Stability of wooded patches in a South African nutrient-poor grassland: do nutrients, fire or herbivores limit their expansion?

Mourik, A.A.; Langevelde, Frank van; Tellingen, Esther van; Heitkönig, Ignas M. A.; Gaigher, I. G.

doi:10.1017/s0266467407004282

Cited by 17 publications

(20 citation statements)

References 35 publications

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“…1). They possess high tree diversity of up to 70 species (Mourik et al 2007). The ground is bare of any herbaceous vegetation.…”

Section: T H E S T U D Y S I T Ementioning

confidence: 99%

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Islands of fear: effects of wooded patches on habitat suitability of the striped mouse in a South African grassland

Baker¹,

Brown

2010

Functional Ecology

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Summary1. As a fundamental unit within a landscape, habitat patches create spatial heterogeneity. On a gradient of habitat patch size, one sees patches of denser vegetation cover occurring in otherwise open habitats (e.g. bushes in the desert, forest fragments in grasslands). 2. The resulting habitat fragmentation and consequent edge effects continue to concern conservation biologists, landscape ecologists, and wildlife managers due to their role in influencing wildlife abundance and distribution on broad geographic scales. 3. Although ecological processes near habitat edges often differ from processes away from edges, an animal's suitable habitat may increase or decrease by 'positive' or 'negative' edge effects. Such effects can be measured using behavioural indicators and experiments based on the costs and benefits of foraging under diminishing returns. 4. We used live trapping, giving-up densities [amount of food left behind in experimental food patches -giving-up density (GUD)] and geographic information system (GIS) analyses to test for spatial and temporal habitat selection by the four-striped grass mouse (Rhabdomys pumilio) inhabiting a grassland containing distinct 'islands' of woody vegetation (500 m 2 of average area). We investigated how these woody islands influence the quality of the grassland in terms of activity patterns, feeding opportunities, predation risk and habitat suitability. We used R. pumilio's GUDs to explicitly map and measure habitats of varying quality using GIS. 5. Our results showed that R. pumilio perceived the wooded patches as habitats with no opportunities and yet highly risky when opportunities are provided. Furthermore, the wooded patches had a negative edge effect, their unsuitability extended for 1-3 m into the otherwise suitable habitats. 6. The combination of live-trapping and giving up densities provided an unbiased and controlled measure of a prey's perception of habitat use and foraging costs when equal opportunities are simultaneously provided. These techniques and concepts should be broadly applicable by conservationists and ecologists interested in understanding and managing edge effects. 7. This approach aims to effectively quantify edge effects and extrapolate predation risk on a landscape scale, thereby developing recommendations for managers to improve the quality or amount of edges for wildlife.

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“…1). They possess high tree diversity of up to 70 species (Mourik et al 2007). The ground is bare of any herbaceous vegetation.…”

Section: T H E S T U D Y S I T Ementioning

confidence: 99%

“…The grass consists of short acidophilic, unpalatable grass species, dominated by Loudetia simplex (Nees) C. E. Hubb. Grass biomass approximates 500 g m )2 (Mourik et al 2007). Dense fern stands of up to 1 m in height partially or completely surrounds several wooded patches.…”

Section: T H E S T U D Y S I T Ementioning

confidence: 99%

Islands of fear: effects of wooded patches on habitat suitability of the striped mouse in a South African grassland

Baker¹,

Brown

2010

Functional Ecology

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Section: Introductionmentioning

confidence: 99%

“…Despite these distinct spatial patterns in C. intratropica distribution, the mechanisms and temporal dynamics that maintain these groves remain unclear. It is well established that frequent savanna fires limit the establishment and recruitment of woody plants (Mourik et al 2007;Hoffmann et al 2009) -especially if they are obligate-seeding species (i.e. incapable of resprouting after fire) like C. intratropica (Cohn et al 2011;Prior et al 2011).…”

mentioning

confidence: 99%

Tree cover–fire interactions promote the persistence of a fire‐sensitive conifer in a highly flammable savanna

