frost damage in spring which may reduce tree radial growth. In equatorward populations of temperate tree species, both late frosts and summer droughts impose two constraints to tree growth, but their effects on growth are understudied. We used a tree-ring network of 71 forests to evaluate the potential influence of late frosts and summer droughts on growth in two tree species that reach their southern distribution limits in north-eastern Spain: the deciduous European beech (Fagus sylvatica L.) and the evergreen Silver fir (Abies alba Mill). The occurrence of late frost events and summer drought was quantified by using a high-resolution daily temperature and precipitation dataset considering the period 1950 2012. Late frosts were defined as days with average temperature below 0 °C in the site-specific frost-free period, whereas drought was quantified using the 18 month-long August Standardized Precipitation Evapotranspiration Index (SPEI). The growth of European beech and Silver fir was reduced by the occurrence of both late frost events and summer drought. However, we did not find a significant interaction on growth of these two climate extremes. Beech was more negatively impacted by late frosts, whereas Silver fir was more impacted by summer drought. Further studies could use remote-sensing information or in situ phenological records to refine our frost index and better elucidate how late frosts affect growth, whether they interact with drought to constrain growth, and how resilience mechanisms related to post-frost refoliation operate in beech. © 2019 Elsevier B.V.

Silver fir (Abies alba Mill.) is a keystone conifer of European montane forest ecosystems that has experienced large fluctuations in population size during during the Quaternary and, more recently, due to land-use change. To forecast the species' future distribution and survival, it is important to investigate the genetic basis of adaptation to environmental change, notably to extreme events. For this purpose, we here provide a first draft genome assembly and annotation of the silver fir genome, established through a community-based initiative. DNA obtained from haploid megagametophyte and diploid needle tissue was used to construct and sequence Illumina paired-end and mate-pair libraries, respectively, to high depth. The assembled A. alba genome sequence accounted for over 37 million scaffolds corresponding to 18.16 Gb, with a scaffold N50 of 14,051 bp. Despite the fragmented nature of the assembly, a total of 50,757 full-length genes were functionally annotated in the nuclear genome. The chloroplast genome was also assembled into a single scaffold (120,908 bp) that shows a high collinearity with both the A. koreana and A. sibirica complete chloroplast genomes. This first genome assembly of silver fir is an important genomic resource that is now publicly available in support of a new generation of research. By genome-enabling this important conifer, this resource will open the gate for new research and more precise genetic monitoring of European silver fir forests.

Ziel dieser Arbeit ist es die Resistenz und Resilienz von Misch- und Reinbuchenwäldern in europäischen Bergregionen gegenüber Störungen und Stressfaktoren in vergangenen Jahren sowie der Gegenwart zu untersuchen und zu analysieren, um daraus auf die Zukunft schließen zu können. Häufiger auftretende Wetterextreme und andere Störfaktoren sind die Konsequenz des Klimawandels, wobei die Auswirkungen in Bergregionen durchschnittlich intensiver sind als anderswo. Die Ziele waren es, herauszufinden ob und wie sich die Resistenz und Resilienz gegenüber den Beeinträchtigungen über die Jahre verändert hat und welchen Einfluss die Baumartenzusammensetzung und die strukturelle Vielfalt in diesen Wäldern darauf hat. Außerdem wurden mögliche Auswirkungen von Höhe, sowie der geografische Standort des Forstes berücksichtigt. Mit den Einzelbaumdaten, die in 51 Standorten vom europaweiten Forschungsnetzwerk CliMo gesammelt wurden, wurden Wachstumsresistenz und -resilienz Indices ausgerechnet. Diese Indices wurden dann als abhängige Variablen in einem generalisierten linear gemischten Modell verwendet. Die Mischung (gemischt oder monospezifisch), die Verteilung (aggregiert, normal oder zufällig), die Bodenfeuchtigkeit (PDSI - trocken, normal oder nass), die Spezies (Buche, Tanne, Fichte) und das Jahr (1987, 2000 und 2013 - Jahre mit auffällig negativem Wachstum) waren feste Faktoren in dem statistischen Modell. Die Höhe, der Standort und das Kambialalter wurden als zufällige Faktoren benützt. Mit zwei verschiedenen Modellen wurde der Einfluss dieser Faktoren auf die Resistenz und Resilienz analysiert. Der geographische Standort war nicht signifikant. Die Höhe hatte Auswirkungen auf die Resistenz der Buche gegenüber Störeinflüssen. Je höher der Forst desto niedriger ist die Resistenz. Die Buche zeigt außerdem eine Steigerung der Resistenz in Mischwäldern von 1987 bis 2013. Reine Buchenwäldern verzeichnen eine umgekehrte Entwicklung. Die Fichte ist heute auch weniger widerstandsfähig al, The main aim of this thesis is to investigate and analyze the resistance and resilience of mixed and pure European beech forests in mountain environments to disturbances in the past and the present to be able to make assumptions for the future. More frequent and extreme disturbances are the consequence of climate change and the effects of this ongoing change are especially strong in mountain regions. The objectives were to find out if the response to disturbances has changed over the years and what kind of influence the species composition and the structural diversity in these forests have on the resistance and resilience. Furthermore, a possible impact of the elevation and/or geographic location of the forest on the growth performance during such disturbances was examined. With the single tree data that was gathered in 51 plots by the European-wide research network CliMo, indices for growth resistance and resilience using the basal area increment were calculated. These indices served as dependent variables in a generalized linear mixed model. The mixture (pure or mixed), the distribution (clumped, regular or random), the soil moisture (PDSI - dry, normal or wet), the species (European beech, silver fir and Norway spruce) and the year (1987, 2000 and 2013 - years with particularly negative growth) were used as fixed factors in the model. The altitude, the plot and the cambial age were used as random factors. By applying two different modeling approaches the impact of these factors on the resistance and resilience could be statistically analyzed. The latitude and longitude of the forest are not significant. A higher altitude implies a lower resistance to stressors and disturbances for beech. There is the tendency to an improvement of the ability to withstand disturbances over time regarding beech in mixed conditions and to a deterioration in monospecific ones. Also spruce shows a lower resistance in more recent years. Fir has higher resilience than Spruce. At dry sit, Lukas Matthias Huss, Arbeit an der Bibliothek noch nicht eingelangt - Daten nicht geprüft, Masterarbeit Universität Innsbruck 2019

