Application of the CBM-CFS3 model to estimate Italy's forest carbon budget, 1995-2020


The estimation of past and future forest carbon (C) dynamics in European countries is a challengingtask due to complex and varying silvicultural systems, including uneven-aged forest management, andincomplete inventory data time series. In this study, we tested the use of the Carbon Budget Model ofthe Canadian Forest Sector (CBM-CFS3) in Italy, a country exemplifying most of these challenges. Our objective was to develop estimates of forest carbon budgets of the Forest Management area (including allforests existing in 1990) for the period 1995?2009, and to simulate alternative scenarios of natural dis-turbance (fire) and harvest rates to 2020. A number of methodological challenges required modifications to the default model implementation. Based on National Forest Inventory (NFI) data, we (i) developed a historic library of yield curves derived from standing volume and age data, reflecting the effect of past silvicultural activities and natural disturbances, and a current library of yield curves derived from thecurrent net annual increment; (ii) reconstructed the age structure for a period antecedent to the refer-ence NFI year (2005), to compare the model results with data from other sources; and (iii) developeda novel approach for the simulation of uneven-aged forests. For the period 2000?2009, the model esti-mated an average annual sink of ?23.7 Mt CO2yr?1excluding fires in Italy?s managed forests. Adding firesto the simulation reduced the sink to ?20.5 Mt CO2yr?1. The projected sink (excluding all fires) for theyear 2020 was ?23.4 Mt CO2yr?1assuming average (2000?2009) harvest rates. A 36% increase in harvestrates by 2020 reduced the sink to ?17.3 Mt CO2yr?1. By comparing the model results with NFI data andother independent studies, we demonstrate the utility of the CBM-CFS3 both for estimating the currentforest sink in even-aged and more complex uneven-aged silvicultural systems in Italy, and for explor-ing the impact of different harvest and natural disturbances scenarios in managed forests. This studydemonstrates the utility of the CBM-CFS3 to national-scale estimation of past and future greenhousegas emissions and provides the foundation for the model?s future implementation to other European countries

PILLI Roberto, SMYTH Caroline, GRASSI Giacomo, KURZ Werner, BLUJDEA Viorel
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Institute for Environment and Sustainability
JRC Institutes
ECOLOGICAL MODELLING p. 144? 171 vol. 266