Local Adaptation To Contrasting Climatic Conditions In Sakhalin Fir (Abies Sachalinensis) Revealed By Long-Term Provenance Trials

Conifer populations across wide geographical ranges often demonstrate adaptation to local environments related to heterogeneous climatic conditions. Long-term provenance experiments are powerful tools for evaluating transfer effect and detecting a home-site advantage in transplant performance. The transplant responses of Sakhalin fir (Abies sachalinensis), which is widely distributed in the boreal forests of Hokkaido, northern Japan, were evaluated by >30-year-old provenance trials using seed sources throughout Hokkaido and conducted at two sites, namely Akkeshi (AKS) and Bibai (BBI), with contrasting conditions in climates of snowfall in winter and sun exposure in summer. Intraspecific variations among seed sources were observed in survival rate, tree height, diameter, and volume (V) at the both sites. To test the home-site advantage, we used the transplant performance (survival rate x V) and two transfer distances; the geographic horizontal distance (GDIST) between seed sources and the sites; as well as the environmental distance (EDIST) that was calculated from principal components of candidate climatic factors. In general, the decrease of the transplant performance with increasing transfer distance was detected at the both sites, thus indicating the remarkable home-site advantage of this species. The best models using EDIST at site AKS and using GDIST at site BBI were selected, and larger transfer effect was predicted at site AKS. Distinct adaptive divergence among seed sources at site AKS was consistent with already known intraspecific variations in juvenile-growth and some tolerances to snowfall-related stresses. The climatic gradient associated with winter conditions in Hokkaido might involve asymmetric local adaptation in A. sachalinensis.