Studies on wood basic density (BD) vertical variations become essential to predict more accurately the within-stem distributions of biomass and wood quality in the forest resource. The vertical ...variation of wood BD in the stem has been little studied until now, most BD studies being based on measurements taken at breast height. The main objective of this work was to observe and to understand the patterns of vertical BD variation within stems in relation to classical dendrometric variables and to propose relevant equation forms for future modelling. Two softwood species were studied:
Abies alba
and
Pseudotsuga menziesii
. Contrasted thinning intensities were studied including strongly thinned plots
versus
control plots without thinning. BD was most of the time highest at the base of the tree for both species. Then, after a strong decrease from the base of the tree, an increase in BD was often observed towards the top of the tree especially for
A. alba
. The variation in BD with height was stronger for the unthinned plots than for the heavily thinned ones of
A. alba
. The opposite was observed for
Ps. menziesii
. The modulation of growth rate and tree size through thinning intensities modifies the observed vertical variations in BD. Two types of biexponential models were proposed to describe BD variations. The first model used the height in the stem and classical easily-measurable tree variables as inputs, the other one additionally used BD at breast height (BD130). The relative RMSE of BD for
A. alba
and
Ps. menziesii
were 9.9% and 8.1%, respectively, with the model without BD130 and 7.6% and 5.9%, respectively, with the model including BD130.
•A suitable GEDI RH metric was selected to represent NFI dominant height at plot level.•A method that pairs up NFI plots with nearby GEDI footprints up to a critical distance suggested by the ...semi-variance examination.•Small area estimation of forest volume was improved with the help of GEDI auxiliary data.
The French National Forest Inventory provides detailed forest information up to large national and regional scales. Forest inventory for small areas of interest within a large population is equally important for decision making, such as for local forest planning and management purposes. However, sampling these small areas with sufficient ground plots is often not cost efficient. In response, small area estimation has gained increasing popularity in forest inventory. It consists of a set of techniques that enables predictions of forest attributes of subpopulation with the help of auxiliary information that compensates for the small field samples.
Common sources of auxiliary information usually come from remote sensing technology, such as airborne laser scanning and satellite imagery. The newly launched NASA’s Global Ecosystem Dynamics Investigation (GEDI), a full waveform Lidar instrument, provides an unprecedented opportunity of collecting large-scale and dense forest sample plots given its sampling frequency and spatial coverage. However, the geolocation uncertainty associated with GEDI footprints create important challenges for their use for small area estimations.
In this study, we designed a process that provides NFI measurements at plot level with GEDI auxiliary information from nearby footprints. We demonstrated that GEDI RH98 is equivalent to NFI dominant height at plot level. We stressed the importance of pairing NFI plots with nearby GEDI footprints, based on not only the distance in between but also their similarities, i.e., forest heights and forest types. Subsequently, these NFI-GEDI pairs were used for small area estimations following a two-phase sampling scheme. We showcased that, with an adequate sample size, small area estimation with GEDI auxiliary data can improve the accuracy of forest volume estimates.
Abstract
Context
Bioenergy from wood can contribute to reach the goals of energy-transition policies. Use of wood as fuel should focus on low-quality wood, e.g. by-products from timber production, ...which production and supply is related to various management decisions. Reaching the policy objectives efficiently remains an issue.
Aims
The aims are (1) to develop a modelling approach that links local management decisions with indicators of the whole wood fuel production and supply chain and (2) to test the model in a case study. The study should further provide first insights on how indicators of energy, nutrient and worktime efficiency vary according to wood fuel chain characteristics and the related management decisions.
Methods
The model depicts the flow of wood (biomass, nutrients, moisture content, heating value) from the forest stand to the heating plant for each silvicultural intervention simulated with a growth and yield model. It further quantifies the energy and worktime spent on different wood fuel chain tasks (e.g. felling, forwarding) set by the user. We defined four scenarios according to the scale of energy production (large vs. small) and the demand for wood fuel (high vs. moderate).
Results
The case study revealed that the model outputs were plausible. Energy efficiency largely varied depending on the type of silvicultural intervention. Large-scale production associated with high demand was most favourable for energy and worktime efficiencies. In contrast, nutrient efficiency was best for small-scale production associated with moderate demand.
