NITROGEN TURNOVER AND DRY-MATTER PRODUCTION OF A SOLIDAGO ALTISSIMA POPULATION

抄録

An attempt was made to specify the sessonal patterns of dry-matter production and nitrogen assimilation of a Solidago altissima population, with special reference to the method. The population as a whole was regarded as a pool of matter (dry matter or nitrogen), the size of which (standing crop, S) grows or declines as the resultant of changes of the rates of inflow (R_<in>) and outflow (R_<out>) of matter. These quantities-S, R_<in>, R_<out>-were determined seasonally. "Turnover rates" (r_<in>, r_<out>), ratios of the inflow and outflow rates to the standing crop, were calculated. The fact that turnover rates of nitrogen are much lower than those of dry matter suggests that nitrogen is more efficiently utilized than dry matter for the population growth by its recycling in the plant body. This was substantiated by determining the matter mobilization between component organs. Finally, "nitrogen utility index" (NUI) as the dry-matter productivity of a unit amount of nitrogen newly absorbed was introduced to elucidate the relationship between dry-matter production and nitrogen assimilation of the plant population.