Relationship of plant diversity and bush cover in rangelands of a semi‐arid Kalahari savannah, South Africa

Dreber, Niels; Rooyen, Salmon E. van; Kellner, Klaus

doi:10.1111/aje.12425

Cited by 9 publications

(7 citation statements)

References 15 publications

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“…Selective removal of trees and shrubs (bush thinning) or total clearance of the woody layer are common measures to restore herbaceous productivity. Annual grasses and forbs are usually the first to colonize resulting bare ground (Smit, 2003;Smit & Rethman, 1999), which may lead to temporarily species-rich forb assemblages of pioneer character (Dreber et al, 2018). With the establishment of perennial grasses and buildup of dry matter production, forbs may decline again due to the increased competition for limiting resources (O'Connor, 1991b;Smit, 2003Smit, , 2005.…”

Section: Active Restoration and Passive Regenerationmentioning

confidence: 99%

“…Forbs provide forage for several herbivore guilds—from insects (Andersen & Lonsdale, ) to megafauna (Clegg & O'Connor, ; Landman, Kerley, & Schoeman, )—as they are a nutritious food class for browsers and mixed feeders in savannas (Du Toit, ), and may constitute an important part of ungulate and cattle diet at certain times of the year (Odadi, Karachi, Abdulrazak, & Young, ; Odadi, Young, & Okeyo‐Owuor, ; Veblen, Porensky, Riginos, & Young, ). Furthermore, forbs constitute the largest component of herbaceous species richness in grassland (Bond & Parr, ; Koerner et al, ; Pokorny, Sheley, Svejcar, & Engel, ; Scott‐Shaw & Morris, ; Zaloumis & Bond, ) and savanna ecosystems (Van Coller, Siebert, & Siebert, ; Pavlovic, Leicht‐Young, & Grundel, ; Shackleton, ; Uys, ), which may vary little across gradients of tree and shrub cover (Dreber, Van Rooyen, & Kellner, ) or grazing intensities (Hanke et al, ; Rutherford, Powrie, & Thompson, ). As part of the herbaceous layer, forbs also contribute to carbon inputs into the soil and accumulation of soil organic matter (Mureithi et al, ; Tessema, De Boer, Baars, & Prins, ).…”

Section: Introductionmentioning

confidence: 99%

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Forb ecology research in dry African savannas: Knowledge, gaps, and future perspectives

Siebert

Dreber

2019

Ecology and Evolution

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Savannas are commonly described as a vegetation type with a grass layer interspersed with a discontinuous tree or shrub layer. On the contrary, forbs, a plant life form that can include any nongraminoid herbaceous vascular plant, are poorly represented in definitions of savannas worldwide. While forbs have been acknowledged as a diverse component of the herbaceous layer in savanna ecosystems and valued for the ecosystem services and functions they provide, they have not been the primary focus in most savanna vegetation studies. We performed a systematic review of scientific literature to establish the extent to which forbs are implicitly or explicitly considered as a discrete vegetation component in savanna research. The overall aims were to summarize knowledge on forb ecology, identify knowledge gaps, and derive new perspectives for savanna research and management with a special focus on arid and semiarid ecosystems in Africa. We synthesize and discuss our findings in the context of different overarching research themes: (a) functional organization and spatial patterning, (b) land degradation and range management, (c) conservation and reserve management, (d) resource use and forage patterning, and (e) germination and recruitment. Our results revealed biases in published research with respect to study origin (country coverage in Africa), climate (more semiarid than arid systems), spatial scale (more local than landscape scale), the level at which responses or resource potential was analyzed (primarily plant functional groups rather than species), and the focus on interactions between life forms (rather seldom between forbs and grasses and/or trees). We conclude that the understanding of African savanna community responses to drivers of global environmental change requires knowledge beyond interactions between trees and grasses only and beyond the plant functional group level. Despite multifaceted evidence of our current understanding of forbs in dry savannas, there appear to be knowledge gaps, specifically in linking drivers of environmental change to forb community responses. We therefore propose that more attention be given to forbs as an additional ecologically important plant life form in the conventional tree–grass paradigm of savannas.

