Predictions in Ungauged Basins: Promise and Progress (Proceedings of symposium S7 held during the Seventh IAHS Scientific Assembly at Foz do Iguaçu, Brazil, April 2005). IAHS Publ. 303, 2006, 334-341.

 

Indirect assessment of flooding duration as a driving factor of plant diversity in wet grasslands

 

CYRILLE VIOLLE1, CHRISTOPHE CUDENNEC2, MANUEL PLANTEGENEST3, CHRISTIAN DAMGAARD4, DIDIER LE COEUR5, JAN-BERNARD BOUZILLE6 & ANNE BONIS6

1       UMR Centre d'Ecologie Fonctionnelle et Evolutive,F- 34293 Montpellier Cedex 5, France

cyrille.violle@cefe.cnrs.fr

2       UMR SAS, Rennes, France and UMR G-EAU, IRD, BP 434, Tunis, Tunisia

3       UMR BIO3P INRA-Agrocampus, 65 rue de Saint-Brieuc,F-35042 Rennes Cedex, France

4       Department of Terrestrial Ecology, NERI, Vejlsovej 25, DK-8600 Silkeborg, Denmark

5       INRA-SAD Armorique, 65 rue de Saint-Brieuc, F-35042 Rennes Cedex, France

6       UMR Ecobio, Campus de Beaulieu,F-35042 Rennes Cedex, France

 

Abstract Flooding duration in wet grasslands represents a crucial indicator for agricultural and biodiversity targets. However, flooding duration in wet grasslands is not an easy variable to observe by itself, all the more so because it is really heterogeneous in space, due to subtle topographic relief. Moreover, actual plant diversity, composition and community structure are the synthetic results of the hydro-meteorological history in the past. Wet grasslands are thus truly ungauged with respect to flooding duration, which has to be simulated in a robust manner both over the spatial territory and back over the past many years. A water-balance modelling with a daily time step, based on available meteorological data and on a precise topographic characterization, was proposed to assess the flooding duration at any location of a studied area situated along the west coast of France and over a period of six years. The simulated (calculated) flooding durations were used in the plant species distribution modelling based on 350 sampled vegetation quadrats. From field-based milestone observations of water level, the hydrological modelling was shown to predict well the annual cumulative flooding duration at any spot. A strong and consistent effect of flooding duration was evident for 29 species. Plant diversity appeared to reach a maximum at an intermediate flooding duration. The hydrology-vegetation modelling approach could thus lead to a robust and versatile tool to predict the consequences of changes in flooding regime on vegetation patterns.

 

Key words  flood-meadows; modelling; PUB; response curve; species richness; water balance