Long-term changes in colonization of bulldozed ski pistes at Cairn Gorm, Scotland.
The long-term effects of grass reseeding on the colonization of bulldozed ground by native species were investigated. Colonization of three bulldozed pistes on Cairn Gorm was monitored over 25 years. Two were sown and fertilized at the time of construction and the third was left unsown. By the end of the study the sown ground blended well with the surrounding ground, but the unsown piste remained visually conspicuous because of the high fraction of bare ground (>60%). Cover on sown ground was mainly sown grasses and mosses for the first 9 years. Subsequently, the cover of sown grasses declined whereas moss cover peaked after 18 years. Cover of local vascular species gradually increased, and after 25 years exceeded that of sown grasses (21% at 1180 m and 32% at 1000 m). On unsown ground, vegetation cover was much lower than on sown ground on every occasion. Mosses, grasses and forbs tended to be more prevalent at sown sites than on intact ground. Some characteristic species of intact ground, such as Empetrum nigrum and Carex bigelowii, were uncommon on reseeded ground. Most local vascular species were more effective colonists of sown than of untreated ground. An exception was Juncus trifidus, which was more successful on unsown ground. Some sown species had persisted for 25 years and might take another 10-15 years or longer to disappear. It seems likely that the vegetation of disturbed ground will remain botanically distinct from that of the surroundings because of ineffective colonization by certain key species, and because of the influence of late snowlie. It is concluded that grass reseeding substantially enhanced colonization by native species.