If only trees could speak -- What trees, society and water have to say about the climate

What effect do large-scale weather patterns have on Bavarian forest ecosystems? What role is played by regional climate conditions? What do school pupils know about climate change? Researchers at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have been investigating these questions in a new joint project named BayTreeNet with the help of so-called talking trees. The project takes a unique interdisciplinary approach linking social sciences to natural sciences by investigating climate modelling and dendroecology on one hand and research into education on the other.

Climate change is one of the major global challenges facing the twenty first century. A total of 18 million euros has been provided by the Bavarian State Ministry for Science and the Arts for the Bavarian climate change research network bayklif, with funding starting in May 2018 and planned to run for a total of five years. Scientists from the Department of Geography and Geosciences at FAU are involved in three joint projects run by bayklif, receiving funding of approximately 1.7 million euros.

In the BayTreeNet project coordinated by FAU, researchers are systematically investigating how forest ecosystems react to climate dynamics. This is the first time that they are doing so over a wide area - until now, researchers have only used small-scale climate reconstructions, for example to investigate the prolonged north-west weather pattern in spring 2015. In Franconia, this led to extremely dry conditions, while in Upper Bavaria it led to flooding due to the moisture-laden air coming from the Northern Alps. Researchers are able to discover how trees reacted to these extreme fluctuations in climate years later by reading the growth rings and comparing them with current data - a branch of science known as dendroecology.

For the BayTreeNet project, Prof. Dr. Achim Bräuning from the Chair of Geography (Physical Geography) at FAU established a dendroecological network with ten so-called talking trees. They are situated in different climatic locations in various regions of Bavaria, five at high elevations and five at low elevations. The clever thing is that the trees are equipped with a transmission unit capable of connecting to the internet - and every time the tree reacts to local weather conditions it can be tracked in real time online. The scientists take monthly wood samples from the growth zone of the trees at each location, measure the current fluctuations in growth with electronic sensors, determine to what extent water has been transported to the trees, and then enter the data into the high-performance computers at FAU. These are also used by Prof. Dr. Thomas Mölg, Professor of Geography, who uses computers to model the future occurrence of major weather patterns and the atmospheric circulation patterns on which they are based. These determine where and when there is likely to be a deficit or surplus of water and how hot or cold the temperatures are expected to be.

The talking trees are cared for by a network of partner schools and are also accessible to the general public. During their lessons, pupils translate the ecological and meteorological data measured by the trees into human language, allowing even the general public to understand what the talking trees have to say. Prof. Dr. Jan Christoph Schubert from the Chair of Teaching of Geography at FAU is overseeing and researching the teaching concept of the talking trees. Using empirical social research methods, he is investigating how to successfully transfer data into a school education context. Pupils fill in questionnaires and take part in guided interviews. This enables Prof. Dr. Schubert to assess the extent of their knowledge and the attitude they have at the outset and monitor how this changes as a result of the lessons.

Overall, the project links plant sciences, climate research and educational research, and strengthens the links between institutes of higher education and schools in STEM subjects.

Researchers from the Department of Geography and Geosciences at FAU are involved in another two joint projects run by bayklif.

Prof. Dr. Perdita Pohle, Chair of Geography (Cultural Geography), is involved in the joint project BLIZ - Interactions between society, land use, ecosystem services and biodiversity in Bavaria until 2100. It is based at Technische Universität München (TUM) and is exploring the effects of climate change on ecological and socio-ecological systems and the related interactions. The sub-project coordinated by Prof. Pohle deals with socio-ecological transformation in agriculture in the context of climate change. She is analysing the acceptance and preference of sustainable land use options from the point of view of various actors from politics, the environment, the economy and civil society, discussing practical possibilities of implementation with partners.

Prof. Johannes Barth, Chair of Applied Geology at GeoZentrum Nordbayern at FAU is actively involved in the project AQUAKLIF. The project is coordinated by Universität Bayreuth and is investigating the effects of climatic factors. These include changes in temperature and precipitation as well as changes to fine sediment yield as significant factors affecting aquatic ecology and water quality. The decisive factor for the desired 'good quality' of a body of water is the level of oxygen dissolved in the water. Prof. Barth is using a new measuring method of 'stable isotope ratios' to investigate oxygen, tracking its occurrence in streams and the sediments found there and in groundwater.

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