ALKALINE FENS IN BRANDENBURG AN EU-LIFE-NATURE PROJECT

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1 Workshop Approaches in WetlAnd Restoration - focus on fen landscapes Warsaw, Poland April 2013 ALKALINE FENS IN BRANDENBURG AN EU-LIFE-NATURE PROJECT Holger RÖßLING 1 Michael ZAUFT 1 Janine RUFFER 1 Pamela HAFNER 1 1 Naturschutzfonds Brandenburg, Heinrich-Mann-Allee 18/19, Potsdam, holger.roessling@naturschutzfonds.de Abstract: From 2010 to 2015 the LIFE Nature Project Alkaline Fens in Brandenburg is currently being implemented by Naturschutzfonds Brandenburg. With this project, the Naturschutzfonds Brandenburg manages conservation activities intended to secure and develop large alkaline fens in fourteen Natura-2000 areas in the federal state of Brandenburg. During the last two centuries, numerous sloping spring fens and percolation fens were converted into arable land and drained by many small ditches. For the last 5-6 decades, the agricultural land use on these fens has beenceased. The first step of revitalization was to remove biomass. This was achieved through mowing, shrub removal and grazing. The next step was to stabilize the water levels to ground level or slightly above. To stop the drainage on sloping fens all ditches had to be filled completely. The filling material was obtained by topsoil removal directly on bordering moorland. The results of the rewetting were evident almost instantly. Groundwater levels have risen up to 20 cm within a few days and typical species of alkaline fens have started to grow on bare soil within one year. Keywords: 7230 Alkaline fens, land use change, nutrient removal, restoration of water dynamics, hydrological measures Introduction 150 years ago, alkaline fens were still abundant in Brandenburg, and represented a rather common ecological fen type. Today only a small portion of these areas remains (Thormann & Landgraf 2010). Alkaline fens are now among the rarest and most endangered habitats in Brandenburg. In 2010 the LIFE Nature Project Alkaline Fens in Brandenburg began. It is implemented by Naturschutzfonds Brandenburg, a public foundation of the federal state of Brandenburg. It is one of the largest and most ambitious projects concerning restoration of alkaline fens in Germany. Until 2015, Naturschutzfonds Brandenburg will manage the project's conservation activities, in order to secure and restore large alkaline fens in fourteen Natura-2000 areas. 6.4 million are available for the project with half of the budget covered by the European Commission and the other half by Naturschutzfonds Brandenburg. Alkaline fens (habitat type 7230) are characterized by rich plant species diversity. Many species can still be found within the project areas: e.g. Menyanthes trifoliata, Succisa pratensis, Parnassia palustris, Dactylorhiza incarnata, Liparis loeselii, Epipiactis palustris. Particularly, peat-forming brown mosses, characteristic for the vegetation of alkaline fens, were found: Drepanocladus vernicosus, Paludella squarrosa, Helodium blandowii, Scorpidium scorpidium and Tomenthypnum nitens. Most of them are endangered in Brandenburg (Klawitter et al. 2002). Fens in the project areas belong mostly to hydrogenetic fen types, such as sloping spring fens, percolation mires and planar mires, which developed by filling up lakes with silt and peat. Almost all alkaline fens were converted into arable land in the last centuries. A large number of small ditches, built by farmers, have significantly contributed to their drainage. However, fens that are subject to this project have not been intensively drained during reclamation in the 1960s and 1970s (Thormann & Landgraf 2010). Over the last decades, when agricultural use of the areas was no longer profitable, these fens have been abandoned. Yet the ditches remained 1

