Plant Interactions Alter the Predictions of Metabolic Scaling Theory

Authored by Volker Grimm, Uta Berger, Yue Lin, Franka Huth, Jacob Weiner

Date Published: 2013

DOI: 10.1371/journal.pone.0057612

Sponsors: Initiative and Networking Fund of the Helmholtz Association (NRB)

Platforms: NetLogo

Model Documentation: ODD Mathematical description

Model Code URLs: https://doi.org/10.1371/journal.pone.0057612.s003

Abstract

Metabolic scaling theory (MST) is an attempt to link physiological processes of individual organisms with macroecology. It predicts a power law relationship with an exponent of -4/3 between mean individual biomass and density during density-dependent mortality (self-thinning). Empirical tests have produced variable results, and the validity of MST is intensely debated. MST focuses on organisms' internal physiological mechanisms but we hypothesize that ecological interactions can be more important in determining plant mass-density relationships induced by density. We employ an individual-based model of plant stand development that includes three elements: a model of individual plant growth based on MST, different modes of local competition (size-symmetric vs. -asymmetric), and different resource levels. Our model is consistent with the observed variation in the slopes of self-thinning trajectories. Slopes were significantly shallower than -4/3 if competition was size-symmetric. We conclude that when the size of survivors is influenced by strong ecological interactions, these can override predictions of MST, whereas when surviving plants are less affected by interactions, individual-level metabolic processes can scale up to the population level. MST, like thermodynamics or biomechanics, sets limits within which organisms can live and function, but there may be stronger limits determined by ecological interactions. In such cases MST will not be predictive.

Tags

Competition models growth Populations Allometry General quantitative theory Tree-dominated communities Density relationships Size symmetry Mass-density