image: The Collm Linden, Spring 2023 view more
Credit: Matthias Goede
It’s an extraordinarily huge sum. For this reason, Prof. Andreas Roloff, forestry scientist with a wealth of expertise in old trees, did the math several times over, always using different methods. But the results remained the same. In order to match the environmental benefits that an old tree with a crown circumference of 20 meters provides – such as air filtration, shade, cooling and carbon storage – you need about 400 saplings.
“The magnitude of this ratio also came as a surprise to me,” says Andreas Roloff. “But it emphasizes how much more we need to respect and care for the old trees in our environment and how the decision to cut them down, for instance to make way for construction projects, should not be made lightly.” Felled trees are required by law to be replaced by one to three saplings. At best, this serves as a pretext only.
Andreas Roloff, former Director of the Institute of Forest Botany and Forest Zoology as well as the Forest Park Tharandt, is now a Senior Professor at TU Dresden. For many years, he has been researching topics such as tree aging, tree species and tree care, as well as their reactions and adaptations to drought stress, especially in residential areas. Along with being the topic of his research, the protection and conservation of old trees is a topic close to his heart. Roloff has penned many texts including a publication on heritage trees and how to conserve them.
For his lecture during this year’s Dresdner StadtBaumtage (Dresden City Tree Days), organized since 2007 by the Chair of Forest Botany and the Office of Urban Green Spaces and Waste Management in Dresden and Tharandt, Andreas Roloff investigated the conditions and factors trees need to live for 1,000 years, to become “Methuselah trees.” He stumbled across this astonishing statistic almost by accident.
“Now, we can define eleven biological properties specific to trees which impact their life expectancy. The more of these a tree species can combine, the older it can theoretically become – if conditions, location and tree care are right and, above all, the tree is not cut down before its time,” explains Roloff.
If you’re thinking more in human lifetimes than Methuselah years and would like to plant a tree in your garden, Dresden’s forestry scientists have developed criteria for choosing the best site using a wide range of categories. Two databases are available for this purpose: In KLimaArtenMatrix, 250 tree and shrub species are listed according to their drought stress resistance. And Citree uses a ranking based on 65 categories or properties to select the best trees from about 400 species and varieties for a specific site.
Even the best of databases can’t help if trees are not properly cared for, especially in residential areas and parks. For this reason, forestry graduates and professionals in Dresden can also learn tree inspection and care from scratch in certification courses from the Deutsches Baum-Institut (German Tree Institute). “We now have very exact provisions to ensure high quality. It is not uncommon for the seemingly cheapest methods, such as tree topping, to turn out to be the most expensive in the long run due to the tree damage and follow-up costs they result in,” explains Andreas Roloff. With regard to the costs of planting new trees and the immense environmental benefits of old trees, it would be fair to ask what will end up costing you more paper.
At the end of March, Andreas Roloff was able to witness an extremely unusual tree rescue thanks to professional care. The Collm Linden, estimated to be 800 years old, is the oldest tree in Saxony and has been listed as a national heritage tree since October 2022. Earlier this year, it was in danger of collapsing when its leaves started sprouting. Armed with hand saws, eight arborists carefully pruned the ancient tree branch by branch in order to save it. “This is of course an exceptional situation and often unaffordable for regional municipalities,” said Andreas Roloff. “But for me, it was an incredibly awe-inspiring and moving experience. Thanks to this work, the Collm Linden is now secured and equipped for the next decades of its life.
Background:
This year’s Dresdner StadtBaumtage (Dresden City Tree Days) took place on March 9 and 10 and focused on pertinent questions of tree care and use, the protection of historical monuments, nature conservation, tree-lined avenues and old tree species. Major discussion topics included the more effective use of rainwater for garden maintenance in cities, using Dresden as an example, as well as the in part immense consequences and challenges that have arisen in Saxony’s gardens and parks due to climate change. The German-language conference transcript is available at www.deutsches-bauminstitut.de.
Nationalerbe-Bäume – Konzeption und Ziele, Umsetzung und Realisierung zum Schutz alter Bäume in Deutschland: die ersten 16 Kandidaten in allen Bundesländern. (National Heritage Trees – Conception and Objectives, Execution and Implementation for the Protection of Old Trees in Germany: The First 16 Candidates in All German States.) Verlag Forstbotanik TU Dresden, Tharandt 2022 (ISBN 978-3-86780-704-3). Available to download at https://nationalerbe-baeume.de/2022/05/01/buch-neuerscheinung-zur-initiative/
Andreas Roloff (2023): Methusalembäume - Wie und warum können manche Baumarten 1000 Jahre alt werden? Ursachen, Prozesse, Wirkungen, Nebenwirkungen und Konsequenzen. (Methuselah Trees - How and Why Can Some Tree Species Reach 1,000 Years of Age? Causes, Processes, Impact, Secondary Effects and Consequences.) Forstwiss. Beitr. Tharandt Beih. 24: 159-179
Andreas Roloff (2023): Inspiration Natur im Jahreslauf. Mentale Stärkung und Motivation durch bewusstes Erleben. (Inspiring Nature Throughout the Year. Drawing Mental Strength and Motivation from Conscious Experience.) Verlag Quelle & Meyer
Andreas Roloff (2017): Der Charakter unserer Bäume. Ihre Eigenschaften und Besonderheiten Beschreibung. (The Character of Our Trees. Their Properties and Distinctive Features.) Verlag Ulmer Eugen Verlag