密度对刺槐幼苗生物量及异速生长模式的影响

The aboveground and underground biomass and allometry relationship between plant height and stem diameter of Robinia pseudoacacia seedling under different planting density were studied. Experiments were designed for cultivated R. pseudoacacia seedling under different planting density （including row spacing 30 cm, and planting distance 15, 20, 25, 30 cm） in March 2005. The seedlings were watered and fertilized regularly to maintain growth under limited resources. At the beginning of September 2005, the seedling leaves, stems and roots were harvested and weighed separately to obtain the wet and dry biomass. The result showed that the biomass of roots, stems and leaves of R. pseudoacacia increased with planting distance increase under row spacing 30 cm. Ratio of root to shoot of R. pseudoacacia increased with planting distance increase, and was all less than 1 under different planting distance. Ratio of root to shoot of R. pseudoacacia was significant between planting distance 15 cm and other distances, but not significant among planting distance 20, 25 and 30 cm. The less effects of low density on aboveground biomass, underground biomass and resource utilization of R. pseudoacacia. The plant height and stem diameter of R. pseudoacacia seedling increased with planting distance increase （p<0.05）. Under low density, there is no notable competition between individual plants, the relationship between height and stem diameter show simple allometry and form of its allometric equation is y=a+bx. However, under high density, there is strong intraspecific competition between individual plants, the relationship between height and diameter is nonlinear allometry and its allometric function can be expressed as y=ax2+bx+c.