Knowledge atlas Science

Prof. em. Dr., Dr. h.c Nikolaj Torelli, forestry, wood science and technology, biological sciences


Since time immemorial, forests and wood have played an essential role in the history of humankind and supported our survival, from the Roman ligna et materia and navies that set out to conquer the world to the cities built on water that still stand today. And then there’s also the mitigation of climate change. “A mature beech tree absorbs 24 kg of CO2 in a year, which is equal to what an average car produces travelling from Ljubljana to Nova Gorica (approx. 110 km). In a day, it produces enough oxygen for 26 people. A hectare of forest in Slovenia absorbs 6.7 tons of CO2, which is equal to two-thirds of the carbon emissions of a transoceanic flight.”

Name of Field in the local language
Biološke znanosti, drevesna fiziologija, zgradba in lastnosti lesa
Area of Expertise
Biological sciences, tree physiology, structure and properties of wood
Scientists / Scientific team
Prof. em. Dr., Dr. h.c. Nikolaj Torelli
Location, Institution, Website
Faculty of Design, Dunajska c. 129, 1000 Ljubljana, Slovenia;
Type of Institution
Years of Active working in the Field
50 years
Collaborators or Successors
Former students of the Biotechnical Faculty, Department of Forestry and Renewable Forest Resources, and the Department of Wood Science and Technology, where he taught; associates of the Slovenian Forestry Institute

Laboratory and research space
Forests in Slovenia and abroad; experimental stations, research institutes, study rooms, and lecture halls; mountain spruce sites; halls with good acoustics
Materials and equipment
Wood and tree species; laboratory to determine basic properties; laboratory testing and processing machines; industry
Technology / Tools / Machines
Forest use and ecology; physical, chemical, and mechanical properties of wood; phytosociology (botanical description of forest composition); laboratory testing and basic analyses (research into biological, physical, chemical, mechanical, and technological properties); grouping by technological processes and end-use; conversations and interviews with the locals and their experiences; etymology
Education of the Scientist
Forestry (BSc), wood science and technology (MSc), biological sciences (PhD)

Most impactful project
Nikolaj Torelli, Biološki vidiki ojedritve s poudarkom na fakultativno obarvani jedovini (Biological aspects of heartwood formation with an emphasis on facultatively coloured heartwood), master's thesis, Biotechnical Faculty, University of Ljubljana, 1974. * Nikolaj Torelli, Prispevek k ekologiji in fiziologiji fakultativnega obarvanja pri bukvi (Fagus sylvatica L.) (Contribution to the ecology and physiology of red heart formation in beech (Fagus SylvaticaL.)), dissertation, Humboldt-Universitat zu Berlin, University of Ljubljana, 1978. * Maya Timbers. Essay on mahogany/caoba (Swietenia spp.), in print. Silva Slovenica, Slovenian Forestry Institute, Ljubljana

Awards, certifications, or scientific recognition
Nikolaj Torelli has run several international projects for the promotion of lesser and unknown tropical timber. With his colleagues from the USA he took part in a project in the Central African Republic (1977) and in the Maya Forest with his Mexican peers (1983). He is the recipient of the Mexican prize for forest merits Merito Nacional Forestal 1986. Between 1996 and 2007 he served as editor-in-chief of Les magazine, and as director of the Slovenian Forest Institute between 1999 and 2008. He was awarded the title of Professor Emeritus of the University of Ljubljana in 2020. He is also a member of the Council for Environmental Protection at the Slovenian Academy of Sciences and Arts (SAZU).

Nature has always been a part of Nikolaj’s life.

His mother a biologist and his father a keen mountaineer and member of the mountaineering club Skala both encouraged his love of nature, and Nikolaj himself became a keen scout already at an early age. For an excellent diploma thesis, Niko was awarded the Prešeren Student Prize (1964) and, thanks to it, got the employment at the Forest Planning Office in Ljubljana, where, with excellent mentors, he studied the botanical and pedological structure of Slovenian forests. In 1974, he completed his master’s degree at the Department of Forestry of the Biotechnical Faculty in Ljubljana. His findings took him abroad and in 1978 he successfully defended his dissertation at Humboldt University in Berlin.

Throughout his career as professor he dedicated many lectures to sustainability. His knowledge of history and etymology led him deeper through the many layers of sustainability concepts. The concept of sustainability can be tracked back to 18th-century Saxony that was then suffering the consequences of timber shortages in the face of excessive exploitation. With strategic economic development in mind, Hans Carl von Carlowitz developed the practice of sustainable forest management with his concept of Nachhaltigkeit (meaning long-lasting, strong), or what we today call sustainability. Etymologically, the word sustainability is derived from the Latin word sustinere, or “hold something up”. The concept is best illustrated by Carlowitz’s core principle that people should only harvest as much wood as they are able to regrow. Nikolaj adds that “sustainability misleadingly leads us to think of something that lasts, like never-ending exploitation. Ecosystemic, on the other hand, means maintaining the natural balance between living and non-living nature,” which is also the aim of modern forestry. In addition to teaching, he is now researching the impact of forests on the threat of climate change in the light of increasing motor traffic.

Forests, both in Slovenia and abroad, are Nikolaj’s essential research space, and he is interested also in their relationship with humans and the way they are used. He began his career as a scientist with research into the red heart, a visual defect in beech wood. During the several decades of his career in research he worked also in the Central African Republic and Mexico, where his research space expanded from Maya forests to experimental stations and research institutes as well as wood processing plants in which they tested research outcomes. The 1990s marked the beginning of his involvement in the education process, and for the next 20 years it was lecture rooms at the Department of Wood Science and Technology that served as his space and one that still feels like home. Today, he passes on his love of wood through lectures at the Faculty of Design.

Mayans can teach us a lot about the forest.

The traditional Maya land management system is known as the milpa forest garden cycle. The first step in the cycle involves burning a forest plot on which they grow a variety of crops, typically featuring the so-called Mesoamerican trilogy of maize, beans, and squash. In the second stage they grow annual, biannual, and perennial plants, and after twenty, even thirty years also trees from the adjacent forest. Owing to “utility-driven forest change” we can no longer speak of natural forests in Amazonia. Nevertheless, these forests still hide a myriad of useful and edible plants that the ancient Mayans knew. “What tourists see are not jungles, but feral, domesticated forests that people abandoned and were gradually overgrown by wildlife.”

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Nikolaj’s scientific career took off with research into the red heart – enzyme-mediated oxidation and dehydration of heartwood. He studied the effect of tree age, height, and crown on the formation of red heart. Later he took part in international projects for the promotion of tropical timbers in Africa and Mexico, where the focus was on the applications of timber species and collaboration with the locals. He developed studies on Mexican tropical timbers, tested their application, and grouped them according to end-use. In the 1980s he took part in the research into the decline of fir due to acid rain, and worked on the development of the Shigometer, a tool that measures the vitality of trees. He is currently working on the monograph Maya Timbers. The original plan to survey 43 timber species has grown into one of the most extensive studies into Mexican tropical timbers, both in terms of the number of species and the number of investigated properties.

Written by Denis Maraž