PARENT SESSION
Oral Session # 46: Evolutionary Ecology I: Plants.
Presiding: P Minchin
Wednesday, August 6. 8:00 AM to 11:30 AM, SITCC Meeting Room 201.

Global allocation rules for plant biomass partitioning: Evolutionary and functional trends across land plants.

McCarthy, Megan^*,1, Enquist, Brian¹, Niklas, Karl², ¹ University of Arizona, Tucson, AZ, US² Deparment of Plant Biology, Ithaca, NY, US

ABSTRACT- Understanding how plant biomass is partitioned between roots, stems, leaves, and reproductive tissues is central for many questions in life history evolution, ecology, and ecosystem studies. Recently, a biomass partitioning model based on the constraints on resource transport and photosynthetic harvesting capacity was developed to explain how plants should divide their energy between leaf, stem and root function. The biomass partitioning model predicts that leaf mass, and total, stem, root and leaf production should scale to the 3/4th power of body size and stem and root mass should scale isometrically to body size. However, while empirical data fit these predictions, there was additional residual variation not explained by the model. Here we assess the relative importance of evolutionary history, functional trade-offs, and large scale environmental variation on explaining additional variation not explained by the predicted allometric constraints. Phylogeny and taxonomy did not influence the predicted biomass partitioning for any of the biomass partitioning relationships examined, suggesting that the constraints acting on the organ mass and production scaling relationships are similar across evolutionary groups. However, taxa differed significantly in the relative proportions of allocation to stems, roots, leaves, and fruits. Angiosperms and gymnosperms only differed in the amount of leaf mass and the amount of production for a given leaf mass. Nested Analysis of Variance across taxonomic hierarchies indicated that most variation in vegetative partitioning exists at the species and genus levels indicating a strong environmental signal. The differences in leaf mass and production for a given leaf mass appear to be due to differences in leaf phenology between angiosperms and gymnosperms. However, variation in allocation to reproduction is deeply rooted within the land plant phylogeny. Thus, it is shown how a general allometric model provides a framework for quantifying the relative influences of environment and functional differences on influencing plant biomass partitioning.

Key words: functional groups, biomass partitioning