Military training areas, where ecosystems are shaped under a complex disturbance regime, are recognized to be favourable pieces of land for maintaining high biological diversity. Our study focused on explosion craters – a small-scale disturbance type of high severity, and their effect on species diversity including vascular plants, bryophytes and lichens. The research was carried out on an active military training area in Nowa Dęba (SE Poland). The examined vegetation represented open communities on nutrient-poor soils with a wide range of soil moisture conditions. We compared 76 pairs of vegetation samples, each pair consisting of a crater and a closely located control plot of the same size. Out of 135 species recorded (72 vascular plants, 33 mosses, 9 liverworts, 22 lichens), 37 were found only in craters, while 19 occurred only in control plots. Both, species number and diversity were significantly higher for craters than controls. In general, the positive effect of cratering on all studied groups rises from dry to wet habitats. The highest increase of diversity was observed in relation to bryophytes in the moist habitats. Moreover, craters within habitats of higher moisture turned out to be more resistant to alien colonization and at the same time were characterized by significantly higher number of red-listed species compared to the control plots. Differences in species composition between craters and undisturbed plots were most visible in moderately moist habitats. We found several species with a strong preference for craters, and the plants of the highest indicative value are Atrichum tenellum and Dicranella cerviculata.