[en] A study on the radiation and leaf area vertical distribution in relation to the growth of 8-year-old Chinese fir plantations of 5 densities was conducted. The leaf area vertical distribution and LAI were closely related to stem density. The crown form varies from conic to cylindric with the increase of stem density. The LAI rises at first and then declines with the increase of density. The extinction of radiation sharpened when the crown density increased. The extinction leveled at the depth of 3/4 forest heights from the tops of forest canopies. Calculating the extinction coefficients by means of accumulated leaf area index separately for each crown layer can minimize the errors caused by the irregularity of leaf distribution. Four indices, i.e., absorption of radiation, LAI,biomass of individual tree and averaged annual increment of biomass were used to have a comprehensive evaluation on the growth of Chinese fir of 5 densities. The results showed that the plantation with a stem density of 2m × 1 m was the best one among the 5 young plantations

[en] Two kinds of lac insect (Kerria chinensis, K.lacca) were radiated in this radiation experiment. The different stage of lac insect (larva, adult) are radiated by several dosages of Co 60. Tests showed that lac insects in the second stage are all dead after radiation of 500-2 000 rad, female insect of K.chinensis with pregnancy egg time 2-3 stage radiated by 1000 rad can produce new generation. Female insect of K.lacca with pregnancy egg time 5-6 stage radiated by 11 000 rad occasionally produce new generation. The egg amount and amount of secreting lac are similar to those of the normal, effective production and sex ratio are higher than those of the normal, group density on branch is lower than the normal in the generation of K.lacca after radiation. The sex ratio of the female, group density on branch are higher than those of the normal, egg amount and amount of secreting lac are normal in the generation of K.chinensis arter radiation. (author)