The effect of Competing Neighborhood Trees on the Basal Area Increments of Cryptomeria japonica and Chamaecyparis obtuse in a Large Scale Mature Urban Forest in Kyoto city

We examined the growth characteristics of two coniferous species, Cryptomeria japonica and Chamaecyparis obtuse, and the factors that influence them with the aim to provide useful information on the growing of these species in an urban forest. To this end, we investigated all woody stems with a diameter at breast height of 10 cm or larger in the whole area (12 ha) of Tadasu-No-Mori forest in Kyoto city in 2002 and 2010. We then calculated the increase in their basal area (BA) from 2002 to 2010. Subsequently, we examined the relationship between ΔBA and selected factors such as initial BA (in 2002) and neighborhood competition. A positive correlation was observed between log-transformed ΔBA and initial BA for both C. japonica and C. obtuse. The ratio of the BA of C. japonica and C. obtuse trees to that of competitor trees had significant influence on ΔBA for the coniferous species. Both C. japonica and C. obtuse were significantly affected by competitive tree species that stood within 9 m and 13 m radii from C. japonica and C. obtuse, respectively. The model used in this study could offer information such as the density and sizes of competitive trees necessary to promote the growth of C. japonica and C. obtuse.