Snowfences driving vegetation change

Last month John Morgan and I travelled to the Old Man Range in central Otago, New Zealand to monitor vegetation change behind an old rickety fence. The Snowfence was built by the (now) old man himself, Emeritus Professor Sir Alan Mark, Otago University in 1959 as part of a forestry experiment – which, of course, failed under the extreme windy conditions and the shallow soils of the Range. The fence remained, and with a few extra supports over the years, has continued to create a snowdrift in spring in its lee.

Just like a natural snowpatch or snowbed in the landscape, the snowfence drift creates a favourable, somewhat sheltered place for specialised alpine plants to live; despite the very short growing season. And like we expected, shrub species (namely Draophyllum muscoides) prefers to live away form the influence of the fence and the more herbaceous, finer species like the protection that the fence provides. John and I have also re-surveyed another (younger) snowfence built in 1993 on the Niwot Ridge, Colorado… its time to see whether the processes and plant responses that have caused change in New Zealand are also operating on the other side of the world. Stay tuned…

Susanna Venn