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The share of assortments by sales revenue and by volume in hybrid aspen and silver birch plantations during the simulated growth period
Source publication
We analysed the economics of hybrid aspen and silver birch which are both fast-growing hardwoods recommended for the establishment of plantations on abandoned agricultural lands in Northern Europe. If managed during one rotation period the internal rate of return (IRR) of hybrid aspen plantations was 4.4-7.3% and the IRR of silver birch plantations...
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Purpose
The purpose of this paper is to analyze the influence of different factors on forestry production, with an aim to explore the degree of connection between forestry economic growth and influencing factors such as forestry investment, labor input, afforestation area, scientific and technologies progress, and the reform of property-rights regi...
We explore the biophysical potential and economic attractiveness of black spruce (Picea mariana) regeneration in eastern Canada under the high greenhouse gas emission scenario (RCP 8.5) of the Intergovernmental Panel on Climate Change (IPCC). The study integrates net primary productivity and net ecosystem productivity estimates from three major glo...
Currently, incentive payment of carbon mechanism has not yet provided significant economic benefit for community who live in the surrounding forest area as the carbon price is relatively low. Consequently, potential carbon owners are likely to invest conserved carbon biomass into other products that give more profitable economic value. This paper d...
Academic research on smallholders’ forestland-use decisions is regularly addressed in different streams of literature using different theoretical constructs that are independently incomplete. In this article, we propose a theoretical construct for modelling smallholders’ forestland-use decisions intended to serve in the guidance and operationalizat...
Citations
... Silver birch (Betula pendula) and hybrid aspen (Populus tremula × P. tremuloides) are fast-growing deciduous tree species that have been widely planted on former agricultural lands in Northern and Eastern Europe (Johansson 2007;Tullus et al. 2012b;Daugaviete et al. 2020). Several comparative studies have been published on the ecophysiological traits (Õunapuu-Pikas et al. 2022), acclimation to elevated air humidity (Rosenvald et al. 2014;Kukk et al. 2015;Tullus et al. 2017) and economics of plantations composed of silver birch and hybrid aspen (Tullus et al. 2012a). In addition, silver birch and hybrid aspen have been included in studies evaluating effects beneficial to the climate (Lutter et al. 2021), impacts on soil chemistry and growth and productivity of trees on abandoned agricultural land (Daugaviete et al. 2020;Rytter and Lutter 2020;Celma et al. 2022;McKay et al. 2022). ...
... All plantations were established in 1999 or 2000 on previous agricultural land, using either 1-year-old micro-propagated plants (for hybrid aspen) or 1-year old seedlings (for silver birch). The initial planting density was considerably higher in silver birch plantations (SBs) than in hybrid aspen plantations (HAs) (Tullus et al. 2012a). No chemical vegetation treatment was applied after planting (Soo et al. 2009a;Tullus 2013). ...
... All plantations were established for timber production. In Northern and Eastern Europe, the predicted rotation length is 20 − 30 years for hybrid aspen (Tullus et al. 2012b) and 30−35 years for silver birch when grown in plantations on former agricultural land (Lutter et al. 2021;Tullus et al. 2012a). ...
Silver birch (Betula pendula) and hybrid aspen (Populus tremula × P. tremuloides) are widely planted tree species on former agricultural lands in Northern and Eastern Europe due to their fast growth, high biomass production and CO2 sequestration. As few comparative studies on the biodiversity of silver birch and hybrid aspen plantations have been carried out, we aimed to evaluate above- and below-ground diversity in silver birch plantations (SBs) and hybrid aspen plantations (HAs) and associate the trends with environmental variables. For this, we collected data on herbs, ground-dwelling bryophytes, epiphytic bryophytes, lichens, closed forest species and soil fungi from 10 SBs and 10 HAs (< 25 years of age) in Estonia. The richness and composition of herbs was similar in SBs and HAs, whereas all other groups differed either in species richness, composition or both. Overall, HAs hosted higher richness of ground-dwelling bryophytes and epiphytic lichens and lower richness of epiphytic bryophytes than SBs, which was associated with differences in litter and light conditions. The richness of closed forest species was similar between HAs and SBs and increased in correlation with the area of surrounding forests, whereas the compositions differed. The HAs hosted higher fungal richness of all soil fungi, as well as ectomycorrhizal, saprotrophic and plant pathogenic fungi and differed compositionally from SBs. Based on our findings, both birch and hybrid aspen plantations provide benefits with respect to biodiversity, as they support compositionally different assemblages of bryophytes, lichens, closed forest species and soil fungi.
