Anke Kahl, Vice-Rector for Planning, Finance and Transfer, and Prof. Dr.-Ing. Gertrud Lohaus were interviewed on film on the grounds of the Uniarboretum on behalf of the Science Transfer Office.

(Please click to download the full interview)
 

Guardian of the campus forest

Botanist Professor Dr Gertrud Lohaus and the university arboretum

It all began in 2012 with 42 trees on the grounds of the main campus on Gaußstraße. Gertrud Lohaus, a scientist appointed from Göttingen, took over the professorship for Molecular Plant Research and Plant Biochemistry at the University of Wuppertal and began by inspecting the site. She knows the soil conditions around the university grounds, knows where compacted soil makes rooting impossible and gradually created the new arboretum on the Grifflenberg campus to mark the 40th anniversary of the Bergische Universität.

In the meantime, she has lovingly added the species of lime, fruit and conifer trees that were initially lacking. In contrast to all the weather-sensitive people in the valley, the experienced tree expert is happy about rain, especially in spring and summer, so that the young trees have a chance. And if nature refuses, she sometimes picks up the watering can herself and helps out. When it comes to pest control, Lohaus does not use chemicals at all and, when in doubt, prunes back rather vigorously.

The arboretum (the name of a collection of different types of trees) is now home to more than 100 tree species, which can be explored along a signposted, designated path of around 1,000 metres around the university grounds. Lohaus has also published a brochure that introduces the user to each individual tree species. Pictures of the leaves allow the layman to recognise the respective tree and additional information on the family, location, occurrence and characteristics specify the species. Under the heading "Special features", the reader can also find a little historical or everyday information.

Tree trails as bachelor's or master's theses

She also advertises other tree walks in Wuppertal on her homepage. These tree trails were created as bachelor's or master's theses, all have a different focus and can be walked independently. GPS-guided or puzzle routes have been developed for children and the university professor hopes that this will increase interest in the forest and the diversity of plants because, as she states: "People are no longer reliant on food from the forest and are no longer dependent on it." Puzzle routes offer a completely new, exciting alternative.

She receives support in maintaining the arboretum from employees of the building department, members of her working group, family and friends as well as an external company that prunes trees or even cuts down trees if they threaten to topple over.

Tree of the year: the spruce

The scientist from north-west Germany is naturally also concerned about climate change. The spruce, this year's Tree of the Year, actually needs cooler, wetter areas. When asked whether we need to worry about this tree, she replies: "Our forests will change, the winters will no longer be so harsh. Trees like the sweet chestnut may spread further north, but the spruce will not disappear." Overall, the antagonists rain and drought will change the tree composition across the board in the long term.

She and her team use two greenhouses for research purposes: on the one hand, she investigates the transport of nutrients in the pathways of trees, and on the other, the nectar composition and pollinator types - i.e. insects, birds or bats - of various tobacco and bromeliad species.

Phloem, a very special sap

Phloem, the pathways of trees, have a very special scientific significance for them. These pathways transport nutrients from the leaves, where they are produced, to the other organs of the trees.

These wafer-thin tubes, which humans cannot pierce with their tools, are where animals come into play: aphids! They have a proboscis that they insert into the phloem tubes to access the plant sap. Lohaus continues, "and when the aphids have pierced, we come and cut the proboscis with a laser beam." The stump of the proboscis remaining in the leaf vein acts as a cannula from which tiny amounts of plant sap (the "blood" of the plants, so to speak) emerge and are collected. These investigations can answer many questions about nutrient transport in plants. The difficulty lies in the amount of plant sap, as the professor only works in the nano-litre range, which is an unimaginably small unit of measurement for the layperson.

You can tell that she is enthusiastic about her work by the fact that she never tires of dispelling misconceptions. That the hornbeam actually belongs to the birch family, that the sweet chestnut has nothing at all to do with the traditional horse chestnut, but belongs to the beech family, or that the ginkgo is planted almost exclusively as a male plant throughout Germany, because the female variant spreads unpleasant odours in its fruit.

Professor Lohaus is pleased that many cities are once again placing more emphasis on green spaces in city centres and points out the benefits for people. In her opinion, trees favour the microclimate of cities, increase humidity, provide shade, retain soil water and filter pollutants from the air.

A Douglas fir you can touch

The botanist also knows the tallest tree in Germany. The almost 70 metre high Douglas fir in Freiburg's city forest came to us from North America as a seedling in 1913. In the Wuppertal University Arboretum, visitors can currently find the small version of this pine tree under the number 69.

Uwe Blass (interview from 21/09/2017)

Prof Dr Gertrud Lohaus completed her doctorate at the Georg August University in Göttingen in 1995 and worked there until 2004 as a research assistant in the Plant Biochemistry section. From 2005 to 2009, she was a lecturer and then deputy professor of tree physiology and forest botany at the same university.

In 2009, she took over the professorship for Molecular Plant Research/Plant Biochemistry at the University of Wuppertal.