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09.05.19

Treetop health check: Research on ash dieback in riparian forest

Whoever goes for a walk in the riparian forest near Neuburg can experience science first-hand: Anna Eisen, doctoral candidate at the KU, placed pollen traps and wind gauges in the forest and uses a mobile man lift to collect blossoms and pollen from the ash crowns. Against the backdrop of climate change, this tree is normally considered as a promising species for forest restructuring due to its resistance to heat and dry periods. However, the existence of ash trees is currently put at risk by a fungal disease: the chronic ‘hymenoscyphus fraxineus’ causes ash dieback. Researchers and forestry are now under immense pressure because the disease spreads rapidly. This is why Anna Eisen, who receives funding from the Bayerische Landesanstalt für Wald und Forstwirtschaft, currently carries out research in order to preserve the genes of the ash. The research project is led by Prof. Dr. Susanne Jochner-Oette (Professorship of Physical Geography/Landscape Ecology and Sustainable Ecosystem Development). The researcher closely cooperates with the Wittelsbacher Ausgleichsfond and the Bayerisches Amt für Waldgenetik.


The microscopic evaluation of the collected ash pollen will reveal their viability. (Photo: Johanna Jetschni/upd)

The microscopic evaluation of the collected ash pollen will reveal their viability. (Photo: Johanna Jetschni/upd)

Anna Eisen uses the man lift to ascend to up to 20 meters to collect samples in the Neuburg riparian forest. (Photo: Anna Eisen/upd)

Anna Eisen uses the man lift to ascend to up to 20 meters to collect samples in the Neuburg riparian forest. (Photo: Anna Eisen/upd)

The scientist also installed eleven pollen traps across the riparian forest in order to be able to measure and record pollination. The specimen slides to which the pollen sticks must be changed on a daily basis. (Photo: Anna Eisen/upd)

The scientist also installed eleven pollen traps across the riparian forest in order to be able to measure and record pollination. The specimen slides to which the pollen sticks must be changed on a daily basis. (Photo: Anna Eisen/upd)

Up to now there is no effective counter-measure against ash dieback. A silver lining could however be that approx. one percent of ash trees seems to be naturally resistant to the disease. One possible measure for containing the disease and the resulting ash dieback is therefore to promote reproduction of resistant trees or foster the development of natural resistance. But we do not yet know why some trees are resistant and how we can reliably detect such resistance.

Anna Eisen now investigates the correlation between the ash trees’ health and their pollen production. To this end, the scientist collects samples in dizzy heights of up to 20 meters by using a mobile man lift and evaluates the pollen’s viability which might provide information on how successful reproduction of the plants could be. She also installed eleven pollen traps in order to track pollination in the riparian forest. Anna Eisen has been working in the forest on a daily basis since March to change the specimen slides that collect the pollen. She also uses the man lift for vertical pollen measurements in five different heights. “By changing the specimen slides on an hourly basis, we can draw conclusions on changes in pollen concentration during the course of the day”, explains Anna Eisen. “This information is of major importance for being able to estimate the reproductive success in fragmented stocks of trees.”

The researcher will continue to work in the forest until mid-May. After that, she will start the evaluation of samples under the microscope in the university laboratory. In spring 2020, a new collection process will be initiated.