101 FAMILIES OF JAPANESE CEDAR (CRYPTOMER IA-JAPONICA DON,D) - ANALYSIS OF GROWTH OVER 50 YEARS

In 1940 some 223 trees were selected in the best stands of Japanese ce dar of each region in Japan. Seed were collected, kept separately by t rees and sown in April 1941. Three years later 50 young trees from 101 families, which were selected out of the total of 223, were planted i n a row at the trial site Tsukawayama in the prefecture of Okayama. Me asurements of height and diameter have been made at intervals up to th e age of 50 years. At age of 23 and 40 the trial plantation has been t hinned. After 50 years of growth 1721 trees were left and the results based on single tree volume have been analysed in a simple and plausib le way. The best family out of 101 reached 1.142 m(3) per stem, which is 171.5% of the standard (0.666 m(3)), the worst family 0.271 m(3) or 40.7% respectively. Three from a group of the 20 best trees at age 50 (Table 2) have also been best at age 15. The other 17 trees joined th e group at different ages between 15 and 50, showing that good 'late g rowers'' can catch up. On the other hand, from another group of 20 tre es best at age 15, only 3 were able to maintain within the group at ag e 50, showing that ''early growers'' often loose their growth potentia l (Table 3). Four types of growth behaviour can be distinguished: Wase typus = trees grow strongest at young ages, Okute typus = trees grow strongest at older ages, Dauerzuwachstyp = trees grow strongly at all ages, Nicht-Dauerzuwachstyp = trees don't grow strongly at all ages. F ield trials, therefore, should be observed for a long time to get reli able results, in this case 40 or 45 years.