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Modelling below- and above-ground biomass for non-woody and woody plants

Niklas, K.J.
Annals of botany 2005 v.95 no.2 pp. 315-321
woody plants, herbaceous plants, roots, shoots, plant growth, dry matter accumulation, growth models, mathematical models
Background and Aims Intraspecific relationships between below- and above-ground biomass (M(B) and M(A), respectively) have been studied extensively to evaluate environmental effects on growth and development at the level of the individual plant. However, no current theoretical model for this relationship exists for broad interspecific trends. The aims of this paper are to provide a model and to test its predictions using a recently assembled, large database (1406 data entries for 257 species). Methods An allometric model was derived to predict the relationship between M(B) and M(A) for non-woody and woody plants based on previously developed scaling relationships for leaf, stem and root standing biomass and annual growth rates. The predictions of this model were tested by comparing the numerical values of predicted scaling exponents (the slopes of log-log regression curves) with those observed for the database. Key Results and Conclusions For non-woody plants and the juveniles of woody species, the model predicts an isometric scaling relationship (i.e. M(B) infinity M(A)). For woody plants, a complex scaling function is predicted. But, for a particular set of biologically reasonable conditions, the model predicts M(B) infinity M(A) across woody plants. These predictions accord reasonably well with observed statistical trends when non-woody and woody plants are studied separately (n = 1061 and 345 data entries, respectively). Although the reliability of regression formulas to estimate M(B) based on M(A) measurements increased with increasing plant size, estimates of M(B) can be as much as two orders of magnitude off, even when using regression formulas with r2 >> 0.90 and F >> 53 000.