Biogeochemical consequences of winter flooding in brook valleys |
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Authors: | Victor Beumer Geert van Wirdum Boudewijn Beltman Jasper Griffioen Jos T A Verhoeven |
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Institution: | (1) Landscape Ecology, Institute of Environmental Biology, Utrecht University, P.O.Box 80084, 3508 TB Utrecht, The Netherlands;(2) TNO Netherlands Geological Survey, Utrecht, The Netherlands |
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Abstract: | Climatic change has great impacts on stream catchments and their ecology. Expectations are that more extreme climate events
will result in undesired flooding in stream catchments. In the Netherlands, former floodplains with a history of agricultural
use are put into use again as flooding areas for the purpose of water retention. This study focuses on the effects of winter
flooding on various plant site conditions in the soil, such as redox, nutrient, pH, and base status. We compared the effects
on groundwater- and rainwater-dominated floodplains. Water chemistry (pH, EC, HCO3, SO4, Cl, Ca, Mg, Na, K,
, NO3, NH4, and PO4) and soil nutrients (Total N and P, and bio-available P) were monitored for one year, including a 3–4 month period with winter
flooding. In both floodplains no direct effect of the flood-water chemistry was detected in the pore water, because the soil
pores had become saturated with groundwater or rainwater, respectively, just before flooding, flood-water did not penetrate
the soil. We found that the increase in pH and ammonium concentration in the rainwater floodplain were due to changes in redox
status, resulting from the completely water-filled state of the soil pores during the flooding event. Furthermore, we noticed
an increase in soil nutrient contents and a shift in plant species composition in the rainwater floodplain: the vegetation
included more plant species characteristic for N-richness. Finally, we conclude that winter flooding has more drastic effects
on biogeochemical conditions and vegetation composition in the atmotrophic conditions characteristic for low-order subcatchments
than in lithotrophic conditions in the larger, higher-order subcatchments of the stream basin. |
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Keywords: | Flooding Streams Natural vegetation pH Pore water chemistry Soil nutrients |
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