The woolly willow (Salix lanata) is a low shrub with woolly, grey-green leaves. It is now restricted to ungrazed areas at high altitude.
Habitat, distribution and abundance
In all non-arid mountain systems, montane scrub, consisting of species like woolly willow, is an important habitat above the tree line. Montane scrub supports a range of unusual plants and invertebrates and 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 formerly occurred in the scrub zone at the upper limit of forest on those mountains with the richest soils. However, it is now largely restricted by grazing to mountain cliffs. Nearly all its present localities are in the central Highlands. Only four of its 13 remaining populations have more than 100 plants and the total is estimated to be less than 1800 plants.
Woolly willow occurs at high-altitude in association with species-rich vegetation on base-rich soils. It occurs as either male or female trees ('dioecious'). Unlike other native catkin-bearing trees, the female catkins of woolly willow are insect-pollinated rather than wind-pollinated. The species can live with grazing at sustainable levels, as demonstrated by those few sites where grazing is limited by the nature of the ground, for example areas where there is very late snow lie.
History of decline, contributory factors and current threats
Montane willow scrub, of which woolly willow is part, once formed an important ecotone above the upper altitudinal limit of forest. Increases in the density of grazing animals, particularly red deer, has led to the loss of woolly willow in Scotland. The remaining populations of woolly willow are restricted to inaccessible areas, and are small, isolated and vulnerable to chance disasters.
Last updated on Wednesday 3rd June 2015 at 16:18 PM. Click here to comment on this page