Ziel dieser Arbeit ist es die Resistenz und Resilienz von Misch- und Reinbuchenwäldern in europäischen Bergregionen gegenüber Störungen und Stressfaktoren in vergangenen Jahren sowie der Gegenwart zu untersuchen und zu analysieren, um daraus auf die Zukunft schließen zu können. Häufiger auftretende Wetterextreme und andere Störfaktoren sind die Konsequenz des Klimawandels, wobei die Auswirkungen in Bergregionen durchschnittlich intensiver sind als anderswo. Die Ziele waren es, herauszufinden ob und wie sich die Resistenz und Resilienz gegenüber den Beeinträchtigungen über die Jahre verändert hat und welchen Einfluss die Baumartenzusammensetzung und die strukturelle Vielfalt in diesen Wäldern darauf hat. Außerdem wurden mögliche Auswirkungen von Höhe, sowie der geografische Standort des Forstes berücksichtigt. Mit den Einzelbaumdaten, die in 51 Standorten vom europaweiten Forschungsnetzwerk CliMo gesammelt wurden, wurden Wachstumsresistenz und -resilienz Indices ausgerechnet. Diese Indices wurden dann als abhängige Variablen in einem generalisierten linear gemischten Modell verwendet. Die Mischung (gemischt oder monospezifisch), die Verteilung (aggregiert, normal oder zufällig), die Bodenfeuchtigkeit (PDSI - trocken, normal oder nass), die Spezies (Buche, Tanne, Fichte) und das Jahr (1987, 2000 und 2013 - Jahre mit auffällig negativem Wachstum) waren feste Faktoren in dem statistischen Modell. Die Höhe, der Standort und das Kambialalter wurden als zufällige Faktoren benützt. Mit zwei verschiedenen Modellen wurde der Einfluss dieser Faktoren auf die Resistenz und Resilienz analysiert. Der geographische Standort war nicht signifikant. Die Höhe hatte Auswirkungen auf die Resistenz der Buche gegenüber Störeinflüssen. Je höher der Forst desto niedriger ist die Resistenz. Die Buche zeigt außerdem eine Steigerung der Resistenz in Mischwäldern von 1987 bis 2013. Reine Buchenwäldern verzeichnen eine umgekehrte Entwicklung. Die Fichte ist heute auch weniger widerstandsfähig al, The main aim of this thesis is to investigate and analyze the resistance and resilience of mixed and pure European beech forests in mountain environments to disturbances in the past and the present to be able to make assumptions for the future. More frequent and extreme disturbances are the consequence of climate change and the effects of this ongoing change are especially strong in mountain regions. The objectives were to find out if the response to disturbances has changed over the years and what kind of influence the species composition and the structural diversity in these forests have on the resistance and resilience. Furthermore, a possible impact of the elevation and/or geographic location of the forest on the growth performance during such disturbances was examined. With the single tree data that was gathered in 51 plots by the European-wide research network CliMo, indices for growth resistance and resilience using the basal area increment were calculated. These indices served as dependent variables in a generalized linear mixed model. The mixture (pure or mixed), the distribution (clumped, regular or random), the soil moisture (PDSI - dry, normal or wet), the species (European beech, silver fir and Norway spruce) and the year (1987, 2000 and 2013 - years with particularly negative growth) were used as fixed factors in the model. The altitude, the plot and the cambial age were used as random factors. By applying two different modeling approaches the impact of these factors on the resistance and resilience could be statistically analyzed. The latitude and longitude of the forest are not significant. A higher altitude implies a lower resistance to stressors and disturbances for beech. There is the tendency to an improvement of the ability to withstand disturbances over time regarding beech in mixed conditions and to a deterioration in monospecific ones. Also spruce shows a lower resistance in more recent years. Fir has higher resilience than Spruce. At dry sit, Lukas Matthias Huss, Arbeit an der Bibliothek noch nicht eingelangt - Daten nicht geprüft, Masterarbeit Universität Innsbruck 2019

