Changes in pollen production rates in Hinoki stands by tree density, soil fertility and stand age.

在不同密度和不同土壤条件的几种不同密度的钝顶松林中，用凋落物诱捕器研究了雄花、种子和球果的年生产量(按数量和干重)，并估算了花粉的生产量。在此基础上，计算出生产单粒种子所需的干物质(成本)、该成本与平均种子重量的比(比成本)、M/F比和P/S比(以陆地面积为单位的雄花与雌花和花粉与种子的数值比)，并进行比较。重点研究了不同密度的林木与坡地上部和下部的制种系统的差异。在相同土壤条件下，高密度林分、坡面上部或土壤条件较差的林分，在相同的相对密度下，种子生产效率较高。至于林分年龄的影响，26年生和77年生的林分在成本或比成本上没有明显的差异。而26年生林分种子和球果的M/F、P/S比值和干物质生产速率较高。结果表明，幼林比老林具有更高的制种效率。在非丰产的年份，雄花的产生率与树木密度、土壤条件或林分年龄没有关系。

In several Chamaecyparis obtusa stands differing in tree density and soil conditions, annual production rates (by number and dry weight) of male flowers, seeds and cones were studied using litter traps, and the production rate of pollen was estimated. Based on these production rates in a productive year, dry matter necessary for producing a single seed (cost), the ratio of this cost to mean seed weight (specific cost) and the M/F and P/S ratios (numerical ratios of male to female flowers and pollen to seeds on a land-area basis, respectively) were obtained and compared with each other. Attention was focused mainly on the differences in seed production sysytem between various degrees of tree density and the lower and upper parts of a slope. High efficiency of seed production was recognized in stands of high tree density under the same soil conditions and on the upper parts of a slope or under poor soil conditions at the same relative tree density. As for the effects of stand age, no differences in cost or specific cost between stands 26 and 77 yr old were evident. However, M/F and P/S ratios and dry-matter production rates of seeds and cones were higher in the 26-yr-old stand. These results indicate a higher efficiency of seed production in the young stand than in the old stand. In an unproductive year, there were no trends in the production rates of male flowers in relation to tree density, soil conditions or stand age.