Above the Tree Line
by Tim Clifford
The restoration and expansion of montane scrub may have wide ranging ecological benefits and it provides an important element to enhance the biodiversity of any forest habitat network.
When I came to the Highlands of Scotland in 1983 I was aware that much about Scotland's native forests was 'incomplete'. The patches of forest were too small; they were isolated from each other so that woodland species could not easily move from one patch to another; there was little new regeneration; most woods no longer had a shrub understorey; many had only one scattered generation of old and senescent trees; there wasn't much deadwood habitat; most of the ground vegetation was grazed flat; and large mammals such as beaver, lynx, wolf and bear had long since become extinct.
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!
This was brought home to me sharply at the beautiful ancient pine forest of Espellandsdalen at the head of the massive Hardanger Fjord. 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.
The real eye-opener came as we reached the upper part of the forest. 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. There were tiny fragments of stunted woodland of birch, rowan and eared willow clinging to inaccessible cliffs above the pinewood at Beinn Eighe, and dwarf shrub heath higher up the hill, but no natural transition zone between the woodland and the high- altitude heaths.
Did Scotland ever have a full natural progression of vegetation zones? An eminent ecologist, Derek Ratcliffe, seemed to think 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."
Proving this montane scrub habitat once existed more extensively in Scotland is, however, difficult.
There are three sources of information that can be used in a historical reconstruction: documentary records, plant remains that have been preserved in peat, and pollen grains. Unfortunately no documentary evidence or plant remains have been found to support the former existence of extensive montane scrub communities since the last deglaciation about 11,000 years ago. Pollen analysis has taken place in the Highlands but it is hard to distinguish the pollen of the montane willows and dwarf birch from the willows and birches that grow at lower altitudes. Nevertheless, evidence from sites in northern Scotland, where grazing exclosures have been established, suggests that herbivores can significantly reduce both the extent and vigour of these communities. In terms of soils and climate, there are still extensive areas of the Scottish uplands suitable for this habitat.
A major seminar on the ecology and restoration of montane scrub habitats was organised by Highland Birchwoods in 1996, as part of the Millennium Forest for Scotland project. The proceedings of this conference were published to form a base-line on our current knowledge and understanding of this habitat. From this beginning a Montane Shrub Action Group has been established and is busy raising the profile of the habitat and the issues associated with its management and expansion. An important pre-requisite for effective conservation action is consistent high quality information on the extent, distribution and current condition of our existing montane scrub communities. In many cases these are our last remaining links with primeval scrub communities and are reservoirs for other rare and vulnerable wildlife. They are a finite resource which it is unlikely that we can re-create once lost, and they must therefore be the priority for conservation action. Trees for Life has already made an important contribution to this with the establishment of numerous exclosures in Strathglass and Glen Moriston. The recent completion of a survey of dwarf birch on the Balnacarn and Wester Guisachan estates, and other initiatives are underway on a wider scale, including scrub surveys and experimental grazing exclosures to encourage regeneration.
At the landscape or catchment scales the restoration and expansion of montane scrub may have wide ranging ecological benefits and it provides an important element to enhance the biodiversity of any forest habitat network. Small mammal populations would likely increase, with benefits for those predators that hunt them, the specialised insect fauna that feeds on the different scrub species such as juniper and dwarf birch could increase and colonise new areas, cover and feeding would be provided for migrant birds and this increased cover might encourage more breeding by scarce nesting birds such as redwings, fieldfares and bramblings. Additionally there could be benefits for soil conservation, water quality, fisheries, and possibly even for hill farming in terms of improved shelter and the effects of enhanced soil water regimes on the quality of the grazings on higher altitude marginal land.
So what do we still need to do? We firstly need to recognise that this habitat is an integral part of the overall forest ecosystem and as such must be fully incorporated into any ecological restoration project targeting native forests in the uplands, and preferably also into any forestry proposals incorporating suitable hill ground. In this way we can ensure that montane scrub will play an important part in the development of forest habitat networks that encompass not only remote wilderness areas and nature reserves but also the wider working upland landscape with its farming, forestry and tourism interests.
Intrinsic to this is an acceptance that, whilst the main drive for the restoration of montane scrub is always likely to be the aesthetic vision of restoring Scotland to its full ecological potential, people are very much part of the ecosystem. Indeed in many parts of rural Scotland this ecosystem may only flourish if local communities develop a 'sense of ownership' and become actively involved in its management.
We must also accept that the restoration and re-creation of this lost habitat will only happen at any reasonable scale if financial incentives are provided for this and if these are at least as attractive to land owners as incentives for alternative land uses. With the publication in 1998 of the Forestry Commission's Guidance Note, Treeline Woodlands and the Woodland Grant Scheme, and confirmation that Woodland Grant Scheme funding may be available in certain circumstances to support the expansion of woodland and scrub above the commercial timberline we have moved a significant step towards this.
This is an edited version of an article, Bonsai Forests and a 'Cinderella' Habitat, which was first published in Caledonia Wild! Spring 2000, the newsletter of Trees for Life.
Tim Clifford serves on the Board of Directors of Trees for Life, and is a professional conservation biologist who has worked for government conservation agencies and NGOs across Britain. He has wide practical experience of the management of woodland habitats including Caledonian pine forest, Atlantic oakwoods, upland birchwoods, and in the management of national scale forest restoration projects. For twelve years he was Warden of Beinn Eighe and Loch Maree Islands National Nature Reserves in Wester Ross. Since 1995 he has worked as Project Manager for the Caledonian Partnership, an innovative broad partnership of voluntary conservation organisations and government forestry, conservation and research agencies led by Highland Birchwoods. He also manages his 30 acre forest smallholding in Strathglass.
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Published: Caledonia Wild! Spring 2000
Last updated: 25 August 2010