... It should be borne in mind that our study compared the productivity two decades after planting. The expected rotation cycle (based on financial maturity) for such birch monocultures is approximately 35-45 years (Tullus et al., 2012) and 50-55 years for Norway spruce (Korjus et al., 2011), which shows that this study reported the progress in productivity at the mid-term rotation phase. ...
In silviculture, tree species mixing is seen as a potential measure to increase ecosystem carbon (C) sequestration due to higher resulting productivity compared to monocultures. Currently, there is a lack of studies on how monocultures and mixtures of the two main boreal tree species, Norway spruce and silver birch, compare regarding C sequestration and storage in planted stands. We evaluated ecosystem C stocks, stand productivity and soil nutritional status in spruce and birch monocultures as well as mixed stands with 50/50 mixing proportion two decades after afforestation of abandoned agricultural lands with homogeneous soil fertility. We found that Norway spruce monocultures had the highest mean annual increment (MAI), highest ecosystem C stock, and the highest periodic annual increment (PAI). In silver birch stands, C was mostly stored in the stems of the trees, whereas Norway spruce monocultures had a significantly higher share of C stored in the canopy. While the growth of individual silver birches was not influenced by the stand type, Norway spruce was suppressed by the inter-specific competition in the mixtures, where the average tree stem MAI was 56 % lower than in the monocultures. In general, the SOC and soil nutrient concentrations were similar in the mixed-species stands and monocultures. Spruce monocultures had a higher SOC stock in the forest floor. In conclusion, we did not confirm a higher productivity of mixed stands compared to monocultures, but different patterns of C allocations indicate the need for longer observations to identify the silvicultural system with the best climate benefit.
... The rotation cycle of silver birch plantations on former agricultural land is about 20-30 years shorter compared to the conventional 60-year cycle on forest land, based on the expected financial maturity (Tullus et al. 2012). Higher productivity is mainly explained by the legacy of agricultural land use that results in higher soil fertility than in regular forest soils (Wall and Hytönen 2005;Falkengren-Grerup et al. 2006). ...
Silver birch plantations on former agricultural lands grow faster than birch stands on forest land in Northern Europe. For optimal management decisions, there is a need to improve understanding of ecological processes such as competition in plantations where stand structure and soil conditions differ from native forests. We analyzed the effects of intraspecific competition on mortality and periodic annual increment during 15–21 years of age (PAI6) in silver birch plantations. We evaluated six individual tree competition indices (CI) and two competitor selection methods, and tested whether weighting competitor trees based on their cardinal direction from the subject tree would improve the goodness-of-fit of growth models based on CIs. Tree growth parameters were measured and tree locations were mapped in the 0.1 ha sample plots of 11 silver birch plantations. The best CI for predicting PAI6 was the sum of diameter ratios combined with the reverse search cone method for competitor selection. Reducing the weight of competitors toward north improved the performance of the best CI for below-average sized trees but not for above-average sized trees, thus size-class-wise estimation of CIs can be advantageous. Asymmetric CIs performed better than symmetric CIs suggesting that light competition was the prevailing mode of competition.
... Due to abundance, productivity, and efficient self-regeneration, trembling aspen (P. tremula) [7], and particularly its hybrids, which have superior productivity, are a promising alternative, allowing a notable reduction in the rotation cycle [11]. The reproductive ...
