Abstract: Only targeted and sustainable management will preserve extensively managed grasslands, one of Europe's most species-rich habitats. Traditionally, largely abandoned irrigation might prove a sustainable management strategy, but the understanding of the interactions among irrigation, soil properties and plant species are low for a generally humid ecoregion. We aimed at advancing our understanding of plant ecology by disentangling plant community responses to traditional lowland meadow irrigation from traditionally low fertilization rates. We studied plant composition and diversity jointly with the underlying links to soil properties (Corg, total N, water holding capacity and mesofaunal activity) and soil nutrients (Nmin, P, K, Mg and B). In a field study, we compared 13 long-term traditionally irrigated and 13 non-irrigated (17 fertilized and 9 non-fertilized) meadows. We surveyed plant diversity, composition and soil nutrients as well as soil properties for 1 year assuming low annual variation. Irrigation and fertilization led to differences in soil properties and soil nutrients without impact on sheer plant species diversity but on plant species composition. Finer grain sizes due to siltation increased water holding capacity and nutrient storage. Hence, resource-acquisitive graminoid species had advantages in irrigated meadows. Thus, irrigation is not only a mean to preserve biodiversity of extensively used meadows of Central Europe but may prove a tool to differentiate between plant functional traits.

Key words: grassland, flood irrigation, fertilization, soil nutrients, phytodiversity, species composition, soil patterns