Abstract
Tree carbon allocation is a dynamic process that depends on the tree’s environment, but we know relatively little about how biotic interactions influence these dynamics. In central Kenya, the loss of vertebrate herbivores and the savanna’s invasion by the ant Pheidole megacephala are disrupting mutualisms between the foundational tree Acacia (Vachellia) drepanolobium and its native ant defenders. Here, we piloted a 13Carbon (C) pulse-labeling method to investigate the influence of these biotic interactions on C allocation to ant partners by adult trees in situ. Trees withstood experimental conditions and took up sufficient labeled 13CO2 for 13C to be detected in various C sinks, including ant mutualists. The δ13C in ants collected shortly after labeling suggested that trees exposed to herbivores allocated relatively more newly assimilated C to native ant defenders. Our results demonstrate the viability of the pulse-labeling method and suggest that C allocation to ant partners depends on the biotic context of the tree, but further investigation with replication is needed to characterize such differences in relation to invasion and herbivore loss.
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Data are available from Dryad: https://doi.org/10.5061/dryad.h9w0vt4q4
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Acknowledgements
We thank the Kenyan government (NACOSTI/P/20/4126, NACOSTI/P/20/3255) for their permission to conduct this project. We also thank the Ol Pejeta Conservancy for logistical support, with special thanks to Samuel Mutusya, Benard Gituku, and Nelly Jepkirui. We thank Jacob Goheen and Corinna Riginos for their contributions to setting up the experimental plots. We are grateful to Susan Trumbore, Mariah Carbone, and Jay Arnone for all of their insights.
Funding
This work was supported by grants from the U.S National Science Foundation to EGP (NSF DEB-1935498) and TMP (NSF DEB-1556905).
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EGP and TMP conceptualized the study, and EGP, GMM, and TK designed the methods. BWS provided methods and resources for gas sampling and analysis. GMM, EGP, TMP, TK, JSL, and JM performed the experiments. GMM conducted statistical analysis advised by EGP. GMM led the writing of the manuscript, and EGP, BWS, and TMP contributed to revisions.
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Mizell, G.M., Kim, T., Sullivan, B.W. et al. Carbon allocation in an East African ant-acacia: field testing a 13C-labeling method for evaluating biotic impacts on the carbon cycle. Plant Ecol 224, 953–963 (2023). https://doi.org/10.1007/s11258-023-01350-0
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DOI: https://doi.org/10.1007/s11258-023-01350-0