Mycorrhizal fungi contribute to crop growth, yields, and stress tolerance. In forests, common mycorrhizal networks are suggested to function as carbon storage and to transfer substances and signals between trees, thus likely contributing to their resilience. Such properties are crucial under increasing environmental stresses, particularly for clonal forestry. However, mycorrhizal communities in relation to tree field performances have been scarcely studied. In this study, mycorrhizal communities on the roots of clones of silver birch and hybrid aspen growing in distinct trials in deep automorphous mineral soils (podzolic and fluvic) under hemiboreal conditions were assessed using internal transcribed spacer sequencing, bioinformatics, and community analysis. The mycorrhizal communities were moderately rich/diverse and were mostly formed by generalist taxa (prevailingly ectomycorrhizal) common for the region. The differences in communities among the tree clones were estimated for silver birch, while for hybrid aspen, the productivity of clones was inversely related to the richness and diversity of the communities, suggesting a top-down effect of the host. Accordingly, some mycorrhizal taxa (e.g., Hyaloscypha sp.) showed clone-specific abundances indicating a preference for a specific host. These findings prompt further functional studies and highlight the need to consider genetic differences of forest regenerative material for maximizing mycorrhizal diversity, as well as for more effective inoculation.
... The categorical variable referring the effect of former agricultural land (Agric) indicated higher growth of DW and G in former agricultural land than in forest site. This was consistent to the previous studies that reported a high growth potential of former agricultural land (Tullus et al., 2012;Lutter et al., 2015;Lutter, 2017;Rytter and Lutter, 2020). Climatic and hydrologic predictors at site level, such as temperature sums, lake index and sea index, were not significant. ...
Great interests in silver birch (Betula pendula) forests have increased in an attempt to handle biodiversity and resilient forest management with more broad-leaved forests. However, up-to-date silver birch growth and yield models are still needed to predict the stand development in the future and support operational forest management and planning. The objectives of this study were to develop site index and stand characteristic models for silver birch plantations. Data for modelling were from the thinning and spacing experiments and tree breeding trials on silver birch plantations in southern and central Finland. The dominant height and site index (SI) models were fitted using the nonlinear mixed effect regression approach based on the Chapman-Richards function with the genetic effect from improved seedlings. The modelling result indicated a logical growth performance over age and higher dominant height with genetically improved seedlings. The stand characteristic models for unimproved seedlings were developed using multivariate mixed-effects modelling approach. The targeted, response variables were the basal area-weighted mean height (HW, m), the basal area-weighted mean diameter (DW, cm) and stand basal area (G, m2 ha−1) of silver birch. Stand biological age (AGE, year), SI estimated based on the model of the current study with the base age of 50 years, and the number of silver birch trees (N, trees ha−1) were all commonly applied as highly significant predictor variables for all of HW, DW, and G models. In addition to these predictors, thinning variables, comprised of the time since last thinning in year and the thinning intensity based on G, were highly significant in the DW and G models with logical behavior. Recent thinning affected negatively at first because trees in thinned stands were slimmer than those in unthinned stands that have grown from the early stage at the same level of N with thinned stands. After 13 years since last thinning, the effect turned positive indicating that the increments were expedited with thinning. Lastly, site type classified as either former agricultural land or forest site was included in the DW and G models. Consequently, all the models developed in this study were evaluated as practicable with easy-to-use predictors and desirable accuracy.
... The method has also been employed in comparing different management regimes under various nature protection scenarios (Sirgmets et al., 2011), analysing pulp and paper assortment recovery, and predicting reductions for roundwood market pricing studies (Sirgmets et al., 2011). Additionally, it has been used to assess management scenarios for hybrid aspen and silver birch plantations established on abandoned agricultural lands (Tullus et al., 2012) and to estimate the potentials and revenue loss of managed forest sites considered for new nature protection areas (Adermann et al., 2015). ...
In this study, assortment yields were studied for Scots pine, Norway spruce, birch spp. (silver and downy birch), European aspen, black alder, and grey alder stand elements. Theoretical assortment yields were calculated using the Ozolinš’ stem taper curve, incorporating tree diameters and heights. The modelled results were compared with actual yields provided by the State Forest Management Centre. During the study, differences in timber assortments and firewood yields were modelled compared to actual data. Changes in wood assortment yields, compared with undamaged and straight trees, depended on the tree species, stand site index, and stand element age. For Scots pine, depending on the stand site index and age, the reduction in log volume ranged from 7 to 28% of the total volume of all assortments. For Norway spruce, it was 5–30%, for birch spp. 30–70%, for aspen 50–90%, for black alder 20–50% and grey alder 5–30%. The increase in firewood volume according to the volume of all assortments was 3–4% for Scots pine, 5–14% for Norway spruce and birch spp., and 5–16% for European aspen. The difference between log and firewood changes represents the change in pulpwood. Over time, the need for new studies arises to adapt to evolving industry practices, including changes in log diameters and quality criteria. The appendix outlines steps that programmers can take to utilize the developed model.
