At high stocking rates, cattle do not functionally replace wild herbivores in shaping understory community composition

HBM Wells, LM Porensky, KE Veblen, C Riginos, LC Stringer, AJ Dougill, M Namoni, J Ekadeli, TP Young

Research output: Contribution to journalArticlepeer-review

Abstract

Over a quarter of the world's land surface is grazed by cattle and other livestock, which are replacing wild herbivores, potentially impairing ecosystem structure and functions. Previous research suggests that cattle at moderate stocking rates can functionally replace wild herbivores in shaping understory communities, but it is unclear whether this is also true under high stocking rates. It is also unclear whether wild herbivore effects on plant communities moderate, enhance, or are simply additive to the effects of cattle at high stocking rates. To evaluate the influence of cattle stocking rates on the ability of cattle to functionally replace wild herbivores and test for interactive effects between cattle and wild herbivores in shaping understory vegetation, we assessed herbaceous vegetation in a long-term exclosure experiment in a semi-arid savanna in central Kenya that selectively excludes wild mesoherbivores (50-1000 kg) and megaherbivores (elephant and giraffe). We tested the effects of cattle stocking rate (zero/moderate/high) on herbaceous vegetation (diversity, composition, leafiness) and how those effects depend on the presence of wild mesoherbivores and megaherbivores. We found that herbaceous community composition (primary ordination axis) was better explained by the presence/absence of herbivore types than by total herbivory, suggesting that herbivore identity is a more important determinant of community composition than total herbivory at high cattle stocking rates. The combination of wild mesoherbivores and cattle stocked at high rates led to increased bare ground and annual grass cover, reduced perennial grass cover, reduced understory leafiness, and enhanced understory diversity. These shifts were weaker or absent when cattle were stocked at high stocking rates in the absence of wild mesoherbivores. Megaherbivores tempered the effects of cattle stocked at high rates on herbaceous community composition but amplified the effects of high cattle stocking rate on bare ground and understory diversity. Our results show that, contrary to previous findings at moderate stocking rates, cattle at high stocking rates do not functionally replace wild herbivores in shaping savanna herbaceous communities. In mixed-use rangelands, interactions between cattle stocking rate and wild herbivore presence can lead to non-additive vegetation responses with important implications for both wildlife conservation and livestock production.
Original languageUndefined/Unknown
JournalECOLOGICAL APPLICATIONS
Volume32
Issue number3
Early online date16 Dec 2021
DOIs
Publication statusPublished - 30 Apr 2022

Bibliographical note

This article is protected by copyright. All rights reserved. This is the peer reviewed version of the following article: Wells, H.B.M., Porensky, L.M., Veblen, K.E., Riginos, C., Stringer, L.C., Dougill, A.J., Namoni, M., Ekadeli, J. and Young, T.P. (2022), At high stocking rates, cattle do not functionally replace wild herbivores in shaping understory community composition. Ecological Applications. Accepted Author Manuscript e2520, which has been published in final form at https://doi.org/10.1002/eap.2520. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley?s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited.

Keywords

  • biodiversity conservation
  • cattle stocking rate
  • elephant
  • forb
  • grass
  • herbaceous plant communities
  • Kenya Long-term Exclosure Experiment
  • livestock-wildlife interactions
  • rangeland ecology

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