Relationships between ratio of belowground biomass (root) to aboveground (shoot) biomass and tree age (a), diameter at breast height (DBH, b), height (c), density (d), latitude (e), longitude (f), and elevation (g).

<p>The model with the best fit among linear, quadratic and power function models is presented. * significant at α = 0.05 level, ** significant at α = 0.01 level. Error bars are standard errors of the ratios.