Herbivory effects on saplings are influenced by nutrients and grass competition in a humid South African savanna

Vadigi, Snehalatha; Ward, David

doi:10.1016/j.ppees.2013.10.002

Cited by 20 publications

(24 citation statements)

References 58 publications

(84 reference statements)

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“…This has also been reported in Australian semi-arid savannas and in bin experiments [41]. In mesic savannas, increased soil moisture contributes to increased grass biomass, therefore higher levels of grass competition, fuel loads and higher fire intensities [13,27,34,66], which maintain the grassy regime.…”

Section: Soil Moisturesupporting

confidence: 69%

Woody Encroachment as a Social-Ecological Regime Shift

et al. 2018

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African savannas are increasingly affected by woody encroachment, an increase in the density of woody plants. Woody encroachment often occurs unexpectedly, is difficult to reverse, and has significant economic, cultural and ecological implications. The process of woody encroachment represents a so-called regime shift that results from feedback loops that link vegetation and variables such as fire, grazing and water availability. Much of the work on woody encroachment has focused on the direct drivers of the process, such as the role of fire or grazing in inhibiting or promoting encroachment. However, little work has been done on how ecological changes may provide feedback to affect some of the underlying social processes driving woody encroachment. In this paper, we build on the ecological literature on encroachment to present a qualitative systems analysis of woody encroachment as a social-ecological regime shift. Our analysis highlights the underlying indirect role of human population growth, and we distinguish the key social-ecological processes underlying woody encroachment in arid versus mesic African savannas. The analysis we present helps synthesize the impacts of encroachment, the drivers and feedbacks that play a key role and identify potential social and ecological leverage points to prevent or reverse the woody encroachment process.

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Section: Soil Moisturesupporting

confidence: 69%

Woody Encroachment as a Social-Ecological Regime Shift

et al. 2018

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“…Unfavorable climate conditions and competition will affect their growth rates, but not necessarily their survival (Cardoso et al 2016). Belowground competition grasses can slow sapling growth particularly during periods of higher than average rainfall (February et al 2013) or if mineral availability is increased (Vadigi and Ward 2012) and can also be amplified by browsing (Vadigi and Ward 2014). Accordingly, competition, nutrient limitations, and herbivory can combine to slow sapling development and prolong the time they require to achieve a size that allows them to competitively dominate grasses and begin to influence microclimate and soil properties that will alter future patterns of community development.…”

Section: Transitioning From Saplings To Adultsmentioning

confidence: 99%

“…Both browsing and fire constrain the progression from sapling to mature shrub or tree (Norton-Griffiths 1979; Augustine and McNaughton 2004;Vadigi and Ward 2014). The frequency and intensity of fire are coupled strongly to grassland productivity (Krawchuk and Moritz 2011) and to grazing (Anderies et al 2002;Fuhlendorf et al 2008).…”

Section: Transitioning From Saplings To Adultsmentioning

confidence: 99%

Woody Plant Encroachment: Causes and Consequences

Archer

Andersen

Predick

et al. 2017

Springer Series on Environmental Management

369

379

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Woody vegetation in grasslands and savannas has increased worldwide over the past 100-200 years. This phenomenon of "woody plant encroachment" (WPE) has been documented to occur at different times but at comparable rates in rangelands of the Americas, Australia, and southern Africa. The objectives of this chapter are to review (1) the process of WPE and its causes, (2) consequences for ecosystem function and the provision of services, and (3) the effectiveness of management interventions aimed at reducing woody cover. Explanations for WPE require consideration of multiple interacting drivers and constraints and their variation through time at a given site. Mean annual precipitation sets an upper limit to woody plant cover, but local patterns of disturbance (fire, browsing) and soil properties (texture, depth) prevent the realization of this potential. In the absence of these constraints, seasonality, interannual variation, and intensity of precipitation events determine the rate and extent of woody plant expansion. Although probably not a triggering factor, rising atmospheric CO 2 levels may have favored C 3 woody plant growth. WPE coincided with the global intensification of livestock grazing that by reducing fine fuels, hence fire frequency and intensity, facilitated WPE. From a conservation perspective, WPE threatens the maintenance of grassland and savanna

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“…This predominance would result in reduced grass‐tree competition as well as a reduced fuel load when the rangelands were burned. This could well have led to the observed increase in woody species (Riginos, ; Grellier et al ., ; Vadigi & Ward, , ). The absence of wood harvesting would exacerbate the increase in woody species.…”

Section: Discussionmentioning

confidence: 92%

Historical Land‐use and Vegetation Change in Northern Kwazulu‐Natal, South Africa

Russell

Ward

2016

Land Degrad Dev

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The role of anthropogenic activity is increasingly recognized as an agent of environmental change. Photographs, taken more than 130 years ago in KwaZulu-Natal, South Africa, show a very different landscape to that viewed today. In attempting to understand some of the dynamics behind the changes in the landscape, we explored the history of land-use in communal rangelands in KwaZulu-Natal from the arrival of Iron Age man through to modern practices. Communal farming is frequently cited as a major cause of environmental degradation. Traditional lifestyles have been eroded by social, political and economic changes since the arrival of European explorers and settlers in the early 1800s. This may have contributed to encroachment by woody plants into the open savannas and grasslands of KwaZulu-Natal in recent times because of increased grazing pressure and, perhaps reduced fires. Furthermore, there is decreasing dependence on wood for everyday needs due to the increased availability of electricity. Interviews with a number of community members indicate that they have noted a change in climate and in vegetation structure. Their observations have been confirmed by climate data and historic photographs. Environmental planners need to view change in a holistic manner, taking cognisance not only of the physical changes but also of the history of land-use and human needs and to give credence to community perceptions.

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Herbivory effects on saplings are influenced by nutrients and grass competition in a humid South African savanna

Cited by 20 publications

References 58 publications

Woody Encroachment as a Social-Ecological Regime Shift

Woody Encroachment as a Social-Ecological Regime Shift

Woody Plant Encroachment: Causes and Consequences

Historical Land‐use and Vegetation Change in Northern Kwazulu‐Natal, South Africa

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