Grow slowly, persist, dominate-Explaining beech dominance in a primeval forest.

Roksolana Petrovska,Harald Bugmann,Peter Brang,Arthur Gessler,Martina Lena Hobi

doi:10.1002/ece3.7800

Roksolana Petrovska, Harald Bugmann + Show 3 more

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https://doi.org/10.1002/ece3.7800

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Abstract

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 a low disturbance rate. While leaf, growth, and storage traits are known to be key components of shade tolerance, their interplay during regeneration development and their influence on juveniles' survival time remains unclear. We assessed the ontogenetic effects of these three traits on the survival time of beech (Fagus sylvatica), and Norway and sycamore maples (Acer pseudoplatanus, Acer platanoides) in a primeval beech forest. Biomass allocation, age, and content of nonstructural carbohydrates (NSC) were measured in the stems and roots of 289 seedlings and saplings in high‐ and low‐vitality classes. Saplings experienced a trade‐off between absolute growth rate (AGR) and storage (NSC) as the leaf area ratio (LAR) decreases with biomass development. High LAR but low AGR and low NSC corresponded to beech with a marked ability to persist in deep shade while awaiting canopy release. In turn, a comparably small LAR in combination with a high AGR and higher storage (NSC), as observed in Norway maple and sycamore maple, reduced sapling survival time, thus offering an explanation for beech dominance and maple disappearance in the undergrowth of old‐growth beech forests.

Highlights

In primeval monodominant Fagus sylvatica L. forests, seedlings (0–130 cm tall) and saplings (131–500 cm tall) often grow in deep shade for extended periods, due to low canopy turnover (Hobi et al, 2015; Runkle, 1985; Valverde & Silvertown, 1997)
High juvenile shade tolerance is pivotal in determining the survival time of F. sylvatica and may be compromised in co-occurring species, explaining the low tree species diversity and F. sylvatica dominance frequently observed during succession (Korpel, 1995; Rey et al, 2019)
We modeled the influence of biomass partitioning to leaves and shoots on traits of shade tolerance such as leaf area ratio (LAR), absolute growth rate (AGR), and nonstructural carbohydrates (NSC) with multivariate analysis of covariance MANCOVA (R package car), the Pillai–Bartlett trace test, and ANOVA type III for unbalanced designs

Summary

| INTRODUCTION

In primeval monodominant Fagus sylvatica L. forests, seedlings (0–130 cm tall) and saplings (131–500 cm tall) often grow in deep shade for extended periods, due to low canopy turnover (Hobi et al, 2015; Runkle, 1985; Valverde & Silvertown, 1997). One of the concepts used to explain shade tolerance, the “carbon gain” hypothesis, postulates that saplings can enhance carbon gain in the shade, either by minimizing CO2 losses via respiration or by investing in the light-harvesting capacity (greater leaf area and crown volume, Givnish, 1988) while maintaining a higher growth rate (Popma & Bongers, 1988; Walters & Reich, 1996). Another concept, the “defence and storage” hypothesis, relates shade tolerance to the resistance to herbivory, pathogens, and mechanical damage (Kitajima, 1994) and to storage (Kobe, 1997). We investigated the following research questions: (a) Which traits relating to leaf, growth, and storage can discriminate between low-and high-vitality regeneration? (b) Is there a trade-off between growth and storage traits among species of low and high vitality? (c) How do these traits affect regeneration survival time?

| MATERIALS AND METHODS

| DISCUSSION

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Findings

| CONCLUSION