Incertitudes pour l’estimation des facteurs d’expansion de la biomasse chez l’épicéa en République tchèque

Abstract

-Nation wide estimates of the changes in forest biomass are needed for the greenhouse gas (GHG) reporting under the Climate Convention. The bases for national GHG reporting concerning forest sector are the national forest inventory (NFI) programmes. Since these programmes were mostly established for monitoring of timber resources, one of the current challenges for the NFIs is the development of methodology, such as biomass expansion factors (BEFs). The methodology for carbon stock change estimation should be transparent and verifiable, but this demand is not currently met due to the fact that the source data and uncertainty in the applied BEFs are not known. Here we developed BEFs with uncertainty estimation applicable to stand wise inventory of Norway spruce forests in the Czech Republic. BEFs were constructed, based on tree wise data from permanent research plots, by applying biomass and volume models to tree-level data. These BEFs were age-dependent and their uncertainty was sensitive to the dependencies among errors. Most of the uncertainty in the BEFs was due to uncertainty in the biomass and volume models applied.biomass expansion factor / Monte Carlo simulation / greenhouse gas inventory / national forest inventory Résumé -Incertitudes pour l'estimation des facteurs d'expansion de la biomasse chez l'épicéa en République tchèque. Les estimations de la biomasse des forêts servent à évaluer les effets des changements climatiques et à dresser des rapports internationaux. En foresterie, les rapports nationaux sur les gaz à effet de serre (GES) sont basés sur l'inventaire forestier national. L'objectif premier de cet inventaire étant la prévision des ressources de bois brut, l'inventaire des GES appelle des méthodes de prévision basée sur les facteurs d'expansion de la biomasse. Les méthodes d'estimation des GES devraient être transparentes et vérifiables -objectif souvent non atteint parce que l'origine et l'incertitude des facteurs d'expansion de la biomasse ne sont pas connues. Dans cette étude nous avons développé des facteurs d'expansion de la biomasse des forêts de sapin dans la République tchèque et calculé l'incertitude de ceux-ci. Les facteurs ont été estimés en fonction des mesures au niveau de l'arbre dans des zones d'échantillonnage permanentes et de l'application des modèles de volume et de biomasse. Ces facteurs d'expansion étaient dépendants de l'âge et leur incertitude sensible aux corrélations entre les erreurs. L'incertitude des facteurs d'expansion était principalement due aux modèles de biomasse et de volume appliqués. facteur d'expansion de la biomasse / simulation Monte Carlo / inventaire des gaz à effet de serre / inventaire forestier national

Biomass expansion factors for Eucalyptus globulus stands in Portugal

“…Brown, 2002;Jalkanen et al, 2005;Lehtonen et al, 2007;Tobin and Nieuwenhuis, 2007). These reports support the findings concerning resource allocation during the growth process: initially low values of stem biomass, resulting from a biomass increase in the root system and leaves in the crown, followed by increased resource allocation to the stem biomass.…”

“…Constant BEFs have been applied (Löwe et al, 2000) despite the fact that BEFs vary depending on growth conditions and the phase of stand development (Lehtonen et al, 2007;Soares and Tomé, 2004;Satoo andMadgwich, 1982 in Lehtonen et al, 2004). To reduce the uncertainty associated with the use of BEFs for biomass estimation, non-constant BEFs have been developed in specific studies to account for variation in the allometry of trees reflecting the stage of stand development.…”

Biomass Distribution and Development of Allometric Equations for Non-Destructive Estimation of Carbon Sequestration in Grafted Mango Trees

“…BEFs are needed as a complement of growth models that do not include biomass predictions. In spite of the fact that the BEFs vary with the phase of stand development, constant BEFs are applied in forestry and agro-forestry studies (Löwe et al, 2000;Lehtonen et al, 2007). But to reduce the uncertainty associated with the use of BEFs for biomass estimation, we estimated the BEF of different age groups as the ratio of the biomass to the volume, resulting in a dimensional variable and expressed in Mg m -3 .…”

Incorporating management history into forest growth modelling

“…The version of BIOME-BGC we use in this study is not designed to simulate mixed-species forest, so the up to 20 percent of non-homogenous species on any plot may have some minor effect. Uncertainty in biomass expansion factors (Lehtonen et al 2007) is also possibly biasing on some plots, where the by-plot ratio of volume to biomass is not the same as the mean by-tree relationship for the dominant species (Tab. 1).…”