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Section: Active Restoration and Passive Regenerationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Forb ecology research in dry African savannas: Knowledge, gaps, and future perspectives

Siebert

Dreber

2019

Ecology and Evolution

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“…Here, the dominant encroacher is Senegalia ( Acacia ) mellifera , a slow‐growing tree that has expanded episodically in this arid region at an average annual rate of ~0.5% (Bester, 1999). Influenced by precipitation, fire and grazing regimes, climate change and increasing atmospheric CO 2 (Venter et al., 2018), S. mellifera encroachment affects plant diversity (Dreber et al., 2018), soil fertility (Ward et al., 2018), and populations of arthropods (Hering et al., 2019) and many types of wildlife (Blaum et al., 2007; Meik et al., 2002; Schwarz et al., 2018).…”

Section: Examples From Two Continents Of Woody Plant Encroachment Eff...mentioning

confidence: 99%

Woody plant encroachment and the ecology of vector‐borne diseases

Loss

Noden

Fuhlendorf

2021

Journal of Applied Ecology

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1. Vector-borne diseases (VBDs) impact human and animal health globally, and their ecology and transmission are affected by human-caused ecosystem and biome transitions. Woody plant encroachment (WPE), a top driver of biome and land cover transitions in grasslands and savannas of the world, greatly changes abiotic conditions, vegetation and animal populations and communities. Although these effects mirror mechanisms by which other ecosystem and land cover changes influence VBD ecology, few studies have evaluated if WPE expands distributions and increases the transmission of VBDs.2. We develop a conceptual framework for WPE effects on VBDs by synthesizing key literature on these topics and on impacts of land cover change on diseases broadly. We also present examples of WPE systems from two continents illustrating documented and likely effects on VBD systems, and we outline a prospectus for future research evaluating such effects.3. This synthesis highlights the potential for WPE to increase the transmission of VBDs world-wide. WPE's effects on landscape composition, local vegetation, abiotic conditions, and vector and host resources, interactions and population and community processes, likely impact VBD distributions, transmission and health outcomes. Much additional research is needed on topics like the effects of WPE management on health risks associated with VBDs. Synthesis and applications. Woody plant encroachment (WPE) is drastically chang-ing grasslands and savannas world-wide. Its well-documented influences on abiotic conditions (e.g. temperature and humidity), vegetation and wildlife are having previously underappreciated effects on the ecology of vector-borne diseases, likely increasing spatial distributions and transmission of diseases. Management to reduce WPE is ongoing in much of the world due to its degradation of ecosystem services like biodiversity, livestock production and water quality and quantity. The ecosystem disservice of elevated disease risk in humans, wildlife and domestic animals should be an additional consideration when making land management and policy decisions related to WPE.

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“…Bush thickening (BT) is caused by a dynamic change in vegetation composition, structure and density over time (De Klerk 2004;Smit, Richter & Aucamp 1999). Bush thickening is caused by established stands of woody species, which increase in density and cover mostly as a result of fire and grazing management, below-average rainfall, competition between C 3 and C 4 type plants and elevated CO 2 levels (Buitenwerf et al 2012;Dreber, Van Rooyen & Kellner 2018;Higgins, Bond & Trollope 2007;Kellner 2008;Kraaij & Ward 2006;Ward 2005).…”

Section: Bush Thickeningmentioning

confidence: 99%

Restoration after bush control in selected rangeland areas of semi-arid savannas in South Africa

Kellner¹,

Mangani²,

Sebitloane³

et al. 2021

BothaliaABC

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Background: One of the main causes of land degradation in South Africa is bush thickening (BT) of mainly Senegalia or Vachellia species. Restoration methods are required to control BT, and to improve grass biomass production and soil conditions in South Africa.Objectives: The objectives of this study were to determine the effect of brush packing (BP) as a restoration method to increase grass biomass production, assess soil moisture after BP on different soil types, and document the perceptions of the local communities towards BP.Method: Methods included cutting the stems of woodies with a diameter of at least 10 cm at knee height by chainsaw and manual clipping after which an arborocide was applied to the stumps. A neutron probe was used to measure volumetric moisture content at two different soil depths. The grass biomass was analysed using ANOVA at a confidence level of 95%. Quantitative and qualitative approaches were used to gather information about the perceptions of local communities towards restoration in group discussions.Results: The short-term data showed that the implementation of BP as restoration method increased grass biomass production. The soil texture influenced the volumetric soil moisture. Higher soil moisture content was found in the deeper clayey soils. The local participants’ interpretation towards the restoration project was positive.Conclusion: The project increased the grazing potential and contributed to job creation to improve the well-being of the people in the community.

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Relationship of plant diversity and bush cover in rangelands of a semi‐arid Kalahari savannah, South Africa

Cited by 9 publications

References 15 publications

Forb ecology research in dry African savannas: Knowledge, gaps, and future perspectives

Forb ecology research in dry African savannas: Knowledge, gaps, and future perspectives

Woody plant encroachment and the ecology of vector‐borne diseases

Restoration after bush control in selected rangeland areas of semi-arid savannas in South Africa

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