Rear-edge tree populations are currently at the forefront of habitat conservation. Understanding the dynamics of such marginal and peripheral populations is necessary to improve their preservation in the face of global change. Focusing on the south-western rear edge populations of silver fir (Abies alba) in Europe (Spanish Pyrenees) and using 763 resampled plots from the Spanish National Forest Inventory (1989–2000 and 2001–2010), we analyzed temporal changes in demographic parameters such as regeneration, growth and mortality as well as changes in diameter distribution and vitality of silver fir to identify shifts in the distribution. For this purpose, montane (900–1600 m a.s.l.) and subalpine (1600–2000 m a.s.l.) silver fir populations were considered separately. We then assessed the relative effects of various biotic and abiotic factors on the observed changes and specifically on each of the studied demographic parameters. In montane forests, early recruitment and the proportion of trees exhibiting high vitality decreased, while the amount of dead trees increased. In subalpine forests, silver fir has become more abundant and displays the highest growth and recruitment rates as well as the lowest mortality rate. The increase in radial growth and saplings were positively related to elevation but negatively associated with warmer and drier conditions, coinciding with the intensified aridification observed in the study area over recent decades. Our findings point to the contraction of montane silver fir forests but also to an upward expansion of subalpine forests. The results also indicate that the dynamics of marginal tree populations are driven not only by climate warming, but particularly, by biotic factors, suggesting a positive impact of interspecific interactions with tree species displaying differentiated ecophysiological traits. Given the singularity of marginal Pyrenean silver fir populations, their importance as regards the conservation of forest biodiversi

Climate warming has lengthened the growing season by advancing leaf unfolding in many temperate tree species. However, an earlier leaf unfolding increases also the risk of frost damage in spring which may reduce tree radial growth. In equatorward populations of temperate tree species, both late frosts and summer droughts impose two constraints to tree growth, but their effects on growth are understudied. We used a tree-ring network of 71 forests to evaluate the potential influence of late frosts and summer droughts on growth in two tree species that reach their southern distribution limits in north-eastern Spain: the deciduous European beech (Fagus sylvatica L.) and the evergreen Silver fir (Abies alba Mill). The occurrence of late frost events and summer drought was quantified by using a high-resolution daily temperature and precipitation dataset considering the period 1950 2012. Late frosts were defined as days with average temperature below 0 °C in the site-specific frost-free period, whereas drought was quantified using the 18 month-long August Standardized Precipitation Evapotranspiration Index (SPEI). The growth of European beech and Silver fir was reduced by the occurrence of both late frost events and summer drought. However, we did not find a significant interaction on growth of these two climate extremes. Beech was more negatively impacted by late frosts, whereas Silver fir was more impacted by summer drought. Further studies could use remote-sensing information or in situ phenological records to refine our frost index and better elucidate how late frosts affect growth, whether they interact with drought to constrain growth, and how resilience mechanisms related to post-frost refoliation operate in beech. © 2019 Elsevier B.V.

