Free access article

Ann. For. Sci. 62 (2005) 845-851
DOI: 10.1051/forest:2005075

Estimation of the biomass stock of trees in Sweden: comparison of biomass equations and age-dependent biomass expansion factors

Anneli Jalkanen^a, Raisa Mäkipää^b, Göran Ståhl^c, Aleksi Lehtonen^b and Hans Petersson<sup>c

a</sup>  University of Helsinki, PO Box 27, 00014 University of Helsinki, Finland
^b  Finnish Forest Research Institute, Unioninkatu 40 A, 00170 Helsinki, Finland
^c  Swedish University of Agricultural Sciences, Forest Resource Management and Geomatics, 901 83 Umeå, Sweden

(Received 13 April 2004; accepted 14 March 2005; published online 15 December 2005)

Abstract - Differences and uncertainties of alternative methods applicable to estimation of biomass in national greenhouse gas inventories are evaluated. The alternative methods employed to obtain biomass estimates of trees are (1) aggregated stand-level volume estimates multiplied by biomass expansion factors (BEF), and (2) biomass equations applied to tree-wise data of a national forest inventory. In comparison to the reference value obtained using tree-wise biomass equations, the age-dependent BEFs for the whole of Sweden resulted in a 6.7% lower aboveground biomass estimate. The estimates were the closest for conifer-dominated forests in central Sweden, and the largest discrepancies were for spruce in southern Sweden. This result indicates that these age-dependent BEFs cannot be applied to conditions where stand development deviates from the conditions under which the BEFs were developed. The degree of uncertainty in both methods was highest in the young age-classes. At the regional level, the relative standard errors of the BEF-based biomass estimates were in the range of 4-13%.

Résumé - Estimation de la biomasse sur pied en Suède : comparaison des équations de biomasses avec les facteurs d'expansion de la biomasse (BEF) liés à l'âge. Nous avons évalué les différences et les incertitudes des méthodes alternatives d'estimation utilisable dans les inventaires nationaux de GES. Ces méthodes sont (1) la multiplication des estimations du volume au niveau des peuplements avec les facteurs d'expansion de la biomasse (BEF) et (2) l'application des équations de biomasses sur les données par arbres de l'IFN. La méthode des BEF a donné, pour la forêt suédoise, une estimation de la biomasse inférieure de 6,7 % par rapport à la méthode de référence (2). Les différences entre estimations étaient minimales dans les forêts de conifères du centre du pays et maximales dans les forêts d'épicéas du sud. Cela indiquerait que les BEF liés à l'âge ne sont pas applicables dans des conditions s'éloignant du développement des peuplements boréaux. Le degré d'incertitude était le plus élevé pour les classes d'âge jeunes. Au niveau régional, l'erreur relative standard des estimations se basant sur les BEF se situait entre 4 et 13 %.

Key words: biomass function / carbon stock of trees / forest inventory / greenhouse gas inventory / uncertainty

Mots clés : équation de biomasses / stock de carbone sur pied / inventaire forestier / inventaire des gaz à effet de serre / degré d'incertitude

Corresponding author: Raisa Mäkipää Raisa.Makipaa@metla.fi

© INRA, EDP Sciences 2005

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