Abstract <p>The ability to form tightly closed thickets or communities is a characteristic feature of many alien plants, which determines their potential to become transformers. The aim of the work was to analyze changes in illumination under the canopy of <i>Sorbaria sorbifolia</i>, soil moisture, and the projective cover of the grass-dwarf shrub and moss layers with increasing distance from the edge of <i>S. sorbifolia</i> thickets to their center. From the edge of <i>S. sorbifolia</i> thickets to their center, the total volume of <i>S. sorbifolia</i> shoots per unit of area increased by an order of magnitude. Differences in illumination under the leaf canopy between the marginal ((30–69) × 10² lx) and central ((2.5–10) × 10² lx) areas of the thickets were also significant and reached an order of magnitude. The projective cover of the grass-dwarf shrub and moss layers significantly decreased from the periphery to the center of the thickets, and the grasses and epigeic mosses were completely absent in most areas in the center of the thickets. Thus, the formation of a dense canopy of <i>S. sorbifolia</i> triggered a sequence of reactions, starting with a decrease in illumination and leading to a decrease in the projective cover of the grass-dwarf shrub and moss layers. This confirms the status of <i>Sorbaria sorbifolia</i> as a transformer and is in a good agreement with the data on the strong influence of clonal invasive plants on natural vegetation.</p>