Differences in growth and areal production between Norway spruce (Picea abies L. Karst) regeneration material representing different levels of genetic improvement

Abstract

Six groups of Norway spruce (Picea abies L. Karst) plants with varying levels of genetic gain and unimproved local provenances were compared in four realised gain trials at four sites in central Sweden. The groups were planted separately in experimental plots and compared in terms of survival rate and height 4 years after planting, as well as survival rate, height, diameter and areal volume production 13–16 years after planting. The genetically improved groups all produced higher volumes than the unimproved local provenances, and the clonal bulk of 23 full-sib families’ volume production per unit area was 56% higher than that of local provenances. The genetic groups followed expected levels of genetic gain, except for individual clones (which varied substantially in performance) and full-sib families. There were greater relative differences between local provenances and genetic groups in areal volume production 13–16 years after planting than in height at 4 years after planting. The results confirm that growth of improved genetic groups is largely consistent with expected values of realized genetic gain. They also indicate that clonal mixes rather than one or a few clones should be deployed in clonal forestry. The comparison of early measured height with areal production showed that early height measurements are good indicators of realized genetic gain and differences in areal production are greater than early differences in height.