GROWTH TRAITS AND YIELD OF BETULA-MAXIMOW ICZIANA REGEL PROVENANCES

Within the scope of studies on the suitability of exotic forest tree s pecies for Central European sites 2 collections with more than 100 sin gle tree progenies from a total of 21 and 16 provenances, respectively , of the East Asian Betula maximowicziana were planted in trials durin g the past 35 years. The seedlots used were collected exceptionally in the natural distribution area of the Japanese islands Hondo and Hokka ido. The evaluation of the 10 field trials located in Schleswig-Holste in, Lower Saxony, and Hesse gave the following results: B. maximowiczi ana is during the early phase a fast growing tree species with straigh t, cylindrical stems and good self-pruning. Height and diameter growth are strongly influenced by site conditions. The growth performance is better on fertile and moist sites than on poor soils. Dry summers cau se mortality and growth depressions. There were statistically signific ant differences between provenances and regions of provenances, respec tively. Provenances from the southern part of the natural distribution in the region ''Nagano'' in the centre of Hondo differed from the oth er provenances by - growth performance above the trial mean; - later f lushing in spring and - later growth cessation in autumn. B. maximowic ziana stares flowering with male flowers at the age of 8 years. Female catkins and germinative seeds were observed rarely at an age of more than 30 years. Natural regeneration did not occur. Timber yield was be tween 130 m(3)/ha and 195 m(3)/ha at age 35 with an annual increment o f about 4 m(3)/ha to 6 m(3)/ha. The wood proper ties of B. maximowiczi ana are not different to those of the 2 native birch species. Summariz ing one can say that B. maximowicziana is a species relatively pretent ious in relation to nutrient and water supply. Considering the right s ite conditions this exotic broad-leaved tree species could be interest ing for forestry.