Simulated predation of Quercus variabilis acorns impairs nutrient remobilization and seedling performance irrespective of soil fertility

Abstract

Background and aims Predators may partially orcompletely consume Quercus spp. acorns, but effectson nutrient remobilization and seedling performance arepoorly understood. We investigated interactions betweensoil fertility and the removal of Quercus variabilisacorn cotyledons at different early developmental stageson seedling nutrition and development.Methods Seedlings were grown in two soils of contrastingfertility and the kinetics of acorn nitrogen, phosphorusand potassium remobilization, and seedling survival,growth and nutrient content were analyzed.Results Acorn mass and macronutrients decreased remarkably<2 weeks after emergence, with nitrogen andphosphorus remobilizing faster than potassium. Acornremoval at or 1 week after emergence inhibited seedlingsurvival, growth and fine root formation, whereas removalfrom 2 to 10 weeks after emergence had minor effects. Acorn macronutrient remobilization and effects of acorn removal on seedling performance were not reversed under high soil fertility. When acorns were removed &#8805; 2 weeks after emergence, fertilization increased root surface and seedling nitrogen content. Conclusions. Acorn nutrients are more important than soil nutrients during very early seedling development. Cotyledon damage at emergence impairs seedling performance despite no direct damage to the remainder of the seedling. This effect cannot be reverted by high soil fertility and has potential ecological and practical implications for oak regeneration.