Key Topic 3
Adaptation for natural regeneration and ecological restoration

The questions we aim to answer within Key Topic 3 are:

1.At what scale does local adaptation occur in three Fraxinus species, and how does this relate to genetic, environmental and geographic distance?
2.Is the scale of adaptation revealed by reciprocal transplant experiments under conditions of natural regeneration similar to that shown in plantation provenance trials?
3.How well does the scale of adaptation relate to existing defined provenance zones and guidelines for sourcing and certifying reproductive material?

Key Topic 3 will estimate the scale of "home-site advantage" (localised adaptation) among populations of Fraxinus excelsior, F. angustifolia, and F. ornus through establishment of a network of trials. Local populations are seen by policy makers as desirable for both conservation and genetic improvement efforts, although defining the limits of "local" is problematic. An additional issue associated with the current shift in Europe towards planting for environmental objectives is that germplasm selection for production forestry is generally based on growth, form and other commercial criteria. In contrast, planting/regeneration under more natural conditions, for instance for ecological restoration, requires an emphasis on different traits such as reproductive vigour, seed and seedling survival, ability to compete with other species, and long-term adaptation. Furthermore, domestication and selection for plantation forestry may compromise adaptive capacity, either through inadvertent selection against such traits, or simply through loss of genetic diversity. A principal aim of Key Topic 3 will be to provide recommendations on seed source selection for natural regeneration and ecological restoration of Fraxinus species within Europe.

Reciprocal transplant experiments (RTEs), which directly estimate localised adaptation to environmental heterogeneity by testing the fitness of "home" and "away" genotypes within the sites from which the genotypes originate, will be used to study adaptive variation in trees. In subjecting the plants to more natural conditions than in most provenance trials, it is possible to study responses to natural processes within the environment at each site, including competition with the native flora. Traditional forestry provenance trials are, in particular, poor at estimating survival at the seed/seedling phase, when there is the highest mortality risk, and therefore the greatest opportunity for selection to occur. A direct seeding trial will therefore be established to study the initial germination, establishment and growth periods, a phase where natural selection is severe. Most reciprocal transplant experiments of plants (grasses, herb and shrub species) have identified localised adaptation at the finest scale examined (ranging from 20m to 8km). The extent and scale at which adaptation occurs in trees is, however, uncertain as few truly reciprocal transplant experiments have been undertaken on trees. Because F. excelsior occurs in a wide variety of site types ranging from heavy lowland soils to thin upland redzinas over limestone, it is likely to exhibit localised adaptation.
At each site two experiments will be established: a) direct seeding, b) seedlings.