Developments in 2002
At the BIHIP annual general meeting on 24 September, there was some welcome news about funding of projects. Horticulture Research International (HRI) has decided to extend their work on cherry into sweet chestnut, oak, ash and walnut, which will be funded jointly by DEFRA and the Forestry Commission, amounting to £120,000 a year for six years. The focus will be on tree selection, propagation and breeding as appropriate to each species, with two species being focussed on in any one year. HRI will be the lead organisation in this work.
The Forestry Commission has also offered £3000 each during 2002 to the BIHIP oak, ash and birch groups to further their work, with an additional £1000 for administration and management to the organisation currently employing the secretary of BIHIP (the Northmoor Trust).
BIHIP has been attempting to set up a sycamore group for several years, and has at last been successful. Dr Michael Carey, who has recently retired from Coillte in Ireland, will chair it. He will be finding members of the group and developing a plan of work over the next few months.
Silver birch group
In recent years there has been a considerable increase in the planting of silver birch. It has been used in "native woodland" planting schemes and in landscape plantings. Much of the planting stock has been derived from unknown or unsuitable seed sources, which may have been from populations that are not adapted to the new sites, or (were?) locally sourced, from stands of inferior growth rate or stem form.
With these problems in mind, the Birch Research and Development Cooperative (B.R.D.C.) was initiated in 1997, bringing together a group of scientists, landowners, nurserymen and other interested parties. The overall aim was to ensure that silver birch, planted for either conservation or production purposes, would provide good quality timber. An additional aspect was the need to investigate the extent of genetic variation within native tree species, still largely unknown, and for which silver birch was a particularly suitable subject, because of its ease of cultivation and early growth rates. The specific objectives of the B.R.D.C. therefore were:-
- To determine the extent of adaptive genetic variation among populations of silver birch in Britain. This would enable limits to the transfer of seed to be assessed and provide evidence for the proposed "seed zones" for native species.
- To initiate a programme of genetic improvement in silver birch, with particular attention being paid to the traits that influence quality timber production. This programme would have a "regional" basis to avoid the introduction of "exotic" genetic material into local populations.
The basis for the first objective has now been established. In 1995 a collection of seed from 45 locations throughout Scotland and North England was made and the plants produced included in four provenance trials, distributed in different climatic zones across Scotland, with an additional one in S.W. Ireland. In 2001, a further collection from 25 stands in England and Wales was made and these origins are being planted this year in another 4 trials located in East Anglia, Wales and mid-Scotland. These latter trials include a range of the Scottish material and some from N.W. Europe for comparison. Early results show large differences in growth rates among origins and in the time of flushing in spring or leaf fall in autumn.
Funding for this work has been obtained from the Scottish Forestry Trust, Woodland Heritage and the University of Edinburgh, while the trials have been established and supported by the Forestry Commission.
The second objective of developing a breeding programme for silver birch is based on the techniques used in Finland. This involves selecting superior trees (plus trees) in the field, grafting scions on young rootstocks and placing clones in polyhouse "seed orchards" where after three years significant amounts of seed can be produced. In the 1990’s such a seed orchard, at the Northern Research Station, was based on a collection of plus trees from N.W. Scotland and the progeny were included in the provenance trials. To avoid alteration of the "local" genepools of existing silver birch, about 50 plus trees will be selected in a "region", broadly defined in terms of watersheds and climatic factors. Once sufficient seed has been produced to meet the planting needs of that regions for some years, the clones may be stored outdoors indefinitely. If necessary, the boundaries of any "region" may be simply altered by changing the clones in the polyhouse.
In Finland, genetic gains in growth rate and stem form have been up to 25% in their silver birch breeding programme. Similar gains here would transform the economic prospects of the species in the UK.
Sweet chestnut group
In the spring of 2002 the Chestnut Group established the first seedling orchard, a 0.9ha former fruit orchard site on the Maunsel estate in the Somerset levels, south-east of North Petherton. The progeny of nineteen superior (plus) trees were planted out as 2-year seedlings, giving a total of 2,300 trees at 1.37x1.37m spacing. Strong grass growth had been a problem at establishment, but overall survival at the end of the first year has been good.
Flushing times will be recorded in the spring of 2003, followed by stumping back in the winter of 2003/4. After this, full recording of growth parameters will be carried out in subsequent growing seasons. The group are grateful to Sir Benjamin Slade for providing the seed orchard site, and to Bill Blight, forestry consultant, who organised the planting. Bill has subsequently become a member of the Group. Woodland Heritage are gratefully acknowledged for grant-aiding the seed orchard establishment.
The Group’s intention to establish clonal seed orchards of chestnut was recently given a boost by the welcome decision of DEFRA and the Forestry Commission to include the species in Horticultural Research International’s (HRI’s) broadleaved improvement programme. This will enable plus tree collection to continue over the next two years, providing the material to establish two orchards in southern England. The Group is especially keen to hear from anyone who can help them to identify candidate plus trees and high-quality stands.
‘Shake’ in chestnut
In another project partly funded by Woodland Heritage, the incidence of shake in chestnut stands is being investigated by Imperial College at their Wye campus in Kent. Five sites, on contrasting soil types, were selected and a total of 150 trees measured in the range 25-60cm at breast height. Of 136 stems felled in the spring of 2002, 52% exhibited shake to varying degrees. There was no obvious correlation of shake with increasing diameter or height, but stems with epicormic shoots, spiral bark and pronounced curvature were more likely to be affected. Late-flushing trees, and trees that took longer to flush, were also prone. Sound trees tended to grow more rapidly and had wider rings, but, as Peter Savill has shown for oak, the early spring vessels of these trees tended to be narrower in diameter than those with shaken stems.
Shoot tips have been taken from the felled tree sample and grafted on to seedling stocks at HRI, as a prelude to further experimental work. Grafts originating from both shaken and sound parents will now be grown under glass in different moisture and nutrient regimes at Imperial College to assess their response in terms of flushing, senescence, growth and wood structure.
BIHIP now has a much improved and up to date website (http://www.bihip.com/).