The vegetation within an ombrotrophic mire expanse in SE Norway is studied in detail. Presence/absence of species and depth to the water table are recorded for 6 976 plots (4 × 4 cm). The cumulative probability distributions along the water-table gradient are calculated Tor 24 species, and inter-transect variability tested. Shifts in realised depth to the water table (niche shifts) are frequent for most species. It is concluded that interactions are of minor importance for species in the field layer. The Sphagnum spp. possess some attributes indicating equilibrium, while others indicate ongoing competition. The patchy distribution of hepatics and lichens depend on chance and successional stage, and coexistence within these guilds depend on creation of new naked peat patches.