Concrete fortifications of the times of the First and Second World Wars are widespread on the territory of Belarus. These structures are an important object for botanical research, because they have a rocky base with carbonate composition (which is a rare phenomenon for alowland country), are of different age (70 and 100 years old), with different degrees of destruction, located in different phytocenotic environments.

The purpose of our work is a comparative description of the cenotic parameters of the briophytes of the fortification structures of the First and Second World Wars on the territory of the Republic of Belarus to identify the species-specific behavior of bryophytes during the development of artificial rocky substrates in the Russian Plain. Briofloristic studies were carried out on more than 140 fortifications, constituting 9 fortified areas, in the period from 2008 to 2015 by the method of specific or local floras. Detailed and detailed route-based approaches, a method of total counting of bryophytes were used. The taxonomic determination of the herbarium material of bryophytes was carried out according to the generally accepted comparative morphological and anatomical methods using microscopy. Assessment of the abundance of mosses on fortifications was carried out using the scale of J. Brown-Blanke. The frequency of occurrence of species was determined for each fortified area, and then for each fortification group (the complex of structures of the First and Second World Wars). The occurrence of taxa was classified by the constancy class: I (1–20%), II (21–40%), III (41–60%), IV (61–80%), V (81–100%).

The cenotic parameters of 144 bryophytes have been studied. The variability of the constancy and abundance of bryophyte species as markers of the succession stages on different-age structures has been studied. The authors’ classification of bryophytes based on the variability of their occurrence (stable, decreasing, increasing, of which the reactive and proactive subgroups were singled out) and abundance (positively dynamic, negatively dynamic, stable) were developed on the basis of which early succession and late succession species were identified. Analysis of the relative position of the cenopopulations of mosses to their out- and synecological optimums showed that most taxa change the occurrence and abundance synchronously. The revealed regularities will allow to carry out nature protection measures more purposefully and effectively.