2 Contribution to the SER Europe Knowledge Base on Ecological Restoration in Europe (2010) - active, due to the sloping surface and the constant flow of water. The drainage systems are still functioning and causing desiccation and mineralization of the peat soils. The result is a dramatic change in the naturally open fen areas. Dueto the increased availability of nutrients, in combination with the lower water levels, reed, willow shrubbery and trees, such as birch and alder overgrow the fens. Only small areas of the habitat alkaline fens (7230) remained open, where the peat soil has not been degraded. However, those remains are threatened by an increasing rate of succession into eutrophic reed communities and woodlands. Large fluctuations of the groundwater levels are a major threat to the vegetation of alkaline fens (Koska 2001). Therefore, the project aims to stabilize the water levels to ground level or slightly above. Materials and methods Figure 1. Alkaline fen in Brandenburg (photo by S. Luka) Large complexes of well-preserved, undisturbed alkaline fens have the highest priority for restoration efforts. Such areas have the potential to regenerate if provided with initial support. Conservation activities of this project mainly focus on rewetting the fens by restoring natural hydrologic conditions. Restoration activities in all project areas follow a similar schedule and combine several steps. First, the land has to be secured for the restoration purposes, either by purchasing or by long-term agreements with public or private land owners. Additionally a good cooperation with farmers is necessary to lay the groundwork for the implementation of conservation actions other than hydrological restoration. The re-establishment of natural hydrological conditions usually makes land use more difficult. Therefore intense cooperation with all stakeholders is essential. In the second step was the mowing of common reed (Phragmites australis) and shrub removal where necessary.this improved the conditions for establishing of mosses and other fen plant species. The biomass was removed where possible, to reduce the amount of nutrients in the area. For mowing on the wet and soft peaty soils, converted Pisten Bullys were used to mow the wet and soft peaty soil. They are used in ski areas, having a low ground pressure due to their caterpillar tracks. In some project areas, pastures for water buffalo and sheep were established to 2

3 allow grazing management, and to reduce dense vegetation. After mowing and shrub removal the drainage system often proved to be more extensive than expected. The third step included activities to restore the hydrological conditions. They varied between sites and hydrogenetic fen types. The goal was to stabilize the water levels to ground level or slightly above, in order to prevent further peat mineralization. To achieve this, the drainage systems had to be eliminated. On moderately to strongly sloping fens it was necessary to fill up the ditches completely. The filling material was obtained by topsoil removal in close proximity of the ditches. Normally 15 to 20 cm of the top peat layer was cut to gain material to fill the ditches. This method created bare soil locations after the degraded topsoil layer was removed. In addition, this soil was an excellent sealing material. To reduce the impact on the soft soils of fens, only machines with a low ground pressure were used. Small excavators loaded the topsoil on track dumpers that poured the material into the ditches. To minimize the ground pressure, wooden pallets were used as a base for the excavators. Areas of intact and valuable vegetation remained undisturbed. Further activities focused on rising and stabilizing water levels in the main drainage channels of the areas. Ground sills (weirs) were built into the river bed and dead wood was inserted. The fourth step was to reintroduce of species that are characteristic of alkaline fens (e.g. Bryum pseudotriquetrum, Campylium stellatum, Plagiomnium elatum, Drepanocladus cossonii, Carex diandra, Carex rostrata, Helodium blandowii, Drepanocladus vernicosus, Dactylorhiza incarnata, Epipiactis palustris) into areas with mesotrophic conditions. Seeds and plant parts that have been collected in undisturbed alkaline fens were dispersed in the restored areas. By doing this, the small plants of alkaline fens have an initial advantage over the larger plants on bare soil locations. The results of rewetting and other conservation actions are monitored. Groundwater measurement points were installed in all project areas, and the development of vegetation has been monitored on permanent plots. Results and discussion At present, restoration measures have been carried out in six project areas in which 21 km of ditches were filled and topsoil was removed on roughly 12 ha. The project area Gramzow Seen has been the first to be rewetted in autumn The valley is located in the east of the nature park Stechlin-Ruppiner Land and runs from north to south for nearly 6 km. Peripheral spring mires are connected with percolation mire as well as with planar mires that have developed on lakes around the Lake Gramzow. Until the 1950sthe area was used as extensive grassland. Alluvial forests later developed on the degraded parts. open fen areas only remained in the northern part of the valley. They are still home to some of the characteristic species of alkaline fens. Prior to blocking the drainage system 14 ha of reed were mowed with pisten-bullies. More than 5 km of ditches were discovered and had to be filled for a successful rewetting. One of the major problems during the rewetting process was a maximum of 5 % sloping of the fen surface. Water that discharged from springs at the edge of fen ran over the sloping moor towards a main channel in the middle of the valley. The ditches sped up this flow In order to re-establish percolation throughout the fen these ditches were blocked. This could only be achieved, if the previous removal of the topsoil had not formed new drainage channels. Therefore, small peat dams were left along the contour lines during the topsoil removal. These dams limited the surface water flow and formed a miniature terraced landscape. Furthermore, the dams provided a starting point for the fen vegetation to colonize bare soil. This method was tested on a large scale for the first time. 60 shallow peat cuts ranging from 50 to 500 m² were excavated. 5.7 km of ditches were filled up completely. This caused the groundwater levels to rise 10 cm or more, within days. 75 ha of moorland have been affected by rewetting. The hydrological radius of action was therefore larger than the conservation area itself. 3

