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

Fagus sylvatica and Fagus orientalis

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%. 

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

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 :

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

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

11/2021 – Summer trials 2021

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!