• The influence of species mixture on carbon accumulation and water use was studied in a boreal plantation. • A large variability in functional parameters was observed among species and mixtures. • The presence of birch in mixtures was the key driver for ecosystem functioning. • Species mixture did not enhance productivity and water use efficiency at a young stage. 2012-07-17 05:53:21 UTC prep Water balance and water use efficiency on different scales Charlotte Grossiord charlotte.grossiord@nancy.inra.fr Forest Ecology and Management 2013-03-01 accepted