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Plant interactions alter the predictions of metabolic scaling theory

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

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 24/3 between mean individual biomass and density during densitydependent
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 24/3 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.
Original languageEnglish
Article number e57612
JournalP L o S One
Issue number2
Number of pages6
Publication statusPublished - 2013

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