Étude des peuplements d’odonates dans une plaine agricole du Sud de la France

Abstract

Summary. — Odonata communities in an agricultural lowland in the South of France. — Odonata communities were studied in an agricultural landscape where semi-natural habitat patches (pastures and woods, with a dense network of deep ditches) are embedded in a crop mosaic (cereals, irrigated maize). We compared species richness and diversity of aquatic plants and odonata in ditches surrounded by pastures or by crops. Ours results showed that this surrounding (pastures vs crops) has no effect on aquatic plant and odonata species richness and diversity. However, in cultivated areas water supply through irrigation and deep ditches with plant-covered borders could promote odonata species. High level of vegetation cover (particularly with Typha sp.) limited odonata richness and diversity. A rare species in Europe, protected and sensible to pollution, Coenagrion mercuriale, occurred in many ditches including those surrounded by crops, particularly those with an intermediate semi-aquatic vegetation cover. The regular maintenance of ditches, by limiting shrubs and trees height, keep them open and facilitate the dispersal of this little mobile species. Although irrigated crops seem to support a high level of odonata diversity, a new intensification of agricultural practices in this area by increasing the pollutant input and/ or by converting pastures to crops could be detrimental to odonata communities and particularly to some species like Coenagrion mercuriale.