... Comparison of the relative proportions (a) and estimated mean diversities (b) of different fungal guilds among PL-AGRI (birch plantation on former agricultural land), NR-AGRI (naturally regenerated birch stands on former agricultural land) and NR-FOREST (naturally regenerated birch stands on native forest land) stands. (Debeljak, 2006;Laarmann et al., 2009;Runnel et al., 2021), whereas the supply of dead organic matter in the stands on agricultural lands is probably lower, because these stands had only grown to 2/3 of the expected financial maturity based on the rotation cycle (Tullus et al., 2012). In line with this, saprotrophs have been reported to prefer higher amounts of tree litter, whereas EcM fungi prefer lower levels of substrate (Marañón-Jiménez et al., 2021). ...
Short-rotation forestry on former agricultural soils is a novel silvicultural system for producing woody biomass and mitigating climate change through CO2 uptake. However, tree plantations are often criticized for their low biodiversity and are sometimes referred to as "green deserts". We hypothesize that regarding biodiversity, the spontaneous natural regeneration of birch on former agricultural lands may be preferable to plantations. In this study, we compared soil fungal diversity and composition of fast-growing silver birch (Betula pendula Roth) plantations on former agricultural lands (n = 11) with naturally regenerated birch stands on former agricultural lands (n = 11) and native forest birch stands (n = 11) at the age of 21-28 years in hemiboreal Estonia. PacBio third-generation sequencing was carried out to analyse fungal species richness and composition in the soil samples. Sequencing of the fungal ITS region from 33 birch stand soil samples yielded 2830 fungal OTUs. We found that the total fungal species richness, per sample species richness, Shannon diversity index, and Pielou's evenness index did not differ significantly between the studied stand types. However, fungal community composition of both plantations and naturally regenerated stands on former agricultural lands differed significantly from the native forest stands, indicating that previous land use (agriculture vs. forest) had a stronger effect on fungal assemblages than the used regeneration method (planting vs. natural regeneration). The relative abundance of ectomycorrhizal and arbuscular mycorrhizal fungi was higher, and the relative abundance of saprotrophic fungi was lower in plantations than in native birch dominated forest stands. Soil chemical properties were found to be weak explanatory variables for describing soil fungal richness and composition. We identified historical surrounding forest cover, stand age, stand distance from a native forest, and soil Mg content as the factors significantly affecting soil fungal communities. These results indicate that fast-growing birch plantations established on former agricultural soils or naturally regenerated stands on such soils in the Northern Europe region harbour soil fungal diversity levels similar to those of same-aged native birch forests.
... The aim of this study was to describe the first 20 years of changes in soil organic carbon (SOC) and nutritional status (i.e., pH, N, P, K, and C:N ratio) based on resampling soil in silver birch (Betula pendula Roth) plantations on former agricultural soils of hemiboreal Estonia. Silver birch is one of the most promising tree species for plantation forestry in Northern Europe, with a rotation cycle of about 30-35 years on former agricultural soils (Tullus et al. 2012). Repeated soil sampling after 20 years is rare (Bárcena et al. 2014b;Lutter et al. 2016a, b;Rytter and Rytter 2020) but it helps us describe long-term soil processes without having to meet the assumptions associated with space-for-time substitution used in chronosequence studies (e.g. ...
