The Impact of Mowing and Flooding on the Diversity of Arthropods in Floodplain Grassland Habitats of the Lower Oder Valley National Park, Germany Dissertation Zur Erlangung des Doktorgrades der Mathematisch-Naturwissenschaftlichen Fakultäten der Georg-August-Universität zu Göttingen vorgelegt von Judith Rothenbücher aus Lahnstein Göttingen, Dezember 2004 D7 Referent: Prof. Dr. M. Schaefer Korreferent: Prof. Dr. U. Ehlers Tag der mündlichen Prüfung: 27. Januar 2005 Contents Contents 1 Introduction ........................................................................................................... 3 2 Study area .............................................................................................................. 7 2.1 Location and characteristics ................................................................................ 7 2.2 History ................................................................................................................. 9 2.3 Plans for future development............................................................................. 10 2.4 Climate .............................................................................................................. 12 2.5 River Oder ......................................................................................................... 13 3 Impact of mowing and flooding on the diversity of plant- and leafhoppers ........................................................................................ 15 3.1 Introduction ....................................................................................................... 15 3.2 Materials and methods....................................................................................... 15 3.2.1 Sampling methods....................................................................................... 15 3.2.2 Study sites................................................................................................... 16 3.2.3 Environmental variables ............................................................................. 19 3.2.4 Species identification.................................................................................. 19 3.2.5 Ecological characteristics of the species..................................................... 20 3.2.6 Analysis ...................................................................................................... 22 3.3 Results ............................................................................................................... 27 3.3.1 Ecological characteristics of the Auchenorrhyncha community ................ 27 3.3.2 Impact of mowing....................................................................................... 31 3.3.3 Impact of flooding ...................................................................................... 40 3.3.4 Differences in the impact of flooding on the communities in fallows and mown sites........................................................................... 50 3.3.5 Similarity of species composition between different sites.......................... 54 3.3.6 Impact of environmental variables ............................................................. 56 3.4 Discussion.......................................................................................................... 60 3.4.1 Impact of mowing and flooding on species numbers, numbers of individuals and diversity.......................................................... 60 3.4.2 Ecological characteristics of the species..................................................... 62 4 Submersion tolerance in floodplain arthropod communities.......................... 66 4.1 Introduction ....................................................................................................... 66 4.2 Materials and methods....................................................................................... 67 4.2.1 Colonisation experiment and sampling procedure...................................... 67 4.2.2 Ecology of species ...................................................................................... 68 4.2.3 Submersion tolerance versus immigration.................................................. 69 4.2.4 Statistical analyses ...................................................................................... 69 4.3 Results ............................................................................................................... 69 4.3.1 Ecology of species: submersion tolerance versus immigration.................. 70 4.3.2 Impact of flooding on the distribution of submersion tolerant and immigrating species ............................................................................. 75 4.4 Discussion.......................................................................................................... 77 4.4.1 Ecology of species: Submersion tolerance versus immigration ................. 77 4.4.2 Impact of flooding intensity........................................................................ 78 1 Contents 5 Conservation management of target species or conservation of processes – Winners and losers of two different conservation strategies........................................................................................ 80 5.1 Introduction ....................................................................................................... 80 5.2 Two conservation strategies .............................................................................. 80 5.3 Three case studies from the Lower Oder Valley National Park, Germany ....... 82 5.3.1 Impact of mowing on the suitability of grassland as habitat of corncrakes (Crex crex) in the Lower Oder Valley National Park............... 82 5.3.2 Impact of flooding on the amphibian community ...................................... 83 5.3.3 Consequences of changes in flooding and land use for the conservation of insects in the Lower Oder Valley National Park .................................... 83 5.4 Discussion: Winners and losers of the two conservation strategies.................. 86 6 Discussion............................................................................................................. 90 6.1 Impact of mowing and flooding on the diversity of arthropods........................ 90 6.2 Conclusions for the conservation of arthropods in floodplain grassland .......... 94 6.3 Evaluation of the plans for future national park development .......................... 97 7.1 Summary .............................................................................................................. 98 7.2 Zusammenfassung............................................................................................. 101 8 References .......................................................................................................... 105 Appendix 1................................................................................................................... 116 Appendix 2................................................................................................................... 121 Appendix 3................................................................................................................... 122 Appendix 4................................................................................................................... 125 Appendix 5................................................................................................................... 132 Acknowledgements ..................................................................................................... 139 Lebenslauf.................................................................................................................... 140 2 1 Introduction 1 Introduction Floodplains are found along streams or rivers and are characterised by regular inundation during periods of flooding. Grassland habitats dominated by reed grass (Phalaris arundinacea), common reed (Phragmites australis) or sedges (Carex spec.) are part of the natural floodplain of lowland rivers in Central Europe (Patt et al. 1998). They occur where floodplains are subjected to a (semi-) natural hydrological regime (RSPB et al. 1997). Natural floodplains are the most species rich habitats in temperate regions (Gerken 1988). Due to the flooding dynamics, they provide high habitat diversity. Plants and animals living in these floodplain habitats have to cope with cycles of wet and dry conditions. Robinson et al. (2002) state that little is known about the ecology of special habitats associated with intact floodplains. In lowland rivers of Central Europe typically long lasting winter floods occur. Terrestrial arthropods living in the floodplains have to cope with these flooding events. Many studies on survival strategies of terrestrial invertebrates inhabiting floodplains have been carried out in the Amazon basin, but much less is known about the situation in Central Europe (Adis & Junk 2002). In Europe, large rivers have experienced a long history of modification by man, which often included building of dykes and drainage of floodplains (Petts 1989). Thus, today, only few reaches of natural river remain (Petts 1989). Consequently, riverine floodplains are among the most endangered landscapes world-wide (Olson & Dinersein 1998, Tockner & Stanford 2002). In Germany, only about 10% of the former floodplains are in a near-natural state (see Jungwirth et al. 2002). Tockner & Stanford (2002) state that there is an urgent need to preserve