1. Short-term versus long-term effects of summer flooding on floodplain biogeochemistry; interacting role of soil use and water quality Artur M. Banach 1, Leon P. M. Lamers 2, Zofia Stępniewska 1 and Jan G. M. Roelofs 2 1) The John Paul II Catholic University of Lublin, Department of Biochemistry and Environmental Chemistry (PL) 2) Radboud University Nijmegen, Department of Aquatic Ecology & Environmental Biology (NL)

2. *Severity assessment is on 1-3 scale Class 1: large flood events: significant damage to structures or agriculture; fatalities; and/or 1-2 decades-long reported interval since the last similar event. Class 2: very large events: greater than 20 yr but less than 100 year recurrence interval, and/or a local recurrence interval of at 10-20 yr. Class 3: Extreme events: with an estimated recurrence interval greater than 100 years. 1 also in Hungary; 2 also in Romania, Slovakia and Czech Republic; 3 also in Slovakia and Hungary; 4 also in Slovakia Source: Darthmouth Flood Observatory (modified).

4. HAY PAS Hayland – mowing and fertilization Pasture – grazing at low density Kosiorów, a former floodplain Grassland with Deschampsia cespitosa and Holcus lanatus as dominant plant species Present use: agriculture Middle Gorge of the Vistula River Kosiorów

5. Experimental Design 2 meadows, 20 sods from each sub-location Scenario I Short-term flooding: 5 weeks Scenario II Long-term flooding: 40 weeks Treatments (n=4) Cm – moist control Cfl – flooded control N – Cfl+1mmol l -1 NO 3 - S – Cfl+1mmol l -1 SO 4 2- SN – Cfl+S+N Analysis: pore water surface water Data processing temp. = 17°C, RH=60%. 16 h day-light temp. = 5-41°C, natural light

6. Short-term effects on vegetation Pasture Pasture : before flooding algae during flooding after flooding Hayland Hayland : before flooding algae during flooding after flooding P P

7. Long-term effects on vegetation Pasture fl+both fl+sulphate fl+nitratefloodedcontrol Hayland P P

8. P mobilization during flooding was a redox-related process......connected with Fe reduction PO 4 3- [µmol L -1 ] CharacteristicsPASTUREHAYLANDSign. Water content [%]50 (2)37 (2)*** SOM [%]54 (1)41 (1)*** pH6.4 (0.2)6.2 (0.1)NS Total S40.86 (1.78)52.32 (4.38)* NO 3 - 2236 (232)946 (107)*** Total P8833 (482)10508 (886)NS Olsen P1863 (238)3818 (435)*** Total Fe100982 (5094)117560 (10480)NS Amorphous Fe78140 (3393)76671 (8668)NS Concentrations are given in µmol l -1 of bulk soil. Soil characteristics

9. Nitrate reduction Phosphate mobilization

10. Nitrate reduction Phosphate mobilization

11. The interaction of soil characterstics and water quality - P mobilization due to both redox related Fe reduction and the effect of water components Die-off most of plants mostly in heavily fertilized sods and luxurious growth of Carex on less ferilized. Flooding timing Soil characteristics as main drivers - P mobilization due to redox related Fe reduction Die-off most of plants

12. Anaerobic decomposition of soil organic matter PO 4 3-, NH 4 +, Mn 2+, Fe 2+ uptake Inundation – the interaction of land use and water quality Reduction of NO 3 -, Mn 4+, Fe 3+ toxicity SO 4 2- H 2 S + alkalinity ← SO 4 2- FeS x Eutrophication, die-off of the non adapted vegetation, algal blooms

13.  Inundation of agricultural soils led to severe eutrophication regardless of the period of flooding.  Soil characteristics (result of cultivation way) play a key role in the observed response.  Water quality is additional key-factor significantly affecting biogeochemical nutrient cycling, especially on long-term.  Floodplain vegetation development was only possible on less fertilized meadow regardless of the floodwater quality.  For successful flood protection and nature development measure scenario II would be more appriopate.  However, additional measures such as P-immobilization by Fe addition or topsoil removal may be needed.  There is a need for further investigations. Conclusions and remarks

14. Thank you for your attention A. M. Banach, K. Banach, E. J. W. Visser, Z. Stępniewska, A. J. M. Smits, J. G. M. Roelofs, L. P. M. Lamers: Effects of summer flooding on floodplain biogeochemistry in Poland; implications for increased flooding frequency. Biogeochemistry, 2009, 92:247–262. A. M. Banach, K. Banach, R. C. J. H. Peters, R. H. M. Jansen, E. J. W. Visser, Z. Stępniewska, J. G. M. Roelofs and L. P. M. Lamers: Effects of long-term flooding on biogeochemistry and vegetation development in floodplains; a mesocosm experiment to study interacting effects of land use and water quality. Biogeosciences, 2009, 6:1–15.