@phdthesis{MufflerWeigel2020,
  author    = {Lena Muffler-Weigel},
  title     = {Phenotypic plasticity and genetic adaptation in European beech: Insights into natural regeneration patterns and adult growth performance across the distribution range},
  journal    = {Ph{\"a}notypische Plastizit{\"a}t und lokale Anpassung in der Rotbuche: Einblicke in nat{\"u}rliche Verj{\"u}ngungsmuster und in Wuchsleistung von erwachsenen B{\"a}umen {\"u}ber das Verbreitungsgebiet},
  url       = {https://nbn-resolving.org/urn:nbn:de:gbv:9-opus-41254},
  pages     = {122},
  year      = {2020},
  abstract  = {Species have to cope with climate change either by migration or by adaptation and acclimatisation. Especially for long-living tree species with a low seed dispersal capacity (e.g. European beech, hereafter called beech), the in situ responses through genetic adaptation and phenotypic plasticity play an important role for their persistence. Beech, the dominant climax tree species in Central Europe, shows a high drought sensitivity and its distribution range is expected to shift northwards. On the other hand, projected northward shifts need to be taken with caution, as some studies suggest a sensitivity of beech to frost events in winter and spring. However, studies on the growth performance of cold-marginal beech populations are still rare. Previous studies on beech populations found local adaptation to drought and phenotypic plasticity in fitness-related traits as well as phenological traits. However, studies on the regeneration of beech under natural conditions are yet missing, although germination and establishment of young trees are a very first selective bottleneck and are crucial for tree population persistence and for successful range shifts. This PhD-thesis aimed to identify the potential of plasticity and local adaptation in the important early life-history traits germination, establishment after the 1st year, and survival after the 2nd year in a reciprocal transplantation experiment at 11 sites across and even beyond the distribution range of beech (Manuscript 1). Moreover, this thesis investigated the climate sensitivity and the adaptation potential of beech populations by conducting dendroecological studies along a large climatic gradient across the distribution range (Manuscript 2) and along a strong winter temperature gradient towards the cold distribution margin in Poland (Manuscript 3). In addition, the impact of local climatic singularities was studied in a local study at the southern margin (Manuscript 4). Warm and dry conditions limited natural regeneration, which was indicated by very low survival of young trees, even though germination rates increased with increasing temperature (Manuscript 1). This was also the case in parts of the distribution centre due to the hot and dry conditions in 2018. Although the transplantation experiment revealed high plasticity in the early life-history traits, this plasticity might thus not buffer against climate change under dry conditions. Local adaptation was not detected for any of these traits along the climatic gradient. In contrast, the results of the dendroecological study across the gradient (Manuscript 2) hint towards an adaptation potential of adult trees to drought at the southern margin. Thus, adult trees seemed to be adapted to drought at the southern margin, whereas tree growth in the distribution centre was sensitive to drought. These results indicate that parts of the centre may become ecologically marginal with increasing drought frequency in times of climate change. Interestingly, Manuscript 4 shows that beech growth was positively influenced by frequent fog immersion at the southern distribution margin in north-eastern Spain. This study underlines the importance of local climatic singularities, as they may allow marginal populations to grow in climate refugia in an otherwise unfavourable climate. At the cold distribution margin, the study in Manuscript 1 found a remarkably higher survival of young trees in Sweden than in Poland. Moreover, the dendroecological studies revealed that beech was hampered by both drought at the cold-dry margin (Manuscript 2) and by winter cold at the cold-wet margin in Poland (Manuscript 3). All these results highlight the importance to study climate sensitivity of adult trees and the response of early life-history traits at the cold margin with a more differentiated view comparing cold-dry against the cold-wet populations and growing conditions. However, the high plasticity of the early life-history traits may allow for an increasing germination rate with climate warming at the northern margin and may thus facilitate natural regeneration there. In contrast, the dendroecological studies suggest that adult trees at the cold distribution margin may suffer either from drought or from winter cold and that the risk for spring frost may increase. Thus, the often-predicted compensation of dry-marginal population decline by a northward range expansion should be discussed more critically. In conclusion, my PhD thesis provides new knowledge about the potential of natural regeneration and about climate sensitivity of adult trees across the distribution range of beech. Moreover, it underlines the importance to study both the young tree stages as well as adult trees to assess the performance and vulnerability of tree species under climate change, as both showed differences in their response to changing environmental conditions.},
  language  = {en}
}