How do social status and tree architecture influence radial growth, wood density and drought response in spontaneously established oak forests?

Abstract

& Key message During the past decades, a multitude of oak stands have spontaneously established across the pinedominated landscapes of the French Landes de Gascogne. Yet their future performance under modern climate change is unknown. We show that coppiced, dominant trees are most prepared to cope with drought episodes, displaying higher basal area increment and lower sensitivity to extreme events. & Context Forest stands dominated by pedunculate oak (Quercus robur L.) have spontaneously established across the pinedominated landscapes of the French Landes de Gascogne. These oak stands are typically unmanaged and unsystematically coppiced, resulting in mixtures of single-and multi-stemmed (coppiced) trees. & Aims To determine the ability of spontaneous oak forest stands to face climate change-related hazards, by analysing differences in growth (tree-ring width and basal area increment-BAI), wood density and climate sensitivity depending on their tree architecture (single-vs multi-stemmed trees) and their social status in the forest. & Methods We exhaustively cored 15 oak stands (n = 657 trees). We compared stand characteristics and climate sensitivity between tree architectures considering two sampling designs, either all sampled trees (the exhaustive sampling) or those with a dominant status (dominant sampling). At the tree level, we used linear mixed effects models to compare wood density and growth between tree architectures and the trees' social status within the canopy layer (dominant-vs non-dominant trees). & Results Multi-stemmed trees exhibited higher wood density than single-stemmed trees for diameters > 30 cm. Dominant multistemmed trees showed lower sensitivity to extreme events (pointer years), higher BAI but lower annual growth rates than dominant single-stemmed trees. & Conclusion Dominant multi-stemmed trees are potentially the most prepared ones to cope with increasing soil water deficit following drought episodes, at least during the first 60 years of the life of the tree. The vulnerability to face harsher climate conditions for Q. robur stands can be misled when using a dominant sampling design. Keywords Dominant trees . Forest expansion . Pointer years . Quercus robur L. . Single-and multi-stemmed trees . Wood density Handling editor: Irene Martin-Fores This article is part of the topical collection on Establishment of secondgrowth forests in human landscapes: ecological mechanisms and genetic consequences

Land‐use legacies influence tree water‐use efficiency and nitrogen availability in recently established European forests

“…Whereas all extant trees in the recent forests naturally grew from seeds (as these patches have never been exploited), some trees in long‐established forests may have resprouted after past logging events carried out as part of the traditional forest management (coppicing) practiced in beech forests in southern Europe (Cullotta et al., 2016). Such trees may have higher SLA and lower iWUE due to the benefits of a deep, well‐developed root system (Alfaro‐Sánchez et al., 2020; Castell et al., 1994), which would set them apart from recently established forests (Mausolf et al., 2018).…”

Tree potential growth varies more than competition among spontaneously established forest stands of pedunculate oak (Quercus robur)

“…Between-year variation in tree growth In old oak forests, 29% of the variance of oak ring-width was explained by climate between 1925 and 1980 (Rozas 2011). Moreover, Alfaro-Sȧnchez et al (2020) found a positive correlation between growth and soil water moisture in June-July of the current year and September-October of the previous year, as well as a negative correlation between growth and temperature in August-September of the previous year. In our study, however, between-year variation in growth rates was overall not synchronous across stands.…”

Provenance Differences in Water-Use Efficiency Among Sessile Oak Populations Grown in a Mesic Common Garden

“…For each population, 30 trees were selected among the different plots, except for four populations (Pontigny, Allogny, Bussières, and Serqueux) where 60 trees were selected to better characterize the diversity within populations (Supplementary Table 2). The selection focused primarily on the tree social status, visually assessed before sampling, in 2014 (thus after canopy closure), favoring when possible dominant trees to avoid additional microclimate variability which could affect δ 13 C (McDowell et al, 2011) and growth (Trouvé et al, 2015;Alfaro-Sánchez et al, 2020). However, the constraints of systematic thinning forced the selection of some codominant (37%) and suppressed trees (14%) in order to reach the required sample size for each population (Supplementary Table 2).…”