Conclusions
Local management decisions all along the wood fuel chain highly influenced efficiency indicators, and thus its relevance for energy-transition policies. Our model may contribute to strategic decision making in different forestry and energy production contexts.
Key message
We provide a database of 52 silvicultural scenarios recommended in French public forests including relevant dendrometric variables and metrics for carbon accounting. The dataset is ...available at
https://doi.org/10.57745/QARRFS
. Associated metadata are available at
https://metadata-afs.nancy.inra.fr/geonetwork/srv/fre/catalog.search#/metadata/f76ed27f-325d-493b-8731-0995dcaa7805
. Special attention was paid to offer carbon metrics required for the French
Label Bas Carbone
offset projects.
Display omitted
•Published data were compiled worldwide to quantify the effects of removing residues.•We found overall reductions in total and available soil nutrients.•This was due to increases in ...nutrient outputs and maybe changes in microbial activity.•Soil fertility loss has a negative effect on the growth of the subsequent forests.•We identified the causes of variability of the effects and hence mitigation measures.
Increasing attention is being paid to using modern fuelwood as a substitute for fossil energies to reduce CO2 emissions. In this context, forest biomass, particularly harvesting residues (branches), and stumps and associated coarse roots, can be used to supply fuelwood chains. However, collecting harvesting residues can affect soil properties and trees, and these effects are still not fully understood. The main objective of the present study was to compile published data worldwide and to quantify the overall effects of removing harvesting residues on nutrient outputs, chemical and biological soil fertility and tree growth, through a meta-analysis. Our study showed that, compared with conventional stem-only harvest, removing the stem plus the harvesting residues generally increases nutrient outputs thereby leading to reduced amounts of total and available nutrients in soils and soil acidification, particularly when foliage is harvested along with the branches. Losses of available nutrients in soils could also be explained by reduced microbial activity and mineralization fluxes, which in turn, may be affected by changes in organic matter quality and environmental conditions (soil compaction, temperature and moisture). Soil fertility losses were shown to have consequences for the subsequent forest ecosystem: tree growth was reduced by 3–7% in the short or medium term (up to 33years after harvest) in the most intensive harvests (e.g. when branches are exported with foliage). Combining all the results showed that, overall, whole-tree harvesting has negative impacts on soil properties and trees that may have an impact on the functioning of forest ecosystems. Practical measures that could be taken to mitigate the environmental consequences of removing harvesting residues are discussed.
To meet growing demand for wood, particularly softwoods, the authors study a number of new silvicultural pathways for planting 3 species: Douglas fir, spruce and maritime pine. The goal of these ...pathways is to achieve specialised production of either industrial and workable timber, or a mixture of industrial and workable timber with medium-diameter workable timber. Pathways of this type have already been standardised for hardwoods, generally on fertile farmland. In a less fertile forest context, softwoods have a significant potential for woody production but specialized pathways and their profitability have yet to be studied. This article describes the innovative work being done to construct and simulate profitable production, new potential pathways, where plantation density, rotation time, the level of fertility are made to vary using the data from the FCBA test network in conjunction with the FCBA growth models (Oasis for spruce and Douglas fir, Sylveco for maritime pine). Economic data is derived from auction sales statistics and the ONF management and forestry work costs for the period 2012-2015. The Economics module developed by FCBA and ONF on the Capsis platform in the framework of the ICI project (Futurol) was used for the economic simulations. The analyses show that compared to conventional pathways, these pathways generally increase productivity but are nonetheless less profitable than current economic assumptions, although results vary according to species, fertility and the particular pathway. The sensitivity study shows that variations in the price of wood could alter the performance ratings as between conventional and specialised pathways.
