Wild herbivore populations are declining in many African savannas, which is related to replacement by livestock (mainly cattle) and the loss of megaherbivores. Although some livestock management practices may be compatible with the conservation of native savanna biodiversity, the sustainability of these integrated wild herbivore/livestock management practices is unknown. For instance, how will these herbivore mixes influence key processes for the long-term functioning of savanna ecosystems, such as soil carbon, nitrogen and phosphorus pools and cycling? The Kenya Long-term Exclosure Experiment studies the ecosystem consequences of manipulating the presence and absence of wild herbivores and cattle at moderate densities in a ‘black cotton’ savanna. Here we show that after 20 years, cattle presence decreased total soil carbon and nitrogen pools, while the presence of megaherbivores (mainly elephants) increased these pools and even reversed the negative effects of cattle. Our results suggest that a mix of cattle at moderate densities and wild herbivores can be sustainable, provided that the assemblage of wild herbivores includes the largest species.
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Late Holocene environmental change and anthropogenic: Ecosystem interaction on the Laikipia Plateau, Kenya
Ambio Open Access 16 June 2021
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The datasets collected and analyzed in this study are available in figshare at https://doi.org/10.6084/m9.figshare.11636595.v1, https://doi.org/10.6084/m9.figshare.11636577.v2 and https://doi.org/10.6084/m9.figshare.11636502.v1. Source data for Figs. 2–4 and Extended Data Figs. 1–4 and 6 are provided as Source Data files.
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This research was carried out under Government of Kenya research clearance permit no. NACOSTI/P/15/0830/4886. We thank F. Erii, J. Lochukuya, M. Namoni, J. Ekadeli, S. Ekuam and B. Kimiti for their invaluable assistance in the field. We also acknowledge the staff at Mpala Research Centre for their logistical support. The KLEE plots were built and maintained by grants from the Smithsonian Institution, The National Geographic Society (grants 4691-91 and 9106-12), the African Elephant Program of the US Fish and Wildlife Service (98210-0-G563) and the National Science Foundation (LTREB BSR-97-07477, 03-16402, 08-16453, 12-56004 and 12-56034). J.S. was funded by grants from the Research Foundation Flanders (FWO), grants 12N2615N and 12N2618N, and the Leopold III Fonds voor Natuuronderzoek en Natuurbehoud. Stable isotope facilities were supported by grants from FWO Hercules (HERC46) and VUB SRP2: Tracing and modelling of present and ancient global changes.
The authors declare no competing interests.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
a, Impact of herbivore treatments on canopy cover estimated with hemispherical photographs. Herbivore treatments (N = 3) include: no large herbivores (O), wild mesoherbivores (W), wild mega- and mesoherbivores (MW), only cattle (C), wild mesoherbivores and cattle (WC), wild mega- and mesoherbivores and cattle (MWC). Boxplots not sharing the same letter indicate significant differences between herbivore treatments. b, Linear regression showing the relationship between tree density and canopy cover. See ref. 31 for details on tree surveys.
Impact of herbivore treatments on plot-level soil C a, N b, and P pools c, calculated using the proportions of plot area located under and outside the canopy of A. drepanolobium trees. Herbivore treatments (N = 3) include: no large herbivores (O), wild mesoherbivores (W), wild mega- and mesoherbivores (MW), only cattle (C), wild mesoherbivores and cattle (WC), wild mega- and mesoherbivores and cattle (MWC). Boxplots not sharing the same letter indicate significant differences between herbivore treatments.
Impact of herbivore treatments on live grass P concentrations a, C:P b, and N:P ratio c, outside (golden boxplots and points) and under (green boxplots and points) the canopy of A. drepanolobium trees. Herbivore treatments (N = 3) include: no large herbivores (O), wild mesoherbivores (W), wild mega- and mesoherbivores (MW), only cattle (C), wild mesoherbivores and cattle (WC), wild mega- and mesoherbivores and cattle (MWC).
Relationships between total soil P pool and live grass P concentrations a, and C:P ratio b, Herbivore treatments include: no large herbivores (O), wild mesoherbivores (W), wild mega- and mesoherbivores (MW), only cattle (C), wild mesoherbivores and cattle (WC), wild mega- and mesoherbivores and cattle (MWC). Sampled locations are outside (golden points) and under (green points) the canopy of A. drepanolobium trees.
Schematic of the Kenya Long-term Exclosure Experiment (KLEE) plots. The letters inside each plot indicate the herbivore treatments.
Coverage of different grass species in the two 25 x 25 cm subplots (one under the canopy and one outside the canopy of an A. drepanolobium tree) we clipped in each KLEE plot. Herbivore treatments include: no large herbivores (O), wild mesoherbivores (W), wild mega- and mesoherbivores (MW), only cattle (C), wild mesoherbivores and cattle (WC), wild mega- and mesoherbivores and cattle (MWC). N = 6 per treatment.
Statistical source data soil C, N and P pools.
Statistical source data grass N and C/N ratio.
Statistical source data soil and grass N.
Statistical source data tree density and canopy cover.
Statistical source data plot-level soil C, N and P pools.
Statistical source data grass P, C/P and N/P ratios.
Statistical source data soil and grass P.
Statistical source data grass composition clipped sub-plots.
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Sitters, J., Kimuyu, D.M., Young, T.P. et al. Negative effects of cattle on soil carbon and nutrient pools reversed by megaherbivores. Nat Sustain 3, 360–366 (2020). https://doi.org/10.1038/s41893-020-0490-0
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