High plasticity in germination and establishment success in the dominant forest tree Fagus sylvatica across Europe

Abstract

Aim Distribution ranges of temperate tree species are shifting poleward and upslope into cooler environments due to global warming. Successful regeneration is crucial for population persistence and range expansion. Thus, we aimed to identify environmental variables that affect germination and seedling establishment of Europe's dominant forest tree, to compare the importance of plasticity and genetic variation for regeneration, and to evaluate the regeneration potential at and beyond the southern and northern distribution margins. Location Europe. Time period 2016–2018. Major taxa studied European beech (Fagus sylvatica (L.)). Methods We investigated how germination, establishment and juvenile survival change across a reciprocal transplantation experiment using over 9,000 seeds of beech from 7 populations from its southern to its northern distribution range margins. Results Germination and establishment at the seedling stage were highly plastic in response to environmental conditions. Germination success increased with warmer and declined with colder air temperature, whereas establishment and survival were hampered under warmer and drier conditions. Germination differed among populations and was positively influenced by seed weight. However, there was no evidence of local adaptation in any trait. Main conclusions The high plasticity in the early life‐history traits found irrespective of seed origin may allow for short‐term acclimatization. However, our results also indicate that this plasticity might not be sufficient to ensure the regeneration of beech in the future due to the low survival found under dry and hot conditions. The future climatic conditions in parts of the distribution centre and at the rear edge might thus become limiting for natural regeneration, as the likelihood of extreme heat and drought events will increase. By contrast, at the cold distribution margin, the high plasticity in the early life‐history traits may allow for increasing germination success with increasing temperatures and may thus facilitate natural regeneration in the future.

High phenotypic variation found within the offspring of each mother tree in Fagus sylvatica regardless of the environment or source population

“…This phenomenon appears to be independent of the trees geographic and environmental origin. The prevalence of phenotypic plasticity over genetic adaptation as the main source of variation in key functional traits of European beech is supported by other recent studies (Gárate-Escamilla et al, 2019;Muffler et al, 2021).…”

“…Our RTE, detailed in Muffler et al. (2021), was conducted along a gradient from Spain towards Poland and Sweden (Figure S2), reflecting two key factors that affect the species' growth and distribution: winter cold and summer drought (Bolte et al., 2007; Kramer et al., 2010; Muffler et al., 2020; Weigel et al., 2018). At eight different forest stands dominated by beech along this gradient, we collected beechnuts from four mother trees, respectively, within a 250 m radius.…”

Tracing the origin of Oriental beech stands across Western Europe and reporting hybridization with European beech – implications for assisted gene flow

“…European beech is strongly affected by climate change: changes to its growth, reproduction, regeneration and mortality have all been linked with the warmer and drier climate, particularly with extreme hot-drought events (Hacket-Pain et al, 2016; Nussbaumer et al, 2020; Peñuelas et al, 2007), resulting in a substantial reduction of its productivity (Reyer et al, 2014; Trotsiuk et al, 2020). The potential advantage of introducing southern European beech provenances has been assessed by many previous studies, however, there are no substantial differences in genetic diversity across the range (e.g., de Lafontaine et al, 2013) and limited evidence for local adaptation and strong evidence for plasticity (e.g., Gárate-Escamilla et al, 2019; Kurjak et al, 2019; Muffler et al, 2021; Sáenz-Romero et al, 2019), suggesting that the benefits of such provenance movements appear limited. In contrast, the introduction of Oriental beech has a high potential to increase genetic diversity, and more drought-resistant provenances could also introgress pre-adapted alleles to European beech populations, thus promoting the evolutionary response of European beech to climate change.…”

The Potential for Future Shifts in Tree Species Distribution Provided by Dispersal and Ecological Niches: A Comparison between Beech and Oak in Europe

“…In addition, further work shows the sensitivity of summer drought on beech growth [95][96][97][98][99][100]. For beech regeneration, the negative influence of drought has also been demonstrated by Silva et al [78] and Muffler et al [101]. The smaller envelopes for beech regeneration compared to the overstorey indicate a reduction in the distribution area in the drier region (Figure 4).…”