Undisturbed, or little disturbed, peat-forming bogs, often taking the shape of a convex lens. Such intact or nearly intact systems have become very rare or even exceptional. They are composed of a number of communities, which form and occupy the topological features of the bog. These communities are interrelated and function as a unit, so that they cannot be regarded as separate subhabitats; their presence and combination, however, characterizes the various types of bogs. Simultaneous use of an appropriate selection of the subunits below can thus contribute to a deERREURion of individual bog systems.