Ecological restoration of the upper river Øle Å
A donation from the foundation VILLUM FONDEN has permitted an ecological restoration of the upper river Øle Å, Bornholm, Denmark. The project is managed by researchers at University of Copenhagen, is running from 2013 to 2017, and is conducted in collaboration and dialogue with local stakeholders through the organization The Green Partnership. In the vicinity of the stream other research projects are also conducted, and this webpage offers you information on all of these subjects.
The ecological restoration of the upper river Øle Å is a scientific project, based on clear principles and expected to:
- Increase significantly the nature and landscape experience of the resident natives and tourists who move along this unique "mountain stream" with its varying expression over a 3.5 km stretch
- Increase water flow and water quality in the river, reducing periods of critically low water flow and increase the diversity of animals and plants in the river
- Restore the natural vegetation and biological diversity of plants and birds along the river by initiating natural succession processes
- Improve our understanding of how we effectively and inexpensively can intervene to achieve the desired results in practical restoration management, thereby developing a new paradigm for evidence-based nature management.
A public path is following the upper river Øle Å. The 3 km tour is a diverse experience, passing through great variety of biotopes, Along the river, there are differences in hydrology and soil properties with outcrops of granite supporting remnants of dry heather vegetation (e.g. Calluna vulgaris) and rich moraine soils supporting remnants of a fen flora (e.g. Carex flacca). Under natural stands of alder and birch the summer guest is met by the yellow flowers of iris (Iris pseudacorus) and the smell of menth (Mentha aquatica), but in other places willows form dense shrubs.
The experience of the landscape is however heavily influenced by planted Norway spruce. These are planted very close to the stream and in most places the ground flora has disappeared and the stream lies in deep darkness. Norway spruce is not a natural tree in this landscape and the trees give the stream and the riparian zone a stereotypic and claustrophobic character. Øle Å accumulates needles, cones, twigs and trunks from the spruce, which are a very poor food source for macroinvertebrates.
River Øle Å originates in the wetland, Ølene on central Bornholm, Denmark. With 22 km it is the longest stream on the island. Bornholm is an island (approx. 600 km2) in the Baltic Sea some 120 km east of Copenhagen. Bornholm is visited by a very large number of Danish, German and Sweden tourists ensuring the largest income to the community. Nice landscapes and nature habitats for visitors are located as relatively narrow strips along the coast and along the streams in close distance to the coast and as large predominantly forested and heather areas in central Bornholm, particularly Paradisbakkerne and Almindingen.
Ecological restoration is “the process of assisting the recovery of an ecosystem that has been degraded, damaged or destroyed”. A further explanation of this definition can be found in the Primer on Ecological Restoration from the international Society for Ecological Restoration.
Reference ecosystem
An important concept in ecological restoration is to compare the result with the status of intact ecosystems, and to accept behaviours and features of intact ecosystems, such as complexity and unpredictable changes. Intactness can be linked with the degree of human influence on ecosystems, where the degraded ecosystem might have little intactness, but where the restored ecosystem again can achieve high naturalness if complexity and unpredictable changes are accepted. Following this, an open-ended approach to restoration might be desirable, and is implemented in the restoration of Øle Å. The open-ended approach does not aim at obtaining specific habitats and ecological structures and processes but seeks to stimulate natural processes with little or no human influence. This approach stands in contrast to efforts aiming at obtaining very specific habitats and desired species.
Successful river restoration
Five criteria for measuring successful river restoration, with emphasis on the ecological perspective, were proposed by Margaret Palmer et al, and are incorporated in the restoration of Øle Å:
- The design of an ecological river restoration project should be based on a specified guiding image of a more dynamic, healthy river that could exist at the site.
- The river’s ecological conditions must be measurably improved.
- The restored river system must be more self-sustaining and resilient to external perturbations such that only minimal follow-up maintenance is needed.
- During the construction phase, no lasting harm should be inflicted on the ecosystem.
- Both pre- and post-assessment must be completed and data made publicly available.
International recognition
Ecological restoration has internationally been recognized as a critical contribution to management of the World’s ecosystems as seen in UN conventions such as the Convention on Biological Diversity (CBD), the Convention to Combat Desertification (UNCCD) and the UN Framework Convention on Climate Change (UNFCCC). This is also evident in the CBD Strategic Plan for Biodiversity 2011-2020 and the Aichi Biodiversity Targets, in which two out of twenty targets aim at restoring degraded ecosystems, read it here.
