Mid-term effect of organic fertilisation on the soil seed bank of moderately species-rich and moderately species-poor mountain meadows

Permanent mountain meadows provide forage for livestock farming and are potential small-scale biodiversity hotspots, but the response of their soil seed bank (SSB) to organic fertilisation is not completely clarified. Studies exploring changes over time are rare and experiments addressing the effect of nutrient input and manure type are lacking. In a six-year field experiment in South Tyrol (Italy), we simultaneously investigated the effects of a nutrient input gradient (0–1.3 Livestock Units ha −1 year −1 ), three manure types (farmyard manure, slurry and farmyard manure + manure effluent), and two meadow classes (moderately species-poor vs. moderately species-rich) on the SSB. The SSB was assessed at experiment start (2018) and after six years (2024). The SSB showed only small changes over time, with high similarity of the SSB between the observation years. Increasing nutrient input resulted in a modest increase of Ellenberg N and Ruderal strategy index, as well as a decrease of the Stress strategy index. Effects of manure type occurred only as interaction with other factors and were inconsistent across response variables. Species relevant to the Natura 2000-status were contained in very low number. Our results, obtained under moderate nutrient input typical of mountain meadows in the study area, are in line with evidence from relevant literature that SSB responds weakly to management changes in the mid-term and offers limited potential to improve the Natura 2000 status, even after cessation of fertilisation. These findings highlight the need to consider other seed sources and recruitment processes to enhance plant species diversity.