Question: What are the responses of Racomitrium lanuginosum moss to altered snow-lie and sheep use?

Location: A Carex bigelowii-Racomitrium lanuginosum heath on a Scottish montane plateau affected since 1986 by a fenced ski corridor.

Methods: Permanent quadrats were set up along transects 45 m long perpendicular to the snow-fence. Cover was assessed over a 12-year period from 1990. Pellet-group clearance counts provided data on sheep usage between 1990 and 1996. Snow-lie was mapped in the springs of 1991–1996.

Results: The snow-fence created a gradient in sheep use and altered the duration of snow-lie. At the start of monitoring Racomitrium cover was lower immediately adjacent to the fence, and after 12 years its cover was significantly reduced within 10 m of the fence. Further away from the fence Racomitrium cover was relatively stable. The loss of Racomitrium was correlated both with increased snow-lie and heavier sheep usage. Grass cover increased near the fence and was related to sheep use. Dicranum fuscescens responded differently to Racomitrium, increasing significantly near the fence.

Conclusions: We found that changes in snow-lie and grazing pressure quickly brought about vegetation change in this montane ecosystem. Racomitrium was the most sensitive species to the changes in grazing and snow-lie caused by the fence, having the biggest initial changes. Loss of Racomitrium permitted increases of species more resistant to grazing including Dicranum fuscescens and grasses.

Nomenclature: Stace(1997)for vascular plants; Smith(1978) for mosses.