Resilience of South African communal grazing lands after the removal of high grazing pressure

Harrison, Y. A.; Shackleton, Charlie M.

doi:10.1002/(sici)1099-145x(199905/06)10:3<225::aid-ldr337>3.0.co;2-t

Cited by 34 publications

(7 citation statements)

References 29 publications

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“…The main factors driving land degradation in communal areas in South Africa are overstocking and overgrazing (Harrison and Shackleton, 1999). Overgrazing leads to reduced vegetation cover and increased soil exposure which has been shown to result in high soil losses and compaction (Elkins et al, 1986).…”

Section: Discussionmentioning

confidence: 99%

Dung beetles (Coleoptera: Scarabaeidae) can improve soil hydrological properties

Brown

Scholtz

Janeau

et al. 2010

Applied Soil Ecology

127

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a b s t r a c tAlthough dung beetles are known to perform a multitude of ecosystem services, their effects on water infiltration, runoff, porosity, moisture and erosion of soil have never been thoroughly researched. Maintenance of these hydrological properties is important in agro-ecosystem functioning where overgrazing results in negative impacts on the soil. The study site was located in the Potshini catchment in KwazuluNatal (South Africa), an area heavily grazed by livestock. We conducted two rainfall simulations on three 1 m −2 control (no dung) and six dung-treated plots in December 2008, and repeated the study in June 2009 on the same plots. Natural populations of dung beetles were allowed to colonise the dung. Simulations were conducted for 30 min at an intensity of 30 mm h −1 . Key variables calculated were pre-runoff amounts (Pi), infiltration ratios (Ki), and soil losses. Samples were collected for bulk density determination during the same time periods in order to measure differences in porosity and moisture in control and dung-treated plots at different depths. Using multivariate statistics we found significant differences between dung-treated and control plots in three of four simulations. After 48 h of beetle activity, Pi and Ki values were significantly increased and remained at elevated levels six months later. Soil losses were initially higher in dung-treated plots than controls, but had declined to less than control values after six months. Bulk density in the A-horizon (0-10 cm) was significantly reduced after 48 h of beetle activity and remained so for six months. No difference in bulk density was observed at greater depths. Soil moisture initially increased significantly in the A-horizon, as well as at 20 and 30 cm depths after six months of activity. We conclude that dung beetles positively influence hydrological properties of the soil by increasing water infiltration and soil porosity, and reducing surface water runoff. Contrasting effects on soil losses are problematic to reconcile from this study. High losses initially observed may be offset in the long-term by reductions associated with the increased infiltration ratios, though this remains to be confirmed.

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Section: Discussionmentioning

confidence: 99%

Dung beetles (Coleoptera: Scarabaeidae) can improve soil hydrological properties

Brown

Scholtz

Janeau

et al. 2010

Applied Soil Ecology

127

View full text Add to dashboard Cite

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“…Where heavy grazing is the primary degradation factor, restoration might consist initially of allowing severely grazed tracts to recover from the biotic legacy of overgrazing [9], although highly-degraded vegetation might not respond to grazing cessation alone [56]. Response time of native vegetation to reduced grazing can vary between several years to several decades depending on level of degradation and ecosystem productivity [57][58][59]. In the Grand River Grasslands, native species abundance might increase following grazing cessation [37], but we hypothesize that relative response to grazing cessation decreases as the severity of degradation increases (pathways R.1, R.2, and R.3, respectively) ( Figure 6).…”

Section: Managing Pathways Between States For Restorationmentioning

confidence: 99%

Multivariate Analysis of Rangeland Vegetation and Soil Organic Carbon Describes Degradation, Informs Restoration and Conservation

McGranahan

Engle

Fuhlendorf

et al. 2013

Land

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Agricultural expansion has eliminated a high proportion of native land cover and severely degraded remaining native vegetation. Managers must determine where degradation is severe enough to merit restoration action, and what action, if any, is necessary. We report on grassland degraded by multiple factors, including grazing, soil disturbance, and exotic plant species introduced in response to agriculture management. We use a multivariate method to categorize plant communities by degradation state based on floristic and biophysical degradation associated with historical land use. The variables we associate with degradation include abundance of the invasive cool-season grass, tall fescue (Schedonorus phoenix (Scop.) Holub); soil organic carbon (SOC); and heavy livestock grazing. Using a series of multivariate analyses (ordination, hierarchical clustering, and multiple regression), we identify patterns in plant community composition and describe floristic degradation states. We found vegetation states to be described largely by vegetation composition associated primarily with tall fescue and secondarily by severe grazing, but not soil organic carbon. Categorizing grasslands by vegetation states helps

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“…Two of the major rangeland biomes in southern Africa are grasslands and savannas [24] , [25] . The vast majority of rangeland studies has focused on single biomes, most often on the grassland biome [26] – [28] followed by the savanna biome [29] – [31] . A recent study analysed impacts of heavy grazing on plant species richness across six South African rangeland biomes [21] , but did not differentiate between land tenure systems.…”

Section: Introductionmentioning

confidence: 99%

Are There Consistent Grazing Indicators in Drylands? Testing Plant Functional Types of Various Complexity in South Africa’s Grassland and Savanna Biomes

et al. 2014

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Despite our growing knowledge on plants’ functional responses to grazing, there is no consensus if an optimum level of functional aggregation exists for detecting grazing effects in drylands. With a comparative approach we searched for plant functional types (PFTs) with a consistent response to grazing across two areas differing in climatic aridity, situated in South Africa’s grassland and savanna biomes. We aggregated herbaceous species into PFTs, using hierarchical combinations of traits (from single- to three-trait PFTs). Traits relate to life history, growth form and leaf width. We first confirmed that soil and grazing gradients were largely independent from each other, and then searched in each biome for PFTs with a sensitive response to grazing, avoiding confounding with soil conditions. We found no response consistency, but biome-specific optimum aggregation levels. Three-trait PFTs (e.g. broad-leaved perennial grasses) and two-trait PFTs (e.g. perennial grasses) performed best as indicators of grazing effects in the semi-arid grassland and in the arid savanna biome, respectively. Some PFTs increased with grazing pressure in the grassland, but decreased in the savanna. We applied biome-specific grazing indicators to evaluate if differences in grazing management related to land tenure (communal versus freehold) had effects on vegetation. Tenure effects were small, which we mainly attributed to large variability in grazing pressure across farms. We conclude that the striking lack of generalizable PFT responses to grazing is due to a convergence of aridity and grazing effects, and unlikely to be overcome by more refined classification approaches. Hence, PFTs with an opposite response to grazing in the two biomes rather have a unimodal response along a gradient of additive forces of aridity and grazing. The study advocates for hierarchical trait combinations to identify localized indicator sets for grazing effects. Its methodological approach may also be useful for identifying ecological indicators in other ecosystems.

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Resilience of South African communal grazing lands after the removal of high grazing pressure

Cited by 34 publications

References 29 publications

Dung beetles (Coleoptera: Scarabaeidae) can improve soil hydrological properties

Dung beetles (Coleoptera: Scarabaeidae) can improve soil hydrological properties

Multivariate Analysis of Rangeland Vegetation and Soil Organic Carbon Describes Degradation, Informs Restoration and Conservation

Are There Consistent Grazing Indicators in Drylands? Testing Plant Functional Types of Various Complexity in South Africa’s Grassland and Savanna Biomes

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