GROWTH VARIATION OF NORWAY SPRUCE (PICEA-ABIES (L) KARST) CLONES IN LOWER SAXONY

Growth of 2820 Norway spruce clones was followed on 6 field test sites in Lower Saxony, Northern Germany, up to age 17. Clones selected from Scandinavian provenances were significantly inferior to clones selected from Central European provenances (Tab. 1). However variability of clonal means of both groups in considerable and the best clones only differ by 10 % in height and diameter. The tested clones show significant variation in growth (Fig. 1) and stability. In height 18 % of the clones contribute more than 50 %, in diameter 14 % of the clones 40 % to genotype x site interaction. Clonal influences explain 43 % in height variation, 60 % in diameter variation and 61 % in single stem volume variation. Under the present selection system (top 20 %) the realized gain at age 17 is 9 % for height, 24 % for diameter and 70 % for single tree volume (Tab. 3). Early selection at age 4 results in 60 % of the gain realized at age 17. The gain under early selection becomes more predictable with groups of clones up to 30 to 50 clones (correlation coefficient > 0.95; Fig.2).