Biomass partitioning for resource conservation might affect plant allometry, accounting for a substantial amount of unexplained variation in existing plant allometry models. Tomlinson et al. compare root carbohydrate storage and organ biomass allometries for juveniles of 20 savanna tree species of different leaf habit – nine evergreen and 11 deciduous – and find that deciduous species have greater root non-structural carbohydrate than evergreens, and lower scaling exponents for leaf-to-root and stem-to-root partitioning. The data provide strong support for the hypothesis that deciduous and evergreen trees differ in juvenile biomass allometries because of differences in allocation to root storage. Substantial unexplained variation in biomass allometry of woody species may be related to selection for resource conservation against environmental stresses, such as resource seasonality.