The Green Partnership is an association of relevant NGO’s on Bornholm and the private forest owner. The partnership was established in 2010 on initiative of the forest owner. The purpose is to incorporate multiple interests in the forest management, and hereby enhance the experience for forest visitors in the forests Poulsker and Bodilsker Plantations.
Partners
The Green Partnership includes the following organizations:
- Skovselskabet Poulsker ApS
- Danmarks Naturfredningsforening, Bornholm
- Svampevennerne på Bornholm
- Friluftsrådet, Lokalkredsen
- Bornholms Regionskommune
- Dansk Ornitologisk Forening, Bornholm
- Foreningen Bornholm
In addition other organizations are in general participating in meetings, including the Danish Nature Agency, the local natural history museum NaturBornholm, local anglers from Vandpleje Bornholm, and eventually neighbors.
There are in the Øle Å project and the other research projects in Poulsker and Bodilsker Planations plenty of opportunities for student assignments and thesis subjects. Intensive monitoring is performed, and various aspects of the ecosystem can thus be in focus, ranging from specific biogeochemical processes, over vegetation ecology to planning of future restoration projects. There are opportunities for students in natural resource management, nature management, forestry, biology, geography etc.
Read more about possible subjects here.
Previous projects
2016
Oxygen dynamics and ecosystem metabolism in Øle Å - A stream under restoration. Master thesis in 'Biology' by Emilie M. F. Kallenbach.
Short-term response of terrestrial vegetation to five restoration treatments in the riparian area of the Øle Å. Master thesis in 'Nature Management' by Alexia López Rodríguez.
Trait-based prediction of vegetation community assembly - an applied case along Øle Å. Master thesis in 'Biology' by Simone Møller Mortensen.
2015
Oxygen, temperature and water flow across the year in Øle Å - critical summer for trouts (In Danish: Ilt, temperatur og vandføring over året i Øle Å – kritisk sommer for ørreder). By Kenneth Thorø Martinsen.
2014
Mapping the carrying capacity of fallow deer in Bodilsker and Poulsker Plantage, Bornholm (In Danish: Kortlægning af bæreevne for dådyr i Bodilsker og Poulsker Plantage, Bornholm - Analyse på baggrund af plantagens fødeproduktion). Bachelor project in biology by Josefine Møller
Metabolism of dissolved and sediment organic carbon in two streams on Bornholm – effects of deciduous and coniferous forest (In Danish: Omsætningshastigheder af opløst organisk kulstof og sediment organisk kulstof i to vandløb på Bornholm – effekter af løv- og nåleskov). Bachelor project in biology by Kenneth Thorø Martinsen.
Differences in macroinvertebrate communities in two stream on Bornholm – effects of riparian vegetation on richness and composition (In Danish: Forskellen mellem invertebratsamfundende i to Bornholmske vandløb, effekt af vandnær vegetation på sammensætning og antal). Bachelor project in biology by Søren Thromsholdt Christensen.
Based on Det Grønne Partnerskab, other research projects are taking place in Poulsker Plantation.
Deer tolerant regeneration of forest by direct seeding
Background
Planting is commonly used to regenerate broadleaves and several conifers following clear-felling or windfall in spruce plantations. Many of the desired species for these sites need protection against the browsing and fraying deer.
Deer fences are expensive to establish, maintain and remove again as well as they exclude the deer from some of the best habitats in the forests. Additionally, this may very well lead to a significantly increased damage on the remaining parts of the forest as well as on farmland and elsewhere in the landscape. Deer fences may therefore lead into an unfortunate and self-reinforcing development including an increased need for fences.
The dense roe deer population on the island makes it impossible to establish broadleaves by planting without protection by fence. Additionally, a fallow deer population has established on the island, too.
Direct seeding has elsewhere been used in some cases to establish very dense forest regenerations that have established well without fencing and have been robust against deer damage. Often natural regeneration of other species such as birch or sycamore maple has contributed. Such unfenced sites with dense forest regeneration serve both their prime objective as well as they are attractive habitats for the deer since they provide good access to both food and shelter for the animals. Additionally, they are cheaper to establish than the common plantings – both because direct seeding is cheaper and because fencing is less needed.
