The first objective was addressed using tree annual growth data from different sites along the latitudinal gradient from Spain to Germany. For Scots pine, 615 trees from 30 sites were used while 2061 trees from 119 sites were used for the three deciduous oak species. Tree annual growth and climate data (temperature and precipitation) of each site were provided by Swiss Federal Research Institute (WSL), Institute of Terrestrial Ecosystems ETH Zurich, Thünen Institute of Forest Ecosystems, Technische Universität München, IRSTEA Aix-en-Provence, Universite de Lorraine, Instituto Pirenaico de Ecologıa (IPE-CSIC), and Ecological and Forestry Applications Research Centre (CREAF).
The distinct role of mother tree’s environmental experience on seedling growth and survival performance was accomplished by applying transplanting experiments with seed from long-term irrigated trees (13 years) and trees growing under natural dry conditions. Two experiments were installed one in the field site and another in the greenhouse of the WSL, Zurich, Switzerland.
From the analysis of first objective, we found that the magnitude of tree growth resilience (i.e. growth after drought relative to growth prior to drought) of Scots pine to extreme drought decreased over the past three decades due to more frequent and severe droughts in the later period. Our study showed that although tree growth resilience to extreme drought of Scots pine was not dependent on geographic location, tree growth resilience of deciduous oak decreased with higher latitudes. However, oak trees had a higher basal area increment during 1996-2005 than the two previous decades indicating higher growth potential of oaks during the warmer years.
Addressing our second objective, we showed that during the lifetime, trees are not only able to adapt quickly to new conditions but can even pass on the 'memory' of such environmental changes to the next generation. This amazing ability of trees of Scots pine has been proved for the first time by this project. The findings provide hope that trees will be better at adapting to climate change than was originally feared.
We prepared four scientific manuscripts from this project and one of them has already been published in the journal Plant, Cell & Environment which can be accessible in this weblink:
https://onlinelibrary.wiley.com/doi/abs/10.1111/pce.13729(odnośnik otworzy się w nowym oknie). The three other manuscripts are currently in the process of publication. In addition, the results of this project were presented on international conferences including EGU General Assembly 2019, Functional Ecology 2018, and Science Day of Swiss Federal Research Institute (WSL).
