Survival and growth responses of Populus nigra, Salix elaeagnos and Alnus incana cuttings to varying levels of hydric stress

Each species responded differently to the experimental treatments. S. elaeagnos demonstrated an ability to establish in stable, declining and inundated conditions by the production of relatively substantial root and shoot biomass in all treatments, along with elongated roots when experiencing water table decline. P. nigra showed high mortality and poor root and shoot production in inundation treatments, suggesting that this species is intolerant to reduced oxygen conditions. A. incana displayed complete mortality in all gravel-based treatments and high mortality or poor growth in the sand-based inundation treatments. All species showed preferences for stable conditions without inundation, along with slow water table decline for S. elaeagnos. Fast rates of water table decline were detrimental to all species. Overall, sand was a much more effective substrate than gravel for supporting cutting establishment. These results suggest that riparian restoration schemes utilizing S. elaeagnos cuttings may experience greater success than those using the other species investigated. P. nigra cuttings may establish more easily if situated where inundation does not occur often or for prolonged periods, and A. incana cuttings should be planted only where very stable conditions dominate. The study highlights the inter-species variability in the survival and growth response of riparian trees to differing hydrological conditions.