Best Practice Knowledge Base
3.1 Conversion of monocultures to mixed stands
Mixed forest between monocultures. Freiburg, Germany © Hernán Serrano-León
Converting plantation forests (i.e., intensively managed planted forests of one or two species, even-aged, and with regular spacing) to mixed, uneven-aged stands, is a critical practice aimed at enhancing ecological resilience, biodiversity, and ecosystem services. This transformation reduces vulnerability to pests, diseases, and climatic extremes by promoting structural and functional diversity. The process typically involves a reduction in density to introduce spatial variability, underplanting or interplanting diverse species, and fostering natural regeneration to create age and species heterogeneity. Key considerations include site conditions, compatibility of selected species, soil fertility, and hydrological impacts. Managing competition among species, protecting young plants, and ensuring sustainable harvesting are vital to maintaining balance during the transition.
I. Guidelines
| Nº | Title | Author | Year | Focus Region | Language | Summary | Link |
| 1 | Transitioning monocultures to complex forest stands in Central Europe: principles and practice | Pretsch | 2019 | Central Europe | English | Principles and practical guidance on the conversion of monocultures to mixed, uneven-aged forests | https://www.waldwachstum.wzw.tum.de/fileadmin/publications/Pretzsch_Transitioning.pdf |
| 2 | Von der Monokultur zum klimastabilen Mischwald – So gelingt der Waldumbau | ForstErklärt | - | World | English | Overall guidelines for conversion of monocultures to mixed forest | https://forsterklaert.de/waldumbau |
| 3 | Paths to Mixed Forests - A Forestry Task for Generations | LWF | 2017 | Germany | German | Principles for conversion of monocultures to mixed forest | https://www.lwf.bayern.de/waldbau-bergwald/waldbau/160293/index.php |
| 4 | Merkblatt zur Förderung von Waldumbauvorhaben | Staatsbetrieb Sachsenforst | 2024 | Germany | German | Standards of the state of Sachsen for conversion projects suitable for public funding | https://waldbesitzerverband.de/images/pdf/foerderung/20240101_Merkblatt_Waldumbau_RL_WuF_2023.pdf |
| 5 | Waldumbau mit einfachen Mitteln: Hinweise für Waldbesitzer im Forstbezirk Plauen | Staatsbetrieb Sachsenforst | 2021 | Germany | German | Guidelines for cost-effective conversion of monocultures to mixed, uneven-aged forests in Plauen | https://www.sbs.sachsen.de/download/BroschuereWaldumbau_barrierefrei.pdf |
II. Books or book chapters
| Nº | Title | Author | Chapter | Chapter author | Year | Focus region | Language | Summary | Link |
| 1 | Waldumbau: Gesunden Mischwald bewirtschaften | Henning | - | - | 2024 | Germany | German | State of the art and extensive, practical advice on the conversion of spruce stands to mixed, uneven-aged stands | https://www.ulmer.de/usd-7986491/waldumbau-.html |
| 2 | Norway Spruce Conversion – Options and Consequences | Spiecker et al. | - | - | 2004 | Europe | English | Synthesis of challenges and solutions around the conversion of Norway spruce monocultures form a variety of perspectives | https://efi.int/publications-bank/norway-spruce-conversion-options-and-consequences |
| 3 | Umbau von Schlag- in Plenterwald | Burschell and Huss | Waldbausysteme: Der Hochwald - Umbau vom Schlag- im Plenterwald | - | 2004 | Europe | German | Silvicultural considerations for conversion of an even-aged, rotational stand, into an uneven-aged, structurally complex stand | - |
| 4 | Selvicoltura generale | Piussi and Alberti | Tecniche particolari di coltivazione: Le conversioni | - | 2015 | Italy | Italian | Specific indications for conversion of even-aged, pure stands, under different scenarios | - |
III. Scientific articles
| Nº | Title | Author | Year | Focus region | Language | Type | Summary | Link |
| 1 | Converting plantations to uneven-aged stands: Effects of harvest type, group opening size, orientation, and canopy position on residual tree development | Shell et al. | 2022 | US | English | Experiment | Effects of different silvicultural treatments on the growth of residual trees when converting plantation forests | https://www.srs.fs.usda.gov/pubs/ja/2022/ja_2022_willis_009.pdf |
| 2 | Restoring mixed forests through conversion of Norway spruce stands: effects of fencing and mechanical site preparation on performance of planted beech and natural tree regeneration | Löf et al. | 2023 | Sweden | English | Experiment | Influence of distance to mixed forests, fencing, and site preparation on the performance of artificial and natural regeneration during conversion | https://link.springer.com/article/10.1007/s10342-023-01554-z |
| 3 | Evaluation of silvicultural alternatives for conversion of Norway spruce, silver fir, and European beech | Reventlow et al. | 2021 | Europe | English | Modelling approach | Simulations of conversion outcomes under different silvicultural approaches and stand ages | https://link.springer.com/article/10.1007/s10342-021-01381-0 |
| 4 | Conversion of Norway Spruce: A Case Study in Denmark Based on Silvicultural Scenario Modelling | Brunner et al. | 2006 | Denmark | English | Modelling approach | Evaluation of silvicultural alternatives for conversion of Norway spruce in Denmark | https://link.springer.com/chapter/10.1007/3-540-31304-4_20 |
| 5 | Silvicultural measures to increase the mechanical stability of pure secondary Norway spruce stands before conversion | Slodiak and Novak | 2006 | Czech Republic | English | Experiment | Evaluates the effect of different thinning treatments on Norway spruce stand stability prior to harvesting for conversion | https://www.sciencedirect.com/science/article/pii/S037811270500784X?casa_token=X-sq2q69B0kAAAAA:hzyRTAuukAMTr5Om2fnvNz-2KMGyZBBYag8JiZxHPs2rgTEivBRrqiA065T-IrMCAvJfFfZcdg |
| 6 | Nutrient return to the forest floor through litter and throughfall under 7 forest species after conversion from Norway spruce | Carnol and Bazgir | 2013 | Belgium | English | Experiment | Evaluates the effect of converting Norway spruce monocultures on soil properties | https://www.sciencedirect.com/science/article/pii/S0378112713002144?casa_token=bZrZtxM0aSkAAAAA:6s4sxbvhmN4gpE7xPvsnk3L_fR2fv3UM3knhfdu_fDfJMFEuWJAQzgzD29EVmCxo87lNsgpWdw |
| 7 | From monocultures to mixed-species forests: is tree diversity key for providing ecosystem services at the landscape scale? | Schüler et al. | 2017 | Central Europe | English | Modelling approach | Evaluates the provision of ecosystem goods and services of different combinations of species when converting spruce monocultures | https://link.springer.com/article/10.1007/s10980-016-0422-6 |
| 8 | Restoring native forests from Pinus radiata plantations: Effects of different harvesting treatments on the performance of planted seedlings of temperate tree species in central Chile | Kremer et al. | 2021 | Chile | English | Experiment | Effects of different harvesting treatments of Pinus radiata plantations on the performance of planted seedlings of native species | https://www.sciencedirect.com/science/article/pii/S0378112720313542 |
| 9 | Restoring native forests from Pinus radiata plantations: natural regeneration of native tree species in response to different harvesting treatments in central Chile | Kremer and Bauhus | 2024 | Chile | English | Experiment | Effects of different harvesting treatments of Pinus radiata plantations on the natural regeneration of native tree species | https://onlinelibrary.wiley.com/doi/10.1111/rec.14309 |