... If the case is one of recovery after 20 years, then this is earlier than found by some other studies in the region, in which SOC levels showed recovery in soils planted with spruce and oak 30 years after afforestation (Vesterdal et al. 2002;Bárcena et al. 2014b). However, the potential of fast-growing tree plantations to mitigate climate change by increasing soil C stocks seems to be challenging to realize (Bárcena et al. 2014a;Noormets et al. 2015;Lutter et al. 2016a;Rytter and Rytter 2020), as the internal nutrient turnover and fast decomposition of organic material supports C accumulation in biomass rather than in soil as the projected rotation cycle is just 35 years (Tullus et al. 2012). SOC stabilization and accumulation in mineral soil are controlled by different factors, such as soil microbial and enzymatic activities, nutrient supply, soil buffering capacity, and litter quality (i.e., tree species) (Guo and Gifford 2002;Fontaine et al. 2004;Vesterdal et al. 2012;Bárcena et al. 2014a;Noormets et al. 2015;Alberti et al. 2017), but mainly by Fig. 2 Twenty-year changes in SOC (%), N (%), C:N ratio, pH, P (mg kg − 1 ), and K (mg kg − 1 ) at different soil depths in the studied plantations (open circles). ...
Purpose
Fast-growing tree plantations on abandoned agricultural soils is a promising management system to sequester atmospheric CO2. However, the effects of fast-growing trees on the nutritional and organic carbon (SOC) status of soils degraded by agriculture, are poorly understood.
Methods
We sampled the soil after 20 years in 10 silver birch plantations on former agricultural soils in hemiboreal Estonia to assess changes in soil chemical properties (SOC, N, C:N ratio, pHKCl, P, and K) in 10-cm vertical mineral soil layers to a depth of 30 cm and to determine the potential environmental drivers of plant-soil interactions.
Results
We observed no depletion of SOC or macronutrients in the upper 0–30-cm soil layer, but found some vertical shifts among the sublayers. The SOC concentration increased by 22% in the upper 0–10-cm soil layer, especially in sites with higher aboveground productivity. Simultaneously, SOC concentration decreased by 17% in the 20–30-cm soil sublayer, which indicating trees’ ability to alter decomposition activity in deeper vertical soil layers. In the 20–30-cm sublayer, SOC mineralization was supported by an 11% decrease in the C:N ratio. Similarly, the total N concentration increased in the 0–10-cm soil layer by 13%. The concentration of plant-available P increased by ~ 30% in the 20–30-cm sublayer.
Conclusion
Two decades of afforestation of former agricultural soils caused vertical stratification of SOC in the upper mineral soil layer (0–30 cm) where trees can access deeper nutrient pools for active cycling, but caused no loss of SOC or nutrients.
... Sa croissance en surface et en volume peut être importante au cours de seulement une à deux décennies. L'abandon et l'afforestation d'un nombre croissant de terres agricoles dans les pays scandinaves, baltiques, d'Europe de l'Est (Tullus et al., 2012 ;European Network for Rural Development, 2010 ;Kund et al., 2010 ;Zasada 2014) et aux Pays-Bas (Schelhaas et al., 2014) profite considérablement à l'expansion de ce colonisateur (Perala et al., 1990 ;Niemistö et al., 2008 ;Hein et al., 2009 ;Hynynen et al., 2010). ...
... Cette méthode, qui imite le processus naturel de facilitation dans les successions forestières, aurait été utilisée en Allemagne et en Suisse depuis près de 200 ans (Pommerening et al., 2004). Le bouleau a démontré son efficacité comme peuplement d'abri du sapin (Abies alba Mill.), de l'épicéa, du hêtre et du chêne dans des conditions hémiboréales (Liziniewicz et al., 2009 ;Hynynen et al., 2010 ;Tullus et al., 2012 ;Dudelis 2013) et en Europe occidentale (Pommerening et al., 2004 ;Stark et al., 2013Stark et al., et 2015, à condition que sa densité soit judicieusement régulée. Ces types de peuplements à deux étages produisent un plus grand volume total de bois, permettent un approvisionnement en bois à court terme grâce à la récolte de l'essence d'abri à croissance rapide et améliorent la conformation des essences du sous-étage. ...
... Des recolonisations de bouleau ont récemment eu lieu à grande échelle dans les pays européens où l'activité agricole a diminué, par exemple dans certaines régions de France (Prévosto et al., 2004), d'Europe du Nord (Hynynen et al., 2010 ;Tullus et al., 2012) et d'Europe de l'Est (Kund et al., 2010 ;Tullus et al., 2013 ;Zasada et al., 2014). ...
