Principles of Forestry

Forests are among the world's most important renewable resources. In the European Union, revenues from forestry and timber harvesting are estimated at €55 billion per year, with more than half a million people employed in the industry (EUROSTAT, 2020).

Forestry is defined as the study and science of managing forested areas. It is founded on the belief that forests can be sustainably managed over long periods with clear objectives. This includes the protection of forests, the continuous production of timber and other products based on sustainability principles, management of watersheds, and the preservation of all other ecosystem services and values that forests provide to humans (Agnoletti et al. 2000).

Forests can be managed in various ways, influencing the length of rotation periods and the progression of different successional stages. The most prevalent approach today is “high forest” management, a practice established in the 19th century (Oldeman 1990; Piussi 1994). "High forest” (“Hochwald”)" refers to stands dominated by single-stemmed trees that arise from natural regeneration, seed-brooding, or planting (core growth). The aim of this method is to produce well-grown long stems as "quality timber" for construction and similar purposes (Röhrig et al. 2006; Ellenberg & Leuschner 2010). 

In contrast, “coppicing” management, involves cutting trees (cutting   ~ "hauen”" → "Hauberg") every 20 to 30 years, allowing them to bud from the remaining stumps until they are harvested again. Historically, Coppiced  forests were primarily utilized for firewood and charcoal production (Hilf 2003; Ellenberg & Leuschner 2010). This practice typically favors species which are able bud from the remaining stumps , such as sessile oak, pedunculate oak, or hornbeam. In the past, after coppicing, the cleared areas were often sown with grain and grazed, resembling heathland management (Ellenberg & Leuschner 2010; Poschlod 2015). The spatial and temporal dynamics of coppice systems contributed to their rich biodiversity.

Medium forests (= “Mittelwald”) serve as an intermediate approach between high and coppiced forest management: the forest is predominantly coppiced, but certain trees (core growths or coppice shoots) are retained beyond the short rotation period to produce high-quality timber with long stems. In Germany, the remaining medium forests of the “Windsheimer Bucht” or the “Rhön-Grabfeld” region, these “overstorey” trees typically consist of oaks. 

Among the various methods of forest management, clear-cutting has historically been the predominant practice for high forests and continues to be common in coniferous stands. In this approach, the entire stand is harvested once it reaches maturity, after which it is replanted (cf. Röhrig et al. 2006). More sustainable alternatives to clear-cutting include shelterwood cutting (= “Schirmschlag”), group selection cutting (= “Femelschlag”, and continuous cover forestry (= “Plenterwald”). These methods primarily aim to replicate natural processes within the stand, particularly by promoting natural regeneration, and are most effective with shade-tolerant species such as beech and fir. In shelterwood cutting, the canopy of the entire stand is typically thinned in three stages: initially, about 15% of the canopy is removed, followed by 40%, and finally 80% before the remaining old trees are harvested in a fourth stage. Group selection cutting involves removing a larger proportion of old trees in a single step, but only from very small, sequentially new areas or "gaps" that are gradually expanded radially until mature timber is harvested across the entire area (cf. Röhrig et al. 2006). Continuous cover forestry, commonly practiced in beech and mixed beech forests today, entails the selective removal of mature trees over several years. This approach allows for small-scale natural regeneration and recruitment to occur in near-to-nature-logging systemss, resulting in a stand structure that resembles a permanent forest (cf. Röhrig et al. 2006; Clarke & Vesterdal 2015). 

A distinctive form of forest management is the “Hutewald” (or “Hudewald”), which derives its name from "Hutung," indicating that these stands are extensively grazed in addition to being forested. Hutewald forests feature a blend of open, grazing-like areas dominated by very old and deadwood-rich single trees, known as "Hutebäume," alongside more densely wooded sections. While the use of Hutewald was once widespread, it is now primarily practiced in certain regions of the Mediterranean but recently experience a come back as a sustainable agroforestry system.

