Long-Term Changes in Colonization of Bulldozed Ski Pistes at Cairn Gorm, Scotland

Abstract

This study examines the long-term effects of grass seeding on the colonization of bulldozed ground by native species. Colonization of three bulldozed pistes on Cairn Gorm was monitored over 25 years. Two were seeded and fertilized at the time of construction and the third was left unsown. By the end of the study the seeded 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 seeded 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 unseeded ground, vegetation cover was much lower than on seeded ground on every occasion. Mosses, grasses and forbs tended to be more prevalent at seeded sites than on intact ground. Some characteristic species of intact ground, such as Empetrum nigrum and Carex bigelowii, were uncommon on seeded ground. Most local vascular species were more effective colonists of seeded 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 clear that grass seeding substantially enhanced colonization by native species.