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Montane scrub and treeline woodlands

This zone of dwarf trees and low shrubs, which once linked forest and open hillside, has almost vanished from Scotland.

In all non-arid mountain systems, montane scrub is an important habitat above the treeline.

As tall forest trees, like pine and birch, begin to reach their altitudinal limit, smaller species become more common and eventually replace them entirely. These trees and low shrubs include juniper, dwarf birch and mountain willows.

Montane scrub:

  • supports a range of unusual plants and invertebrates
  • is an important foraging area for birds and mammals

In Scotland, this habitat is now virtually absent due to grazing by red deer and sheep.

Woolly willow

Woolly or sub-arctic willow (Salix lanata) was once found in the montane scrub of mountains with rich soils. But this low shrub, with its woolly, grey-green leaves, is now largely limited to ungrazed areas at high altitude.

Nearly all of its present localities are in the central Highlands. In 2007, only four of its 13 remaining populations had more than 100 plants, with the total estimated at fewer than 1,800 plants. Conservation work and new planting through the Species Action Framework programme has increased this to five sites with more than 100 plants, and a total current estimate of 2,100 plants.

Woolly willow plants are either male or female, and insects pollinate the female catkins of the plant. Effective pollination, and thus successful reproduction, relies on the two sexes growing within 50m of one another.

Increases in the density of grazing animals, particularly red deer, has led to the loss of woolly willow in Scotland. The species can tolerate grazing at sustainable levels – e.g. at a few sites grazing is limited by very late snow lie.

Scottish Natural Heritage and Royal Botanic Garden Edinburgh planted more than 800 young montane willow shrubs in Corrie Fee National Nature Reserve in 2009. Prior to this, Corrie Fee NNR had the UK’s largest population of montane willow scrub – but the plants were isolated and unable to reproduce.

Woolly willow is a UK Biodiversity Action Plan priority vascular plant species.

Learn more about woolly willow on the NBN Atlas Scotland website.

Find out more

To find out more about montane scrub and treeline woods in general, visit the Montane Scrub Action Group website

How you can help

At several sites across Scotland, people are surveying the mountain woodlands, gathering seed and growing new trees.

Find out about getting involved in the Mountain Woodlands Project.

Further reading

Mountains: Scotland’s Living Landscapes

Montane Scrub: Natural Heritage Management

The ecology and restoration of montane and subalpine scrub habitats in Scotland: SNH Review No. 83