One notable example is the "Dehesa" in Extremadura, Spain, which can be described as a more or less dense Hutewald composed of stone and cork oaks, grazed by various livestock breeds, particularly pigs. Hutewald-forests are structurally diverse, incorporating a range of habitats within the same area. Together with similar medium and coppiced forests, they are recognized for their multifunctional use and high species richness. These forests are especially important for critically endangered species that prefer forest edges and  semi-shaded transitions, commonly referred to as “light forest species” (= “Lichtwaldarten”).

All forms of forest management aiming at timber production affect the structure of forests, as well as the quantity and diversity of habitats present. The intensity of these management practices significantly impacts biodiversity at various levels (Gavin et al. 2022). The EU Biodiversity Strategy 2030 requires member states to maintain forests in good condition and preserve their functions in supporting biodiversity and addressing climate change.

A widely accepted approach to sustainable forest management today is the concept of multifunctional forests, developed in the mid-20th century (Palleto et al. 2008). This concept emphasizes that management should integrate multiple forest functions within the same area by combining timber harvesting with the fundamental principles of forest conservation. These include preserving enough deadwood and maintaining habitat trees and groups of older trees (German National Academy of Sciences 2017). 

The new EU Forest Strategy for 2030, adopted by the European Commission in July 2021, proposes the concept of "Close-to-Nature Forest Management” which largely base upon “near-to-nature-managed forests”  (=”naturnaher Waldbau”) (see Gossner et al,. 2013, Bässler et al. 2014). This strategy aims to provide a vision and guidelines for managing forests across Europe. Close-to-nature forest management is based on a full understanding of the forest ecosystem as a continuous, diverse, and dynamic system with the goal of imitating natural processes.

Close-to-nature forest management aims to promote the essential components, structures, and processes of forests to enhance the diversity of tree species, structures, sizes, developmental stages, and habitats, including habitat trees and deadwood. Currently, 22-30% of forest areas in Europe are managed according to nature conservation principles, with this practice on the rise. In Germany, this approach is already legally required in several federal states (European Forest Institute 2022).

Sources

Agnoletti M., Dargavel J., Johann E. (2000): The role of food, agriculture, forestry, and fisheries in human nutrition – Vol. II - History of Forestry.

Clarke N., Per Gundersen, Jönsson-Belyazid U., Kjønaas O. J., Persson T., Bjarni D. Sigurdsson, Stupak I., Vesterdal L. (2015): Influence of different tree-harvesting intensities on forest soil carbon stocks in boreal and northern temperate forest ecosystems, Forest Ecology and Management, Volume 351.

Ellenberg H., Leuschner C. (2010): Vegetation of Central Europe with the Alps: An Ecological, Dynamic and Historical Perspective. Ulmer Verlag, Stuttgart.

German National Academy of Sciences Leopoldina (eds.) (2017): Multi-functionality and sustainability in the European Union Forest, EASAC policy report 12, April 2017. Berlin.

Larsen, J.B., Angelstam, P., Bauhus, J., Carvalho, J.F., Diaci, J., Dobrowolska, D., Gazda, A., Gustafsson, L., Krumm, F., Knoke, T., Konczal, A., Kuuluvainen, T., Mason, B., Motta, R., Pötzelsberger, E., Rigling, A., Schuck, A. (2022): Closer-to-Nature Forest Management. From Science to Policy 12. European Forest Institute.

Palleto A., Sereno C., Furuido H. (2008): Historical evolution of forest management in Europe and Japan, Bull. Tokyo Univ. For. 119: 25–44.

Poschlod P. (2015): History of Cultural Landscapes. Ulmer, Stuttgart.

Röhrig E., Bartsch N., v. Lüpke B. (2006): Forest Management on Ecological Principles. Ulmer, Stuttgart.

Scolastri A., Cancellieri L., Iocchi M., Cutini M. (2017): Old coppice versus high forest: the impact of beech forest management on plant species diversity in central Apennines (Italy). Journal of Plant Ecology 10: 316–323.