A database of Native Tree Seed Sources in Scotland: by Scott Wilson for The Scottish Forestry Trust.

This article first appeared in the Reforesting Scotland Journal.

With the recent increase in planting of new native woodlands in Scotland, there has been corresponding interest in finding sources of locally native planting material. This has highlighted the incomplete scientific knowledge we currently have of the distribution and population genetics of our native tree species (with the exception of Caledonian pine). Against this background there has been a lot of discussion as to how the sourcing of locally native tree planting stock should best be organised and regulated.

During the last two years the Forestry Commission (FC) has reacted to the heightened interest in local seed origins by producing a Practice Note (Herbert et al, 1999) on the subject. This presents a map of 'Local Seed Zones' for native tree species covering the whole of the UK and sets out a scheme of voluntary certification for locally-collected seed. These provisions operate in addition to the Forest Reproductive Materials Regulations (FC, 1987) which cover certain native species, including Scots pine and oak in Scotland. How the new scheme will affect the supply of native tree seed remains to be seen, but it seems likely that there will be demand for planting stock from specific Local Seed Zones.

The project

The Scottish Forestry Trust responded to these information needs by creating a comprehensive database of natural tree populations in Scotland which have the potential to act as sources of native seed. This was an eighteen-month independent project which I conducted on behalf of the Trust with the valuable advice of colleagues Dr Douglas Malcolm (formerly of Edinburgh University Forestry School) and Dr David Rook, Director of the Trust.

Methods

The tree species included in the project were Scots pine, sessile and pedunculate oaks, silver and downy birches, ash, alder, wych elm, aspen, hazel, rowan, holly, juniper and wild and bird cherries. The objective was to identify at least forty populations for each species, spread throughout its natural range in Scotland to represent the various Local Seed Zones. The populations should ideally contain at least thirty unrelated individuals, to ensure that sufficient internal genetic variation is represented. The work began with a review of the published scientific literature on the population genetics of native tree populations and their conservation. The literature for Scotland specifically is rather limited, mainly relating to Scots pine and to a lesser extent oak, birch and aspen. For this reason, published literature from the rest of the UK and beyond was also studied. A review was then undertaken of unpublished native woodland survey records held by a variety of parties, including the Forestry Commission, Scottish Natural Heritage, voluntary conservation agencies, nurseries, seed collectors and researchers. This produced a large register of candidate populations for inclusion in the database. The majority of these populations were then visited in the field in the summer of 1998 and spring of 1999 to confirm their suitability and to record site ecological details. Where populations were already recorded on a species-specific inventory, such as the Forestry Commission Caledonian Pinewood Inventory (FC,1998), it was not always necessary to revisit them.

Results

The final version of the database has now been prepared. This records details of some 800-900 tree populations, with almost all species having passed the target of forty populations, some by a considerable margin. Site photographs taken in the field for many populations can be examined in association with the database. Distribution maps for each species can be readily generated and used to query the database through a Geographical Information System (GIS).

Implications

The project has highlighted certain issues relating to the genetics of native tree populations which require further research. These include:

the degree to which native tree populations are adapted to local ecological conditions within Scotland ('adaptive variation');

the genetic structure, history and viability of native tree populations; and

the possible need for specific measures to conserve genetic diversity of native trees through seed movement controls and establishment of ex-situ gene-banks.

The populations recorded on the Scottish Forestry Trust database can now form the basis for future research work in these areas, as well as providing numerous potential sources of native seed for woodland planting.

Owner consultation

The Scottish Forestry Trust undertook to consult all owners of tree populations selected for inclusion on the database before any information was made public. This process has now been completed, with many hundreds of owners having been contacted, of whom a large majority agreed to publication of site locations. It should be emphasised that those wishing to collect seed from woodlands should always obtain the permission of the site owner at the time, before proceeding. In some cases seed may not be available for collection or owners will wish to charge for seed.

Publication

The Trust has recently published an independent report of the findings of the project, including listings of many natural populations for each native tree species (Wilson et al, 2000) Those wishing to obtain a copy of the full report, entitled 'Locations of populations of Scottish native trees', should contact the Scottish Forestry Trust (Director Dr David Rook) at 5 Dublin Street Lane South, Edinburgh EH1 3PX. Tel 0131 478 7044. The cost of the report is £12.50.

In addition, the Trust has agreed to make copies of the database itself available to three research organisations - Forest Research, Scottish Natural Heritage and the Royal Botanic Garden, Edinburgh. These organisations are expected to have particular use for the extra ecological information about each population which it was not feasible to include in the published report.

A fuller description of the methods and scientific results of the project was also published in Scottish Forestry (Winter 1999 issue - Wilson et al 1999), although this article does not present listings of the individual populations recorded.

Dr Scott McG. Wilson is a freelance forester and forest ecologist providing a scientific consultancy service throughout the UK in the fields of ecological forest planning and silvicultural management. The Scottish Forestry Trust is a charitable trust which was established in 1983 to promote education, training and research in forestry and silviculture. For contact details see the treetrader subscribers page Dr. Scott McG. Wilson, Consultant Forest Ecologist and Soil Scientist.