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2023-2028 trial participants: observations start on 1 September
10/2025 – Different responses of fir and beech to heat and drought in their early life stages
10/2025 – Different responses of fir and beech to heat and drought in their early life stages
Climate change is making natural regeneration increasingly uncertain. In our climate chamber experiments – using the same seed lots later sent to participants — we tested two key stress factors: shorter, warmer winters that reduce seed chilling, and warmer, drier springs that increase evaporative stress when seedlings. Analyses by our PostDoc researcher, Leo Zeitler, show that fir seedlings are more resilient under these conditions, while beech struggles to establish when faced with climate stress.
In the climate chambers we tested over 34,000 seeds collected from 32 fir and beech populations across Europe, including around 10 seed families per population. Seeds were exposed to two types of winter chilling or stratification (long vs. short) and two spring conditions (cool vs. warm/dry). We then followed seedling development every few days for three months — roughly the length of a natural first growing season. We looked at the very first stages of tree development — from seed to young seedling.
Short stratification delayed germination in both species, while dry/warm germination conditions accelerated it (see figure below). Fagus showed reduced germination rates (i.e., the proportion of seeds that emerged with a shoot) under warm winter conditions, Abies maintained high germination rates even with reduced chilling and dryer, warmer spring conditions. However, the effects of reduced stratification emerged later in development: in both species, seedlings from some provenances exhibited halted growth under warmer conditions, revealing interactions between the genetic background of provenances and the environment where they grow. Abies development was more influenced by provenance, suggesting stronger adaptive divergence, while Fagus showed more consistent growth across provenances, indicative of a greater colonization potential.
Overall, life history strategies differ greatly between Abies and Fagus: while Abies seeds germinated well, both in terms of capacity and speed, we observed a plastic response to stress later in the development through reduced developmental speed under stress. Contrary to this, Fagus sensed stress already during germination, producing fewer seedlings that grow at a steady rate but face higher mortality later.
Our findings show that early seedling development is shaped by both genetic background and environmental conditions, including winter chilling, spring water and heat accumulation. Using predictive provenancing could help maintaining fir populations that regenerate naturally even under shorter winters and warmer/dryer springs and summers expected in the future. In contrast, natural regeneration in beech could be further reduced under future climate change scenarios, a finding that is largely confirmed by recent research on adult beech trees.
06/2023 – Trials 2021-2023: Germination rates results
06/2023 – Trials 2021-2023: Germination rates results
We continue to analyse the data from the pilot trials 2021-2023! In these trials, 18 participants from 7 different countries (100 to 1400 m a.s.l.) planted seeds of 13 provenances of Abies spp and 10 provenances of Fagus spp. Participants monitored germination, phenology and survival during the 2022 growing season. The observations continue in 2023 and will be analysed after the end of this growing season.
Here we summarize the success and pace of germination in the climate chambers (at the WSL) and in the micro-gardens followed by foresters in different countries. We chose to show the cumulative percentage of germinated seeds as a function of the Growing degree days, or GDD, which is a measure of heat accumulation. Indeed, in order for the seeds to germinate and to develop into healthy seedlings, they need to be exposed to cold during the winter (chilling), and then to heat and humidity during the growing season. GDD indicates how much heat had been accumulated since the daily mean temperature reached the 5°C. Using GDD, instead of the date, is not only biologically meaningful, but also allow us to compare the development of seedlings across different environments. The lines indicate the performance of different provenances and the dots indicate when the were observations performed.
Regular observations are precious and necessary. The success and development of different provenances across different environments can only be understood by regular observations! We thank all our participants for their time and work! We also encourage future participants to observe even when the germination rate is low because these data can help us identify the limiting conditions for seedling development.
Important differences between provenances and micro-gardens. Differences between provenances in tree growth are known to foresters. However, it has been less known that provenances may differ also in early life-stages and consistently across environments! For example, the Abies nordmanniana from Georgia and the beech from Slovenia, performed well at most sites and in the climate chambers. For some provenances, the environment played a more important role: beech from Iran, performed very well in the climate chambers but less well in the field.
Germination in the field can be as high as in the climate chamber! For example, the fir from Corsica and beech from the Massif Armoricain showed equally high germination in the chamber and in the field, and beech from Slovenia and fir from Romania had higher germination in the field compared to the climate chamber.
Abies alba and Abies nordmanniana
Abies alba and Abies nordmanniana
Fagus sylvatica and Fagus orientalis
Fagus sylvatica and Fagus orientalis
07/2022 – Estimating germination rates: continuation of the climate chamber experiment with new provenances
07/2022 – Estimating germination rates: continuation of the climate chamber experiment with new provenances
Our student Mert Celik continued the climate chamber experiment started by Johannes Alt (see below results from April 2022) and finished testing all provenances used for the trials 2021-2023. This includes provenances of Abies alba, Abies nordmanniana, Fagus sylvatica and Fagus orientalis.
Using the same dark-light cycle (16 h dark, 8 h light), this time the experiment was maintained for 16 weeks to see if germination rates reached a plateau. Ambient temperature was kept at 5-15 oC for the first nine weeks, and it was increased to 10-20 oC for the rest of the experiment duration. For all species and provenances, germination rates reached the plateau in 80 to 85 days after the beginning of the experiment.
