Regeneration biomass (AGB & BGB), age, NSCs and light: F. sylvatica and Acer spp.

Being able to persist in deep shade is an important characteristic of
juvenile trees often leading to a strong dominance of shade-tolerant
species in forests with low canopy turnover and disturbance rate. While
leaf, growth and storage traits are known to be key components of shade
tolerance, their interplay during regeneration development and influence
on juveniles’ survival time remains unclear. We assessed the ontogenetic
effects of these three traits on survival time of beech  (Fagus
sylvatica), Norway and sycamore maples (Acer pseudoplatanus, Acer
platanoides) in a primeval beech forest. Biomass allocation, age and
content of non-structural carbohydrates (NSC) were measured in stems and
roots of 289 seedlings and saplings in high and low vitality classes.
Saplings experience a trade-off between absolute growth rate (AGR), and
storage (NSC) at decreasing leaf area ratio (LAR) with biomass
development. High LAR but slow AGR and low NSC confer beech with a marked
ability to persist in deep shade awaiting canopy release. In turn, a
comparably small LAR in combination with fast AGR and higher storage
(NSC), as observed in Norway maple and sycamore maple, reduces their
survival time, thus offering an explanation for beech dominance and maples
disappearance in the undergrowth of old-growth beech forests.