Genotype x environment interactions in Alnus rubra:: developing seed zones and seed-transfer guidelines with spatial statistics and GIS

Multiple provenance trials of red alder (Alnus rubra Bong.) were used to demonstrate how geostatistical methods can be applied to develop better seed-transfer guidelines and seed-procurement zones for forestry. Height and survival of 65 provenances from British Columbia were measured at four test sites. Significant genotype x environment interactions were found at the population and family level. Provenances close to each planting sire showed superior performance in growth and survival, suggesting adaptation of red alder to local environments. The environmental basis of local adaptations was evaluated using redundancy analysis. Geographic and climatic variates accounted for approximately equal amounts of the variation in height growth (21 and 23%, respectively), while geographic variates accounted for 60% Of the variation in climatic variables. Loadings of the redundancy variates suggested that both, gene flow and selection by environmental factors shaped geographic patterns of genetic differentiation in red alder. Performance of seed sources at unknown locations was predicted with ordinary kriging throughout the natural range of red alder in British Columbia. General seed-transfer guidelines were then generated with principal component analysis of predicted reaction norms. We found clinal differentiation of reaction norms along the coast from northwest to southeast. Further, the Georgia depression was identified as an area of genetic differentiation. Based on predicted height and survival at two trials that most realistically represented operational planting sites, we derived simple rules for seed transfer. A transfer of 100 km in either direction along the coast was associated with a decline of 2.5% in survival, and approximate to 5 cm in 2-year height. Finally, we showed how maps of predicted performance and associated variance surfaces can be used to develop seed zones for specific objectives, where seed zones are given as maps of probabilities of a seed source performing above or below a given threshold for any combination of traits. (C) 2000 Elsevier Science B.V. All rights reserved.