Once concluded, Mert combined the results of the first and the second experiment and showed that germination rates of the species belonging to the Abies genus ranged between 9% and 65% with a mean germination rate of 33%. Caucasian fir (Abies nordmanniana) outperformed all other silver fir provenances with a germination rate of 65%. In the Fagus genus, the oriental beech from the Iranian Alborz Mountains reached the highest germination rate of 72%. Across provenances, germination rates ranged between 0% and 72%, with a mean rate of 29%. Beech from Romania (SE Carpathians) and Switzerland (Salenstein) did not germinate at all during the experiment.
These results partly reflect what is happening in the micro-gardens in the field (check the preliminary results in the section below!).
In a nutshell: Germination rates of the Abies genus ranged between 9% and and 65% with a mean germination rate of 33%. In the Fagus genus,germination rates ranged between 0% and 72%, with a mean rate of 29%.
In a nutshell: Germination rates of the Abies genus ranged between 9% and and 65% with a mean germination rate of 33%. In the Fagus genus,germination rates ranged between 0% and 72%, with a mean rate of 29%.
Germination curves obtained from the germination data for silver fir and caucasian fir (top graph), and European and oriental beech (bottom graph); dotted lines indicate moist treatments, solid lines indicate dry treatment.
Germination curves obtained from the germination data for silver fir and caucasian fir (top graph), and European and oriental beech (bottom graph); dotted lines indicate moist treatments, solid lines indicate dry treatment.
06/2022 – Trials 2021-2023: preliminary results
06/2022 – Trials 2021-2023: preliminary results
Our participants from the trials 2021-2023 have been collected data for an entire growing season already, starting in spring 2022. Have a look at the graphs below to find out what happened in each micro-garden installed, which provenance performed better where and more.
In the dropdown menu, you can select different variables. Depending on what you choose, you can explore :
the percentage of germinated seeds in each garden ("Micro-garden")
the number of germinated seeds for each germination stage ("Germination stage")
the percentage of germinated seeds for each provenance ("Provenances-Abies" or "Provenances-Fagus")
the evolution of the percentage of germinated seeds in each garden ("Evolution-Abies" or "Evolution-Fagus")
the number of germinated seeds for each provenance and in each garden ("Heatmap-Abies" or "Heatmap-Fagus")
NOTE: In the heatmaps you can compare the results from the micro-gardens with the results from the climate chamber experiments. Please keep in mind that not all provenances were tested in the climate chamber so some information is missing. Similarly, some provenances were planted in only some micro-gardens and we have fewer data on them.
04/2022 – Estimating germination rates using a climate chamber experiment
04/2022 – Estimating germination rates using a climate chamber experiment
Master thesis by Johannes Alt
Master thesis by Johannes Alt
Part of the seeds provenances used in the trials 2021-2023, have been tested in our climate chamber at WSL by master student Johannes Alt. Johannes' objective was to assess the germination rate of the provenances under a dry and moist water regime. The germination test was done in a climate chamber using a cycle of 16h night and 8h day at 5 – 15°C for eight weeks and 10 – 20°C for additional two weeks.
European beech reached a mean germination rate of 38.2% (ranging from 29% to 59% between provenances) while for silver fir it was 25.4% (9% to 39%). The different water regimes had no significant effect on the germination rate. Nevertheless, for both European beech and silver fir Johannes found a significant provenance effect on the germination rate, indicating that not all origins are equally suitable for the conditions tested.
The second germination experiment with the rest of the provenances is currently ongoing. The combined results from all provenances will provide a solid baseline for comparison with germination in the micro-gardens. This will help us generate information on the suitability of the different provenances and their potential for assisted migration!
Germination curves obtained from the germination data for silver fir (A), and European beech (C); dotted line indicates higher temperature cycle (10-20°C); line defines the end of the experiment; day 72 equals absolute germination rate
Germination curves obtained from the germination data for silver fir (A), and European beech (C); dotted line indicates higher temperature cycle (10-20°C); line defines the end of the experiment; day 72 equals absolute germination rate
11/2021 – Summer trials 2021
11/2021 – Summer trials 2021
The very first trials of MyGardenOfTrees!
The very first trials of MyGardenOfTrees!
Enthusiastic citizens and NGOs from Scotland, France, Italy, Switzerland and Hungary helped us develop different steps of the project. Together, we tested the first version of the experimental design and particularly the effect of seed predation by rodents (using mesh cages) and competition (using weed exclusion sheets).
While competition from other seedlings seemed not to have a strong effect, seeds and seedlings predation from mice and snails was a clear issue. Because of these results, we designed a new kind of seed protector that we used for the following trials.
Citizen science is a beautiful way to do research which benefits both the scientific community and the public. Thanks to our early participants, we could go through the different steps of engaging and working with citizens and prepare us for the large-scale participation of the next trials!
Check out this great video from our participants in Scotland to learn more about the summer trials 2021!
Check out this great video from our participants in Scotland to learn more about the summer trials 2021!
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