Inventory-based carbon stock of Flemish forests: a comparison of European biomass expansion factors (original) (raw)
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Growing stock-based assessment of the carbon stock in the Belgian forest biomass
Annals of Forest Science, 2005
Belgian forests covered 693 181 ha in 2000, representing 22.7% of the total land area. As no biomass or carbon stock data are included in the Flemish and Walloon regional forest inventories, species-specific wood densities, biomass expansion factors s.s. and carbon content values were critically selected from the literature. Based on these conversion and expansion factors, and on data from the forest inventories, the total C-stock in the living biomass of productive Belgian forests was assessed at 60.9 Mt C in the year 2000. The overall mean C-stock amounted to 101.0 t C ha -1 . This value was in the higher range of values reported for the neighbouring countries, mainly due to a high mean growing stock in the Belgian forests (261.9 m 3 ha -1 ). The conversion from wood volume to wood biomass based on wood density values reported in the literature appeared to introduce the largest variability in the assessment of the carbon stocks. Additional measurements of wood densities in Belgian forests could help to reduce the uncertainty related to this factor. Because of the time-consuming and destructive character of the determination of biomass expansion factors s.s. (BEFs), the establishment of new BEFs does not have the highest priority in the framework of improving the assessment of the biomass carbon stock in the Belgian forests. As the median C-content value for all species except beech was equal to the default IPCC-value of 50% carbon in dry matter, it seems appropriate to use this value for future calculations.
The overall objective of this workpackage was to ensure that existing information on allometry of various tree species (expressed as biomass functions and conversion factors) is effectively exploited, and integrated with, national forest inventories. We also identified, quantified and reduced uncertainties related to the expansion from stemwood volumes to biomass and carbon contents of trees. On the basis of established expansion factors we developed a procedure for assessment of national carbon stocks and stock changes in forest trees.
Carbon exists as carbon dioxide in the atmosphere and constitutes about 0.04% of the atmosphere. In the recent past, it has gained a lot of attention as a greenhouse gas, as it has potential to influence the climate pattern of the world. Anthropogenic activities like industrialisation, deforestation, forest degradation and burning of fossil fuel, has caused an increase in the level of carbon in the atmosphere and disrupted the global carbon cycle. However, nature has its own mechanism of sequestering and storing the carbon in its "reservoirs" or "sinks''. Forest plays an important role in the global carbon cycle as carbon sinks of the terrestrial ecosystem. The carbon sequestered or stored on the forest trees are mostly referred to as the biomass of the tree or forest. The Intergovernmental Panel on Climate Change identified five carbon pools of the terrestrial ecosystem involving biomass, namely the aboveground biomass, below-ground biomass, litter, woody debris and soil organic matter. Among all the carbon pools, the above-ground biomass constitutes the major portion of the carbon pool. Estimating the amount of forest biomass is very crucial for monitoring and estimating the amount of carbon that is lost or emitted during deforestation, and it will also give us an idea of the forest's potential to sequester and store carbon in the forest ecosystem. Estimations of forest carbon stocks are based upon the estimation of forest biomass. Forest's carbon stocks are generally not measured directly; however, many authors assume the carbon concentration of tree parts to be 50% or 45% of the dry biomass. This paper, aims to review and summarise the various methods and studies that were carried out to estimate the above-ground biomass of the forest.
A comparison of two modelling studies of environmental effects on forest carbon stocks across Europe
Annals of Forest Science, 2005
Two modelling approaches to describing the variation in the carbon balance of forests in different parts of Europe are presented. A forest growth model (Eurobiota) was parameterised for 3 eco-climatic zones. The parameter values were derived from process-based forest growth models developed to describe the situation at forest locations within each zone. The model was separately run for conifers and broadleaves on a 30' grid across Europe. Daily climate data covering the period from 1830 to the present and then projected to 2100 were used. European forests were shown to be a net sink of carbon of 0.06 Pg y-1 at present. The Boreal and Temperate zones are likely to continue at their present rate or more for the next century but the net sink in the Mediterranean zone may become smaller due to projected drier conditions. The effect of temperature using the surrogate of latitude on net ecosystem productivity is also discussed. A complex forest growth model (EFM) was parameterised for Norway spruce and Scots pine, and tested against measurements from 22 forest locations across Europe. This second model showed that the main driver of increased forest growth in the 20th century has been increased nitrogen deposition, rather than increased [CO 2 ] or climate change, as indicated by EuroBiota. Increased growth has led to increased carbon storage in the system, but most of it in tree biomass rather than stably sequestered in recalcitrant soil organic matter. Carbon stocks were increased more in Central Europe than in Scandinavia, except for some high-fertility sites where N-deposition had little impact. The EFM model was also used to predict the effects of future environmental change, and suggested that climate change and [CO 2 ] may become the dominant environmental drivers for forest carbon exchange. The two models thus give similar results when considering only climate change and [CO 2 ] but EFM can in addition describe the effects of N-deposition when appropriate. European forests / carbon balance / modelling / climate change Résumé-Comparer les impacts de facteurs environnementaux sur les stocks de carbone des forêts européennes : deux exercices de modélisation. Cette étude présente deux approches de modélisation permettant de décrire la variabilité du bilan de carbone des forêts européennes. En premier lieu, le modèle de croissance d'arbres, Eurobiota, fut paramétré pour trois zones éco-climatiques différentes. Les valeurs des paramètres furent dérivées de modèles basés sur les processus simulant la croissance d'arbres dans chacune ces zones. Le modèle fut exécuté séparément pour les conifères et les feuillus, sur une grille de modélisation de 30' à travers l'Europe. Une base de données climatique à échelle quotidienne fut utilisée, couvrant une période de 1830 jusqu'à maintenant, et projetée jusqu'en 2100. Cet exercice de modélisation démontre que les forêts européennes actuelles représentent un puits de carbone de 0.06 Pg an-1. Dans les zones boréales et tempérées, il est probable que ce taux d'accumulation demeure ainsi mais pourrait aussi s'accroître au siècle prochain. Cependant, dû aux conditions climatiques prévues plus arides, le puits net méditerranéen pourrait décroître. Une discussion sur les effets occasionnés par la substitution de la température par la latitude pour simuler la productivité nette est aussi présentée. En second lieu, un modèle complexe basé sur les processus (EFM) fut paramétré pour l'épicéa (Norway spruce) et le pin sylvestre (Scots pine) et testé à partir de données en provenance de 22 forêts européennes. Ce dernier modèle démontre qu'au XX e siècle, le dépôt d'azote plutôt que les changements climatiques ou l'accroissement de CO 2 , tel que suggéré par Eurobiota, détermine principalement l'augmentation du taux de croissance des forêts. De plus, cette augmentation conduit à une accumulation de carbone dans le système se retrouvant principalement dans la biomasse des arbres plutôt que de manière stable dans la matière organique récalcitrante du sol. Les stocks de carbone de l'Europe centrale s'accroissent plus que ceux de Scandinavie, à l'exception des sites scandinaves hautement fertiles, où le dépôt d'azote influence peu la croissance. EFM fut aussi exécuté afin de prédire les impacts des changements climatiques futurs sur les échanges de carbone. Celui-ci indique que dans le futur, ce sont les changements climatiques ainsi que le CO 2 qui risquent de devenir les principaux facteurs déterminant de ces échanges. Les deux modèles démontrent des résultats similaires en ce qui a trait aux changements climatiques et au CO 2. Cependant, EFM permet également de décrire l'influence du dépôt d'azote. forêts européennes / bilan de carbone / modélisation / changement climatique