Rehabilitation of aquatic invertebrate communities in raised bog landscapes Van Duinen G.A. (2013) Rehabilitation of aquatic invertebrate communities in raised bog landscapes. PhD thesis, Radboud University Nijmegen, the Netherlands. © 2013 G.A. van Duinen, all rights reserved. ISBN: 978-90-7752200-4 Layout: H.A. van Duinen Printed by: Ipskamp Drukkers B.V., Enschede. This research project was fi nanced by the program Development and Management of Nature Quality (O+BN) of the Dutch Ministry of Economic Affairs, Agriculture and Innovation. Rehabilitation of aquatic invertebrate communities in raised bog landscapes PROEFSCHRIFT ter verkrijging van de graad van doctor aan de Radboud Universiteit Nijmegen op gezag van de rector magnifi cus prof. mr. S.C.J.J. Kortmann volgens besluit van het college van decanen in het openbaar te verdedigen op maandag 17 juni 2013 om 10:30 uur precies door Gerrit Andries van Duinen geboren op 5 januari 1974 te Dordrecht Promotoren: Prof. dr. ir. A.J. Hendriks Prof. dr. H. Siepel Copromotoren: Dr. R.S.E.W. Leuven Dr. G. van der Velde Manuscriptcommissie: Prof. dr. J.C.J.M. de Kroon (voorzitter) Prof. dr. L. De Meester (Katholieke Universiteit Leuven) Prof. dr. M.G.C. Schouten (Wageningen UR) Paranimfen: Dr. H.H. van Kleef Dr. W.C.E.P. Verberk Aan mijn ouders Aan Angela en Anna Contents Chapter 1 Introduction 9 Chapter 2 Do restoration measures rehabilitate fauna diversity in raised 27 bogs? A comparative study on aquatic macroinvertebrates (Wetlands Ecology and Management 11: 447-459, 2003) Chapter 3 Effects of rewetting measures in Dutch raised bog remnants on 45 assemblages of aquatic Rotifera and microcrustaceans (Hydrobiologia 565: 187–200, 2006) Chapter 4 Pristine, degraded and rewetted bogs: Restoration constraints for 63 aquatic macroinvertebrates (Submitted) Chapter 5 Differential response of aquatic oligochaete species to increased 89 nutrient availability - a comparative study between Estonian and Dutch raised bogs. (Hydrobiologia 564: 143–155, 2006) Chapter 6 Methane as a carbon source for the food web in raised bog pools 107 (Submitted) Chapter 7 Synthesis 131 Summary 151 Samenvatting 157 Kokkuvõte 163 Dankwoord 169 Curriculum vitae 173 List of publications 175 Chapter 1 Introduction Gert-Jan van Duinen ◄ The peat moss Sphagnum cuspidatum and common cottongrass Eriophorum angustifolium growing in a lagoon created by black peat bunds in the bog remnant Bargerveen, The Netherlands. Chapter 1 1.1 Characteristics of raised bog landscapes 10 Peatlands are considered as one of the most important natural ecosystems of the world, because of their key value for biodiversity, regulation of climate and water supply, and important support for human welfare. However, the degradation of peatlands is ongoing in many parts of the world. This is due to cultivation, drainage, afforestation, peat extraction, increased atmospheric deposition of nitrogen and sulphur, and climate change. In Europe the total area of still accumulating peat is estimated to be less than 50 % of the former peatland area. In Germany and The Netherlands this percentage is even 1 % or less. Therefore, global priority should be given to the protection, restoration and wise use of peatlands (Joosten & Clarke 2002, Parish et al. 2008). The accumulation and storage of peat is an essential feature of peatlands. This feature depends on a water level close to the surface and waterlogging of the peat deposit, reducing the rate of decay of organic material to an extent that it is slower than its production rate (Joosten & Clarke 2002, Parish et al. 2008). Peatlands where peat is currently forming and accumulating are called mires. Mires are generally divided into bogs and fens. Bogs typically have peat deposits raised above the surrounding landscape, receiving water, minerals and nutrients only by precipitation (therefore called ombrogenous or ombrotrophic mires), whereas fens receive infl ow of groundwater or surface water which has been in contact with mineral soil (therefore called geogenous or minerotrophic mires). Consequently, bogs are characterised by a low mineral and nutrient availability and are only present in regions with a surplus of precipitation (Gore 1983, Joosten & Clarke 2002). Peat mosses (Sphagnum spp.) are keystone species in the functioning of bogs. They create their own acidic and moist environment and play a key role in peat accumulation, development of the surface microtopography (especially hummocks and hollows), and the hydrological self-regulation of bog ecosystems (Van Breemen 1995, Rochefort 2000). Raised bogs are the principal class of Sphagnum bogs in the boreal and cool temperate zone. They typically form a dome-shaped bog massif and have a surface pattern of microtopes: hummocks, hollows, lawns, ridges, and