Carbon assimilation and water use efficiency of a perennial bioenergy crop (Cynara cardunculus L.) in Mediterranean environment

• H2O and CO2 fluxes were measured by eddy covariance method on a bioenergy crop.
• We investigated cardoon crop adaptation to Mediterranean environment in 3 seasons.
• H2O and CO2 exchanges have been quantified at ecosystem level.
• Water use efficiency (WUE) were evaluated at ecosystem and agronomic level.
• WUE increased from the first to the third season at both levels.

Here we investigate how cardoon (Cynara cardunculus L.), energetic crop cultivated under Mediterranean climate in rainfed conditions, is adapted to the environment. Two main resources used for producing biomass are analysed in detail: water (H2O) and carbon dioxide (CO2). Following micrometeorological approach, the eddy covariance technique has been used for monitoring H2O and CO2 exchanges between canopy and atmosphere in order to investigate the dynamics of the cardoon growth at field level and to compute the Gross Primary Production (GPP). The dynamics of canopy CO2 assimilation in terms of GPP, evapotranspiration (ET) and water use efficiency (WUEGPP, as ratio between seasonal GPP and seasonal ET and WUEagro as ratio between yield and seasonal ET) were analysed during three successive growth seasons in a south Italy site. The environmental drivers of CO2 assimilation and ET were analysed at instantaneous scale. The crop showed increasing resource use efficiency along the three seasons of experiment for all considered resources: in particular, for the last two seasons cumulated GPP increased and cumulated ET decreased. It seemed to require a season for its establishment to the environment, improving the use of water and CO2 assimilation in the second and third season.