Pour répondre à une demande croissante en bois, en particulier résineux, les auteurs étudient de nouveaux itinéraires sylvicoles en plantation pour 3 essences : le Douglas, l’Épicéa et le Pin maritime. Ces itinéraires visent une production spécialisée soit exclusivement en bois d’industrie et bois énergie (BIBE), soit un mixte BIBE et bois d’œuvre (BO) de diamètre moyen. De tels itinéraires sont déjà référencés pour les feuillus, plutôt sur terrains agricoles fertiles. En contexte forestier moins fertile, les résineux présentent un potentiel de production ligneuse intéressant, mais dont les itinéraires spécialisés, et leur rentabilité économique, restent à étudier. L’article présente le travail original réalisé pour construire et simuler les productions associées aux résultats économiques de nouveaux itinéraires potentiels, en faisant varier les densités de plantation, les durées de révolution, les niveaux de fertilité, à partir de données du réseau d’essais FCBA et à l’aide de modèles de croissance du FCBA (Oasis pour Épicéa et Douglas ; Sylveco pour Pin maritime). Les données économiques proviennent des statistiques des ventes de bois et des coûts de travaux et de gestion de l’ONF sur la période 2012-2015. Les simulations économiques ont été réalisées avec le module Economics développé par FCBA et ONF sur la plateforme Capsis dans le cadre du projet ICIF (Futurol). Les analyses montrent que par rapport aux itinéraires classiques, ces itinéraires augmentent en général la productivité mais restent moins rentables dans les hypothèses économiques actuelles, avec cependant des résultats différenciés selon l’essence, la fertilité et l’itinéraire. Les résultats de l’étude de sensibilité montrent que les variations des prix du bois pourraient moduler le classement des performances entre les itinéraires classiques et spécialisés.
La plantation forestière est un outil important pour l’adaptation des forêts aux changements globaux. Les échecs parfois récurrents dans certains contextes, les coûts associés à la plantation, la ...pénibilité du travail pour les ouvriers forestiers ainsi que les impacts environnementaux parfois négatifs sont autant de facteurs qui freinent le recours à la plantation et peuvent ainsi limiter la capacité d’adaptation des forêts. Un ensemble de travaux ont été menés pour répondre aux besoins en innovation technique sur les méthodes de plantation exprimés par les praticiens. Ces travaux portent sur le processus d’innovation en sylviculture et sur l’amélioration technique des méthodes de plantation. L’analyse du processus d’innovation indique une faiblesse des réseaux sociotechniques associée à un mauvais partage des connaissances entre acteurs, et une réticence à l’investissement dans du nouveau matériel, dans un contexte économique perçu comme incertain. Ces observations suggèrent qu’un des leviers possibles serait une meilleure mise en réseau des acteurs, à travers différents liens fonctionnels: partage d’information, échanges de services, construction de partenariats économiques. Des exemples de méthodes innovantes pour réaliser chacune des différentes étapes de l’itinéraire de plantation (préparation du site, plantation, entretiens), répondant aux besoins d’innovation technique exprimés par les praticiens, sont ensuite présentés.
The area of French forest has grew by 60% in a century, and is at the fourth position on the European rank; Its harvesting was doubled at the same time; however the national trade-balance of the wood ...products sector is still in deficit. This forest is also facing important changes: climatic (composition and productivity of forest are affected, frequency and intensity of forest disturbances increase), societal (workers are fewer in the forest and we are more aware of benefits and services to society provided by forest) and bioeconomic (fossil resources decrease and we need of renewable materials). Wood is a versatile material which is renewable and can be used from construction, furniture to pulp and composite material, with a final recycling in energy. This cascading use of wood products enables a low carbon production of materials and energy, particulary effective for new challenges in bioeconomy. To address this joint challenge of stronger and differentiated demands on wood resource and threats and constraints on the forest, some innovations and research of the public forest service are presented in this paper. The diversity of solutions (in harvesting, silvicultural treatment, species, soil monitoring…) underlines the potential of innovations in forest management and the need to mix and transfer them.
