Long-term high densities of African elephants clear the understorey and promote a new stable savanna woodland community

Ferry Nicolas, Dray Stéphane, Fritz Hervé, Ipavec Audrey, Wigley Benjamin J., Charles‐Dominique Tristan, Bourgarel Mathieu, Sebele Lovelater, Valeix Marion. 2021. Long-term high densities of African elephants clear the understorey and promote a new stable savanna woodland community. Journal of Vegetation Science, 32 (6), 15 p.

Url - jeu de données - Entrepôt autre : https://doi.org/10.5281/zenodo.5564836

Quartile : Q1, Sujet : FORESTRY / Quartile : Q2, Sujet : ECOLOGY / Quartile : Q2, Sujet : PLANT SCIENCES

Résumé : Questions: Species defined as ecosystem engineers (e.g. elephant) are able to strongly shape their habitat. In African savannas, elephants have often been shown to reduce woody-plant abundance and diversity. However, recent studies highlight more complex elephant-induced effects on vegetation. Here, we assessed if long-term high elephant densities (>2 km−2) in a large open landscape resulted in the depletion of savanna woodland woody communities or if it led to a new alternative equilibrium. Location: Woodland savanna of Hwange National Park, Zimbabwe. Elephant densities at the study site have remained high for the past two decades (>2 km−²). Methods: We measured long-term (>15 years) elephant utilisation of woody-plant communities and their effects on vegetation structure, species composition and functional traits (e.g. N leaf concentration, specific leaf area) in 12 vegetation plots. Results: We observed opportunistic foraging behaviour by elephants with only a slight temporal shift in species composition, mainly explained by changes in rare species. Further, we did not observe any modification in mean functional trait values, overall height, and stem diameters of the woody-plant communities. However, we found differential changes in woody-plant abundance according to the height layer (decrease in the number of tall plants [>200 cm] and increase in the number of short plants [<50 cm]) and a strong reduction in crown diameter for plants in the 50–200 cm height class. Conclusion: Our study strongly suggests that long-term high elephant densities have led to a stable state in savanna woodland vegetation in terms of plant community composition and their functional traits. However, high elephant densities did affect vegetation structure, which would have several important indirect effects on this ecosystem (e.g. predator–prey interactions). We hope that this study stimulates more work on the long-term effects of ecosystem engineers in large and open ecosystems.

Mots-clés Agrovoc : éléphant d'Afrique, écosystème, gestion de la faune et de la flore sauvages, forêt claire

Mots-clés géographiques Agrovoc : Zimbabwe

Mots-clés libres : Ecosystem engineer, Herbivore– plant interactions, Loxodonta africana, Plant diversity and structure, Semi- arid woodland savanna

Agences de financement hors UE : Centre National de la Recherche Scientifique, Centre de Coopération Internationale en Recherche Agronomique pour le Développement, Ambassade de France au Zimbabwe, Ministère des Affaires Etrangères

Auteurs et affiliations

• Ferry Nicolas, CNRS (FRA)
• Dray Stéphane, UCLB (FRA)
• Fritz Hervé, Université de Lyon (FRA)
• Ipavec Audrey, RWCP Northern (GBR)
• Wigley Benjamin J., Nelson Mandela University (ZAF)
• Charles‐Dominique Tristan, CNRS (FRA)
• Bourgarel Mathieu, CIRAD-BIOS-UMR ASTRE (ZWE) ORCID: 0000-0001-9774-7669
• Sebele Lovelater, Zimbabwe Parks and Wildlife Management Authority (ZWE)
• Valeix Marion, CNRS (FRA)

Source : Cirad-Agritrop (https://agritrop.cirad.fr/605082/)

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