Rear-edge tree populations are currently at the forefront of habitat conservation. Understanding the dynamics of such marginal and peripheral populations is necessary to improve their preservation in the face of global change. Focusing on the south-western rear edge populations of silver fir (Abies alba) in Europe (Spanish Pyrenees) and using 763 resampled plots from the Spanish National Forest Inventory (1989–2000 and 2001–2010), we analyzed temporal changes in demographic parameters such as regeneration, growth and mortality as well as changes in diameter distribution and vitality of silver fir to identify shifts in the distribution. For this purpose, montane (900–1600 m a.s.l.) and subalpine (1600–2000 m a.s.l.) silver fir populations were considered separately. We then assessed the relative effects of various biotic and abiotic factors on the observed changes and specifically on each of the studied demographic parameters. In montane forests, early recruitment and the proportion of trees exhibiting high vitality decreased, while the amount of dead trees increased. In subalpine forests, silver fir has become more abundant and displays the highest growth and recruitment rates as well as the lowest mortality rate. The increase in radial growth and saplings were positively related to elevation but negatively associated with warmer and drier conditions, coinciding with the intensified aridification observed in the study area over recent decades. Our findings point to the contraction of montane silver fir forests but also to an upward expansion of subalpine forests. The results also indicate that the dynamics of marginal tree populations are driven not only by climate warming, but particularly, by biotic factors, suggesting a positive impact of interspecific interactions with tree species displaying differentiated ecophysiological traits. Given the singularity of marginal Pyrenean silver fir populations, their importance as regards the conservation of forest biodiversi

Avhandling (ph.d.) - Norges miljø- og biovitenskapelige universitet, Ås, 2018

Condensed tannins extracted from European softwood bark are recognized as alternatives to synthetic phenolics. The extraction is generally performed in hot water, leading to simultaneous extraction of other bark constituents such as carbohydrates, phenolic monomers and salts. Characterization of the extract's composition and identification of the extracted tannins' molecular structure are needed to better identify potential applications. Bark from Silver fir (Abies alba [Mill.]), European larch (Larix decidua [Mill.]), Norway spruce (Picea abies [Karst.]), Douglas fir (Pseudotsuga menziesii [Mirb.]) and Scots pine (Pinus sylvestris [L.]) were extracted in water at 60°C. The amounts of phenolic monomers, condensed tannins, carbohydrates, and inorganic compounds in the extract were determined. The molecular structures of condensed tannins and carbohydrates were also investigated (HPLC-UV combined with thiolysis, MALDI-TOF mass spectrometry, anion exchange chromatography). Distinct extract compositions and tannin structures were found in each of the analysed species. Procyanidins were the most ubiquitous tannins. The presence of phenolic glucosides in the tannin oligomers was suggested. Polysaccharides such as arabinans, arabinogalactans and glucans represented an important fraction of all extracts. Compared to traditionally used species (Mimosa and Quebracho) higher viscosities as well as faster chemical reactivities are expected in the analysed species. The most promising species for a bark tannin extraction was found to be larch, while the least encouraging results were detected in pine. A better knowledge of the interaction between the various extracted compounds is deemed an important matter for investigation in the context of industrial applications of such extracts.

Condensed tannins extracted from European softwood bark are recognized as alternatives to synthetic phenolics. The extraction is generally performed in hot water, leading to simultaneous extraction of other bark constituents such as carbohydrates, phenolic monomers and salts. Characterization of the extract's composition and identification of the extracted tannins' molecular structure are needed to better identify potential applications. Bark from Silver fir (Abies alba [Mill.]), European larch (Larix decidua [Mill.]), Norway spruce (Picea abies [Karst.]), Douglas fir (Pseudotsuga menziesii [Mirb.]) and Scots pine (Pinus sylvestris [L.]) were extracted in water at 60°C. The amounts of phenolic monomers, condensed tannins, carbohydrates, and inorganic compounds in the extract were determined. The molecular structures of condensed tannins and carbohydrates were also investigated (HPLC-UV combined with thiolysis, MALDI-TOF mass spectrometry, anion exchange chromatography). Distinct extract compositions and tannin structures were found in each of the analysed species. Procyanidins were the most ubiquitous tannins. The presence of phenolic glucosides in the tannin oligomers was suggested. Polysaccharides such as arabinans, arabinogalactans and glucans represented an important fraction of all extracts. Compared to traditionally used species (Mimosa and Quebracho) higher viscosities as well as faster chemical reactivities are expected in the analysed species. The most promising species for a bark tannin extraction was found to be larch, while the least encouraging results were detected in pine. A better knowledge of the interaction between the various extracted compounds is deemed an important matter for investigation in the context of industrial applications of such extracts.