[fr] Cinq essences, souvent en peuplement monospécifique, composent près de 80 % du volume de bois sur pied des forêts d’Europe occidentale. Celles-ci souffrent de plus en plus du changement climatique et de bioagresseurs, confirmant la nécessité de les diversifier. Dans ce contexte, un nombre croissant de forestiers s’interroge sur l’intérêt du bouleau, qui colonise les trouées forestières, notamment après les coupes rases et chablis. L’objectif de la thèse est d’analyser quelles pourraient être les voies de valorisation des bouleaux verruqueux (Betula pendula Roth) et pubescent (B. pubescens Ehrh.) dans la gestion forestière et sur le marché du bois et, en regard des résultats, de proposer des recommandations sylvicoles. Premièrement, la ressource en bouleau (Chapitre 2) a été décrite au niveau : a) de sa distribution et de son abondance par l’intermédiaire des inventaires forestiers disponibles ; b) de sa façon d’occuper les peuplements, à travers l’exemple de la Wallonie, avec les données de l’Inventaire Permanent des Ressources Forestières de Wallonie (IPRFW) ; c) de son évolution sur base de la littérature et des données de l’IPRFW. L’aire de distribution du bouleau est très étendue à l’échelle de l’Eurasie, principalement à base de bouleau pubescent dans le nord, où le bouleau est le principal feuillu, et de bouleau verruqueux dans les climats plus tempérés. En Europe occidentale, le bouleau représente de 0,5 à 6 % du volume forestier total selon le pays. En Wallonie, la boulaie pure concerne 30 % du volume de bouleau, et le restant se répartit dans des peuplements d’autres essences, surtout à base de chênes indigènes, dans les régénérations naturelles, les taillis et taillis sous futaie. Les bouleaux sans défaut apparent (nœud et branche) et de plus de 38 cm de diamètre sont rares (moins de 0,3 % du volume de bouleau). D’autre part, la ressource en bouleau s’accroit rapidement en volume et en surface occupée. Deuxièmement, le potentiel du bouleau pour la gestion forestière et l’industrie du bois est analysé sur base de la littérature, et les résultats sont organisés selon ses atouts, faiblesses, opportunités et menaces (AFOM)(Chapitre 3). Parmi ses atouts, de nombreuses conditions climatiques lui conviennent ; il est performant sur une large gamme de sols ; il a une capacité d'adaptation physique aux modifications de son environnement et une grande diversité génétique ; à ce jour, il n'est pas sérieusement affecté par des ravageurs ou maladies ; il favorise la biodiversité ; il optimise le fonctionnement du sol ; il peut intégrer une diversité de peuplements mélangés et, en essence d’abri, il facilite le développement d’autres essences ; ses propriétés permettent des utilisations polyvalentes, également en bois d’œuvre, comme illustré par le marché très développé dans le Nord de l’Europe, les Pays baltes et la Russie. Ses faiblesses, telles que la grande sensibilité de sa cime à la compétition et de son bois à la pourriture, et son abondance dans les mélanges avec d’autres essences, doivent être maîtrisées par une sylviculture adaptée. Le contexte socio-économique et climatique lui offre des opportunités de colonisation dans les trouées forestières non replantées, ou dans lesquelles il est l’une des seules essences à résister au gibier. Il bénéficie également des politiques promouvant la diversification des forêts, et d'une perception favorable du public pour ses rôles écologiques. Les principaux obstacles au développement du bouleau en Europe occidentale sont le manque d'information sur ses atouts et sur les utilisations de son bois, et l’absence de consignes de sylviculture adaptées à ses faiblesses, ainsi que des normes pour son utilisation en construction. Sur base de la ressource et de l’organisation de l’industrie, le forestier devrait viser la production rapide de grumes de haute qualité (de grande dimension et sans défaut). La sylviculture d’arbres-objectif (AO) permet d’optimiser la croissance diamétrique des AO désignés par le détourage et de contrôler leur qualité par l’élagage. Troisièmement, nous avons analysé le développement de 704 AO détourés dans 38 régénérations naturelles denses de bouleau dans le sud de la Belgique et le nord-est de la France (Chapitre 4). Il en résulte que le bouleau peut atteindre un diamètre de 50 cm en moins de 60 ans. La modélisation de l’évolution du diamètre de cime indique que les AO de 40, 50 et 60 cm de diamètre forment respectivement des cimes d’environ 8, 10 et 12 m de large. Dans 3 sites, l’accroissement diamétrique des AO en réponse à différentes précocités de détourage est comparé à celui de bouleaux témoins. Sans intervention, l’accroissement diamétrique décline à cause de la compétition