Diaspore bank and dark diversity of bryophytes: Insights into fen vegetation and restoration potential

Fens are species‐rich wetlands that host many threatened plants but are rapidly declining across Europe. Understanding processes that are shaping fen vegetation, including aspects not visible to the naked eye, such as diaspore banks and dark diversity, is essential for conservation and restoration. We surveyed bryophytes and vascular plants in 145 plots (1 m 2 ) across 15 rich fens located in Estonia, Latvia and Lithuania (Baltic region, Northern Europe) and collected soil samples for bryophyte diaspore bank germination under controlled conditions. We quantified cover, richness, species pools, dark diversity (using co‐occurrence models) and species composition and tested relationships among these metrics using Spearman correlations and Mantel tests. Vascular plant cover was negatively correlated with total bryophyte cover but positively correlated with brown moss cover, indicating selective interactions among functional groups. Bryophyte and vascular plant dark diversity were positively correlated, suggesting similar historical drivers of species loss. Diaspore bank richness exceeded above‐ground bryophyte richness, with nearly half of the germinated taxa being fen specialists, including rare and regionally extinct species. Species occurring in the diaspore bank also tended to have higher dark diversity probabilities, indicating partial overlap between the diaspore bank and ecologically suitable dark diversity. Practical implication: Bryophyte diaspore banks represent a hidden reservoir of fen biodiversity, complementing insights from dark diversity to guide conservation priorities and improve understanding of unrealized biodiversity potential in fen communities. Bryophyte diaspore banks can be a substantial complementing source for fen restoration.