Avhandling (ph.d.) - Norges miljø- og biovitenskapelige universitet, Ås, 2018

In this version 13 new plots of White elder and 13 new plots of Sitka spruce were added, both from the collection of the former Stichting Industriehout. This database is part of the FEM growth and yield database, a collection of growth and yield data from even-aged monocultures.

The knowledge of macrofungal diversity associated with Silver Fir forests in Italy is quite scarce. Only a little information is available about macrofungal communities from some Ligurian and Tuscan Silver Fir sites. This study aims to assess the macrofungal diversity of a Silver Fir plantation in Sardinia by the application of a standardized sampling procedure. A total of 606 sporomata were collected and 52 Basidiomycota were identified. The high value of the Shannon Index indicated a considerable level of macrofungal diversity in this plantation. The results were also compared with the diversity indices obtained by a previous 3-years long sampling methodology in the same site. The comparison of the macrofungal diversity values of the Sardinian site with those of the Ligurian Silver Fir forest revealed interesting similarities among natural versus planted coniferous forests.

The response of forest ecosystems to increased atmospheric CO2 is constrained by nutrient availability. It is thus crucial to account for nutrient limitation when studying the forest response to climate change. The objectives of this study were to describe the nutritional status of the main European tree species, to identify growth-limiting nutrients and to assess changes in tree nutrition during the past two decades. We analysed the foliar nutrition data collected during 1992-2009 on the intensive forest monitoring plots of the ICP Forests programme. Of the 22 significant temporal trends that were observed in foliar nutrient concentrations, 20 were decreasing and two were increasing. Some of these trends were alarming, among which the foliar P concentration in F. sylvatica, Q. Petraea and P. sylvestris that significantly deteriorated during 1992-2009. In Q. Petraea and P. sylvestris, the decrease in foliar P concentration was more pronounced on plots with low foliar P status, meaning that trees with latent P deficiency could become deficient in the near future. Increased tree productivity, possibly resulting from high N deposition and from the global increase in atmospheric CO2, has led to higher nutrient demand by trees. As the soil nutrient supply was not always sufficient to meet the demands of faster growing trees, this could partly explain the deterioration of tree mineral nutrition. The results suggest that when evaluating forest carbon storage capacity and when planning to reduce CO2 emissions by increasing use of wood biomass for bioenergy, it is crucial that nutrient limitations for forest growth are considered. © 2014 John Wiley & Sons Ltd.

Forest dieback is one of the most widespread responses to global-change drivers, such as climate warming-related drought stress and the spread of pathogens. Although both climatic and biotic stressors have been studied separately, much less is known on how drought and pathogens interact and induce dieback, particularly in formerly used forests. We determine the roles played by each of those drivers as factors causing recent dieback in three Pyrenean silver fir stands a managed site subjected to past logging and two unmanaged sites not logged for the past 50 years. The age, size, recent competition, and basal-area increment (BAI) trends of non-declining and declining trees, and the presence of fungal pathogens were investigated. Growth patterns at yearly to decadal time scales were compared to distinguish the roles and interactions played by the different stressors. In the managed site, declining trees displayed low growth already before logging (1950-1970s). In both unmanaged sites, declining and non-declining trees displayed divergent growth patterns after extreme droughts, indicating that dieback was triggered by severe water deficit. We did not find indications that fungal pathogens are the primary drivers of dieback, since a low proportion of declining trees were infested by primary pathogens (10%). However, trees with the primary fungal pathogen Heterobasidion showed lower BAI than non-declining trees. On the other hand, the secondary fungal pathogen Amylostereum was isolated from a higher number of trees than expected by chance. These findings highlight the importance of legacies, such as the past use in driving recent forest dieback. Past forest use could predispose to dieback by selecting slow-growing trees and thus, making some them more vulnerable to drought and fungal pathogens. © 2015 Elsevier B.V.

