John Fennessy (COFORD, Tree Improvement Programme Manager), Jason Hubert (Forest Research, Improvement of Broadleaves), Sam Samuel (Forest Research, Genetics), Peter Savill (Chairman of BIHIP)
There are three ways of improving the genetic quality and productivity of your broadleaved forest:
- by using seed from the most appropriate provenances
- by collecting seed from registered selected superior stands
- by breeding improved trees from individually selected ‘elite’ or ‘plus’ trees
A potenial seed stand of Oak (Quercus petraea), in Normandy, France
This short paper is concerned mainly with the second of these three options. The first is normally observed anyway with broadleaved trees, since only native and reasonably local provenances are used that should be well adapted to the local conditions.
Considerable progress has also been made with the third (tree breeding) in recent years, but quantities of seed currently available are still very small because breeding programmes are at such an early stage of development. As genetically superior seed becomes available from seed orchards, the need for seed stands will decline and may eventually vanish.
Gains achieved by using seed from selected stands
Selected seed stands need to contain trees with superior and desirable visible characteristics. Before they can be used for seed collection, the forestry authorities responsible for the Forest Reproductive Material Regulations will inspect the stand to confirm its acceptability for inclusion into the National Register. All seed collectors must also be certified by the forestry authority. (See Stop Press)
The progeny derived from an excellent stand of trees will generally out-perform unselected stock. This has been clearly demonstrated for Oak in field trials. The advantages of raising plants from seed collected from selected stands are that it is cheap and can be applied immediately while more intensive methods of breeding usually require a much longer time and are carried out in parallel.
The gains achieved by using seed from such stands are not particularly well documented because they are rarely progeny-tested. For any individual character, they are probably in the region of 2 to 5% compared with unselected seed from a suitable provenance.
Though these improvements may appear modest individually, improving several characteristics simultaneously in the same generation can have much larger additive economic effects so they can result in significant returns as a consequence of increases in recoverable timber per tree. This can be particularly important for broadleaved trees where a small increase in overall quality of the stand can result in a very large increase in value.
There are also advantages to the owners of selected seed stands. In 2006, for example, unselected Ash seed was selling for about £12/kg, while £35/kg was paid for seed from selected stands; for Birch the prices were £85-90/kg for unselected, and £130- £150/kg for selected seed.
Management of seed stands
Seed stands are usually managed to produce large quantities of healthy seed by, for example, thinning to favour the best potential parents, and removing nearby sources of genetically inferior pollen. This procedure leaves only the good trees to interbreed. Seed stands are registered by the forestry authority. The seed from them generally has the following characteristics:
- it produces plants with better genetic qualities than seed from unselected stands in terms of adaptability, vigour, stem and crown characteristics and pest resistance
- the geographical locations of the parent trees are known, and information is available to the grower about the soil and climate of the parent stand
- selected seed provides a reliable source of welladapted plants at a modest cost
Though the cost of seed from selected stands may be several times that of unclassified seed, it is modest compared with the advantages to be gained from using it. Seed costs are only a minute proportion of the total establishment costs and should not be the determining factor when deciding between different seed sources.
Straightness and branching are heritable characteristics as these two roadside stands in the Netherlands illustrate
Ideally a potential seed stand should be fully stocked, and, for broadleaves, contain 50-75 trees ha. They should be of an age to produce seed. The trees should be:
- Well-grown dominant or co-dominant trees of above average quality, with large uniform crowns
- Vigorous
- Straight stemmed with little taper, no spiral grain or significant buttressing, or fluting
- Have a desirable branch form (fine and at a flat angle), with good natural pruning
- Free from insect and disease attack
The minimum area should be about 2 ha (a population of at least 200 trees is preferred) to minimise contamination from outside pollen, though smaller areas are sometimes acceptable.
To maximise seed production, it is important that the crowns of seed trees are released to full sunlight on at least three sides. Selective thinning of the poorest phenotypes is the recommended form of management for selected seed stands, even if this results in gaps.
In Great Britain, owners, or their agents, can apply to have a stand considered for inclusion in the National Register. Details can be obtained either by writing to Cathleen Baldwin at Forest Research, Northern Research Station, Roslin, Midlothian, EH25 9SY, or from the Forestry Commission website. If using the website search for “national register”, the first link under general information provides details of the register and a FRM1A form can be downloaded to make an application. The second page of this form gives fuller guidance on the requirements for registration. The full National Register is now available from the website as a pdf file and is an essential source of information for growers when considering what to buy.
In Ireland to have a stand registered the owner should contact the Forest Protection and Forest Reproductive Material Section of the Forest Service who will then arrange for the stand to be inspected. If the stand meets the selection criteria it will be issued with a Stand Number and be added to the National Register.
STOP PRESS
The Forestry Commission announced in late February 2007 that charges for inspecting and registering potential seed stands will be abolished. There has never been a charge in Ireland.