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Termites facilitate and ungulates limit savanna tree regeneration

  • Plant-animal interactions - Original research
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Abstract

Both large herbivores and termites are key functional groups in savanna ecosystems, and in many savanna areas, large termite mounds (termitaria) are associated with distinct woody clusters. Studies on the effect of large mammals on tree regeneration are few, and the results are conflicting. Large herbivores have been found to be important seedling predators in some areas, but facilitate tree regeneration by outcompeting small mammals and reducing grass cover in other areas. Through the use of the experimental fencing of termite mounds and adjacent savanna areas in this study, we investigated how termites and large herbivores influence tree regeneration. Termite mounds had a higher number of seedlings, more species richness, more alpha diversity (OD) and lower evenness (E) than savanna plots. Large herbivores did not significantly affect overall seedling density, species richness, OD or E. Beta diversity was higher in savanna areas than on termitaria, and beta diversity decreased in savanna areas when herbivores were excluded. Herbivore exclusion increased the density of the 12 (40 %) most common seedling species, representing 79 % of all seedlings, and fenced plots had relatively taller seedlings than open plots. Thus, termites were the main determinants of tree regeneration in our study area, but large mammals regulated the most common species. Although our study confirms previous work suggesting that large herbivores affect tree regeneration, we found that termites were an even more important determinant. Termite impacts on tree regeneration deserve increased attention by savanna ecologists.

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Acknowledgments

We thank James Nkwatsibwe, Patrict Bodo, Antonia Nyamukuru and Protase Rwaburindore for field assistance. We also thank Rose Kentalu who ensured that the meals were always ready, and the Chief Park warden, Adonia Bintora, for help and support in providing field work permits. We also thank Jon E. Swenson for reading a former draft and for his useful comments. The experiments comply with the current laws of the country (Uganda) in which the experiments were performed.

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  1. Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, 1432, Ås, Norway

    Ole-Gunnar Støen, Paul Okullo, Tron Eid & Stein R. Moe

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  1. Ole-Gunnar Støen
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  2. Paul Okullo
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Correspondence to Ole-Gunnar Støen.

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Communicated by Peter Clarke.

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Støen, OG., Okullo, P., Eid, T. et al. Termites facilitate and ungulates limit savanna tree regeneration. Oecologia 172, 1085–1093 (2013). https://doi.org/10.1007/s00442-012-2561-z

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