20% of all greenhouse gas emissions worldwide are due to deforestation. In addition, terrestrial ecosystems are extremely vulnerable to climate change (Cox et al 2000; Schröter et al 2005), and especially to extreme meteorological events (Ciais et al 2005). In this context, GRACCIE will devote efforts for a better understanding of the carbon cycle in Mediterranean ecosystems. These will involve the use of the most recent methods for carbon flux measurements (eddy covariance) in land use and cover types representative of Spanish ecosystems, contributing to GCOS (FLUXNET) and to GCP. Efforts to improve the understanding of the processes and factors determining primary production, as well as the different components of respiration will be implemented. This work will be based on continuous systematic measurements allowing observation of both the general temporal patterns and the effects produced by special events.

The development and optimization of models which can be coupled to climatic or dynamic models at different scales will also be considered. Model availability is essential, like ORCHIDEÉ, which has already been validated in different contexts (EUROFLUX project) and has also been used in different EU projects that assess the forests response to different climate change and management scenarios. Carbon sequestration capacity of soils and the vulnerability of soil carbon pools to climate and land use change will be assessed on the basis of analyses of soil databases and chronosequences. These research efforts will ultimately lead to propose effective strategies for ecosystems management which take into account the efficiency and potential of ecosystems for carbon sequestration, but also its vulnerability to climate and/or land use changes. These initiatives are of great importance due to the Spanish commitments in Kyoto. This protocol also considers the implementation of efficient measures for increasing atmospheric CO2 sequestration by land use, land use change and forestry (Schultze et al., 2002).