Abstract
The Nezasa type grassland is spread over infertile soils of Aso mountain area, and Nezasa grows well in deciduous broad-leaved forests in Kyushu, south western Japan. To understand the growth characteristics of Nezasa growing in such poor environment, seasonal changes in the amounts of standing crop, nitrogen, and potosynthetic rates of Nezasa were measured. 1. Nezasa growing in forests Nezasa growing in forests from May to June had a high photosynthetic rate under low light intensity (0.68 mgCO_2・s^<-1>・m^<-2> under the condition of 600 μmol・s^<-1>・m^<-2>) and transferred the large amount of photosynthate into a small number of culms. The rapid elongation speed of the culm (1.3 cm/day) in spring is considered to be a consequence of this. These growth characteristics of Nezasa seem to be an important factors in the development of Nezasa-dominamt communities in forests. 2. Nezasa type grassland in infertile soil even though the amount of nitrogn absorbed from soil was small (0.84-1.03 mgN・m^<-2> from April to August), a lot of nitrogen was stored in underground plant parts at the start of the growing season (8.18-9.27 mgN・m^<-2>). Nezasa then transferred stored nitrogen to aboveground plant parts in the first half of the growing season (1.60-1.68 mgN・m^<-2>). In autumn, the nitsogen in the aboveground plant parts was again translocated to underground plant parts. This characteristic of Nezasa is an important element to preserving Nezasa type grasslands in the infertile soil of the Aso mountain area.
