The Vertical Structure of Rich Fen Vegetation and the Development of Bryophyte Cover

The vertical structure of fen vegetation has received little attention, despite its obvious relevance to interactions between herbaceous plants and bryophytes. The main objective of this study was to determine relationships among the vertical herbaceous-rich-fen vegetation structure and the overall cover and species diversity of bryophytes. The study was conducted in eight fens in Lithuania and covered 210 subplots (0.5 m × 0.5 m). Within each subplot, the total and individual percentages of bryophyte and vascular plant cover, and of each visually distinct vertical vegetation layer, were estimated. In vertical vegetation structure, five distinct structural groups were identified, ranging from a simple two-layer group to a four-layer group. Vertical structural differences in herb cover were primarily associated with water level and microrelief. Our results revealed that an open structure is favourable for entire bryophyte cover; shading does not necessarily lead to a decline in total bryophyte cover but rather drives a structural rearrangement of the bryophyte community. The abundant development of higher vegetation layers in highly hummocky areas negatively affects the bryophyte cover. Monitoring visually distinct vertical structures can help predict negative trends in plant community structure, including shifts in bryophyte diversity and cover.