City Forest Freiburg Living Lab, Germany

Albert-Ludwigs-Universität Freiburg (ALUFR)

Name of site: City Forest Freiburg, Germany.

Responsible  institution: Albert-Ludwigs-Universität Freiburg (ALUFR).

Responsible person: Rasoul Yousefpour

Contact e-mail: rasoul.yousefpour@ife.uni-freiburg.de

 

The living lab City Forest Freiburg (Stadtwald Freiburg) is located in the southwest of Germany between the Upper Rhine Valley and the edges of the Black Forest.

The City Forest Freiburg is a corporate forest mainly owned by a public body, the city of Freiburg, being one of the largest community forest owners in Germany. The City Forest Freiburg occupies a large ecological range, which extends from broadleaf forests of the climatically mild Rhine plain to montane coniferous and mixed forests that expand to an altitude of almost 1,300 meters.

The independent city forest office manages the forest according to strict ecological criteria certified by the Forest Stewardship Council (FSC), where it was the first forest to be certificated in South-West Germany in 1999. The management focuses equally on four main objectives: timber production, nature conservation, climate change mitigation and recreation.

LL Temperate peri-urban forest Freiburg Germany
Coordinates: 47°59'45.24" N, 7°51'7.99" E
Climate: Temperate
Ecoregion: Western European forests
LL size: 52 km2
Mean Stand Volume: 380 m3 * ha-1

 

Introduction

The City Forest Freiburg can be divided into two distinct types, the lwoland broadleaf forest of the Rhine plain in the north-west of the city and the montane coniferous and mixed forest on the edges of the Black Forest in the east and south-east of the city.

Broadleaf forest of the plain.
Figure 1. Broadleaf forest of the plain. Picture: CC BY-SA 4.0, commons.wikimedia.org/wiki/File:Naturschutzgebiet_Teninger_Unterwald_%282%29.jpg © Juliana Chr B.

 

The broadleaf forests of the Rhine plain make up around 40% of the City Forest area and consist mainly of the species oak (Quercus spp.) as well as European Ash (Fraxinus excelsior R.), Sycamore maple (Acer pseudoplatanus L.) and hornbeam (Carpinus betulus L.). The climate of the Rhine plain is mild (mean annual temperature 10.4°C) and mean annual precipitation is moderately high (880mm).

 

 

 

 

 

Mountain forest with cable car and Freiburg in the background
Figure 2. Mountain forest with cable car and Freiburg in the background. Picture: CC BY 2.0, www.flickr.com/photos/dirk_olbertz/3716400012 © Dirk Olbertz

The montane and mixed forest stands on the edges of the Black Forest cover around 60% of the City Forest Freiburg area and consist mostly of the species Norway spruce (Picea abies (L.) H. Karst.), Silver/Douglas fir (Abies alba Mill., Pseudotsuga menziesii (Mirb.) Franco) and European beech (Fagus sylvatica L.). In contrast to the climate of the plain, the climate of the montane forest varies highly by altitude with mean annual temperatures ranging from 5 – 9°C and mean annual precipitation from 950 – 1800mm.

 

In general, the stand volume of the City Forest Freiburg is increasing with a total plus of 4% compared to 2010. Management aims on ecosystem stability and rejuvenation. Rejuvenation is dominated by European beech, Sycamore maple, Silver fir, hornbeam and oak. Nevertheless, the ecosystem of City Forest Freiburg is challenged by multiple climatological factors thus needs adaptation strategies to achieve forest resilience.

 

Forest Resilience Challenges

The broad-leaf forests of the plain are affected by water stress caused by low groundwater tables as well as summer droughts. Upward trends in frequency and duration of droughts due to climate change impact groundwater recharge and thus levels. Especially oak forests are impacted by both lower groundwater tables in combination with hot temperatures and summer droughts which not only cause ecological harm but also production challenges (Skiadaresis et al., 2019).

Regarding the montane forests, recent increases in the frequency and intensity of windstorms and droughts events accompanied by high temperatures have highly affected the forest. Water stressed forest stands favor pest infestation causing with the above-mentioned problems major tree mortality. These observed events are forecasted to continue in the future and become harsher in the midterm and as climate changes.

 

Stakeholders & management

The mountain and plain forests around Freiburg define the identity of the city as the “Green City Freiburg” for its residents and contribute largely to its attractions as a Black Forest center for eco-tourism and recreation. Freiburg’s local sustainable wood production creates jobs and brings in revenues of more than 2 million Euros per year for the city admission. However, maintaining the forest conditions (e.g., trails, roads, safety) needs high investments. Hereby, the city supports the forest service with an annual budget. Nature protection includes the services of wildlife and plant biodiversity as well as soil protection, air and water filtration that are supported by protection areas (e.g., Natura 2000). To improve climate change mitigation by carbon storage in biomass, rejuvenation and continuous growth is promoted for in-situ storage as well as sustainable production of forest products for long term CO2-sequestration ex-situ to meet the anticipated mitigation goals.

The key stakeholders of the City Forest Freiburg are the forest office Freiburg (“Forstamt Freiburg”) being the planning and executive as the main service point for managing the city forests, and subordinated as well as accountable to the city council. The city council of Freiburg as the owner and final decision maker. The city council of Freiburg is dominated by parties representing “green politics” with high interest in ecological sustainability and nature protection. Residents of the “Green City Freiburg” are much involved and engaged in developing frontier eco-projects for example the “Bergwald Projekt” where locals take part in afforestation.  Finally, Freiburg as a center for forest studies hosts two main academic and research institution namely the Baden-Wurttemberg Forest Research Institute FVA-BW and the Faculty of Environment and Natural Resources at the University of Freiburg with a long experience in advance forest studies and approaches for sustainable forest management.

 

Outlook

The objective of all stakeholders of the City Forest Freiburg is maintain and promote the forest’s diversity and stability under climate change conditions. Overall, a key objective is the increase of heat and drought tolerant species as well as the promotion of mixed uneven-aged forests by higher amount of management interventions and rejuvenation. Harvesting amount should be kept stable aiming on good quality wood for sustainable production and ex-situ carbon storage. For recreation and tourism, highly frequented areas are managed focusing on aesthetics and forest care (e.g., safety and trails).

In the year 2020, clear action has been defined to safeguard the future of the City Forest Freiburg. However, the planning horizon of the key objectives is only for the next decade. Climate change will become harsher in all likelihood with destructive impacts amplifying in the distant future. Therefore, it is highly important to analyze the conditions and challenges of the City Forest Freiburg in 2050 or even 2100 as well as discuss the robustness (ecological and social resilience) of the decisions of the 10-year planning in the long-term future.

 

References

Stadt Freiburg 2020: Waldkonvention, https://www.freiburg.de/pb/site/Freiburg/get/params_E-341610784/1690178/G-20_119_Waldkonvention_Anlage_Stand_02062020_inkl-titelseite.pdf

Skiadaresis, G., Schwarz, J. A., and Bauhus, J.: Groundwater Extraction in Floodplain Forests Reduces Radial Growth and Increases Summer Drought Sensitivity of Pedunculate Oak Trees (Quercus robur L.), Frontiers in Forests and Global Change, 2, 2019.

Schmalfuss, N. and Vítková, L.: 5.2 Douglas fir in Freiburg City Forest: an introduced tree species in the light of multifunctional management objectives, Opportunities and challenges, 316, 2016.