• National Forest Inventories supply invaluable long term time series of forest state. Recent developments and international harmonization of modern NFIs widen the scope to even include ecosystem goods, e.g. biodiversity and carbon sequestration. The combination of NFI field data with remote sensing techniques can give good estimates for areas smaller than national and regional level. AbstractNational Forest Inventories (NFIs) are becoming increasingly important worldwide in order to provide information about the multiple functions of forests, e.g. their provision of raw materials to industry, biodiversity and their capacity to store carbon for mitigating climate change. In several countries the history of NFIs is very long. For these countries a specific challenge is to keep the inventories up-to-date without sacrificing the advantages associated with long time series. At the turn of the 20th century European NFIs faced some major challenges. In this article we describe the history and the recent developments of the Swedish NFI as an example from which general observations are made and discussed. The Swedish NFI started in 1923 and has evolved from an inventory with a narrow focus on wood resources to an inventory today which aims to provide information about all major forest ecosystem services. It can be concluded that the traditional approaches of most European NFIs, e.g. to collect data through sample plot field inventories, has proved to be applicable even for a wide range of new information requirements. Specifically, detailed data about land use, trees, vegetation, and soils has found new important uses in connection with biodiversity assessments and the estimation of greenhouse gas emissions. Though time-consuming and difficult, making NFI information comparable across countries through harmonization appears to be a useful approach. The European National Forest Inventory Network (ENFIN) was formed in 2003 and has been successful in pan-European NFI harmonization.

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-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%.biomass function / carbon stock of trees / forest inventory / greenhouse gas inventory / uncertainty 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 %.équation de biomasses / stock de carbone sur pied / inventaire forestier / inventaire des gaz à effet de serre / degré d'incertitude