Seasonal Dependent Effects of Flooding on Plant Species Survival and Zonation: a Comparative Study of 10 Terrestrial Grassland Species |
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Authors: | W H J M van Eck J P M Lenssen H M van de Steeg C W P M Blom H de Kroon |
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Institution: | (1) Department of Experimental Plant Ecology, Institute for Wetland and Water Research, Radboud University Nijmegen, Toernooiveld, 6525, ED, Nijmegen, The Netherlands |
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Abstract: | Past research has provided compelling evidence that variation in flooding duration is the predominant factor underlying plant
species distribution along elevation gradients in river floodplains. The role of seasonal variation in flooding, however,
is far from clear. We addressed this seasonal effect for 10 grassland species by testing the hypothesis that all species can
survive longer when flooded in winter than when flooded in summer. We carried out an inundation experiment under simulated
conditions of summer and winter flooding in the greenhouse. The results showed that all species survived longer under winter
floods than under summer floods. However, responses upon flooding were species-specific. All summer flood-tolerant species
had high tolerance for winter floods as well, but summer flood sensitive species survived either a little longer, or dramatically
longer when flooded under simulated winter conditions. Next, we examined whether winter or summer survival best predicted
the lower distribution limits of the species as measured in a natural flooding gradient after an extremely long winter flood.
We found a strong significant relationship between the lower distribution limits of species in the field and their tolerance
to summer floods, although we measured the lower limits 14 years after the latest major summer flood. In contrast, no such
significant relationship existed with species tolerance to winter floods. Some relatively intolerant species occurred at much
higher floodplain elevations as was expected from their tolerance to winter inundation in the experiments. This suggests that
zonation patterns as created by occasional summer floods may be maintained for a long time, probably due to the limited ability
of species to re-colonise lower positions in the floodplain. |
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Keywords: | floodplain plants riparian grassland river Rhine season species distribution summer flood winter flood |
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