Early effects of two planting densities on growth dynamics and water-use efficiency in Robinia pseudoacacia (L.) and Populus deltoides (Bartr. ex Marsh.) × P. nigra (L.) short rotation plantations

Key message Black locust is an interesting option for biomass production at sites prone to water shortage because the species combines water-use efficiency and a biomass yield largely superior to that of poplars under the conditions of the study. Context Black locust ( Robinia pseudoacacia L.) is an interesting tree species for woody biomass production. However, its potential for this purpose has been much less studied and characterized than that for species from the Salicaceae family (i.e., poplar and willow). Aims The objective of our study was to evaluate the potential of black locust for biomass production as compared to that of poplar. Methods We estimated biomass production, growth habit, and efficiency of water use of two provenances of black locust (1) compared to those of poplar ( Populus deltoides Bartr. ex Marsh. × P. nigra L.), (2) at two planting densities, and (3) 2 and 4 years after planting. Results Black locust had a very different growth habit, much higher biomass production, and larger water-use efficiency than poplar. These differences were exacerbated during the driest year of the experiment. However, black locust responded very badly to harvesting. Conclusion Black locust was more productive and more efficient in terms of water use than poplar, especially during the driest year of the experiment.