A review of the ecology, hydrology and nutrient dynamics of floodplain meadows in England No. 446 - English Nature Research Reports working today for nature tomorrow English Nature Research Reports Number 446 A review of the ecology, hydrology and nutrient dynamics of floodplain meadows in England David J.G. Gowing1, Jerry R.B. Tallowin2, Nancy B. Dise1, Joanne Goodyear2, Mike E. Dodd1 and Rebecca J Lodge1. 1Open University, Walton Hall, Milton Keynes MK7 6AA 2Institute of Grassland and Environmental Research, North Wyke, Okehampton, Devon EX20 2SB You may reproduce as many additional copies of this report as you like, provided such copies stipulate that copyright remains with English Nature, Northminster House, Peterborough PE1 1UA ISSN 0967-876X © Copyright English Nature 2002 Contents Executive summary 1. Introduction ................................................................................................................. 13 1.1 Scope of the review..................................................................................................... 13 1.2 Review methodology................................................................................................... 13 1.3 Current distribution of Floodplain meadows in England............................................ 14 1.4 Perceived threats to the habitat.................................................................................... 15 2. Hydrology of floodplain meadows.............................................................................. 20 2.1 Introduction ................................................................................................................. 20 2.2 Water balance on floodplains...................................................................................... 20 2.3 Soil aeration................................................................................................................. 22 2.4 Soil moisture ............................................................................................................... 24 2.5 Soil temperature.......................................................................................................... 25 2.6 Hydrological management .......................................................................................... 26 2.6.1 Channel management ...................................................................................... 26 2.6.2 Flood defence .................................................................................................. 27 2.6.3 Surface drainage.............................................................................................. 27 2.6.4 Sub-surface drainage....................................................................................... 28 2.6.5 Mineral extraction ........................................................................................... 29 2.6.6 River restoration.............................................................................................. 29 3. Nutrient dynamics ....................................................................................................... 30 3.1 Ecosystem productivity............................................................................................... 30 3.2 Limiting nutrients........................................................................................................ 31 3.3 Mitigation of high nutrient availability....................................................................... 33 3.4 Nitrogen budget........................................................................................................... 35 3.4.1 Sources of nitrogen.......................................................................................... 35 3.4.2 Sinks for nitrogen............................................................................................ 36 3.4.3 Critical loads................................................................................................... 37 3.5 Phosphorus budget ...................................................................................................... 38 3.6 Sulphur budget ............................................................................................................ 40 3.7 Source of floodwater ................................................................................................... 41 3.8 Hay mineral content .................................................................................................... 42 3.9 Trends in nutrient deposition ...................................................................................... 42 3.10 Impact of nutrient supply on vegetation production ................................................... 43 4. Agronomy and vegetation management...................................................................... 46 4.1 Introduction ................................................................................................................. 46 4.2 Traditional management.............................................................................................. 46 4.3 Agronomic data........................................................................................................... 47 4.3.1 Dry matter yield .............................................................................................. 47 4.3.2 Hay mineral content and effects on animal nutrition ...................................... 51 4.3.3 Grazing animal output..................................................................................... 52 4.3.4 Grazing versus cutting..................................................................................... 53 4.4 Summary ..................................................................................................................... 54 5. Vegetation response to hydrology and nutrient availability........................................ 55 5.1 Community composition............................................................................................. 55 5.2 Effect of hydrology on community composition ........................................................ 56 5.3 Effect of nutrient availability on community composition patterns............................ 58 5.4 Rates of community change ........................................................................................ 59 5.5 Restoration of the MG4 community............................................................................ 60 6. Deficiencies in our understanding of floodplain meadow ecology............................. 62 6.1 Botanical data on vegetation change........................................................................... 62 6.2 Nutrient budgets.......................................................................................................... 62 6.3 Community reassembly............................................................................................... 62 6.4 Drivers of community change..................................................................................... 62 6.5 Impacts of eutrophication and climate change............................................................ 63 6.6 Economic analysis of floodplain management............................................................ 63 6.7 The role of flood water in maintaining surface pH ..................................................... 63 6.8 Physiological ecology ................................................................................................. 63 7. Conclusions ................................................................................................................. 64 7.1 Hydrology.................................................................................................................... 64 7.2 Nutrition ...................................................................................................................... 64 7.3 Vegetation management.............................................................................................. 64 7.4 Conservation management .......................................................................................... 65 8. Recommendations for further research ....................................................................... 66 9. Acknowledgements ..................................................................................................... 68 10. Bibliography................................................................................................................ 69 Appendices 82 Appendix 1 List of MG4 sites in England .......................................................................... 82 Appendix 2 Hay yields from North and East Yorkshire flood meadow SSSIs .................. 85 Appendix 3 Site questionnaire for English Nature Local Teams........................................ 87 Figures Figure 1-1 The distribution of sites containing the MG4 flood-plain meadow in England ....15 Figure 1-2 Threats to the integrity of MG4 grassland sites, as perceived by local conservation officers..............................................................................................................................16 Figure 1-3 The proportion of sites which have undergone an alteration to their hydrological system in the past 30 years...............................................................................................17 Figure 1-4 The percentage of sites known to have received fertilizer applications during the past 30 years.....................................................................................................................17