pools. The cross-sectional shape of the dome and the microtopography of the raised bog surface vary depending on the climatic conditions. These include air temperature, precipitation and its distribution over the year, and evapotranspiration (Gore 1983, Lindsay et al. 1988). These climatic conditions affect processes involved in natural self-organisation in bog ecosystems including mineralisation, lateral water fl ow, and intraspecifi c competition between Sphagnum and vascular plant species (Couwenberg & Joosten 2005, Eppinga et al. 2007). Raised bog massifs are embedded in the wider landscape (Figure 1a). Therefore, raised bog landscapes are characterised not only by the ombrotrophic, extremely nutrient limited and acid bog massif mainly formed by Sphagnum mosses, but also by gradients from the bog massif to the more minerotrophic surroundings, where the harsh conditions of the bog massif are gradually offset (Wheeler & Proctor 2000). The conditions at the interfaces of bog margins with the adjoining mineral soil are shaped by the character of both the surrounding landscape and the bog massif, including the steepness of the marginal slope of the bog massif (called ‘rand’; Wheeler & Shaw 1995). Depending on the topography of the landscape and mineral soil type a narrow or more extensive transitional mire, fen, or swamp is present (Howie & Tromp-van Meerveld 2011). The wet margin around raised bogs is called lagg (Osvald 1933). This term is more recently used for various sharp or diffuse transitional zones receiving water from both the Introduction bog massif and the surrounding mineral soil (Howie & Tromp-van Meerveld 2011). Many raised bog landscapes consist of a complex of multiple bog massifs and sometimes include rivulets or mineral soil ‘islands’ partly or completely surrounded by mires. The variation in environmental 11 conditions within mire landscapes can be described by various environmental gradients, including gradients in acidity and availability of minerals and nutrients (Sjörs 1948, Bridgham et al. 1996, Wheeler & Proctor 2000). These gradients can be identifi ed at different spatial scales. A gradient of poor to rich in nutrients and minerals is present between the ombrotrophic centre of the bog massif and the lagg or fen at its margin. Gradients of wet to dry are present within hummock-hollow complexes and may be found between the wet centre of a bog massif, its relatively dry margin, and a wet lagg. Spatial scales in raised bog landscapes The identifi cation of different organisational levels of mire ecosystems and corresponding spatial scales proved to be practical in the investigation, conservation, and restoration of raised bogs and other types of mires (Table 1; Sjörs 1948, Lindsay et al. 1988, Couwenberg & Joosten 1999, Schouwenaars et al. 2002, Schouten 2002). A complex of two or more hydrologically interdependent mire massifs is called a macrotope. Schouten (2002) described the macro- scale as the scale level that comprises the bog and the wider landscape in which the peatland is embedded (Figure 1A), also referred to as ‘bog landscape’. Consequently, Schouten (2002) considers the bog, lagg and surrounding mineral soil system as different ecological systems at meso-scale. A single raised bog massif is identifi ed as mesotope. A microtope is defi ned as a characteristic arrangement and combination of surface features (microforms) within the mire massif (e.g., hummock-hollow complex, or the arrangement of ridges and pools, corresponding to the community-complex level identifi ed by Schouten 2002). The individual features within the surface patterning of a mire (e.g., a single hummock, hollow, or pool) are termed microforms, or nanotope. This level corresponds to the micro-scale identifi ed by Schouten (2002). Table 1. Organisational levels and spatial scales in mire ecosystems. Name of level Synonyms Indication of Scale Example (Couwenberg & size (m2) (Schouten 2002) Joosten 1999) Nanotope Mire micro-form, 10-1-101 Micro-scale Hummock, hollow, pool feature Microtope Mire site 104-10 6 (community- Hummock-hollow complex, complex) pool-ridge complex Mesotope Mire massif 105-107 Meso-scale Raised bog, lagg, surrounding mineral soil system Macrotope Mire system, mire 107-109 Macro-scale Bog landscape, including complex wider landscape Chapter 1 12 Figure 1. Schematic representation of pristine raised bog landscapes (A) and the situation after degradation (B) and implementation of restoration measures (C). Spatial scales identifi ed by Schouten (2002) are indicated above scheme A, with each section of the lines representing a unit at the respective spatial scale levels. 1.2 Fauna and habitat diversity in raised bog landscapes Fauna species assemblages vary along the gradient across raised bog