How to balance forestry and biodiversity conservation – A view across Europe
Kottenforst – The Regional Forest District Office Rhein-Sieg-Erft: forestry, nature conservation and recreation in urban areas
U. Schölmerich¹, K. Striepen²
¹Head of the Regional Forest District Office Rhein-Sieg-Erft, Germany
² Project Manager LIFE+ Project ‘Ville Forests‘, Germany
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< Fig. C 4.1. The Kottenforst in the foreground and the city of Bonn with the high tower in the background shows the interface between forest, landscape and densely settled area in the ‘Rhein-Sieg Erft’ close to Bonn and Cologne (Photo: Klaus Striepen).
Aims of the enterprise
The aim of our forest management is to increase forest resilience against climate change impacts in order to guarantee all relevant forest ecosystem
services for society in the long term. Recreation, nature conservation and wood production are always considered but may be given different pri- orities depending on the geographic location of the forest area.
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Germany
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Table C 4.1. Key figures: Regional Forest District Office Rhein-Sieg-Erft (state forest).
Forest community Mixed oak – beech forest in both lowlands and low mountain ranges Total forest area Forested area 211 km²/non-wooded areas 20 km²
Main management types 94 % high forest; 1 % coppice with standards, 5 % without manage- ment
Total volume 206 m³ under bark/ha (4 339 459 m³ under bark) Annual growth 7.6 m³ under bark/ha (159 692 m³ under bark)
Annual use 4 m³ under bark/ha (85 000 m³ under bark) according to the latest forest management plan
Altitude 100 to 400 a.s.l.
Ownership State of North Rhine-Westphalia
Geology Right bank of the Rhine: Rhenish Slate Mountains
Left bank of the Rhine: Lower, Mid and High Rhine Terraces
Protected area (total) 144 km²
Nature protection area (Natura 2000) 106 km²
Protective function Protection forests: against noise and emissions
Statement
“Combining forestry, nature conservation and recreation in urban areas.”
Background
The Rhineland in the west of North Rhine-West- phalia is one of the most populous regions in Ger- many. The area of the Forest District Office includes the cities Cologne and Bonn as well as the counties
‘Rhein-Sieg’ and ‘Rhein-Erft’. Altogether 2.4 million inhabitants live in cities and counties correspond- ing to about 40 people for each hectare of forest.
The Forest District Office manages all forests owned by the state of North Rhine-Westphalia and offers services to both private and municipal forest own- ers. It implements tasks as set out by the forestry authority.
Two types of landscapes are typical for the region. In the west, the terraced landscape of the Rhine Valley lies at an altitude of between 100 and
200 m above sea level. It is characterised by varying, small-scale site conditions. The mild sub-Atlantic cli- mate with an average annual temperature of about 10 °C displays slightly continental characteristics with low annual precipitation of 600 mm. Mixed oak (Quercus spp.) forests (fig. C 4.2), lowland beech (Fagus sylvatica) forests and mixed conifer- ous and broadleaved forests with Norway spruce (Picea abies) and Douglas fir (Pseudotsuga men- ziesii) prevail depending on edaphic conditions. In the northwest there are also extensive areas that have been afforested following extensive brown coal mining.
East of the Rhine, the Rhenish slate mountains dominate. The altitude rises rapidly to 400 m. In weather exposed areas, annual precipitation can reach up to 1000 mm, while the average annual
Timber/Biomass
Non-timber products
Erosion
Protection
Biodiversity Recreation
Landscape Climate Groundwater
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temperature drops to 8 °C. Soils are alkaline and nutrient poor and thus characterised by beech with a few sessile oaks (Luzulo-Fagetum) and extensive spruce forests.
In the Rhine Valley, human influence has shaped the landscape especially around metropoli- tan areas. The main challenges include not only the fragmentation of forests and their intensive use for recreation, but also the increasingly critical attitude of the urban population towards the wood use.
Portrait
Ownership structure
The total forest area in the forest district is 620 km².
The highest proportion is private forest (43 %), fol- lowed by state forest (38 %), municipal forests (14 %), and federal forest (5 %). The high propor- tion of small private forest properties is characteris- tic of the ownership in the region, and 53 % of the forests are less than 20 ha. The private forest own- ers are organised into 16 Forest Management Asso- ciations, and in 2018 14 of these associations (rep- resenting about 4000 forest owners) were serviced
by the foresters of the Rhein-Sieg-Erft Regional Forest District Office.
Table C 4.2. Tree species distribution in the Rhein-Sieg- Erft Regional Forest District Office (state forest).
Tree species ha
Oak (Quercus robur, Q. petraea) 4625.0
Beech (Fagus sylvatica) 4229.4
Poplar (Populus spp.) 634.0
Other broadleaves 4193.6
Norway spruce (Picea abies) 4400.4
Scots pine (Pinus sylvestris) 1725.7 Douglas fir (Pseudotsuga menziesii) 692.3
Larch (Larix decidua) 767.0
Forest history and cultural heritage
The oldest settlements in the Rhine Valley date back 7000 years to the Neolithic era, and the region has been continuously inhabited since Roman times. Throughout the centuries, people have worked and shaped the forests according to their needs. From the Middle Ages to the Napoleonic period, many woodlands were owned by the Fig. C 4.2. Mixed oak forest in the Rhein-Sieg-Erft Regional Forest District Office (Kottenforst near Bonn) (Photo: Klaus Striepen).
How to balance forestry and biodiversity conservation – A view across Europe
church, such as the Kottenforst to the west of Bonn or the Königsforst on the outskirts of Cologne.
Owing to the importance of forests for supplying timber to these cities and serving as the hunting grounds of the ‘Electorate of Cologne’, the forests have preserved their characteristics over the centu- ries and are characterised by a high level of habitat continuity. The special cultural and historical signif- icance of this forest is documented in the redesign of the Kottenforst as a ‘par force’ (the ritualised hunting of game by the nobility) hunting area by Clemens August of Bavaria (Archbishop-Elector of Cologne) in the middle of the eighteenth century.
The star-shaped network of forest roads is pre- served to this day.
Nature conservation
About 62 % of the state forest managed by the Regional Forest District Office Rhein-Sieg-Erft is pro- tected either as nature reserves or Natura 2000 areas, and thus the area has a crucial role in protect- ing biodiversity in the region. Protected areas of European significance include: (i) the old beech for- ests in the ‘Siebengebirge’ near Bonn, (ii) Atlantic heaths and oak forests on sand dunes in the ‘Wah- ner Heide’ and (iii) mixed oak forests in the
‘Villewälder’ between Cologne and Bonn. Manage- ment of protected forest areas is based on Natura 2000 management plans. This includes the promo- tion of natural forest communities and the safe- guarding of old trees and deadwood in managed forest stands. To promote natural forest develop- ment, the harvesting and extraction of wood is com- pletely banned in an area of 1862 ha (wilderness development areas, strict forest reserves). The old- est forest areas in which natural development pro- cesses are protected were already set aside in 1970.
The conservation of old trees and deadwood is also carried out outside protected areas to safe- guard biological diversity. This is implemented by the Forest Service of North Rhine-Westphalia (Wald und Holz NRW) based on the Tree-Biotope-Concept
‘Xylobius’. An aim of management is either a total deadwood volume of 40 m³/ha or 10 biotope or habitat trees/ha in all forest stands with near-natu- ral tree species composition and an age of above 120 years (for oak forests above 140 years). Biotope wood is defined as trees with cavities or nests, as standing or lying deadwood, or trees displaying (potential) habitat features as well as ancient/mon- umental trees.
The Regional Forest District Office is the initia- tor and partner in large-scale nature conservation projects, such as: the European LIFE+ project ‘Ville Forests – LIFE forests and waterworlds’ and the Fed- eral project ‘Chance 7’ funded by the Federal Pro- gramme for Biological Diversity.
Population and recreation
About 2.4 million people live in the Cologne/Bonn region, and forests represent important retreats from the rush and noise of the cities. The ‘peace and quiet’ of the forests has been shown to have a positive effect on people’s health. Good access to forests makes them a prime location for recrea- tional sports. The near-natural of these forests also offer visitors the chance to experience nature and thus counteract the alienation of the urban popu- lation from nature. The number of forest visitors is high, especially at weekends. However, their demands vary considerably. They range from the desire for an undisturbed nature experience to the demand for well-developed and accessible forests for family outings and sports activities. Such inten- sive leisure time use can lead to possible conflicts with conservation objectives, and in turn can lead to questions concerning the type and intensity of forest management. To address such conflicts, the Regional Forest District Office pursues various approaches, ranging from public relations work throughout the whole region to a wide range of forest related educational services and activities.
The office cooperates with three information cen- tres, namely ‘Haus der Natur’ in Bonn, ‘Steinhaus’
in Bergisch-Gladbach, and the exhibition of the
‘Verschönerungsverein für das Siebengebirge’ in Königswinter. New educational tools, so-called
‘outdoor forest classrooms’, or Marteloscopes, are also applied for public outreach.
Economy
The State Forest Enterprise in North Rhine-West- phalia derives about 70 % of its income from wood products (fig. C 4.3), and 30 % from non-wood products such as rentals, leasing, hunting, fishing, transfer revenues, eco-points, and the sale of seeds. The total revenue of the enterprise is in the magnitude of 20–50 €/ha. A number of ecosystem services can be only partially marketed in Ger- many. For example, owing to the free right of
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access to forests, visitors are not charged for recre- ation.
Integrated management often leads to good results. It can, however, cause lower revenues and additional costs as for example, by preserving old trees and leaving large amounts of deadwood in the forest. Additional costs can also arise when applying, for example, more expensive timber har- vesting methods to support soil protection. One of the benefits of such approaches is that they help to improve public acceptance for forestry measures, in this timber extraction.
The Rhein-Sieg-Erft Forest District Office bene- fits from easy access to high-quality seed stands and seed plantations, which is a unique situation for North Rhine-Westphalia. The favourable loca- tion also makes the sale of firewood to the end consumer an important source of income.
The proportion of spruce in the state forest will decline drastically in future as a consequence of the predicted increase in the frequency and severity of storms, heatwaves, drought, and bark beetle infes- tations. Such developments will have negative effects on income, as coniferous wood currently contributes considerably more to the overall reve-
nue as compared to its area share. This is due to a generally low prices for hardwood and the high proportion of non-marketable assortments.
Example Kottenforst near Bonn – Finding the balance
In forests close to cities, wood production, nature conservation and recreation need to be adequately considered. Each forest area poses its own chal- lenges, making it necessary to apply tailored solu- tions. This is illustrated by an example from the Kottenforst forest area near Bonn. The following statements refer only to the Kottenforst state for- est situated in the Rhein-Sieg-Erft Forest District Office (fig. C 4.7)
The Kottenforst is one of the most important oak forests in North Rhine-Westphalia. Oak and beech are up to 250 years old. The forest is located at the gates of the city of Bonn and covers an area of about 4000 ha. The altitude is approximately 170 m a.s.l., with an annual average temperature of 9.4 °C and annual precipitation of 670 mm. The dominant soil type is moderately base-rich, heavily Fig. C 4.3. High-quality timber is marketed mainly through submission sales (i.e. the public announcement of timber for sale and the offers for the timber) (Photo: Klaus Striepen).
How to balance forestry and biodiversity conservation – A view across Europe
waterlogged pseudogley derived from Löß overlay- ing glacial terrace gravel of the Rhine. As the occur- rence of oak-hornbeam forests on temporarily wet sites is of Europe-wide significance, the core area has been protected as a Natura 2000 site since 1999.
The Kottenforst is habitat for protected species of European interest including the middle spotted woodpecker (Dendrocoptes medius) (fig. C 4.5a), the Bechstein‘s bat (Myotis bechsteinii) (fig. C 4.5b), the stag beetle (Lucanus cervus), and the wildcat (Felis silvestris). At the same time, it is one of the most important areas for amphibians in North Rhine-Westphalia with occurrences of agile frog (Rana dalmatina) and crested newt (Triturus crista- tus).
The main management aim in Kottenforst is the production of high-quality oak timber along
with the integration of nature conservation aspects.
The structural diversity of these oak forests and their large amounts of old trees and deadwood are decisive factors that safeguard species diversity under this management scheme.
Preserving old trees and deadwood
Combining unmanaged and near-natural forest stands serves as the basis for preserving old trees and standing and lying deadwood. Timber removal is banned on 235 ha of ecologically valuable forest areas. These areas are left to develop freely with- out human intervention and serve as a retreat for animal, plant, and fungal species, that are closely linked to old-growth and decay phases. Further they act as so-called donor stands for enhancing the spread of such species to neighbouring com- mercially managed forests.
Managed forests of oak and beech are enriched with old trees (fig. C 4.6.) and deadwood once they reach an age of 100 years. For this purpose, 10 habitat trees per hectare are selected and marked. These trees are left to develop without intervention and will not be harvested. The distri- bution of these habitat trees is not uniform in all stands but takes into account both their ecological importance in terms of the occurrence of protected animal and plant species and their economic value.
A number of additional protective elements have also been applied. Particularly valuable old forest stands larger than one hectare have been protected as so-called ‘wood island biotopes’ or
‘stepping stones’. Interventions directed at the con- servation of ecologically valuable old oak trees under competition from beech and hornbeam are allowed. If such measures are no longer acceptable for reasons of worker safety the stand is temporar- ily left for free development until the old trees in the stand are well into the decay phase. To locally increase the amount of deadwood, cohorts of 10 to 15 trees have been identified as so-called ‘biotope tree groups’. These groups were mostly clumped around already designated habitat trees. The groups were established mainly in stands with low wood quality and sufficiently far from frequently used hiking trails to ensure public safety. Particular attention was given to protecting valuable tree microhabitat structures such as tree cavities or severe tree damage (e.g. crown breakage, cankers), standing large deadwood, and veteran/ancient trees.
Oak Beech
Other broadleaves Spruce
Other coniferous 38
17
19 15
11
Fig. C 4.4. Tree species composition of the state forest area of Kottenforst (in %).
Table C 4.3. Key figures of the forest district Kottenforst near Bonn (state forest).
Forest community
Oak-hornbeam (Quercus robur-Carpinus betulus) forest admixed with small-leaved lime (Tilia cordata) and beech (Fagus sylvatica) on waterlogged soil Total forest area 3900 ha
State forest area 2400 ha Main management
types 89 % high forest; 1 % coppice with standards; 10 % no management Total volume 225 m³/ha
Annual growth 7.9 m³/ha Annual use 4.1 m³/ha Nature protection
area (Natura 2000) 2456 ha
Expanding natural forest communities
The state of North Rhine-Westphalia aims at increasing the proportion natural forest communi- ties to meet the conservation goals of the Natura 2000 areas in the long term. At present, the propor- tion of coniferous forest e.g. in Kottenforst is still at 26 %. This relatively high proportion is because of the large pure Norway spruce stands, which have often been planted on unsuitable waterlogged soils. These stands are being converted towards more climate-stable mixed oak stands. Dying spruce stands are regenerated with pedunculate oak (Quercus robur) and other suitable tree species.
This will help to achieve the protection objectives of promoting oak forest habitat types and better adaptation of forests to the effects of climate change. Managing those stands towards high-qual- ity oak assortments will also create a favourable economic return in the long term.
Minimising human disturbance
Anthropogenic impacts on forest sites are being reduced e.g. by dismantling old drainage ditches.
The competitiveness of pedunculate oak is thus improved as beech is more sensitive to waterlog- ging. Measures like these, support the conservation of protected forest habitats. The removal of ditches also reduces surface runoff after heavy rainfall and improves water supply of forest stands during dry summers, yet another contribution to the adapta- tion of forests to the consequences of climate change.
Fig. C 4.5. The middle spotted woodpecker on an old oak tree and on the left a Bechstein‘s bat in a hollow oak (Photos a: Klaus Striepen and b: Martin Koch).
Fig. C 4.6. Large tree cavities such as the one found on this 180-year-old oak are rare as they require many decades to develop and are thus of particular ecological importance (Photo: Klaus Striepen).
b a
How to balance forestry and biodiversity conservation – A view across Europe
Promoting coppice with standards
Coppice with standards is a traditional form of for- est use in Kottenforst. It was abandoned in the middle of the nineteenth century. Today, only a few oak and beech trees remind us of this tradi- tional form of forest management. Owing to the importance of open, sunlit forests for many plant, animal, and fungal species, selected stands have been transformed to coppice forests. Such stands allow visitors to experience this traditional form of forest management and the biodiversity associated with it.
Safeguarding forest habitats
An important component of the protection con- cept is the conservation and promotion of small- scale habitats within forests. Examples are the maintenance of small water bodies serving as habi- tats for amphibians, dragonflies, and water dwell- ers, and the extensive use of species-rich forest meadows. The forest meadows include such species
as tall oat-grass (Arrhenatherum elatius), bristle mat-grass (Nardus stricta) and moor grass (Molinia caerulea) meadows with occurrence of Arnica (Arnica montana), Devil’s-bit (Succisa pratensis), and various orchid species.
Informing forest visitors
The forest area is located about 10 km from the city centre of Bonn and serves as a local recreation area of outstanding importance. To sensitise visitors to the vulnerability of forest ecosystems and their numerous habitats, the Rhein-Sieg-Erft Regional Forest District Office engages in comprehensive public relations work. Jointly with the City of Bonn the Regional Forest District Office operates the for- est information centre ‘Haus der Natur’ (House of Nature). In addition to the permanent exhibition
‘Großstadtwald’ (city forests), the forest informa- tion centre offers guided tours and workshops (fig. C 4.8).
Fig. C 4.7. Biodiversity concept for the Natura 2000 area ‘Forest Reserve Kottenforst’.
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European funding helps
The nature conservation concept has been imple- mented between 2014 and 2020 as part of the LIFE+ nature conservation project ‘Ville Forests – LIFE forests and waterworlds’. The project is coordi- nated by the Rhein-Sieg-Erft Regional Forest Dis- trict Office in cooperation with the conservation organisation Biologische Station Bonn / Rhein-Erft e.V. The project budget is € 3.3 million, half of which is financed by North Rhine-Westphalia Minis- try of the Environment. The remaining funds are provided by the European Union.
For more information
www.wald-und-holz.nrw.de/ueber-uns/einrichtungen/
regionalforstaemter/rhein-sieg-erft
www.wald-und-holz.nrw.de/naturschutz/xylobius-lebens- raum-bewahren
www.villewaelder.de www.chance7.org
Fig. C 4.8. Guided excursion in the Kottenforst, where interested visitors learn about tree microhabitats (Photo: Klaus Striepen).
