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Research Project: Interplay of the Physical Environment, Social Domain, and Intrapersonal Factors on Nutrition and Physical Activity Related Health Behaviors in Children and Adolescents

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Title: Life history scaling in a tropical forest

Author
item GRADY, JOHN - Washington University
item Read, Quentin
item RECORD, SYDNE - University Of Maine
item RUGER, NADJA - German Centre For Integrative Biodiversity Research (IDIV)
item ZARNETSKE, PHOEBE - Michigan State University
item DELL, ANTHONY - Washington University
item HUBBELL, STEPHEN - Smithsonian Tropical Research
item MICHALETZ, SEAN - University Of Arizona
item ENQUIST, BRIAN - University Of Arizona

Submitted to: Journal of Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/25/2023
Publication Date: 1/18/2024
Citation: Grady, J., Read, Q.D., Record, S., Ruger, N., Zarnetske, P., Dell, A., Hubbell, S., Michaletz, S., Enquist, B. 2024. Life history scaling in a tropical forest. Journal of Ecology. https://doi.org/10.1111/1365-2745.14245.
DOI: https://doi.org/10.1111/1365-2745.14245

Interpretive Summary: In this study, a long-term dataset of tree growth, establishment, and survival from a tropical forest in Panama is used to explore fundamental ecological questions about how different species can coexist in diverse communities. Ecological theory predicts that energy should be roughly equally divided between small and large individuals – data from all kinds of species communities, including land animals, marine animals, and trees support this prediction. But on the other hand, large trees in forests create a shaded canopy, preventing light from reaching the forest floor where seedlings and saplings live. This would seem to contradict those predictions. Our study helps to resolve this paradox by exploring how energy is divided among trees with different life strategies: some are slow-growing, some are fast-growing, some tolerate shade well and some can only grow in high light conditions. We use a novel set of mathematical scaling equations to document and explain patterns of diversity and energy use by trees in tropical forests. These results shed light on important questions in the field of ecology, explaining how organisms divide up resources and how biodiversity comes to be.

Technical Abstract: Life history variation in trees is a ubiquitous feature of tropical forests that may facilitate the niche partitioning of light. However, many tests have failed to show support for light partitioning of saplings in gaps, which may reflect the stochastic nature of understory light penetration and recruitment. We argue that tree size is a critical component of niche partitioning that is more tightly linked to light availability. To account for size, we use a scaling framework to assess patterns of growth, abundance, mortality, and richness across life histories from >114,000 trees in a primary, neotropical forest. Relative abundance, productivity, and richness shift ~1-2 orders of magnitude with tree size: from shade tolerant, slow trees dominating the understory to parity with rapidly growing fast and long-lived pioneer species in the canopy. Life history tradeoffs promote vertical niche partitioning in tropical forests.