Short-term versus long-term effects of summer flooding on floodplain

biogeochemistry; interacting role of soil use and water quality

Artur M. Banach1, Leon P. M. Lamers2,Zofia Stępniewska1 and Jan G. M. Roelofs2

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)

*Severity assessment is on 1-3 scaleClass 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 SlovakiaSource: Darthmouth Flood Observatory (modified).

HAY

PAS

Hayland – mowing and fertilizationPasture – grazing at low density

Kosiorów, a former floodplainGrassland with Deschampsia cespitosa and Holcus lanatus as dominant plant species

Present use: agriculture

Middle Gorge of the Vistula River

Kosiorów

Experimental Design

2 meadows,20 sods from each sub-location

Scenario IShort-term flooding:

5 weeks

Scenario IILong-term flooding:

40 weeks

Treatments (n=4)Cm – moist controlCfl – flooded control N – Cfl+1mmol l-1 NO3

-

S – Cfl+1mmol l-1 SO42-

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

Short-term effects on vegetation

Pasture: before flooding algae during flooding after flooding

Hayland: before flooding algae during flooding after flooding

P

P

Long-term effects on vegetation

Pasture

fl+bothfl+sulphatefl+nitratefloodedcontrol

Hayland

P

P

P mobilization during flooding was a redox-related process...

...connected with Fe reduction

PO43-

[µm

ol L

-1]

PO43- [µmol L-1]

Characteristics PASTURE HAYLAND Sign.Water content [%] 50 (2) 37 (2) ***SOM [%] 54 (1) 41 (1) ***pH 6.4 (0.2) 6.2 (0.1) NSTotal S 40.86 (1.78) 52.32 (4.38) *NO3

- 2236 (232) 946 (107) ***Total P 8833 (482) 10508 (886) NSOlsen P 1863 (238) 3818 (435) ***Total Fe 100982 (5094) 117560 (10480) NSAmorphous Fe 78140 (3393) 76671 (8668) NS

Concentrations are given in µmol l-1 of bulk soil.Soil characteristics

Nitrate reduction

Phosphate mobilization

Nitrate reduction

Phosphate mobilization

•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

Anaerobic decomposition of soil organic matter

PO43- , NH4

+,Mn2+, Fe2+

uptake

Inundation – the interaction of land use and water quality

Reduction of NO3-,

Mn4+, Fe3+

toxicity

SO42-

H2S + alkalinity ← SO42-FeSx

Eutrophication, die-off of the non adapted vegetation, algal blooms

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

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.