Woody Plants and Large Herbivores in Savannas

Scogings, Peter F.; Sankaran, Mahesh

doi:10.1002/9781119081111.ch21

Cited by 13 publications

(17 citation statements)

References 134 publications

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“…Mean annual rainfall in the area is approximately 1400 mm (Pillay & Ward 2012), which eliminated the need for irrigation. The soil at the site was sandy and acidic, which limited nutrient availability (Scogings 2018). During the rainy season (October to April), weeds were manually cleared within 30 cm of the base of each sapling every two months and the saplings were sprayed monthly with a pyrethroid insecticide.…”

Section: Methodsmentioning

confidence: 99%

“…It has been successfully calibrated for indirectly measuring condensed tannin concentrations (acid‐butanol assay, Sorghum tannin standard) in some savanna woody species including S. birrea (Scogings et al . 2014) and has been successfully used to determine S. birrea chemical responses to nutrient fertilisation (Scogings 2018).…”

Section: Methodsmentioning

confidence: 99%

“…Resource availability and browsing by large mammal herbivores are important determinants of woody plant abundance in African savannas (Sankaran et al 2008;Anderson et al 2015;Staver et al 2017;Scogings & Sankaran 2020). Both factors are especially critical at the seedling and sapling stages of woody plants (Vadigi & Ward 2014;Churski et al 2017;Ib añez et al 2017;Swemmer & Ward 2020), yet their combined effects have been poorly studied in savannas (Scogings et al 2017).…”

Section: Introductionmentioning

confidence: 99%

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Severe simulated herbivory constrains Sclerocarya birrea saplings regardless of resource availability

Scogings¹,

Fortier

2020

Austral Ecology

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Allocation of carbon to growth and defences in plants is affected by resource availability and herbivory, two determinants of woody plant abundance in savannas. Both factors are critical at the sapling stage of woody plants, yet their combined effects on sapling growth and defence have been poorly studied in savannas. Sclerocarya birrea is an iconic keystone species in southern African savannas, widely used by herbivores and humans. We hypothesised that low resource availability or high herbivory intensity would reduce growth and nutritional value for herbivores, but high resource availability or low herbivory intensity would increase growth and nutritional value. Support for our hypothesis would imply that any level of browsing intensity (relative to unbrowsed plants), regardless of resource availability, would potentially hold saplings in a browser trap because of reduced growth or improved nutritional value. We explored responses of S. birrea saplings to five levels of nutrient fertiliser and six levels of simulated browsing intensity. Low fertiliser application rates did not affect growth, but the highest fertiliser rate increased canopy growth. The most severe intensities of simulated browsing negatively affected growth and nutritional value. Our results suggested that either resource limitation throughout the growing season, or extremely intense browsing early in the growing season, is potentially able to retard long‐term growth of saplings and delay recruitment of adults. Although saplings that are severely browsed early in the growing season might not be re‐browsed later in the same season because of their reduced nutritional value, their weakened nitrogen status would be an additional limitation to regrowth. No significant interactions between resource availability and herbivory intensity were detected, which we suggest resulted from responses to resource availability and herbivory operating at different temporal scales. We recommend that future experiments of this type include carefully timed measurements to detect transient responses.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Severe simulated herbivory constrains Sclerocarya birrea saplings regardless of resource availability

Scogings¹,

Fortier

2020

Austral Ecology

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“…Since the extinction of the Australian megafauna species 45 000 to 50 000 years ago, soft‐footed macropods represent the largest extant native herbivores in Australian savannas (Freeland 1990; Skarpe 1991; Scogings & Sankaran 2019). Australian macropod species exhibit a variety of feeding strategies ranging from grazing to browsing, however, given their lower metabolic biomass compared to herbivores in other savannas, Australian savannas have received considerably less historical grazing pressure (Calaby 1980; Skarpe 1991).…”

Section: Introductionmentioning

confidence: 99%

An overview of the impacts of feral cattle, water buffalo and pigs on the savannas, wetlands and biota of northern Australia

Mihailou

Massaro

2021

Austral Ecology

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Since the extinction of the megafauna some 45 000 to 50 000 years ago, grazing pressure on Australian savannas has been relatively low compared to that on savannas in other continents. However, the introduction of several species of ungulate, primarily during the 1800s, and the establishment of large feral populations in northern Australia has resulted in an increase in grazing pressure compared to pre-colonial times when soft-footed macropods were the largest extant grazers. Here, we provide an overview of the introduction of three key ungulates to northern Australia: cattle (Bos taurus, B. indicus), Asian water buffalo (Bubalus bubalis) and pigs (Sus scrofa), and the impact of these populations on both abiotic and biotic elements of savanna habitats in northern Australia. Feral ungulate populations have considerable impacts on soil, water quality, waterhole hydrology, vegetation, fire regimes and the spread of exotic plants, and resulting changes to habitat have flow-on effects for native wildlife. Ungulate impacts on vegetation communities and associated changes in fire regimes are particularly concerning given that sustained grazing can lead to the permanent removal of key grass species and changes in fire intensity and frequency can result in the conversion of grassland to woodland. Native wildlife can be affected by ungulate disturbance in a multitude of ways, but overwhelmingly, habitat loss or degradation is the main driver for declines in biodiversity. Based on current knowledge gaps, we discuss potential directions for future research about how feral ungulate activity affects Australian native species and their impact on savanna habitats.

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“…Elephants have been extensively studied across several landscapes and different environments. For instance, studies have assessed the spatial distribution of elephants along with their vital ecological drivers (Bohrer et al, 2014; Gara, 2014; Kamau & Sluyter, 2019; Ngene, 2010; Ngene et al, 2009; Scogings & Sankaran, 2020). Also, studies have assessed movement metrics as a function of environmental factors across time (Gara, 2014; Ngene et al, 2009; Wall et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Home range and space use by African elephants (Loxodonta africana) in Hwange National Park, Zimbabwe

et al. 2021

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This study examined the African elephant's (Loxodonta africana) seasonal space use and movement using elephant telemetry data in Hwange National Park. The adaptivelocal convex hull (a-LoCoH) was adopted to understand the elephant movement metrics and home range. Paired t test was used to compare the mean seasonal speed of each group (n = 10) of elephants, while the Wilcoxon signed-rank test was used to determine differences in the 50% and 90% home range. Results show that mean elephant movement speed significantly differed (t = −3.07, df = , p < 0.01) for all elephant groups across seasons. Moreover, significant differences (W = 3, Z = 2.4973, p < 0.012) were observed between core a-LoCoH home-range distributions for the wet and dry seasons. However, no significant differences (W = 10, Z = 1.7838, p > 0.05) were detected between the two seasons for the total (90%) a-LoCoH ranges. NDVI, Distance to water sources and Slope were positively related with elephant movement speed while Aspect and Distance to roads were negatively related with elephant speed.These findings underscore the importance of resource variability in driving elephant movement and foraging behaviour in a semi-arid savannah ecosystem.

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Woody Plants and Large Herbivores in Savannas

Cited by 13 publications

References 134 publications

Severe simulated herbivory constrains Sclerocarya birrea saplings regardless of resource availability

Severe simulated herbivory constrains Sclerocarya birrea saplings regardless of resource availability

An overview of the impacts of feral cattle, water buffalo and pigs on the savannas, wetlands and biota of northern Australia

Home range and space use by African elephants (Loxodonta africana) in Hwange National Park, Zimbabwe

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