Abstract: An investigation was made on the growth indices of Iris japonica growi ng on the yellow soil and Karst soil within a subtropical evergreen broad-leaved forest and in the forest gaps, aimed to approach the clonal plasticity of I. japonica  in heterogeneous habitats. The results showed that the ramet height and diameter and the rhizome diameter of I. japonica were significantly higher in yellow soil habitat than in Karst soil habitat, while the individual density was in adverse. Light had significant effects on rhizome diameter, but soil condition had lesser effects under the same light environment. Within the forest of Karst soil habitat, the bud number and flower number of I. japonica were zero, possibly due to the double pressure from soil quality and light environment for the balance between resources uptake and energy assignment and for the sustaining of growth. In a certain extent, I. japonica  in yellow soil habitat tended to K strategy via decreasing the individual number for improving competition to adapt environment, while I. japonica in Karst soil habitat tended to r strategy via increasing individual number for sustaining competition capability.

Key words: habitat, Iris japonica, clonal plasticity