Long-term performance of Norway spruce in two provenance trials in Latvia

Norway spruce is economically important tree species in the Baltic Sea region, covering large areas and being productive in pure plantations. The species is often regenerated with planting. It is important to choose not only productive, but also robust reproductive material with good adaptability, hardiness and quality traits. The use of appropriate transferred provenances can be an option to increase forest productivity at final-harvest moment. Thus, it is necessary to know long-term fitness of different seedlots. We examined two provenances trials in Western and Eastern Latvia at the age of 34 and 29 years, respectively. We assessed effect of provenance on growth performance, stem quality, and budburst time. In milder climate of Western Latvia, superior growth showed northward-transferred later flushing provenances from the Carpathian Mountains and Lithuania, resulting in by up to 32 % higher yield than the trial mean. No advantages were observed for early flushing Western Russian seedlots facing southward transfer. Latvian provenances showed variable performance regarding productivity and stem quality. In harsher climate of Eastern Latvia, selection of productive local seedlots seemed reasonable option due to relatively lower probability of trees with stem defects comparing to transferred material.