Programmes to select and improve genetic material, whatever stage reached, must be supported by measures to ensure that adequate quantities of the desired reproductive material continue to be produced, and that improvements in genetic quality are maintained.
All activities that conserve and improve seed sources will also help to ensure that seed or vegetative material is made available. Production from natural and planted stands can be improved by establishing dedicated seed production areas and using techniques such as thinning to improve crown size and promote flowering, fruiting and vegetative growth, and remove undesirable phenotypes. Special grafted seed orchards can be established to concentrate production and make harvesting easier, since grafts can produce seed earlier and at a smaller size than trees raised from seed.
There are many biological constraints to tree seed production. Flowering and seed production of forest trees is often erratic, and so far cost-effective methods of stimulating seed production have not been devised, as in agriculture. Even if fruiting is abundant, actual pollination may be poor so that many seeds are empty. The actual time of seed harvest is important to ensure that seed is at its peak physiological maturity. Tackling these constraints requires a good understanding of the reproductive biology of the species.
