关键词: 光皮桦木, 扁穗牛鞭草, 细根, 草根, 生物量

Abstract: On the basis of the research of the fine root of the Betula luminifera-Hemarthria compressa compound mode and grass root biomass in Hongya county, Sichuan province, we discuss the underground spatial distribution pattern of this mode. The result shows:on horizontal distribution, the difference between the fine root and grass root in every diameter is small, the curve of the biomass of the living fine root is coincident with that of the grass root grow th on horizontal distribution in a way, which shows:100 cm > 150 cm > 50 cm;the living fine root (diameter 1~2 mm) on horizontal distribution takes on the shape "V", with horizontal distribution change of 50 cm > 100 cm > 150 cm, while on vertical distribution the difference is notable. The biomass of the living fine root on upper layer (diameter 0~1 mm) takes 63.73% percentage of the whole root, the biomass of the fine root on the whole upper layer takes 40.02% and that on the lower layer takes 59.98%;and at the same time the upper layer biomass of the grass root takes 81.27% percentage of the grass root, which means that the gross of the grass root makes the greatest contribution to the total biomass. The curve of annual dynamic growth change of the fine root of diameter 0~1 mm and diameter 0~1 mm and gross root is consistent, showing a single-apex line. The changes of the spatial distribution show that in the 0~10 cm layer, there is competition between the Betula luminifera and Hemarthria compressa to some degree, while under 10 cm, there is no competition at all. So Betula luminifera has been collocated with Hemarthria compressa and the competition on biomass accumulating underground is symbiont.

Key words: Betula luminifera, Hemarthria compressa, fine root, grass root, biomass