The Apple Does Not Fall Far From the Tree and How This Affects the Abiotic Stress Tolerance in Juvenile Trees

ABSTRACT Juvenile trees are generally considered less tolerant to abiotic stress than adult trees. Yet this could be a case where, at least partially, conspecific shade tolerance may outweigh the sensitivity to other stress factors in determining their persistence. While studies report lower drought, cold, and heat tolerance in seedlings and saplings than in adults, numerous studies indicate that juveniles display higher shade tolerance than mature individuals. Because tree regeneration usually occurs under closed canopies, having higher shade tolerance can compensate for reduced tolerance to other stresses—the latter stress factors being generally significantly mitigated in forest ecosystems. Shade tolerance may thus be the nonintuitive, yet decisive factor in tree recruitment success, outweighing the vulnerability of juveniles to other abiotic stress factors.