Establishing the first marteloscope in an Urban Forest and discovering the transition of Gelsenkirchen
How do marteloscopes – these forest demonstration sites, where all trees are mapped and measured – and Gelsenkirchen, a city located in the so-called Ruhrpott fit together? You might be surprised that after being known as the “City of Thousand Fires” characterised by the coal, iron, and steel industry, and being a target of several air raids during World War II, Gelsenkirchen went through different economic and social changes. To boost its attractiveness for citizens, the city is now “shaping” its sustainability, investing in solar energy and converting numerous former mining sites into small city parks and urban forests . The city of Gelsenkirchen is also a partner in the CLEARINGHOUSE project, which connects China and Europe and explores the potential of Urban Forests for more liveable cities. And as part of this big international project, we – four researchers from European Forest Institute’s Bonn Office – established two new marteloscopes in the Urban Forest in Gelsenkirchen. This was not only an interesting experience because they were the first marteloscope sites we set up in urban forests, but also because of the vegetation and the fact, that these forests are not used for wood production.
The urban forest we visited appears as an opportunity to create biodiversity hotspots, recreational space, to foster social integration, and education. Schools commonly take children there to experience and learn about nature, in an area otherwise dominated by housing blocks and streets. Marteloscopes are usually used for the training of foresters and conservationists, but its interactive feature using Tablets allows it to be integrated in the environmental education of local schools. For this reason, colleagues at the city of Gelsenkirchen and at the Regionalforstamt Ruhrgebiet asked EFI Bonn to set up two sites in the city as well as to include them in the European Network Integrate.
Forests as history books
Together with city officials and the regional forester, we selected two very different sites for establishing our two marteloscopes. The first stand is a so-called Industriewald, a rather young forest located on the top of a deposit for mining leftovers, on industrial soil. The other site is Rheinelbepark, with 180 years old beech trees, who survived both the industrialisation and the destructions of WWII. The Rheinelbepark is a historical place, which was formerly owned by the industrialist Emil Kirdorf. Kirdorf was a staunch supporter of Adolf Hitler which gave him an honorary burial in the adjacent Zeche Rheinelbe in Hitler´s presence, but his support of National Socialism also let to the revocation of his honorary citizenship after the war. Today, the park is not only open to the public but also owned and managed by the City of Gelsenkirchen. Both forests are frequently visited by neighbours walking their dogs, scholars, families, and young and old couples. They also serve as a history book, where one can still find the remains of mining sidings and bullets embedded in old trees.
On the pleasure to measure biodiversity
On our first day, we started taking the measurements in the Industriewald, which has not been managed since its establishment. It was impressive to see the result of a natural development process started from a wasteland: a Sycamore maple and Birch stand mixed with thorny Blackberries, a few other shrubs, and some dead trees. One large Oak was dominating the stand with its diameter reaching 659 cm. It took us one day and a half to measure 126 trees: we painted numbers on every tree, measured diameter at breast height (DBH), distance and angle from the centre, tree height and looked for microhabitats. Normally, we would evaluate the wood quality for a Marteloscope, but this was not needed as these trees do not have any commercial value. Besides the spines we got from the Blackberries, it was pleasant to walk from tree to tree and get to know the nature around us, particularly listening to woodpeckers and observing little birds helping us discover new microhabitats to include in the marteloscope.
Rheinelbepark was much easier to measure. The large Beech and Oak trees were standing like columns of a cathedral with the sunlight directly reaching the clean forest floor. We even had long lying dead trees to sit on during the lunch break. Biodiversity was showing its signs also there: cavities at different heights, fungi and several types of cracks or injuries on the bark. On a tree close by the stand, we even saw the large nest of a Goshawk! The commercial value was better than the other stand, but still the wood qualities were not the best. No drama, since also this stand is managed for nature conservation and recreation, not for wood production. Regeneration was quite diverse: we found Cherry, Maple, Ash and Hazel trees.
At both sites, several curious visitors were asking what we were doing. It was a good opportunity to hear some views on how nature is perceived by locals: In general, they seemed very interested by the idea of a forest training site, and they were happy to have such a nice forest in their area. In the industrial forest the previous day, the opinions had been a bit more mixed, with several recreationists expressing their discontent with the “messiness” of the spontaneously established forest. On top of their value in the education of school children, tools like marteloscopes can hopefully help to facilitate a constructive dialogue with visitors and citizens in the future.
Now that the marteloscopes are installed, students can play with different management scenarios, learning what forest management means in their local urban forest. The app will help them understand the multifunctionality and the long horizon that need to be considered in forestry. As it was for our team during these three days of fieldwork, students won´t be learning only about nature, but also see the cultural and historical baggage that a forest can carry through time.
 Story of the Urban Forest Nature Based Solution of Gelsenkirchen: https://connectingnature.eu/oppla-case-study/22324
 Tree microhabitats catalogue: http://iplus.efi.int/uploads/Tree%20Microhabitat%20Catalogues/Catalogue_TreeMicrohabitats_EN.pdf
Blogpost written by Cecilia Fraccaroli, Jakob Derks and Dennis Roitsch