Spatial and temporal patterns of ground vegetation dominants in mountain spruce forests damaged by sulphur air pollution (Giant Mountains, Czech Republic)

We studied ground vegetation dynamics during the decline and recovery of mountain Norway spruce forests damaged by SO 2 air pollution and associated stress factors.Changes in areal extent of the ground vegetation dominants, moss layer and spruce litter and trajectories of these changes, recorded at a spatial resolution of 5 5 cm, were analysed in 1-m 2 squares located in plots differing in dynamics of spruce canopy cover.Spruce litter patches diminished during spruce stand decline being colonised by Avenella flexuosa, Calamagrostis villosa (in canopy gaps) and Vaccinium myrtillus (under gradually defoliating tree crowns).After several years of spatially dynamic coexistence of the grasses, C. villosa began to retreat being replaced by A. flexuosa.Vaccinium myrtillus then re-entered these grass stands.In less affected spruce stands, the dominants partially retreated without competing with other ground vegetation.Moreover, the applied GIS spatio-temporal analysis revealed substantial spatial movements of the dominants over the plots.