Summary: In 1972 the Jastrebarsko Forestry Research Institute joined in the international project (IUFRO) for studying the provenances of Sitka Spruce (Picea sitchensis) in Europe. Seed samples were obtained with the help of the Seed Husbandry Centre Humlbek, Denmark, which organise the procurement and distribution of seeds for the majority of European countries. The research programme includes 14 provenances of Sitka Spruce from the USA and Canada (Table I). Seed samples were sown in the Spring of 1974. Saplings 2+0 years old were transplanted into seedbeds in the Spring of 1976, where they were cultivated for the following two years. In the Autumn of 1977 seedlings 2+2 years old were transferred to a field experiment. The experiment was established in the region of the Varaždin Forest District, G.j. Vinica-Plitvica, Compartment 25. It is a region with a humid climate, soil is dystric cambisol on gravel, height above sea-level approximately 240 m, eastern exposition. With regard to vegetation it is a region with forests of Sessile Flowered Oak and Common Hornbeam (Querco carpinetum croaticum Horv.)The experiment was established in a randomised block design with four replications, spacing between plants 2x2m. From each provenance 676 plants were planted (13x13 rows x 4 replications). Results of measuring in the 5th and 10th years after establishment of the experiment have been published (Orlić, Ocvirek, 1990). This paper presents the results of the last measuring, i.e. in the 18th year after establishment of the experiment.
The results of the last measuring show that those from the Federal State of Washington (prov. 3003, 3005 and 3006) were among the best provenances, approximately 47 degrees of northern latitude and from lower heights above sea level. The provenances from British Columbia (prov. 3060 and 3064 and South Oregon (prov. 3016) showed the worst results, i.e. from the northernmost and southernmost regions of natural range. With regard to stem quality and branching characteristics (straightness, sweep, branching characteristics, vitality) none of the provenances were entirely satisfactory. On the basis of the results of the last measuring extensive introduction of Sitka Spruce into the forests of north-west Croatia is not recommended.
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