Ever walked uphill through British woodland onto the open moorland above? The chances are that you will have passed through an abrupt boundary between trees and open ground.

In a natural setting, trees gradually phase-out through the treeline, becoming stunted and twisted due to the more extreme conditions. In the mountain areas of Scotland (and rarely in northern England) this is where you may find specialist montane scrub species. These species of trees are just as important as the main woodland species – to create a full and natural woodland we must understand their relationship with the landscape. This is why we partnered with the Mountain Woodland Project to collect seed, monitor growth, undertake experimental work and aid regeneration.

This is how the author Tim Clifford described his discovery of the mountain woodland habitat…

It was not until I visited western Norway to study native pinewoods in 1987 that I really appreciated that a whole woodland habitat was virtually absent from Scottish forests! At the beautiful ancient pine forest of Espellandsdalen we walked from the valley floor at about 200 metres above sea level, up to just over 800 metres, where forest finally gave way to open ground.

Gradually the forest canopy thinned, open boggy areas with scattered small trees became more frequent, the stature of the main trees reduced and pines and juniper became multi-branched and contorted. Climbing still higher the canopy disappeared completely and the vegetation became a mosaic of gnarled and twisted 2 metre-high birch, various shrub willows, dwarf birch in the damper areas and small peaty pools. We had passed through a real, natural tree line and were crossing a wide montane scrub zone that gradually merged with open vegetation dominated by low growing dwarf shrubs. I’d never seen anything like this on Scottish hills.

Did Scotland ever have a full natural progression of vegetation zones? The eminent ecologist, Derek Ratcliffe, thought so when he wrote:

Originally a fringe of scrub 3-4 feet high girdled the upper edge of the forest. This scrub zone, which has been destroyed almost totally by fire and grazing, gave way still higher up to much lower growths of dwarf juniper, heather and other dwarf shrubs forming alpine heaths.


The mountain woodland project

It’s of great importance to restore these treeline and montane scrub habitats in the Highlands. At our Dundreggan Conservation Estate, where were a partner in the lottery funded Mountain Woodland Project (ended 2017), we have an unusually extensive population of dwarf birch across the higher ground. Our new planting sites extend up to this treeline area around 500m and three exclosures above this height are dedicated to montane scrub restoration. Here we are collecting seed, monitoring growth in the absence of deer browsing and undertaking experimental work to aid regeneration.

Student research projects have included looking at scrub on higher elevation lochan islands; investigating dwarf birch vigour in relation to soils; and genetic studies which are throwing light on the past distribution of dwarf birch in the uplands. Biological surveys have recorded some rare associated invertebrates, including 2 sawflies new to Britain. Our Tree Nursery is growing around 10,000 dwarf birch each year and we are developing our expertise in the propagation of some of the rare montane willows eg. downy willow Salix lapponum and woolly willow Salix lanata.

The process of bringing back the “wee trees” to the Scottish hills has begun; and with this natural transitional habitat comes the associated wildlife, for instance birds of conservation concern like the black grouse and ring ouzel. Natural treelines and montane scrub communities are also good for retaining soils and will help with better water management in the uplands.