Resilience of soils and vegetation subjected to different grazing intensities in a semi‐arid rangeland of Kenya

Mworia, John K.; Mnene, W. N.; Musembi, David K.; Reid, Robin S.

doi:10.1080/10220119.1997.9647915

Cited by 20 publications

(19 citation statements)

References 11 publications

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“…Most researchers support the findings of this study that rangeland degradation usually leads to increased soil compaction due to a decrease in plant cover (Donaldson et al, 1984;Du Toit, 1986;Warren et al, 1986a;Friedel, 1987;Chanasyk and Naeth, 1995;Mworia et al, 1997;Broersma et al, 1999;Snyman, 2005), reduced soil aggregate stability (Warren et al, 1986b) and reduced soil fertility (Dormaar and Willms, 1998). The loss of vegetative and litter cover with degradation (Warren et al, 1986a,b;Thurow et al, 1988;Hoffman and Ashwell, 2001;Holm, 2000;Snyman, 2005) allows direct impact of raindrops on soils (Lal and Elliot, 1994;Russel et al, 2001), and may also produce hydrophobic substances that can reduce infiltration (DeBano et al, 1970(DeBano et al, , 1976Emmerich and Cox, 1992;Snyman, 1999aSnyman, , pp.…”

Section: Soil Compactionsupporting

confidence: 71%

Rangeland degradation in a semi-arid South Africa—II: influence on soil quality

Snyman

Preez

2005

Journal of Arid Environments

102

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Section: Soil Compactionsupporting

confidence: 71%

Rangeland degradation in a semi-arid South Africa—II: influence on soil quality

Snyman

Preez

2005

Journal of Arid Environments

102

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“…This agrees with the findings of a few other researchers who reported a decrease in cover due to high stocking rates in semi-arid rangelands (Roux, 1967;Friedel, 1991;O'Connor, 1995;Mworia et al, 1997;Ingram, 2003;Wood et al, 2008;Hoshino et al, 2009), while others have found either a positive or inconclusive relationship (Belsky, 1992;O'Connor, 1994). A further increase in stocking rate for the same grazing periods, as applied in this study, should lead to a still higher decrease in canopy and canopy-spread cover.…”

Section: Discussionsupporting

confidence: 82%

“…The higher the stocking rate, the higher the decrease in canopy and canopy-spread cover and the longer resting period is needed for rangeland to recover (Milton et al, 1998;Sparrow et al, 2003;Tongway et al, 2003;Kraaij & Milton, 2006). According to Mworia et al (1997), the herbaceous biomass and cover in heavily grazed semi-arid rangeland did not recover after a two-year resting period. Various researchers found that too much severe defoliation with relatively short resting periods in between, are detrimental to vegetation cover and dry matter production (Du Preez, 1972;Hobson & Sykes, 1980;Van der Westhuizen, 1980).…”

Section: Discussionmentioning

confidence: 99%

Physical impact of sheep grazing on arid Karoo subshrub/grass rangeland, South Africa

Toit¹,

Snyman²,

Malan³

2011

SA J. An. Sci.

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________________________________________________________________________________ AbstractGrazing levels and rotational schemes need to be tailored to each individual farm or pasture, and more studies are needed on the resilience of rangelands and on separating the effects of grazing and climate. The direct short-term impact of three rates of stocking (4, 8 and 16 Small Stock Units-SSU/ha) was quantified in terms of composition and cover of arid Nama Karoo vegetation (subshrub/grass). Mature Merino wethers grazed in one hectare plots during May in 1995 and 1996 (the plots were not subjected to grazing at any other time). The basal cover of the Karoo bushes (shrubs) showed a decrease at the highest stocking rate only, with the species Phymaspermum parvifolium the most sensitive to intensive grazing. An increase in stocking rate caused a significant decrease in both canopy cover and canopy-spread cover. The canopy cover of palatable Karoo bushes such as Felicia muricata, Salsola calluna and Walafrida geniculata decreased most. Light stocking (4 SSU/ha) was apparently the least detrimental to the vegetation composition and cover. Regardless of stocking rate, an 11-month resting period was possibly sufficient for all the vegetation parameters concerned to be fully restored after grazing took place. The rangeland rapidly reacted to rainfall as the ephemeral cover increased temporarily. The higher the stocking rate was, the greater the increase in ephemerals occurring. The ecological sustainability of the Nama Karoo ecosystem, utilised by high stocking densities, is questioned. _______________________________________________________________________________

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“…The direction of change is not, however, predictable and the ecological processes involved are controversial (Hibbard et al, 2001). High livestock stocking rates can also result in a loss of vegetation cover and an associated decrease in soil nutrient status, organic matter, water content and infiltrability (Seitlheko et al, 1993;Mworia et al, 1997;Allsopp, 1999). Robin- Figure 1.…”

Section: Introductionmentioning

confidence: 97%

Transformation of thicket to savanna reduces soil quality in the Eastern Cape, South Africa

Mills

Fey

2004

Plant Soil

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Xeric succulent thicket in the Eastern Cape, South Africa has been used for farming goats since the early 1900s. This habitat is characterised by a dense cover of the succulent bush Portulacaria afra and by a warm, semi-arid climate with evenly distributed annual rainfall of 250-400 mm. Heavy browsing by goats results in the loss of P. afra and transforms the thicket to an open savanna dominated by annual grasses. Eight fence-line comparisons between thicket and savanna were used to investigate differences in soil quality associated with the vegetation change. Composite soil samples were taken to a depth of 10 cm from 1 ha plots on either side of the fence-line. Associated with the change from thicket to savanna, a significant decrease (paired t-test, P < 0.05) was found in total C (respective means of 5.6 vs. 3.0%), total N (0.33 vs. 0.24%), labile C (2.8 vs. 1.5%), CO 2 flux (1.9 vs. 0.5 µmol m −2 s −1 ), soil respiration in the laboratory (144 vs. 79 ng C kg −1 s −1 ), (NH 4 )OAc-extractable Mg (55 vs. 28 mmol c kg −1 ), and laboratory infiltration rate (51 vs. 19 mm h −1 ). In the same direction there was a similarly significant increase in modulus of rupture (16 vs. 34 kPa), water-soluble Ca (2.3 vs. 3.4 mmol c kg −1 ) and pH (6.7 vs. 7.7). The soil C content of 5.6% in thicket is surprisingly high in this warm, semi-arid climate and suggests that the dense P. afra bush strongly regulates soil organic matter through microclimate, erosion control, litter quantity and perhaps chemistry. Savanna soils had a greater tendency to crust (as evident in a lower rate of laboratory infiltration and greater modulus of rupture) than thicket soils. This was attributed to their lower organic matter content, which probably reduced aggregate stability. Savannas are likely to be more prone to runoff and erosion not only because of sparser vegetation but also because of a decline in soil quality.

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Resilience of soils and vegetation subjected to different grazing intensities in a semi‐arid rangeland of Kenya

Cited by 20 publications

References 11 publications

Rangeland degradation in a semi-arid South Africa—II: influence on soil quality

Rangeland degradation in a semi-arid South Africa—II: influence on soil quality

Physical impact of sheep grazing on arid Karoo subshrub/grass rangeland, South Africa

Transformation of thicket to savanna reduces soil quality in the Eastern Cape, South Africa

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