TY - JOUR A1 - Lin, Yue A1 - Berger, Uta A1 - Grimm, Volker A1 - Huth, Franka A1 - Weiner, Jacob T1 - Plant interactions alter the predictions of metabolic scaling theory JF - PLoS one N2 - 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. Y1 - 2013 U6 - https://doi.org/10.1371/journal.pone.0057612 SN - 1932-6203 VL - 8 IS - 2 PB - PLoS CY - San Fransisco ER - TY - JOUR A1 - Lin, Yue A1 - Berger, Uta A1 - Grimm, Volker A1 - Ji, Qian-Ru T1 - Differences between symmetric and asymmetric facilitation matter - exploring the interplay between modes of positive and negative plant interactions JF - The journal of ecology N2 - Facilitation (positive interaction) has received increasing attention in plant ecology over the last decade. Just as for competition, distinguishing different modes of facilitation (mutualistic, commensal or even antagonistic) may be crucial. We therefore introduce the new concept of symmetric versus asymmetric facilitation and present a generic individual-based zone-of-influence model. The model simultaneously implements different modes of both facilitation and competition among individual plants via their overlapping zone of influence. Because we consider facilitation modes as a continuum related to environmental context, we integrated this concept with the stress-gradient hypothesis (SGH) by exploring differences in spatial pattern formation in self-thinning plants along a stress gradient in our model. The interplay among modes of interaction creates distinctly varied spatial patterns along stress gradients. When competition was symmetric, symmetric facilitation (mutualism) consistently led to plant aggregation along stress gradients. However, asymmetric facilitation (commensalism) produces plant aggregation only under more benign conditions but tends to intensify local competition and spatial segregation when conditions are harsh. When competition was completely asymmetric, different modes of facilitation contributed little to spatial aggregation. Symmetric facilitation significantly increased survival at the severe end of the stress gradient, which supports the claim of the SGH that facilitation should have generally positive net effects on plants under high stress levels. Asymmetric facilitation, however, was found to increase survival only under intermediate stress conditions, which contradicts the current predictions of the SGH. Synthesis. Our modelling study demonstrates that the interplay between modes of facilitation and competition affects different aspects of plant populations and communities, implying context-dependent outcomes and consequences. The explicit consideration of the modes and mechanisms of interactions (both facilitation and competition) and the nature of stress factors will help to extend the framework of the SGH and foster research on facilitation in plant ecology. KW - asymmetry KW - competition KW - metabolic scaling theory KW - plant population and community dynamics KW - plant-plant interaction KW - self-thinning KW - spatial pattern KW - stress-gradient hypothesis KW - symmetry Y1 - 2012 U6 - https://doi.org/10.1111/j.1365-2745.2012.02019.x SN - 0022-0477 VL - 100 IS - 6 SP - 1482 EP - 1491 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Lin, Yue A1 - Huth, Franka A1 - Berger, Uta A1 - Grimm, Volker T1 - The role of belowground competition and plastic biomass allocation in altering plant mass-density relationships JF - Oikos Y1 - 2014 U6 - https://doi.org/10.1111/j.1600-0706.2013.00921.x SN - 0030-1299 SN - 1600-0706 VL - 123 IS - 2 SP - 248 EP - 256 PB - Wiley-Blackwell CY - Hoboken ER -