Managing for conservation: The case study of Marsilea quadrifolia L. in wet meadows of 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 assessed the effects of traditional management − seasonal grazing and annual mowing − implemented by an organic farm on M. quadrifolia and plant community composition in a wet Nature Reserve in Lombardy Region (N Italy), which hosts the extant wet meadow population and the largest known to date. Managed and unmanaged (exclusion) areas were compared using vegetation surveys over four years (2021–2024), assessing species cover, diversity indices, functional Grime’ strategies, Ellenberg indicator values, water table fluctuations and M. quadrifolia chlorophyll content as a stress indicator. M. quadrifolia abundance was significantly higher in traditionally managed areas, while plant diversity did not significantly differ among treatments. Unmanaged areas exhibited higher percentage of stress-tolerant and competitive strategies, and a marked reduction in ruderal species, including M. quadrifolia, along with lower light demand. Drought limited M. quadrifolia in 2022, whereas wetter conditions in 2024 promoted its expansion. Chlorophyll measurements indicated no ecophysiological stress associated with exclusion. Low-intensity, seasonal grazing combined with mowing maintains open patches, reduces competition, and supports threatened species such as M. quadrifolia. Traditional management within Natura 2000 sites remains essential 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.