Même si la surface de la forêt française a progressé de 60% en un siècle, la plaçant à la quatrième place au rang européen, que sa récolte a dans le même temps doublé, la balance commerciale du bois et des produits dérivés est la seconde déficitaire au niveau national. Cette forêt est également confrontée à d’importants changements : climatiques, pouvant faire varier sa composition et son étendue spatiale ; sociétaux, avec de moins en moins de main-d’oeuvre en forêt simultanément à une prise de conscience des nombreux services écosystémiques rendus par ces espaces naturels ; mais surtout mondiaux avec la diminution des ressources fossiles, qui peuvent être pour partie remplacées par ce matériau polyvalent qu’est le bois. Le bois est effectivement une ressource renouvelable qui peut répondre à différents besoins de nos sociétés (construction, meubles, emballage, papier, chimie, matériaux composites, énergie), avec une utilisation des produits en cascade, jusqu’à un recyclage final ou une valorisation énergétique, assurant une production de matière et d’énergie à faible niveau de dioxyde carbone, particulièrement efficace. Pour relever ce défi conjoint de demandes plus fortes et plus différenciées sur la ressource, et de menaces importantes sur son évolution, quels sont les leviers à la disposition des gestionnaires de la forêt publique ? Cet article présente quelques pistes d’innovations à l’interface entre recherche et gestion, qui explorent des solutions différentiées mais ciblées sur des attentes des gestionnaires. La diversité des exemples en exploitation, renouvellement des peuplements, sylviculture et suivi de la fertilité des sols, souligne la richesse des innovations potentielles et le besoin de les mêler pour répondre aux attentes de la société. La forêt publique est façonnée par l’homme depuis des siècles, permettons-lui ensemble de s’adapter, et de nous aider à relever le défi d’une société plus sobre, valorisant les matériaux renouvelables, tout en continuant à assurer les multiples services écosystémiques.
La biomécanique étudie les réactions et adaptations des êtres vivants à leur environnement mécanique, par exemple aux oscillations et forces exercées par le vent. Au-delà des théories anciennes de la ...sécurité mécanique constante, la mécanobiologie a récemment formalisé les signaux mécaniques, la perception des cellules vivantes et les réponses de croissance. Ces mécanismes physiologiques font que l’arbre ne forme vraiment du bois, tissu de soutien, que lorsqu’il est mécaniquement stimulé. La croissance est contrôlée par les déformations mécaniques perçues, qui deviennent alors pour l’arbre de bons indicateurs de sécurité. Pour appliquer ces connaissances aux forêts, le projet ANR FOR-WIND a l’ambition de développer une mécanobiologie adaptée aux temps longs et aux conditions naturelles complexes. L’enjeu est de concevoir les pratiques d’aménagement avec de nouveaux indicateurs de vulnérabilité aux vents forts, qui raisonnent l’effet du changement climatique, de la structure du paysage, de la sylviculture ou de l’amélioration génétique au travers des processus clés mais négligés d’endurcissement des arbres aux vents usuels.
Key message
This article presents a specific methodology for assessing the scaling of the frequency distribution of the branch diameters within a tree from terrestrial laser scanning (TLS), using ...large oak trees (
Quercus petraea
(Matt.) Liebl.) as the case study. It emphasizes the potential of TLS in assessing branch scaling exponents and provides new insights in forest ecology and biomass allometric modelling.
Context
Many theoretical works invoke the scaling allometry of the frequency distribution of the branch diameters in tree form analyses, but testing such an allometry requires a huge amount of data that is particularly difficult to obtain from traditional measurements.
Aims
The aims of this study were (i) to clarify the theoretical and methodological basics of this allometry, (ii) to explore the possibility of establishing this allometry from terrestrial laser scanning (TLS) and geometric modelling for the solid wood structure (i.e. diameters > 7 cm) of large trees, and (iii) to highlight the major methodological issues.
Methods
Three large oak trees (
Quercus petraea
(Matt.) Liebl.) were digitized in leaf-off conditions from multiple points of view in order to produce accurate three-dimensional point clouds. Their woody structure was modelled using geometric procedures based on polyline and cylinder fitting. The allometry was established using basics found in literature: regular sampling of branch diameters and consideration of the living branches only. The impact of including the unpruned dead branches in the allometry was assessed, as well as the impact of modelling errors for the largest branch diameter classes.
Results
TLS and geometric modelling revealed a scaling exponent of − 2.4 for the frequency distribution of the branch diameters for the solid wood structure of the trees. The dead branches could highly influence the slope of the allometry, making essential their detection in TLS data. The accuracy of diameter measurement for the highest diameter classes required particular attention, slight errors in these classes having a high influence on the slope of the allometry.
Conclusion
These results could make it possible automated programs to process large numbers of trees and, therefore, to provide new insights in assessing forest structure, scaling, and dynamics for various environments in the context of climate change.
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