The purpose of this study is to analyze the data of root biomasses measured in a sapling cultivation experiment reported by Oda et al. (2009). In the experiment, Eucalyptus rudis × E. camaldulensis, E. camaldulensis and E. sargentii were cultivated in a glasshouse at Tsukuba, Japan, and those were watered with 0, 100 and 200 mmol-NaCl/L solution. The dry weight of the roots tended to decrease with increase of NaCl concentration. The significant relationship were observed between the tree height and the dry weight of the roots (r = 0.818-0.851, p < 0.001). These suggest that the root biomass of the tree species may be able to be estimated by the allometry equations. The biomass ratios of the root to the shoot did not increase with NaCl concentration despite that the reduction of shoot growth is generally much greater than the reduction of root growth under saline condition. The biomass ratio of the root to shoot of Eucalyptus saplings might not increase with NaCl concentration because same tendency was reported by Marcar (1993)
