The Ecological Drivers of the Mosaic Structure of Bryophyte and Vascular Plant Cover in the Rich Fens of Lithuania

The composition and structure of vegetation have been recognised as the main determinants of habitat quality, which influences biodiversity. The presented research focuses on the mosaic structure of Lithuanian rich fens and their relationship to ecological conditions. This study was conducted across 98 study plots amongst 15 fens distributed throughout Lithuania. This research included the cover and abundance of vascular plants and bryophytes, water parameters (conductivity, pH, and concentrations of Ca²⁺, Fe³⁺, K⁺, Mg²⁺, NH₄⁺, NO₃^-, and PO₄^3-), topography type, and the cover of hummocks. Vegetation studies resulted in the distinction of two clusters containing ten bryophyte groups and two clusters containing eleven vascular plants groups. The main diagnostic species for bryophyte clusters were <i>Scorpidium cossonii</i> and <i>Calliergonella cuspidata</i>, and those for the vascular plant clusters were <i>Carex lepidocarpa</i> and <i>Carex rostrata</i>. The mosaic distribution of vegetation observed in both the bryophyte and vascular plant layers is primarily shaped by local hydrological regimes, microtopographical variation, and the amount of iron present. The habitats of bryophyte groups, as compared to those of vascular plants, were determined by narrower ecological conditions. This study emphasised the specificity of Lithuanian fens, which are located at the junction of the boreal and continental biogeographical regions.