Aim: Climate change is expected to modify growth trends of forests around the world. However, this modification may vary in strength and intensity across a species' biogeographical range. Here, we study European populations of silver fir (Abies alba) across its southern distribution limits in Spain, Italy and Romania. We hypothesized that growth trends of silver fir will differ across its distribution range, with a marked decline in growth in drought-prone regions near the species' southernmost biogeographical limits. Location: Europe (Spain, Italy, Romania). Methods: We collected tree-ring data from at least 1300 silver fir trees located in 111 sites. The dataset was used to assess and model growth trends, quantified as changes in basal area increment, and to determine how growth responds to climate. Results: We found contrasting patterns of basal area increments among countries and sites. Populations of silver fir located outside the Mediterranean area (e.g. northern Italy, Romania) have shown a clear increase in growth over the last two decades, whereas most populations in Spain and southern Italy have displayed a marked decline in growth since the 1980s. The growth of silver fir forests at the south-western distribution limit is severely constrained by low spring-summer water availability, whereas growth of silver fir forests in non-Mediterranean areas is limited by cold conditions in late winter to early spring. Main conclusions: Climate warming is distinctly modifying growth patterns and responses to climate in silver fir across most of the species' European distribution area. In south-western Europe the reduction in growth of many populations is related to an observed increase in aridity, whereas in more temperate areas warming is enhancing growth. Our results confirm a decline in the growth of silver fir at its south-western distribution limits as a consequence of climate warming. © 2015 John Wiley & Sons Ltd.

Forest dieback is one of the most widespread responses to global-change drivers, such as climate warming-related drought stress and the spread of pathogens. Although both climatic and biotic stressors have been studied separately, much less is known on how drought and pathogens interact and induce dieback, particularly in formerly used forests. We determine the roles played by each of those drivers as factors causing recent dieback in three Pyrenean silver fir stands: a managed site subjected to past logging and two unmanaged sites not logged for the past 50 years. The age, size, recent competition, and basal-area increment (BAI) trends of non-declining and declining trees, and the presence of fungal pathogens were investigated. Growth patterns at yearly to decadal time scales were compared to distinguish the roles and interactions played by the different stressors. In the managed site, declining trees displayed low growth already before logging (1950-1970s). In both unmanaged sites, declining and non-declining trees displayed divergent growth patterns after extreme droughts, indicating that dieback was triggered by severe water deficit. We did not find indications that fungal pathogens are the primary drivers of dieback, since a low proportion of declining trees were infested by primary pathogens (10%). However, trees with the primary fungal pathogen Heterobasidion showed lower BAI than non-declining trees. On the other hand, the secondary fungal pathogen Amylostereum was isolated from a higher number of trees than expected by chance. These findings highlight the importance of legacies, such as the past use in driving recent forest dieback. Past forest use could predispose to dieback by selecting slow-growing trees and thus, making some them more vulnerable to drought and fungal pathogens. © 2015 Elsevier B.V.

Warming-induced drought stress has been hypothesized as a major driver of forest net primary production (NPP) reduction, but we lack reliable field data to assess if higher temperatures lead to forest NPP reduction, particularly in humid sites and at basin to landscape spatial scales. The use of a landscape approach would allow considering the feedbacks operating between climate, topography, soil vegetation and water resources. Here we follow that approach by simulating NPP using the regional hydro-ecologic simulation system (RHESSys) model and by comparing the results with radial growth data (tree-ring widths and intrinsic water-use efficiency - iWUE). We evaluate the relationships between climate, growth, NPP, atmospheric CO2 concentrations (ca) and iWUE in xeric and mesic silver fir forests subjected to contrasting water balances. The growth data successfully validated the 11-month NPP cumulated until spring. The main negative climatic driver of growth and NPP was the summer evapotranspiration deficit, which shows a negative association with tree-ring width indices. Sensitivity analyses indicate that rising ca do not compensate the severe NPP reduction associated to warmer and drier conditions. The positive effect of rising ca on NPP is mediated by climatic site conditions being detected only in mesic sites, whereas the negative effects of drought on NPP override any ca-related enhancement of NPP in xeric sites. Future warmer and drier conditions causing a higher evaporative demand by the atmosphere could lead to a NPP decline in temperate conifer forests subjected to episodic droughts. © 2015 Elsevier B.V.

Wood heat treatment is an attractive alternative to improve decay resistance of wood species with low natural durability. Durability and mechanical properties are strongly correlated to thermal degradation of wood cells wall components. Mass loss resulting from this degradation is a good indicator of treatment intensity and final treated wood properties. Several types of convective heating processes exist currently differing mainly by the nature of the inert atmosphere used during treatment: nitrogen, steam or oil. Conductive heat treatment using vacuum as inert atmosphere is an attractive new alternative to previous classical methods. Heat transfer by conduction has been reported to provide better treatment homogeneity than heat transfer using convection. The aim of this study is to investigate the effect of vacuum comparatively to nitrogen on the thermal degradation pathways and on the conferred properties tothe material. It appears that utilization of vacuum permit a better control of thermal degradation reactions limiting the mass loss resulting from degradation of wood cell wall polymers. Chemical analysis indicates that wood heat treated under nitrogen present higher Klasonlignin and carbon contents, lower hemicelluloses and neutral monosaccharides contents comparatively to wood heat treated under vacuum. At the same time, mechanical properties are less affected under vacuum, which constitute another advantage of this technology.

