Analysing Shrub Encroachment in the Southern Kalahari: A Grid-Based Modelling Approach

Jeltsch, Florian; Milton, Suzanne J.; Dean, W. R. J.; Rooyen, N. van

doi:10.2307/2405265

Cited by 130 publications

(95 citation statements)

References 40 publications

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“…10-year periods, i.e., 1962-1972 and 1978-1988 (expansion rates of 0.45 and 1.2, respectively), may as well have resulted from climatic influences, specifically differences in rainfall over both 10-year periods. In this case, the higher cerradão expansion rates observed during periods of higher precipitation show similarities with the results reported by Jeltsch et al (1997), Bowman et al (2001), Fensham et al (2003 and Tews et al (2005), and some proposed models such as that developed by Jeltsch et al (1998) to explain competition for hydric resources between woody and herbaceous components of African semi-arid savannas.…”

Section: Geostatistic Analysis and Edaphic Characteristicssupporting

confidence: 88%

Spatial-temporal distribution of fire-protected savanna physiognomies in Southeastern Brazil

Pinheiro

Azevedo

Monteiro

2010

An. Acad. Bras. Ciênc.

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The analysis of the influence of edaphic finer textures, as a facilitating factor for the expansion of forest formations in the absence of fire, was possible thanks to rare characteristics found in a savanna fragment located in the State of São Paulo, Brazil. The total suppression of fire for over four decades, and the occurrence of two savanna physiognomies, cerrado sensu stricto and cerradão, allowed the conduction of this study based on the hypothesis that cerradão, a physiognomy of forest aspect consisting of fire-sensitive tree and shrubs species, is favored by fire absence and higher soil hydric retention capacity. Edaphic samples were collected from a regular grid of 200 m 2 for the production of isopletic maps of the distribution of clay, fine sand, coarse sand and silt edaphic textures by the geostatistic method of ordinary kriging. Changes in the areas occupied by both savanna physiognomies, defined on the basis of aerial photographs taken over a period of 43 years, were assessed through mean variation rates. Besides corroborating the hypothesis of edaphic hydric retention as a facilitating factor for the expansion of forest physiognomies in savanna areas, we were able to infer the positive influence of higher precipitation on the increase in cerradão expansion rates.

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Section: Geostatistic Analysis and Edaphic Characteristicssupporting

confidence: 88%

Spatial-temporal distribution of fire-protected savanna physiognomies in Southeastern Brazil

Pinheiro

Azevedo

Monteiro

2010

An. Acad. Bras. Ciênc.

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“…They are most often the only possibility to investigate the long-term dynamics of range management systems in arid ecosystems, because their impact becomes visible only after decades (Wissel et al 1996, Jeltsch et al 2001. In numerous studies, the spatially and temporally heterogeneous response of vegetation dynamics to grazing and precipitation is investigated with the aid of modeling (Pickup 1996, Wiegand and Milton 1996, Jeltsch et al 1997, Illius et al 1998, Janssen et al 2000, Weber et al 2000, Adler et al 2001, van de Koppel et al 2002, Pu¨tz 2005, Mu¨ller et al 2007. However the few modeling studies of mobile management systems of pastoral nomads are mainly focused on socioeconomic issues (Rouchier et al 2001, Kuper et al 2003, Thornton et al 2003, 2006, MilnerGulland et al 2006 and not on the impact on vegetation (as exception Coughenour 1992, Illius and O'Connor 2000.…”

Section: Introductionmentioning

confidence: 99%

Learning From Local Knowledge: Modeling the Pastoral‐nomadic Range Management of the Himba, Namibia

Müller

Linstädter

Frank

et al. 2007

Ecological Applications

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Abstract. It is widely accepted that successful grazing management strategies in semiarid ecosystems need to be adapted to the highly temporal and spatially heterogeneous forage production. Nevertheless, a full understanding of the key factors and processes for sustainable adaptive management has yet to be reached. The investigation of existing, successful range management systems by simulation models may help to derive general understanding and basic principles.The semi-nomadic Himba in northern Namibia applied a sophisticated management system until the mid-1990s which combined season-dependent pasture use (resulting in rainy-season pastures and dry-season pastures), preservation of reserves for drought and sanctions for rule breaking. A stochastic ecological simulation model has been developed here which represents the main aspects of this management system. With this model we analyze (1) which components of the traditional Himba strategy are essential for sustainability and (2) what happens to the state of the rangeland system under socioeconomic changes.This study shows that temporally and spatially heterogeneous pasture use yields higher productivity and quality of a pasture area than the pressure of homogeneous permanent grazing. Two aspects are of importance: (1) intra-annual heterogeneous use (resting of the dry-season pastures during the rainy season) and (2) interannual heterogeneous use (spatial extension of grazing in years of drought). This management system leads to an effective build-up and use of a buffer in the system: the reserve biomass (the non-photosynthetic reserve organs of the plants), an indicator for grazing and management history.Analyzing purchase as one form of socioeconomic change, we demonstrate that easier market access to purchase livestock may lead to a decline in vegetation quality. However, cattle production increases as long as rest periods on parts of the pasture during the rainy season are granted.Methodologically, we emphasize that simulation models offer an excellent framework for analyzing and depicting basic principles in sustainable range management derived from local knowledge. They provide the opportunity of testing whether these basic principles are also valid under different ecological and socioeconomic settings.

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“…The spatial model developed by Weber et al [1998] was used to determine the effects of grazing intensity and grazing heterogeneity applied to the southern Kalahari and shows that high levels of grazing lead to shrub invasion. Jeltsch et al [1997] also reported that when grazing intensity reaches a critical level, shrub cover increases, drastically lowering the productivity of the range.…”

Section: 0mentioning

confidence: 97%

Biodiversity Conservation in Managed Landscapes

Rensburg¹,

Thomas²

2010

A Handbook of Environmental Management

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Analysing Shrub Encroachment in the Southern Kalahari: A Grid-Based Modelling Approach

Cited by 130 publications

References 40 publications

Spatial-temporal distribution of fire-protected savanna physiognomies in Southeastern Brazil

Spatial-temporal distribution of fire-protected savanna physiognomies in Southeastern Brazil

Learning From Local Knowledge: Modeling the Pastoral‐nomadic Range Management of the Himba, Namibia

Biodiversity Conservation in Managed Landscapes

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