Les écosystèmes prairiaux de la plaine alluviale de la Meuse Lorraine : phytosociologie, dynamique et fonctionnement, en relation avec les gradients hydriques et les modifications des pratiques agricoles

The alluvial meadows constitutes original ecosystems host to numerous, rare, or slowly decreasing, animal and vegetal species. The vegetal communities are structured along the topographical gradient. In the alluvial flood plain of the Meuse, the phytosological study permitted to distinguish three meadow associations, the Colchico-festucetum pratensis, the Senecioni-oenanthetum mediae and the Gratiolo-oenanthetum fistulosae, two pastured communities the Hordeo-lolietum perennis and the Rumici-alopecuretum geniculati and different semi-aquatic associated groups. The flood-plain vegetation is in balance with the hydrous (water-table and flood levels) and the agronomic factors. The modification of one of these parameters leads to the modification of the floristic composition. The, (1) synchronic study of patches situated on the same topographic level and under different agricultural managements, (2) diachronic historic (thanks to the work of Duvigneaud in 1958) and (3) diachronic experimental studies permit to show the dynamic of the vegetation after the variation of agricultural practices. The evaluation of the quantitative and qualitative productivity of the alluvial meadows shows, even if there are no fertiliser applications, a quite good herbaceous production. The use of fertilisers increases the productivity and the total and digestible protein contents in the fodder. The fertilisation conducts to a 15 or 30 days earlier cutting of the meadows. When there is no fertiliser application, these meadows could be later cut (after the 1st of July) keeping a still acceptable fodder quality. These results permit to define and argue the conservatory modalities of this meadow ecosystem within the Agri-environemental measuresLes prairies alluviales constituent des écosystèmes originaux, qui abritent de nombreuses espèces animales et végétales rares ou en voie de disparition. Les groupements végétaux y sont zones le long du gradient topographique. Dans la vallée de la Meuse, l'étude phytosociologique a permis de distinguer trois associations de prairies de fauche, le Colchico-festucetum pratensis, le Senecioni-oenanthetum mediae et le Gratiolo-oenanthetum fistulosae, deux associations de prairies pâturées l'Hordeo-lolietum perennis et le Rumici-alopecuretum geniculati ainsi que différents groupements palustres associes. La végétation des prairies alluviales est en équilibre avec les facteurs hydriques (niveaux de la nappe et inondations) et les pratiques agricoles. La modification d'un des paramètres conduit à des changements de leur composition floristique. Les études, (1) synchronique de parcelles situées au même niveau du gradient topographique et subissant différents types de pratiques agricoles, (2) diachronique historique (grâce aux données de Duvigneaud, 1958), et (3) diachronique expérimentale (sur des carrés permanents mis en place et suivis sur 5 ans) mettent en évidence la dynamique de la végétation suite a la variation des pratiques agricoles. L'évaluation de la productivité quantitative et qualitative des prairies alluviales a permis d'y mettre en évidence une production herbacée convenable, même sans apports d'engrais. La fertilisation augmente la biomasse produite ainsi que les teneurs en matières protéiques totales et digestibles du fourrage. Elle nécessite cependant un avancement des dates de fauche (de 15 jours a un mois). En l'absence d'apports d'engrais, les prairies peuvent être fauchées assez tardivement (après le 1#e#r juillet) en conservant une valeur fourragère encore importante. Ces résultats peuvent permettre de définir et d'argumenter les modalités d'une gestion conservatoire des prairies alluviales dans le cadre des mesures agri-environnementale

Restoration of species-rich flood-plain meadows from abandoned arable fields in NE France

Attempts to restore species-rich flood-plain meadows from abandoned arable fields in the valley of the river Meuse, NE France, were studied. The study area was sown with a commercial seed mixture, composed of Phleum pratense, Festuca pratensis, Lolium perenne and Trifolium repens. The above-ground vegetation in the study area 1, 2 and 3 yr after restoration was compared to (1) the vegetation present during the previous 5-yr fallow stage and (2) target flood-plain meadows. Before restoration, the above-ground fallow vegetation was dominated by ruderal and annual species, while only very few meadow species were present. Sowing led to tall, dense vegetation, mainly dominated by the sown species. Ruderal and annual species had decreased 3 yr after restoration, but target species were still poorly represented. Species richness was significantly lower in the sown site than in the semi-natural target meadows and the vegetation had a different composition. Analysis of the soil seed bank of the restored meadow showed that only a few meadow species were present and that it was dominated by a few ruderal species. Three years after sowing, the vegetation of our experimental site is moving slowly towards the target communities but impoverished seed sources seem to limit the success of this restoration operation and will lead to under-saturated communities

Restoration of species-rich flood-plain meadows from abandoned arable fields in NE France

Attempts to restore species-rich flood-plain meadows from abandoned arable fields in the valley of the river Meuse, NE France, were studied. The study area was sown with a commercial seed mixture, composed of Phleum pratense, Festuca pratensis, Lolium perenne and Trifolium repens. The above-ground vegetation in the study area 1, 2 and 3 yr after restoration was compared to (1) the vegetation present during the previous 5-yr fallow stage and (2) target flood-plain meadows. Before restoration, the above-ground fallow vegetation was dominated by ruderal and annual species, while only very few meadow species were present. Sowing led to tall, dense vegetation, mainly dominated by the sown species. Ruderal and annual species had decreased 3 yr after restoration, but target species were still poorly represented. Species richness was significantly lower in the sown site than in the semi-natural target meadows and the vegetation had a different composition. Analysis of the soil seed bank of the restored meadow showed that only a few meadow species were present and that it was dominated by a few ruderal species. Three years after sowing, the vegetation of our experimental site is moving slowly towards the target communities but impoverished seed sources seem to limit the success of this restoration operation and will lead to under-saturated communities