Objectives
The objective of this research and development project is to test, adapt and demonstrate the deer tolerant regeneration methods at a larger clear-cut area (6 hectares) following Norway spruce under the site conditions commonly found at the island. The mature spruce plantation becomes more and more unstable and susceptible to thinning as they grow older which is why they need to be clear-cut when regenerated.
A successful establishment by direct seeding of several desired broadleaves and conifers without protective deer fences will pave the road for better integration of objectives in forest management regarding
- nature conservation and biodiversity by supporting regeneration of a larger number of tree and shrub species
- deer and hunting by avoiding or minimizing the use of fences and by the attractive densely stocked forest regeneration including many tree and shrub species which are attractive for the deer
- long term forest stability, adaptability and productivity.
Further, the regeneration methods based on direct seeding offers lower regeneration costs which is an important feature in efficiently supporting the establishment of a wider range of forest tree species.
Financial support
The project tittle is “Bornholm exhibition of sustainable and integrated game, forest and nature management in ecological and economical balance” and it is supported by 15. Juni Fonden
Research
The project of restoring the upper part of Øle Å is managed by researchers at the University of Copenhagen, and many aspects are monitored intensively. This is due to recognition that only through monitoring we will know the long term development trajectory of the system, and thus be able to assess the success. Further the intensive monitoring set-up is intended to improve future restoration projects.
Due to the land use history at the site and the disturbance’ character the intervention is well defined and limited to biotic components. This will hopefully ensure significant and clear results. The monitoring can be divided within the following four areas:
Recent research has emphasized the importance of riparian ecosystems as centers of biodiversity and links between terrestrial and aquatic systems as being particularly important. Riparian ecosystems also belong to environments that are most strongly disturbed by humans and are particularly in need of restoration to maintain biodiversity and ecological integrity. The riparian system is a transition zone between land and water ecosystems and it is disproportionately plant species-rich when compared to surrounding ecosystems because many species with variable adaptations to water drought and flooding can segregate their appearance and abundance across this land to water gradient.
Along Øle Å the riparian vegetation is largely limited by the Norway spruces. This is manily due to deficiency of light and water, in combination with a thick layer of hardly decomposed needles. The needles are also a poor food source for aquatic macroinvertebrates, which thus might be limited in number in Øle Å.
Our research is based on yearly monitoring of riparian plants, aquatic plants, fish population, aquatic macroinvertebrates and breeding birds.
The flow regime has our strong focus for several reasons. (1) It directs the succession of riparian plant communities and ecological soil and stream processes. (2) The stream serves as a pathway for redistribution of organic and inorganic material that influences plant communities along and within rivers. (3) The widespread plantation of spruce is believed to reduce the amount of water available from the catchment.
Our research focusses on monitoring the stream flow through permanently monitoring the stream flow at the beginning of the project area, in the middle and at the end of it, and comparing these data with the stream flow in a similar stream nearby. Further we measure the precipitation locally.
The undisturbed parts of Øle Å display a great variety of biotopes, and in a longterm perspective it is expected that this pattern will spread to the parts which are presently with Norway spruce.
Our research focusses on prediction of future herbaceous plant communities through comparison with the undisturbed references. Further we are testing methods for speeding up the establishment of natural deciduous trees in the riparian zone.
The thick layer of spruce needles may become a legacy limiting future establishment of a natural vegetation cover. The decomposition will be accelerated after felling by additional light and water, and a leaching to the stream might happen.
Our research focuses on following the mineralized carbon and nitrogen etc. Soil water samples are obtained from suctions cubs installed in transects along the stream, and continuous water samples are taken in the stream at the beginning of the project area, in the middle and at the end of it. These data are compared with water samples from a similar stream nearby, and further more we measure the ion availability in the precipitation.
Funded by:
Contact
Jonas Morsing
Ph.D. student
Department of Geosciences and Natural Resource Management, SCIENCE
Rolighedsvej 23
1958 Frederiksberg C
Email: jmt@ign.ku.dk
Phone. +45 3533 0739
Fax +45 3533 1508
The restoration of the upper Øle Å is coordinated by Department of Geosciences and Natural resource management, SCIENCE, University of Copenhagen, and is led by professor Jørgen Bo Larsen (jbl@ign.ku.dk).