dès que le peuplement atteint l’âge de 4 à 5 ans. Avec le détourage dès cet âge, il est doublé, et pourrait rester supérieur à celui de bouleaux détourés plus tardivement pendant au moins 20 ans. Les bouleaux détourés après 9-12 ans semblent amoindrir durablement leur accroissement diamétrique, et pourraient ne jamais atteindre les dimensions nécessaires pour une utilisation en bois d’œuvre. La discussion (Chapitre 5) commence par une réflexion sur le lien entre la science et les connaissances empiriques pour cette recherche. Deuxièmement, elle articule les acquis des 3 chapitres sous forme d’une suite de questions que peut se poser le gestionnaire forestier quant aux essences à favoriser. Le bouleau semble être une essence forestière d’avenir, d’un point de vue autécologique, pour ses fonctions écologiques et sylvicoles au service des autres essences, et pour la production rapide de bois et de PFNL, dans une gestion globale basée sur le mélange d’essences. L’utilisation industrielle de son bois, également en bois d’œuvre, est réaliste dans le contexte de l’Europe occidentale. Dès lors, nous proposons des consignes de sylviculture pour produire des grumes de haute qualité, et des consignes générales de gestion des peuplements comportant du bouleau. Enfin, des perspectives sont proposées. Du point de vue pratique, il faut sensibiliser et informer les gestionnaires forestiers et l’industrie du bois sur le potentiel du bouleau. Il est nécessaire d’éditer un guide de sylviculture, de proposer des formations techniques, et de développer des normes pour l’utilisation de son bois. Du point de vue de la recherche, il faudrait étudier le lien entre la productivité du bouleau et la station, multiplier les dispositifs expérimentaux de mesure de l’accroissement diamétrique pour pouvoir le modéliser, et créer des groupes de travail incluant les scientifiques, les gestionnaires forestiers et l’industrie du bois.
[en] Five tree species comprise nearly 80% of the forest standing stock volume in Western Europe, often in monoculture. These forests are increasingly suffering from climate change and bio-aggressors, confirming the need for forest diversification. In this context, birch colonising forest gaps, e.g., after clear-cuts or windfalls, may be an interesting tree species. The aim of the thesis is to analyse the potential of silver (Betula pendula Roth) and downy (B. pubescens Ehrh.) birch for forestry and the forest-based industry sector, and to provide silvicultural recommendations. Firstly, we described birch resource (Chapter 2) in terms of a) distribution and abundance, using available forest inventories; b) stand structure and composition, through the example of Wallonia, using data from the Permanent Inventory of Forest Resources in Wallonia (IPRFW); c) evolution, based on literature and on the IPRFW data. Birch has a very wide distribution across Eurasia, dominated by downy birch in the north, where birch is the main hardwood species, and dominated by silver birch in temperate climates. In Western Europe, birch comprises 0.5-6% of the forest standing stock volume, depending on the country. In Wallonia, only 30% of the birch volume concerns pure birch stands. Most of the birch resource is distributed in all kinds of stand composed by other species, mostly with European oaks, and in natural regenerations and in coppice and coppice-with-standards forests. Birch stems with diameter at breast height (dbh) larger than 38 cm and with no visible defect (e.g., branches and knots) are rare (less than 0.3% of the standing stock volume). On the other hand, birch standing stock volume appears to rapidly increase over time. Secondly, we analysed the potential of birch for forestry and the forest-based industry sector by compiling and discussing literature, and we organised the results according to its strengths, weaknesses, opportunities and threats (SWOT) (Chapter 3). Among the strengths, birch is suitable for a wide variety of climatic conditions; it performs well on a wide range of soils; it has the capacity to adapt physically to changes in its environment and it has a high genetic diversity; to date, it has not been seriously affected by pests or diseases; it promotes biodiversity; it optimises soil functioning; it can compose a variety of mixed stands, and as a nurse species, it facilitates the development of other tree species; wood properties allow versatile timber uses, as illustrated by the market in Northern Europe, in the Baltic States and in Russia. Foresters should manage its weaknesses, such as high sensitivity to crown competition and to wood decay, and its abundance in tree species mixtures. Socio-economic and climatic context offers opportunities to