Diversity under threat

Kiel-based ecologists receive 2.4 million euros from the federal and regional governments for research project on ash dieback

severely damaged ash tree
© Institute for Ecosystem Research

An ash tree severely damaged by the harmful fungus. The results: significant leaf loss and dead branches.

The ash, which is native to Europe, grows up to 40 meters high and can live to be 300 years old – if it is healthy. But it is under threat – and with it, too, the biodiversity of ash woodlands. The cause is an invasive fungus from Asia, which makes the leaves wilt and kills saplings. A research team from the Institute for Ecosystem Research at Kiel University (CAU) is studying how the disease – ash dieback – affects biological diversity of ash woodlands in Schleswig-Holstein and what measures can help to preserve them. The preparation is done and the project “Bedeutung des Eschentriebsterbens für die Biodiversität von Wäldern und Strategien zu ihrer Erhaltung” (FraDiv - significance of ash dieback to the biodiversity of woodlands and strategies for their preservation) is now taking shape.

FraDiv is led jointly by Professor Alexandra Erfmeier and Professor Joachim Schrautzer. In February of this year it was granted total funding of 2.4 million euros for six years under the Federal Programme for Biological Diversity of the Federal Agency for Nature Conservation (BfN) using funds from the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU) and from the Schleswig-Holstein Ministry of Energy, Agriculture, the Environment, Nature and Digitalization (MELUND).

Rare fungus and plant species, entire woodland ecosystems and even people are under threat

Numerous plant species that are mainly only found in ash woodlands are affected by ash dieback in Germany; among these are, in particular, 29 so-called responsibility species of fungus. They live in symbiosis with ash trees. Like the Red Lists, responsibility analyses of certain species provide important information for the protection of biodiversity. “The fungus species Clavaria straminea, a representative of the Clavaria genus of fungus, or Hygrocybe conica, also known as the witch’s hat, could die out as a result of the disappearance of the ash tree,” explained Schrautzer, stressing that: “This and many other ground-level species of fungus perform important functions that keep the woods healthy. Which ecosystem functions and services will be affected by this and what impact this loss will have on people cannot yet be predicted. What we do know is that woodlands store a lot of CO2 and that will be released by the loss of wooded areas. In addition, as a result of the loss and forestry restructuring, the woodlands, which people find attractive, would lose their local recreational value. Ash dieback therefore has an indirect effect on every one of us.”

straw-coloured Clavaria straminea fungus
© Matthias Lüderitz

The straw-coloured Clavaria straminea is one of 29 responsibility species of fungus under threat from ash dieback.

witch’s hat fungus
© Tanja Böhning

The witch’s hat (Hygrocybe conica) is also affected.

Ash dieback: a Europe-wide problem

Ash trees grow from southern Norway to Italy and from Ireland across to the Caucasus. Ash dieback and the already comprehensive loss of this species of tree in some places significantly threatens the biodiversity of ash woodlands throughout Europe. The infestation in Europe was first observed in Poland at the start of the 1990s. The trigger is the sac fungus Hymenoscyphus fraxineus. It kills ash trees – regardless of whether they are young plants or mature trees.

“In the past few years the fungus has spread out from North Eastern and Northern Europe through Central Europe to Western Europe,” said Erfmeier. “The first sighting of the fungus in Germany was recorded in 2002. Since then, ash dieback has been seen throughout Germany. Minimising the effects and assisting with appropriate measures is a declared objective of FraDiv.”

From effects to concrete measures

FraDiv has four main foci. “On the one hand, through our studies, we want to find out how ash dieback affects the biocenosis, i.e. the living community of organisms in a biotope. On the other, we will be analysing the characteristics of the infestation as well as a possible rejuvenation of ash tree populations with regard to diversity of woodlands,” explained Erfmeier. Schrautzer added that: “We will also, however, be considering aspects that are relevant to forestry: such as how best to grow ash saplings so that they have a good start even in woodlands already infested or what the situation is with the development of forestry measures and recommendations for action from the perspective of nature preservation.”

Many open questions

In order to study the many aspects in closer detail, the six-member research team from the Institute for Ecosystem Research asked itself a series of questions: How does the extent of ash dieback affect the prevalence and vitality of the species of fungus associated directly and indirectly with the ash tree and the plant biodiversity of the ash woodland locations? How important is the continuity of the woodland and/or location to the characteristics of ash dieback and the prevalence of fungus species associated with the ash tree? What influence do biotic and abiotic factors have on the vulnerability of older and younger ash trees? Biotic factors are understood as the influence of organisms on the processes of the ecosystems, for example, competition or frass. Light, water and nutrients are examples of abiotic factors.

Can the ash be replaced?

“We are examining whether other native tree species such as the European white elm, the small-leaved lime, the Norway maple or the hornbeam could take on the role of the ash in the ecosystem, at least in part,” said Erfmeier. “For this purpose, species of trees with local origins are being grown in mixed plantings with ash trees on twelve trial plots in Schleswig-Holstein – six in woodlands between the Flensburg Fjord and Kiel Fjord and six in woodlands in Ostholstein. The size of each trial plot is between half a hectare and one hectare.”

Hand in hand with forestry

In their work, the Kiel-based ecologists rely on the expertise of freelance fungus experts as well as on the experience of forestry managers to ensure that scientific findings can be transferred directly to nature conservation work and recommendations can be developed for concrete forestry and restoration measures. The research team hopes this will improve the chances of survival for the ash trees and their associated species.


Prof. Dr Alexandra Erfmeier
FraDiv project leader
+49 (0)431 880-1010

Prof. Dr Joachim Schrautzer
FraDiv project leader
+49 (0)431 880-4595


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Farah Claußen
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