Do tree-ring traits reflect different water deficit responses in young poplar clones (Populus x canadensis Monch 'I-214' and P. deltoides 'Dvina')?

Poplar clones are known to display a wide range of tolerance to drought and water-use efficiency, but the effects of water deficit on stem growth and tree-ring characteristics are rarely taken into account. This study was conducted in order to investigate whether the main tree-ring traits correlate with irrigation regimes during the growing season in 'I-214' and 'Dvina' 4-year-old poplar clone saplings grown in concrete tanks, during three consecutive years. Total carbon, stable carbon isotope, Klason lignin and ?-cellulose contents were analyzed to characterize wood biochemistry; ring width, wood density, mean vessel density and mean vessel lumen area were analyzed to characterize wood anatomy to assess the influence of irrigation regime. In both clones, wood formed in 2005 was more enriched in 13C, suggesting drought-induced stomatal closure. Wood formed in 2006 was less variable in ?13C in relation to irrigation regimes. 'Dvina' showed higher Klason lignin content and wood density than 'I-214', whatever the irrigation regime, despite the larger ring widths. 'Dvina' has the potential to recover promptly after drought stress, but at the expense of poor wood technological properties, while 'I-214' could continue to grow more uniformly under limited water availability, though at a lower rate.