birch for colonising forest gaps that have not been planted or in which birch is one of the rare species to resist to game overpopulation. It also benefits from policies promoting forest diversification and from favourable public perception for its ecological roles. The main obstacles to birch development in Western Europe are the lack of information on its strengths and uses, the absence of silvicultural guidelines adapted to its weaknesses, and the lack of standards for wood use in construction. Based on birch resource and on industry’s organisation, foresters should aim at the rapid production of high quality (large and free from defect) birch logs. Crop tree silviculture is a means to optimise dbh growth by crown release and quality by pruning. Thirdly, we analysed dbh growth and crown development of 704 crown released target birches in 38 dense birch natural regenerations in southern Belgium and north-eastern France (Chapter 4). We found that birch can reach a dbh of 50 cm in less than 60 years. Crown diameter evolution model indicates that target birches with a dbh of 40, 50 or 60 cm have a crown of about 8, 10 or 12 m wide, respectively. We also compared dbh growth of target birches in response to different crown release earliness in three subsamples. Without intervention, dbh growth declines due to competition as soon as the stand reaches the age of 4-5 years. With crown release at this age, dbh growth is doubled and could remain higher than that of birches later crown released, at least for 20 years. When crowns are released later than 9-12 years of age, birches appear to have reduced their dbh growth potential, and they may never reach the needed dimension for best timber uses. The discussion (Chapter 5) begins with a reflection about the link between science and empirical knowledge in this research. Secondly, the chapter articulates findings of the three research through successive questions that the forester may ask when choosing which tree species to favour. Birch seems to be an interesting forest tree species, from an autoecological point of view, for its ecological and silvicultural functions at the service of other species, and to produce valuable wood. Industrial use of birch wood is realistic in the Western European context. We therefore proposed silvicultural guidelines for producing high-quality logs, and general management guidelines for common stands composed with birch. Finally, perspectives are proposed. From a practical point of view, there is a need to inform foresters and timber industry about the potential of birch and to develop guidelines and technical training about birch silviculture, and standards for the use of birch wood. Concerning research, we should study the link between birch productivity and site, add experimental plots for dbh growth measuring, and create working groups including scientists, foresters and timber industry.
... Hybrid aspen clones are grown for multiple purposes (for example, to produce sawlogs, pulpwood, or energy wood), and they provide raw materials for diversified forest product markets [1]. For first rotation plantations, a high yield of quality assortments with reduced harmful biotic and abiotic risks is desired [3,4]. Considerable damage is caused by stem rot, which is commonly associated with fungus species such as Phellinus tremulae (Bond) Bond et Boris. ...
Hybrid aspen (Populus tremula L. × Populus tremuloides Michx.) plantations may produce valuable sawlogs for the growing timber market and contribute to carbon sequestration. However, environmental risks such as stem rot, the spread of which is facilitated by insect or frost damage, may reduce the proportion of valuable timber. It is important to understand the various factors affecting the spread of aspen rot to mitigate negative impacts with tree breeding. This study aimed to assess the impact of frost cracks and large poplar borer on stem rot in hybrid aspen clones in two clonal trials in Latvia. Genetic parameters for the traits were also estimated. The presence of insect passages substantially increased the probability of stem rot without distinct clonal differences. A negative and mainly insignificant correlation was observed between rot and stem cracking. The highest broad-sense heritability (H² = 0.21) and strong site-site genotypic correlation (0.86) showed that the probability of stem rot is genetically determined in the study material. Significant differences in diameter at breast height, the presence of stem rot, and its severity were found among the clones, albeit without undesirable positive correlation between growth and presence of decay. This indicated its potential to improve both productivity and rot resistance.
