Megabrowser Impacts on Woody Vegetation in Savannas

Owen‐Smith, Norman; Page, Bruce R.; Teren, Gabriella; Druce, Dave J.

doi:10.1002/9781119081111.ch17

Cited by 9 publications

(8 citation statements)

References 114 publications

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“…The effect of herbivores, elephants in particular, on vegetation has been thoroughly studied 49 , yet not in the perspective of the two factors addressed in our study or directly exploring the role of seasonal rivers. With high population densities, elephant herds influence the savanna ecosystem not only by consuming large amounts of plant tissue (mainly leaves) but also by damaging or uprooting grown trees 18 , 50 , hence changing woody savanna into more open grass dominated states 51 , 52 .…”

Section: Discussionmentioning

confidence: 99%

Water availability, bedrock, disturbance by herbivores, and climate determine plant diversity in South-African savanna

Hejda

Čuda

Pyšková

et al. 2022

Sci Rep

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To identify factors that drive plant species richness in South-African savanna and explore their relative importance, we sampled plant communities across habitats differing in water availability, disturbance, and bedrock, using the Kruger National Park as a model system. We made plant inventories in 60 plots of 50 × 50 m, located in three distinct habitats: (i) at perennial rivers, (ii) at seasonal rivers with water available only during the rainy season, and (iii) on crests, at least ~ 5 km away from any water source. We predicted that large herbivores would utilise seasonal rivers’ habitats less intensely than those along perennial rivers where water is available throughout the year, including dry periods. Plots on granite harboured more herbaceous and shrub species than plots on basalt. The dry crests were poorer in herb species than both seasonal and perennial rivers. Seasonal rivers harboured the highest numbers of shrub species, in accordance with the prediction of the highest species richness at relatively low levels of disturbance and low stress from the lack of water. The crests, exposed to relatively low pressure from grazing but stressed by the lack of water, are important from the conservation perspective because they harbour typical, sometimes rare savanna species, and so are seasonal rivers whose shrub richness is stimulated and maintained by the combination of moderate disturbance imposed by herbivores and position in the middle of the water availability gradient. To capture the complexity of determinants of species richness in KNP, we complemented the analysis of the above local factors by exploring large-scale factors related to climate, vegetation productivity, the character of dominant vegetation, and landscape features. The strongest factor was temperature; areas with the highest temperatures reveal lower species richness. Our results also suggest that Colophospermum mopane, a dominant woody species in the north of KNP is not the ultimate cause of the lower plant diversity in this part of the park.

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Section: Discussionmentioning

confidence: 99%

Water availability, bedrock, disturbance by herbivores, and climate determine plant diversity in South-African savanna

Hejda

Čuda

Pyšková

et al. 2022

Sci Rep

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show abstract

“…Thereby, their selective browsing of palatable species affects tree mortality and recruitment, which can explain the observed differences in tree communities between the disturbed and undisturbed forests. Finally, similarly as in savanna, we can reasonably expect different resistance of tree species to repeated disturbances by forest elephants, or differences in their ability to recover from damages 35 . The revealed higher species richness of Euphorbiaceae trees to the disturbed forest could indicate some resistance to elephant disturbances.…”

Section: Discussionmentioning

confidence: 96%

Effects of disturbances by forest elephants on diversity of trees and insects in tropical rainforests on Mount Cameroon

Maicher

Delabye

Murkwe

et al. 2020

Sci Rep

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Natural disturbances are essential for tropical forests biodiversity. In the Afrotropics, megaherbivores have played a key role before their recent decline. Contrastingly to savanna elephants, forest elephants’ impact on ecosystems remains poorly studied. Few decades ago, forests on Mount Cameroon were divided by lava flows, not being crossed by a local population of forest elephants until now. We assessed communities of trees, butterflies and two guilds of moths in the disturbed and undisturbed forests split by the longest lava flow. We surveyed 32 plots, recording 2025 trees of 97 species, and 7853 insects of 437 species. The disturbed forests differed in reduced tree density, height, and high canopy cover, and in increased DBH. Forest elephants’ selective browsing and foraging also decreased tree species richness and altered their composition. The elephant disturbance increased butterfly species richness and had various effects on species richness and composition of the insect groups. These changes were likely caused by disturbance-driven alterations of habitats and species composition of trees. Moreover, the abandonment of forests by elephants led to local declines of range-restricted butterflies. The recent declines of forest elephants across the Afrotropics probably caused similar changes in forest biodiversity and should be reflected by conservation actions.

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“…Thereby, their selective browsing of palatable species affects tree mortality and recruitment, which can explain the observed differences in tree communities between the disturbed and undisturbed forests. Finally, similarly as in savanna, we can reasonably expect different resistance of tree species to repeated disturbances by forest elephants, or differences in their ability to recover from damages (Owen-Smith et al , 2019). Unfortunately, the knowledge of African forest elephants’ browsing preferences and/or Afrotropical trees’ resistance to disturbances are not enough to decide which effect prevails in the alterations of rainforest structure by elephants.…”

Section: Discussionmentioning

confidence: 99%

Does rainforest biodiversity stand on the shoulders of giants? Effect of disturbances by forest elephants on trees and insects on Mount Cameroon

Maicher

Delabye

Murkwe

et al. 2020

Preprint

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other field assistants for their help in the field; Štěpán Janeček, Szabolcs Sáfián, Jan E.J. 38 Mertens, Jennifer T. Kimbeng, and Pavel Potocký for help with Lepidoptera sampling at the 39 elephant-disturbed plots; Karolina Sroka, Ewelina Sroka, and Jadwiga Lorenc-Brudecka for 40 Lepidoptera setting; Elias Ndive for tree identification; Yannick Klomberg for reviewing 41 distribution of trees; Axel Hausmann for access to the Bavarian State Collection of Zoology; 42 and the Mount Cameroon National Park staff for their support.

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Megabrowser Impacts on Woody Vegetation in Savannas

Cited by 9 publications

References 114 publications

Water availability, bedrock, disturbance by herbivores, and climate determine plant diversity in South-African savanna

Water availability, bedrock, disturbance by herbivores, and climate determine plant diversity in South-African savanna

Effects of disturbances by forest elephants on diversity of trees and insects in tropical rainforests on Mount Cameroon

Does rainforest biodiversity stand on the shoulders of giants? Effect of disturbances by forest elephants on trees and insects on Mount Cameroon

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