Diversity and management effects on forest evolution
Extreme weather events such as the dry years of 2018, 2019, and 2022 threaten the health and, thus, the ecosystem functions of temperate forests. Even tree species formerly thought to be less affected by climate change, like the European Beech (Fagus sylvatica), were found to be vulnerable.
However, drought affected individual beech trees within stands differently, with some trees being damaged while others remained healthy, as was demonstrated in a recent genomic study.
Fagus sylvatica has a massive lifetime production of seeds of which only a tiny fraction survives to maturity, leading to a considerable selection potential during early life stages that should favor adaption to the changing climate. During years with extreme weather events, seedlings with traits relevant to endure the stress pulse should be selected, facilitating future beech forests to better overcome early summer drought events.
In addition, forest management has pronounced effects on the stand structural complexity, which influences the microclimate and may enforce or attenuate beech climate adaptation. For example, beech saplings may experience enforced selection under an open canopy.
The reported high genetic diversity in temperate beech forests provides a reasonable basis for selection to adapt future forests. However, we know little about the dynamics of this process or which life-history transition selects the strongest.
In TREEvolution, we aim to investigate the genetic adaptation potential of European beech saplings to new climatic conditions. While previous studies focused on adults, the younger generation may be better adapted to drought and heat. We will genomically examine one to five-year-old saplings and compare them with neighboring old trees to determine if forest land use types affect these changes. We will also consider micro- and macroclimatic environmental conditions.
The results from TREEvolution will provide insights into the population structure and early selection regime of beech under natural conditions accounting for management effects, which helps to understand how the high genetic variation corresponds to the drastic changes in climate conditions.
We will collect leaf material from adult and juvenile trees (seedlings and saplings), measure whole plant and leaf traits (e.g. plant size, specific leaf area), and permanently mark the juveniles for future monitoring. From the collected material, we will extract DNA and prepare libraries for reduced representation sequencing (e.g. ddRAD) or low-coverage whole-genome sequencing. In the following, using bioinformatic- and population-genomic tools, we will investigate how forest structure, microclimate, forest management, and the year of establishment shape the genomic composition of the next generation.