Allometric scaling relationship between above- and below-ground biomass within and across five woody seedlings

Allometric biomass allocation theory predicts that leaf biomass (M(L)) scaled isometrically with stem (M(S)) and root (M(R)) biomass, and thus above-ground biomass (leaf and stem) (M(A)) and root (M(R)) scaled nearly isometrically with below-ground biomass (root) for tree seedlings across a wide diversity of taxa. Furthermore, prior studies also imply that scaling constant should vary with species. However, litter is known about whether such invariant isometric scaling exponents hold for intraspecific biomass allocation, and how variation in scaling constants influences the interspecific scaling relationship between above- and below-ground biomass. Biomass data of seedlings from five evergreen species were examined to test scaling relationships among biomass components across and within species. Model Type II regression was used to compare the numerical values of scaling exponents and constants among leaf, stem, root, and above- to below-ground biomass. The results indicated that M(L) and M(S) scaled in an isometric or a nearly isometric manner with M(R), as well as M(A) to M(R) for five woody species. Significant variation was observed in the Y-intercepts of the biomass scaling curves, resulting in the divergence for intraspecific scaling and interspecific scaling relationships for M(L) versus M(S) and M(L) versus M(R), but not for M(S) versus M(R) and M(A) versus M(R). We conclude, therefore, that a nearly isometric scaling relationship of M(A) versus M(R) holds true within each of the studied woody species and across them irrespective the negative scaling relationship between leaf and stem.