For the purpose of obtaining ecological information necessary for vegetation management after clear-cutting, the mortality rates and tree height growths of the pioneer tree species, Mallotus japonicus, Zanthoxylum ailanthoides, Clerodendrum trichotomum and Aralia elata were investigated in a suburban secondary forest. In addition, the relationships between growth characteristics of these four species and initial size, surrounding competitive tree density or site environment were examined. As a result, the mortality rate was the highest for A. elata at 16.4%/year, followed by C. trichotomum at 10.1%/year and M. japonicus at 8.3%/year. On the other hand, it was the lowest value of 1.2%/year in Z. ailanthoides. The highest mean value for the relative growth rate of tree height was 0.139 cm/cm/year in Z. ailanthoides. The next highest was 0.089 cm/cm/year for A. elata and 0.056 cm/cm/year for M. japonicus. C. trichotomum had the lowest mean value of 0.035 cm/cm/year. For the four tree species, under the same conditions for tree height class and soil moisture content class at the habitat, the relative growth rate of tree height tended to decrease as the density of competing trees increased. On the other hand, the effects of soil moisture content at the habitat on the mortality rate and the relative growth rate of tree height were not clear for the four species.
