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Biodiversity helps against extreme weather: interview with disturbance ecologist Prof. Dr. Anke Jentsch

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University of Bayreuth, Press release No. 100/2020, 29 June 2020

Extreme weather events such as late frost, drought, and torrential rain are meanwhile being taken for granted. After two hot summers, the soil is not yet sufficiently moist to withstand another hot summer, meaning foresters are worried about forest fires while farmers fear crop failure. Prof. Dr. Anke Jentsch holds the Professorship for Disturbance Ecology at the University of Bayreuth, and concerns herself with the resilience of nature. She will talk about these research questions in this interview and in the digital “Stadtgespräch” on July 1rst at  6 p.m. You can find the ZOOM-Link here: www.stadtgespraeche.uni-bayreuth.de. After the lecture, she will be available to answer questions from the audience.

Prof. Dr. Anke Jentsch, Professur für Störungsökologie Universität Bayreuth

Can the countryside endure a third hot summer in a row?

At the moment, it is not yet possible to predict how this summer will turn out. Climate change in Central Europe is characterised precisely by increasing variability in temperatures and precipitation. In recent years, for example, there have been sudden drops in temperatures in winter and extreme drought in summer with temperatures far beyond the long-term average. The dry June of 2019 was the warmest since records began, whereas this changeable June in 2020, with its abundant rainfall and cooler temperatures, has offered some respite from the exceptionally dry spring. Yet soil water reserves are far from being full. A third hot summer would be an enormous challenge for our agricultural production and for the extensive, monodominant commercial forests, but not for the species- and structurally-rich cultural landscapes of the “Mittelgebirge” German Central Uplands or for the foothills of the Alps.

Why do species-rich landscapes cope better with extreme weather conditions?

Agricultural landscapes and commercial forests are optimized for high yield, and based on a reduced spectrum of plant species that are extremely productive under certain conditions. However, many of these species are particularly sensitive to disruption from multiple stressors such as drought and heavy rainfall, chemical stress, fungi, and bark-dwelling or leaf-eating insects. Species-rich communities, on the other hand, consist of a coexistence of alternating performers, while the contribution of seemingly insignificant "hangers-on" or "under-performers" can be of enormous importance when conditions suddenly and repeatedly change. Changing competitive hierarchies for the available resources as well as varying tolerance for disturbances play a special role here. The diversity of functional characteristics and strategy types within a community acts as an excellent insurance against environmental fluctuations and extreme weather events.

What does that mean effectively? 

In species-rich meadows, for example, papilionaceous flowers are considered key species for biomass production, as they can fix nitrogen from the air in addition to resources in the soil. However, this mechanism works less well during severe droughts meaning their contribution to community production declines rapidly, and other grasses and herbs then take over. In fact, in our experiments, something quite amazing happens: Under extreme conditions, some species out-do themselves, grow stronger, and higher than usual, virtually replacing the contributions of their otherwise highly productive partners. This happens even though all members of the plant community are suffering from water shortages during drought. However, we suspect that this overcompensation is made possible by their being relieved of competitive pressure. Competition can therefore have a more restrictive effect than a lack of resources. Hence, biodiversity is accompanied by a mutually complementary effect of functional properties in communities, which makes it possible to maintain performance in the event of a sudden change in external conditions.

Recovery and resilience - can insights learnt from nature be transferred to society?

There are some fascinating parallels. As a disturbance ecologist, I study the paradox of disturbance and stability in ecosystems. It is about understanding rhythms, but also about the mechanisms of regeneration after extreme events, about balance and continuing performance despite disturbances. The scientific findings also give rise to social questions. How do we deal with the resources available? What role do individuals play in various communities? How does life go on in extreme locations or in the face of multiple stressors? Our research results show that complementary characteristics among the actors involved are an important key to functional stability and rapid recovery after extreme events. 

How do you research that in practice?

We use unusual experiments to simulate future extreme events. For example, we create once-in-a-century droughts by constructing rain roofs over natural or specially planted meadows, simulate increasing global warming by relocating plant communities from the cool-humid highlands of the Alps to the warmer and drier lowlands of Bayreuth, manipulate winter warm spells and freeze-thaw cycles by means of infra-red lamps or heating cables buried in the ground, or simulate late night frosts by placing young trees in rented cooling trucks overnight. Then, for example, we measure the resilience of different species, record leaf damage and yield losses, quantify changes in material flows, and analyse the importance of origin, plasticity, and diversity of communities for resilience and ecosystem functions. We map the occurrence of plant species and measure their functional properties, we compare wilderness and cultural landscapes, and cooperate with remote sensing and modelling experts. Basically, we work "glocally".

What is “glocally”?

Global and local in one. We investigate the local impacts of global climate change, e.g. along altitude gradients in the Alps or precipitation gradients within Europe. To this end, we join forces with other scientists in global networks, conduct identical experiments in different countries and continents, investigate and localize the local effects, and place them in an overall context. By comparing local results on a global scale, we can identify fundamental ecological mechanisms and at the same time identify the most sensitive ecosystems on earth. Here at the University of Bayreuth, I am active in "Scientists for Future", I involve students in experimental research, and contribute to the Student Research Centre, for example.  Excursions and mountain hikes with Bayreuth students to see melting glaciers and to the research stations of glaciologists and vegetation ecologists make it particularly clear that local action has long since had global consequences, and vice versa! 

Join the digital “Stadtgespräch” on July 1rst at  6 p.m. where Anke Jentsch will talk abpot these issues. You can find the ZOOM-Link here: www.stadtgespraeche.uni-bayreuth.de. After the lecture, she will be available to answer questions from the audience.

Contact:

Prof. Dr. Anke Jentsch
Professorship for Disturbance Ecology
University of Bayreuth
Phone: +49 (0) 921 / 55- 2290
E-mail: anke.jentsch@uni-bayreuth.de

Editorial office:

Anja-Maria Meister
Press & PR Manager
University of Bayreuth
Phone: +49 (0) 921 / 55-5300
E-Mail: anja.meister@uni-bayreuth.de

Translation:

Ralph Reindler

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