Understory plant assemblages present distinct short-term responses to the clear-cutting of an old-growth spruce forest near an alpine timberline

Forest clear-cutting is a prominent disturbance influencing understory plant communities. We implemented a before-after, control-impact (BACI) designed experiment in a high-elevation, old-growth spruce forest in the eastern Tibetan Plateau to understand the response in cover and species richness of the understory plant community and its assemblages, as well as the driving roles of environmental alteration (e. g., radiation, temperature, humidity, and nutrients), physical disturbance (e.g., direct damage by trampling and tree-felling), and interplay effects (e. g., shading or burial from logging residue) during a 2-year period. The decrease in cover for the understory vegetation was predominantly due to a decrease in bryophytes; the grass cover, however, increased. While bryophyte species richness decreased, the total number of understory and vascular plants changed minimally. Furthermore, the environmental alteration drove the increase in grass cover, as well as the cover and species richness decline for bryophytes and its two species groups. It was also found that physical disturbances and interplay effects caused the decrease in cover for bryophytes. The total effects influenced the understory community and bryophytes in terms of cover, but not in terms of species richness. We conclude that the short-term responses of understory vegetation to clear-cutting are distinct across different assemblages due to various mechanisms. Bryophytes are more sensitive than vascular plants, and cover percentage responded more swiftly than species richness to clear-cutting