A so-called Baseline Study has provided an answer. Now you can get the first overview of the collected experiences with the conversion of coniferous plantations.
>> Download the report (123 pages)
"It is intended as an inspiration catalog. Our hope from IGN's side is that the report will provide practitioners and forest owners with a better decision basis when trying to convert various types of coniferous forest plantations to close-to-nature forestry. It is thus a work that can be inspired by and subsequently adapted to the very local conditions, which the manager always knows best," says the main author of the report, Ditlev Reventlow.
Systematic Collection of Experiences
Conversion of Traditional Coniferous Plantations
Back in 2005, the action plan for close-to-nature forestry was implemented in public forests and used as a management form in coniferous plantations.
>> Read the definition of close-to-nature forestry
However, despite implementation in several state forests and to some extent in private forestry, there was a lack of systematic collection of experiences with the conversion of traditional coniferous plantations into forests with a more varied structure. The systematic collection is now compiled in the baseline study conducted by the Department of Geosciences and Natural Resource Management - IGN - a partner in LIFE4forest.
45 Examples of Conversions
Approximately 45 examples of conversions of coniferous plantations were selected by asking foresters in the Nature Agency, HedeDanmark, Salten Langsø, Sorø Academy, and Schleswig-Holstein State Forestry. There are examples of both successful and unsuccessful conversions, but they all share the characteristic that we know the entire history. We know what happened and when. Therefore, we can build future studies on the experiences that have been gained.
Instructions Already Now
Even though the study is based on systematic data collection and previous research, the baseline study is not a scientific work.
“We can already give some instructions on what we think you should do to convert to close-to-nature management. We can control it reasonably well, but we also know that there are problems with controlling the tree species composition and, in some places, the number of trees,” says Karen Poulsen, project manager for LIFE4forest.
A Study for Forestry Practitioners
The report uses as many illustrations as possible and is especially aimed at forestry practitioners but also landowners who want to know more about the conversion to close-to-nature forestry in specific coniferous stands.
The Report Is Continuously Updated
"The current report should not be understood as the final end product (that version will come in 2028). But it serves as an ongoing summary of what we know about the conversion of coniferous plantations today in the LIFE 4Forest region. It is quite unique because generally there has been very little of that type of summary – even when looking abroad," says Ditlev Reventlow.
Forest With Multiple Functions
The goal of close-to-nature forestry is to create a more diverse forest with many different functions. It is a multifunctional forest that not only produces sustainable building materials but also can contribute to biodiversity, biomass, CO2 sequestration, groundwater, recreation, landscape value, etc.
The project deals not only with conversion in existing forests but also with afforestation and how to plant a forest that hopefully, in the next generation, can be managed as close-to-nature.
>> A collection of examples for afforestation with high climate effect in close-to-nature forestry has been created (Danish)
Get Guidelines for Converting Coniferous Forests
In the baseline study, you can read about the conversion of these types of forests:
- Young Norway spruce (25-50 years), poor locality
- Young Serbian spruce (30-50 years), poor locality
- Older Norway spruce (mostly 50-80 years), intact, relatively stable, poor locality
- Older Norway spruce (>50 years) with gaps/destabilized, poor locality
- Norway spruce, good locality
- Older Sitka spruce (>50 years)
- Douglas fir (mainly >50 years)
- Older larch (>50 years)
- Mixed older Scots pine and Norway spruce (>50 years)
- Mixed older Sitka spruce and larch (>50 years)
- Other mixed old coniferous plantations (>50 years)
- Stands with dense uniform coniferous regeneration
- Scots pine
- Overgrown Noble fir and Nordmann fir stands
Examples of Conversion
The conversion of Norway spruce to close-to-nature forestry is the largest task in converting Danish coniferous plantations.
Old Norway Spruce Plantations
Therefore, the majority of the stands investigated in the baseline study are also stands of older Norway spruce. Typically, large plantation areas are covered by Norway spruce monoculture from 1930-1970, and these stands have good potential for conversion with increasing age.
The manual divides the older Norway spruce stands into more or less intact stands and stands that are starting to become destabilized with storm and bark beetle holes. In practice, the two types of stands will, however, overlap.
Old Norway Spruce, Intact, Relatively Stable, Poor Site
An example of the report's guidelines for conversion is older Norway spruce stands with (mostly 50-80 years), intact, relatively stable, poor site.
The goal of the conversion is especially to introduce new species under the still more or less intact canopy. The next generation is established under the canopy of the old forest, which is gradually harvested over a period of 20-30 years based on target diameter felling.
A number of seed trees are left to ensure a stable seed supply. The next generation will consist of a naturally mixed coniferous stand of original species, but including the desired species introduced in the recommended model here.
The area or proportion of new species will depend on the regeneration method, but the goal is to have a large percentage of conifers, including long-lived species like Douglas fir, grand fir, noble fir, and on poorer soils, Scots pine.
Which Trees Replace Norway Spruce?
The most intuitive species to introduce under the canopy are shade-tolerant species like beech, grand fir, and noble fir. An species like Douglas fir is less adapted to be introduced into intact stands under the canopy, as its introduction requires a fairly significant reduction in canopy density (the ground area should not exceed 20 m2/ha).
Douglas fir is more intuitive to introduce in the other type of older Norway spruce stands that have already started to become somewhat gappy. Noble fir, on the other hand, is tricky because it is heavily browsed by wildlife and is frost-sensitive. Therefore, beech and grand fir are the most obvious species to introduce in this situation (unless the soil is very poor). These two species should be introduced in groups due to the remaining uncertainty about how the two species develop in a more uniform mixture with each other.
| Year | Description of Intervention |
| 0 | First preparatory thinning: Thinning from above (i.e., felling the tallest trees) and removal of whip shoots that can damage other trees. Remove approximately 20% of the volume. |
3-4 | Second preparatory thinning: Logging described as "year 0." |
6-7 | Third and final preparatory logging before planting: Logging approximately 30% of the volume from above. Thinning around the trees with the deepest crowns, expected to be healthy and therefore long-lasting. |
8-9 | One to two years after the last preparatory felling, hole boring and planting are carried out. DO NOT bore too close to the larger "anchor roots" of the screen trees. |
11-13 | First post-planting thinning: Logging approximately 25% of the volume from above to assist the most stable overstory trees and the underplanting. |
15-18 | Second post-planting thinning: Logging approximately 30% of the volume from above to assist the most stable overstory trees and the planting. |
21-24 | Third post-planting thinning: Logging 30-40% of the volume from above to assist the most stable overstory trees and the planting. |
28-32 | Final overstory thinning: Remove 80-90% of the remaining volume and allow the remaining trees to stand for natural decay. |
>> Download the report (123 pages, Danish)
Join Us on an Excursion
There are plans to invite for a forestry excursion in the first half of 2023, where examples of conversions to close-to-nature forest management will be showcased.
Knowledge About Close-To-Nature Forest Management and Forestry in General
If you don't have experience and knowledge about forestry, these books might be a good place to start:
“Naturnær Skovdrift” by J. Bo Larsen
“Skovdyrkning i Praksis” by Andres Bergstedt
“Skoven og dens dyrkning” by H. A. Henriksen.