Yield and Survival of Shrub Willow Clones over Two Rotations Reveal Important Patterns About Selection for an Evapotranspiration Cover on a Former Industrial Site

Shrub willow (Salix spp.) is a promising candidate for evapotranspiration (ET) covers due to its rapid growth and high water use. This study assessed 30 willow clones over two three-year rotations on a former industrial waste site in Solvay, NY, with alkaline, low-organic substrates and intermittent hardpan. Survival was high after the first rotation (87.9% ± 1.7 SE), but yield was lower and more variable (6.55 Mg ha−1 y−1 ± 0.25 SE) than on mineral soils. In the second rotation, both survival (42.6% ± 3.0 SE) and yield (5.08 Mg ha−1 y−1 ± 0.38 SE) declined. Clone rankings shifted between rotations (Spearman ρ = 0.13, p = 0.48), suggesting that short-term trials poorly predict long-term performance on degraded sites. Survival emerged as the primary driver of yield, with a smaller interaction from hardpan. Clone 05X-295-014 showed notable resilience, maintaining strong performance despite widespread hardpan. Five clones from S. miyabeana and S. purpurea x S. miyabeana groups demonstrated sustained or increasing yield and survival above 60%. These findings emphasize the importance of selecting for survival alongside yield in multi-rotation trials to ensure effective long-term deployment for biomass and phytoremediation in challenging sites.