Background Forest ecosystem functioning is strongly influenced by the absorption of photosynthetically active radiation (APAR), and therefore, accurate predictions of APAR are critical for many process-based forest growth models. The Lambert-Beer law can be applied to estimate APAR for simple homogeneous canopies composed of one layer, one species, and no canopy gaps. However, the vertical and horizontal structure of forest canopies is rarely homogeneous. Detailed tree-level models can account for this heterogeneity but these often have high input and computational demands and work on finer temporal and spatial resolutions than required by stand-level growth models. The aim of this study was to test a stand-level light absorption model that can estimate APAR by individual species in mixed-species and multi-layered stands with any degree of canopy openness including open-grown trees to closed canopies. Methods The stand-level model was compared with a detailed tree-level model that has already been tested in mixed-species stands using empirical data. Both models were parameterised for five different forests, including a wide range of species compositions, species proportions, stand densities, crown architectures and canopy structures. Results The stand-level model performed well in all stands except in the stand where extinction coefficients were unusually variable and it appears unlikely that APAR could be predicted in such stands using (tree- or stand-level) models that do not allow individuals of a given species to have different extinction coefficients, leaf-area density or analogous parameters. Conclusion This model is parameterised with species-specific information about extinction coefficients and mean crown length, diameter, height and leaf area. It could be used to examine light dynamics in complex canopies and in stand-level growth models.

Wood heat treatment is an attractive alternative to improve decay resistance of wood species with low natural durability. Durability and mechanical properties are strongly correlated to thermal degradation of wood cells wall components. Mass loss resulting from this degradation is a good indicator of treatment intensity and final treated wood properties. Several types of convective heating processes exist currently differing mainly by the nature of the inert atmosphere used during treatment: nitrogen, steam or oil. Conductive heat treatment using vacuum as inert atmosphere is an attractive new alternative to previous classical methods. Heat transfer by conduction has been reported to provide better treatment homogeneity than heat transfer using convection. The aim of this study is to investigate the effect of vacuum comparatively to nitrogen on the thermal degradation pathways and on the conferred properties tothe material. It appears that utilization of vacuum permit a better control of thermal degradation reactions limiting the mass loss resulting from degradation of wood cell wall polymers. Chemical analysis indicates that wood heat treated under nitrogen present higher Klasonlignin and carbon contents, lower hemicelluloses and neutral monosaccharides contents comparatively to wood heat treated under vacuum. At the same time, mechanical properties are less affected under vacuum, which constitute another advantage of this technology.

Background Forest ecosystem functioning is strongly influenced by the absorption of photosynthetically active radiation (APAR), and therefore, accurate predictions of APAR are critical for many process-based forest growth models. The Lambert-Beer law can be applied to estimate APAR for simple homogeneous canopies composed of one layer, one species, and no canopy gaps. However, the vertical and horizontal structure of forest canopies is rarely homogeneous. Detailed tree-level models can account for this heterogeneity but these often have high input and computational demands and work on finer temporal and spatial resolutions than required by stand-level growth models. The aim of this study was to test a stand-level light absorption model that can estimate APAR by individual species in mixed-species and multi-layered stands with any degree of canopy openness including open-grown trees to closed canopies. Methods The stand-level model was compared with a detailed tree-level model that has already been tested in mixed-species stands using empirical data. Both models were parameterised for five different forests, including a wide range of species compositions, species proportions, stand densities, crown architectures and canopy structures. Results The stand-level model performed well in all stands except in the stand where extinction coefficients were unusually variable and it appears unlikely that APAR could be predicted in such stands using (tree- or stand-level) models that do not allow individuals of a given species to have different extinction coefficients, leaf-area density or analogous parameters. Conclusion This model is parameterised with species-specific information about extinction coefficients and mean crown length, diameter, height and leaf area. It could be used to examine light dynamics in complex canopies and in stand-level growth models.

