It was decided that a more systematic approach was needed to supplement the birch trails and hence ash and rowan were chosen on the grounds of their wide natural ranges and contrasting reproductive and dispersal systems:
- Ash - wind pollinated and having wind dispersed seeds
- Rowan - insect pollinated and birds disperse the seed.
A collection of ash seed was undertaken in 2003 and rowan in 2004. Where possible seed was collected from two stands of native origin in each native seed zone across Britain as defined in Forestry Commission Practice Note 8. The distribution of the populations sampled can be seen from the maps here:
The seed was stratified for sowing in the spring of 2005 in four nurseries located around GB. At each nursery the seedlings were assessed for their dates of bud burst and leaf fall in addition to growth and survival.
After one year in the nursery the rowan seedlings were planted out into provenance trials at four sites located close to the nurseries for further research. The ash followed a year later.
East Malling Research, who are working in collaboration with Forest Research, are comparing the genetic variation present in the parent populations for both species.
Reciprocal transplant experiments (RTEs)
In an RTE the seed from the local site is planted at that site plus all other sites in the experiment. This allows direct comparison of whether the local seed has any adaptive traits that confer a competitive edge to it in its “home” environment.
Eight RTEs have been established for ash in England and Wales in 2004 to explore the effects of geographic distance, i.e. different climates, and different soil types on survival and growth. These have been set up with David Boshier of the Oxford Forestry Institute as part of the EU funded FRAXIGEN project.