et al. 2012

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Summary1. Callitris intratropica is a long-lived, obligate-seeding, fire-sensitive overstorey conifer that typically occurs in small groves (<0.1 ha) of much higher tree densities than the surrounding, eucalypt-dominated tropical savanna in northern Australia. We used C. intratropica groves of varying canopy cover to examine the role of feedbacks between fire and tree cover in the persistence of a fire-sensitive tree species and the maintenance of habitat heterogeneity in a highly flammable savanna. 2. We examined the population structure and floristic composition of C. intratropica groves and conducted controlled burns with Aboriginal landowners to test the prediction that groves of C. intratropica with closed canopies inhibit savanna fires by physically altering the fuel arrays below trees. We measured pre-and post-burn fuel availability, the probability of burning and fire intensity along transects (55-75 m) spanning entire C. intratropica groves and extending into the surrounding savanna matrix. 3. We found that closed-canopy groves of C. intratropica had higher densities of seedlings and saplings than open-canopy groves and supported a distinct plant community. Closed-canopy groves also had a lower probability of burning and less severe fires due to a lower availability of fine fuels than the surrounding savanna. 4. Synthesis. Our results suggest that the observed regeneration within closed-canopy C. intratropica groves within frequently burnt savanna reflects a vegetation-fire feedback. A significant, negative relationship between canopy cover and the probability of burning provides strong evidence that closed-canopy C. intratropica groves are capable of excluding low-intensity savanna fires, thereby enabling the persistence of patches of fire-sensitive forest or woodland amid open, highly flammable savanna vegetation. We present our findings as evidence that alternative stable state dynamics may play a role in determining savanna diversity and structure.

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“…a; Abu Baker & Brown, ). They possess high tree diversity and bare ground underneath (Mourik et al ., ). The boundaries of the islands showed heavy browse marks (up to 1.8 m) and sharp transitions to grassland.…”

Section: Methodsmentioning

confidence: 97%

Foraging and habitat use of common duikers,Sylvicapra grimmia, in a heterogeneous environment within the Soutpansberg, South Africa

Baker

Brown

2013

Afr. J. Ecol.

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We investigated aspects of the foraging behaviour and activity patterns of free-ranging common duikers (Sylvicapra grimmia) within the Soutpansberg, South Africa. We used giving-up densities (GUD) and camera traps to test for habitat selection and patch-use behaviour by common duikers inhabiting a grassland containing distinct 'islands' of woody vegetation. Foraging in or around a wooded island was affected by its surrounding vegetation. GUDs were significantly lower in portions dominated by tall grass and scattered ferns and highest in areas with open short grass and thick fern. Using grids of 5 9 5 stations, we mapped the duikers' foraging on a larger scale that incorporated neighbouring rocky hillsides. The duikers preferred feeding in areas with tall grass and scattered fern (sufficient cover and escape routes), followed by the wooded islands and thick fern (lack of sightlines/escape routes and presence of predatorambush sites), whereas little foraging occurred at the edges and rocky areas (hard substrate that impede escape potential). Photos (total 873) revealed solitary activity, highest in the late afternoon. Photos of vigilant individuals were mostly from rocky and fern habitats. Our results suggest that the duikers allocated their feeding efforts, activity and vigilance patterns to attune to their perceived risk of predation within their heterogeneous environment. selon le risque de pr edation qu'ils perc ßoivent dans leur environnement h et erog ene.

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Stability of wooded patches in a South African nutrient-poor grassland: do nutrients, fire or herbivores limit their expansion?

Cited by 17 publications

References 35 publications

Islands of fear: effects of wooded patches on habitat suitability of the striped mouse in a South African grassland

Islands of fear: effects of wooded patches on habitat suitability of the striped mouse in a South African grassland

Tree cover–fire interactions promote the persistence of a fire‐sensitive conifer in a highly flammable savanna

Foraging and habitat use of common duikers,Sylvicapra grimmia, in a heterogeneous environment within the Soutpansberg, South Africa

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