Alien plants are subjected to different biotic and environmental barriers that limit their establishment success in the introduced range. Pseud- otsuga menziesii (Douglas fir), a native conifer from Northwest America, is considered one of the most invasive forestry conifers in Europe. However, little is known about the ecological filters that constrain plant establishment at early life-cycle stages and differences in habitat invasibility to this species. We conducted field experiments to compare the establishment potential (i.e. post-dispersal seed removal, seed ger- mination, seedling survival and growth) of Douglas fir in beech forests, holm-oak forests and heathlands; and compared it with the taxonomically close native conifer Abies alba (Silver fir). Douglas fir seeds were more removed than Silver fir in holm-oak and in heathlands. In all habitats, seed germination was significantly higher for Douglas fir compared to that of Silver fir and, seedling mortality was extremely high in both species due to soil disturbance by wild boars and drought stress. Douglas fir mortality was only lower than Silver fir in beech forests. However, species did not differ in seedling growth. Overall, the probability of invasion success of Douglas fir decreased along the sequential stages of plant estab- lishment in all habitats. Only high seed germination rates of Douglas fir would predict its high invasive capacity but these advantages are counterbalanced by high seedling mortality. Results showed a mismatch between invasibility and current pattern of Douglas fir invasion in the study area. Therefore, future research focused on seed production and on different compo- nents of biotic resistance is recommended to eluci- date which processes are favoring its establishment success.

L'objectif de cette thèse est l'étude de la plasticité phénotypique du sapin pectine à l'aide de l'approche architecturale. Ces travaux se placent dans le contexte plus large de compréhension du développement des plantes pérennes en lien avec leur environnement et l'impact des changements climatiques en région méditerranéenne. Pour mener à bien ces objectifs, des études ont été menées ex-situ en conditions contrôlées (gradient d'ombrage et de disponibilité en eau) et in-situ au Mont Ventoux (gradient d'ombrage et altitudinal). Ces études ont consisté en l'analyse de la variabilité de différents traits architecturaux, généralement mesures à l'échelle de la pousse annuelle, en lien avec l'architecture et l'environnement. Ces études ont permis de caractériser quantitativement le développement du sapin jusqu'à l'expression durable de la sexualité et de quantifier la réponse plastique à l'environnement lumineux, hydrique et climatique. Enfin, ce travail a permis d'approfondir le concept de plasticité architecturale et ses implications.

L'objectif de cette thèse est l'étude de la plasticité phénotypique du sapin pectine à l'aide de l'approche architecturale. Ces travaux se placent dans le contexte plus large de compréhension du développement des plantes pérennes en lien avec leur environnement et l'impact des changements climatiques en région méditerranéenne. Pour mener à bien ces objectifs, des études ont été menées ex-situ en conditions contrôlées (gradient d'ombrage et de disponibilité en eau) et in-situ au Mont Ventoux (gradient d'ombrage et altitudinal). Ces études ont consisté en l'analyse de la variabilité de différents traits architecturaux, généralement mesures à l'échelle de la pousse annuelle, en lien avec l'architecture et l'environnement. Ces études ont permis de caractériser quantitativement le développement du sapin jusqu'à l'expression durable de la sexualité et de quantifier la réponse plastique à l'environnement lumineux, hydrique et climatique. Enfin, ce travail a permis d'approfondir le concept de plasticité architecturale et ses implications.

Silver fir presents a great hierarchised architecture with a strict monopodial development (Massart's architectural model). Moreover silver fir presents neither polycyclism nor immediate branching (often involved in the plastic response of primary growth). Despite these limitations, silver firs present a large range of distribution: from Central Europe to Mediterranean mountains. The aim of this poster is to test the hypothesis that silver firs offset this limitation with a strong plasticity at the annual shoot scale and on needle morphology. The study was done in Mont Ventoux, a French Mediterranean mountain which provides contrasted forest environments in terms of elevation and with a marked summer drought. Quantitative traits of annual shoots of 2 years old branches (length, diameter and number of needles, dry mass) and needles (surface and dry mass) where recorded on 80 saplings growing in different light environments. Effects of tree size and architectural position of annual shoot within tree crown on measured traits were higher than any environmental fluctuation. These morphogenetic gradients are consistent with the concept of physiological age of meristems (Barthélémy & Caraglio 2007): huge effect of tree development, branching order and position. All studied traits present a significant plasticity which may be implies in the success of silver firs in the studied site. No clear hierarchy was found between the phenotypic plasticity of annual shoot plasticity and the one of needles. We can suggest that all measured traits act simultaneously during tree development and in response to environmental fluctuations ('a variational module' sensu Wagner et al 2007). (Texte intégral)