Soil and vegetation changes across a Succulent Karoo grazing gradient

Beukes, P.C.; Ellis, F.

doi:10.2989/10220110309485793

Cited by 26 publications

(16 citation statements)

References 20 publications

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“…Furthermore, managed grazing is the single most extensive form of land use on the planet (Asner et al 2004). Even for extensive systems where rotational grazing is not practiced, there are still important issues of animal concentration around water holes and camping areas where animals congregate (Beukes and Ellis 2003;Betteridge et al 2010).…”

Section: Introductionmentioning

confidence: 98%

A urine patch framework to simulate nitrogen leaching on New Zealand dairy farms

Romera

Levy

Beukes

et al. 2012

Nutr Cycl Agroecosyst

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On New Zealand dairy farms, it is the nitrogen excreted directly onto pasture, particularly urine, that drives nitrogen (N) leaching from the farm. A new framework (UPF: Urine Patch Framework) is presented that post-processes the results of a whole farm model and runs a mechanistic soil model to simulate the urine patches. Two alternative methods to simulate the spatial distribution of urine patches were implemented and compared (Grid: spatially explicit, and Probabilistic: based on the probability of different temporal urination patterns). This paper describes the implementation of these two methods in connection with a Whole Farm Model; and compares the N leaching predictions with observed data. Two examples are provided, one analyzing the impact of urine patch overlap and another, the relative risk of N leaching at different times of urinary N deposition. The model showed good correlation and predictive ability between simulated annual N leaching results and observed data [R 2 = 94 %, mean relative prediction error (MRPE) = 10 % for Grid and R 2 = 72 %, MRPE = 20 % for Probabilistic]. The two methods produced similar results across an 8-year period for monthly and annual N leaching (R 2 = 96 %, MRPE = 10 % and R 2 = 86 %, MRPE = 8 %; respectively). Only 8 % of the paddock area was covered with multiple urinations during 1 year, but as much as 39 % of the total urine volume was deposited on overlapped patches. Systematically removing all urinary N for 1 month in either May or June reduced N leaching by approximately 20 %. Avoiding urinary N deposition during autumn or early winter could be highly effective in mitigating N leached during the following winter.

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Section: Introductionmentioning

confidence: 98%

A urine patch framework to simulate nitrogen leaching on New Zealand dairy farms

Romera

Levy

Beukes

et al. 2012

Nutr Cycl Agroecosyst

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“…1994; Jeltsch et al . 1997; Thrash 1998a,b) and a pair of unreplicated studies from the Succulent Karoo (Beukes & Ellis 2002; Riginos & Hoffman 2003). To date, no published studies have assessed the impact of watering point provision on the structure and species richness of Nama‐Karoo shrublands in South Africa.…”

Section: Introductionmentioning

confidence: 99%

Gradients in vegetation cover, structure and species richness of Nama‐Karoo shrublands in relation to distance from livestock watering points

Todd

2006

Journal of Applied Ecology

120

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Summary 1.Gradients of animal impact known as piospheres tend to develop around artificial watering points, particularly in arid zones. Such grazing gradients represent a potential opportunity for differentiating the long-term effects of livestock activity from other environmental patterns. In this study, the impact of watering point provision on the plant cover, species richness and community structure of Karoo shrublands, South Africa, was investigated in the context of the evolutionary history and current grazing management practices of the region. 2. The impacts of watering point provision were investigated by sampling plant cover and composition along transects placed at set distances, ranging from 10 m to 2200 m, from 11 watering points. 3. Karoo vegetation cover and structure are relatively resilient to livestock grazing. Karoo plant diversity, as measured by species richness, evenness and dominance, was not as resilient. Twice as many species decreased as increased near watering points. The majority of species that decreased were regarded as being highly palatable to livestock. Heavy grazing, leading to death or repeated reproductive failure, is the most likely mechanism leading to the decline of such species. 4. The highly disturbed area immediately adjacent to watering points was dominated by forbs and contained a large proportion of alien species. Adjacent to this was a zone dominated by widespread shrub species of medium to low palatability. Areas most distant from watering points contained a greater proportion of species known to be highly palatable to livestock. The ability of dominant Karoo shrubs to tolerate heavy grazing may have allowed rangeland managers to maintain stocking rates above that which can be tolerated by the majority of species but which are supported by a minority of grazing-tolerant species. 5. Synthesis and applications. Highly palatable species are more abundant in areas distant from water points. Larger paddocks therefore provide a refuge for sensitive species that might otherwise be lost from the rangeland as a whole. Species that tend to occur away from watering points represent potentially useful indicators of grazing pressure. The use of these species as indicators of rangeland condition among landowners should be promoted.

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“…Soil compaction alters soil structure and hydrology which can affect water absorption by plants (Kozlowski, 1999). Depending on the intensity and period of livestock stocking rates these factors can cause vegetation change, as has been observed along a piosphere in the Tanqua Karoo part of the Succulent Karoo biome (Beukes and Ellis, 2003). Haarmeyer et al (2010) found that intense stocking of livestock reduced species richness and the abundance of endemic species on quartz field vegetation.…”

Section: Introductionmentioning

confidence: 97%

Livestock paths on Namaqualand quartz fields: Will the endemic flora disappear?

Tonder

Milton

Cameron

2014

South African Journal of Botany

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a b s t r a c tQuartz fields are rare features that contribute significantly to vegetation diversity and endemism of South Africa's Succulent Karoo Biome. The Riethuis-Wallekraal quartz fields in the north-western Namaqualand area of South Africa contain 17 quartz field specialist species of which seven are endemic to this specific area. Hoofaction by livestock has formed paths of approximately 0.30 m on these quartz fields. It would be important to conservationists to understand whether direct (e.g. trampling) and indirect effects (e.g. burial of flora by sediment movement) associated with the livestock paths holds any threat to the dwarf succulent (b 0.05 m) and micro-chamaephytes (0.06-0.15 m) endemic to the quartz fields. We tested the hypotheses that the unique quartz field vegetation and biological soil crusts would be affected by loose soil particles transported downslope from the paths. The soil stability index, total vegetation cover, cover of specialized quartz field species and species diversity were lower on livestock paths but did not differ between upslope and downslope locations. Livestock paths also had lower cover and fewer quartz field specialist species. It is concluded that under conditions of intense and continuous grazing, livestock are likely to have an even stronger negative impact on the specialist quartz field flora.

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Soil and vegetation changes across a Succulent Karoo grazing gradient

Cited by 26 publications

References 20 publications

A urine patch framework to simulate nitrogen leaching on New Zealand dairy farms

A urine patch framework to simulate nitrogen leaching on New Zealand dairy farms

Gradients in vegetation cover, structure and species richness of Nama‐Karoo shrublands in relation to distance from livestock watering points

Livestock paths on Namaqualand quartz fields: Will the endemic flora disappear?

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