4 Contribution to the SER Europe Knowledge Base on Ecological Restoration in Europe (2010) - Almost two years after the rewetting the water levels in the area have remained stable. Fluctuations have been reduced. After mowing and topsoil removal, small alkaline fen species have been provided with better conditions to grow. In some peat cuts, species such as brownmosses and Bog-bean (Menyanthes trifoliata) could be found a few months after the restoration actions. In autumn 2012 reintroduction of characteristic fen species took place and brown mosses have established themselves on the edges of peat cuts. Figure 2. Groundwater level in Gramzowseen. Brown mosses after reintroduction in a peat cut area in Gramzowseen (photo J. Ruffer) After decades of draining an immediate development of characteristic fen plant communities after restoration cannot be expected (Jansen et.al. 2001). The fluctuation of water levels cannot be compensated completely, in particular, in terrestrialization mires, with strongly degraded, eutrophic peat. In such locations, a slow succession is very likely. To establish and develop the typical alkaline fen vegetation, it will be necessary to keep a land use scheme that is adapted to these sensitive habitats. After the end of the project, the land owners will be responsible to carry on nature management that was established during the project. In some areas pastures are established and fenced, and farmers are provided with water buffaloes. First results of grazing show a decrease in species such as reed. In other areas equipment, such as sickle bar mowers were bought in exchange for a long term agreement to mow certain areas. A reliable and competent land use management after the end of the LIFE project will be crucial for the success of restoration of alkaline fens. Conclusions The results of the conservation measures carried out by the LIFE Nature project Alkaline Fens in Brandenburg give hope that initial moor restoration has succeeded. During the next years and decades it will become evident if the extent of damages caused by drainage are reversible. In some areas, land use will have to be continued after the rewetting measures. In each case the experience gained is an asset for the further implementation of this LIFE Project as well as for future projects. References Jansen, A. J. M., Eysink, F. T. W. & Maas, C. (2001). Hydrological processes in a Cirsio-Molinietum fen meadow: Implications for restoration. Ecological Engineering, Vol. 17: Klawitter, J., Rätzel, S. & Schaepe, A. (2002). Gesamtartenliste und Rote Liste der Moose des Landes Brandenburg. Naturschutz und Landschaftspflege in Brandenburg 11 (4): Beilage, 104 S.. 4

5 Thormann, J. & Landgraf, L. (2010). Neue Chancen für Basen- und Kalk-Zwischenmoore in Brandenburg. Naturschutz und Landschaftspflege in Brandenburg, 19 (3,4): Koska, I. (2001) Ökohydrologische Kennzeichnung. In: Succow, M. & Joosten, H. (Hrsg.) Landschaftsökologische Moorkunde, 2. Auflage, Stuttgart: