Speaker
Description
Recent recurrent drought years have imposed water and heat stress on trees across Germany. However, it is unclear how demographic rates of broadleaved tree species were affected by the drought. Moreover, it is likely that climate change leads to an increasing frequency of drought years and associated changes of demographic rates, and it is unclear whether current forests will still be viable in the future. To explore these questions, we carried out a forest inventory in 2023 in a 28-ha beech-dominated forest in the Hainich National Park that had previously been surveyed in 1999, 2007, and 2013. We calculated growth, mortality, and recruitment rates for the four most abundant tree species (beech, ash, sycamore maple, and hornbeam, ≥1 cm diameter) before 2013 (1 drought year/decade) and after 2013 (4 drought years/decade) and projected forest dynamics for both climate scenarios until 2100 using a demographic forest model.
Growth rates were similar across census intervals. However, mortality rates were increased after 2013 for all tree species, especially strongly for small trees, as compared to mortality rates before 2013. As an example, the annual mortality rate of beech was ~0.5% higher. Model simulations using demographic rates from before 2013 predict that the forest could increase in above-ground biomass from 410 t/ha to >500 t/ha until the end of the century. However, when using demographic rates from after 2013, the forest was predicted to decline to ~300 t/ha. These simulations also suggested that all species except hornbeam would decrease in biomass. We conclude that an increasing frequency of drought years threatens the viability of beech-dominated broad-leaved forests in Central Germany.
| Status Group | Senior Scientist |
|---|
