Managing wet meadows for conservation: the case of Marsilea quadrifolia L. in a Natura 2000 site (N Italy)

Wet meadows are biodiversity-rich habitats in Europe, central to the Natura 2000 network, hosting threatened species. Marsilea quadrifolia L., an aquatic pteridophyte of conservation concern, is a pioneer, disturbance-dependent species relying on open semi-natural wetlands, threatened by changing agricultural practices. We evaluated the effects of traditional management – seasonal grazing and annual mowing – implemented by an organic farm on M. quadrifolia and plant community composition in the Natura 2000 site “Pian di Spagna e Lago di Mezzola”, Lombardy Region (N Italy), which hosts the only extant Italian wet meadow population of the species. Managed and unmanaged (exclusion) areas were compared over four years (2021–2024) through vegetation surveys, diversity indices, functional Grime’s CSR strategies, Ellenberg indicator values, hydrological monitoring and M. quadrifolia chlorophyll content as a stress indicator. Traditionally managed plots supported higher abundance of M. quadrifolia, while unmanaged areas showed increasing dominance of competitive and stress-tolerant species, associated with denser vegetation and lower light availability. Drought conditions limited M. quadrifolia in 2022, whereas wetter conditions promoted its expansion in 2024. Chlorophyll measurements indicated no ecophysiological stress associated with exclusion. Our results highlight how low-intensity seasonal grazing and mowing maintain open patches, reduce competition, and support threatened species of conservation concern such as M. quadrifolia. Traditional management within Natura 2000 sites remains crucial for integrating conservation and agricultural use. Adaptive, context-specific management aligned with hydrological dynamics and plant phenology is essential to sustain wet meadows under changing water availability driven by climate change.