The Rangeland Journal The Rangeland Journal Society
Rangeland ecology and management
RESEARCH ARTICLE

Do elephants influence the organisation and function of a South African grassland?

D. M. Parker A C , R. T. F. Bernard A and J. Adendorff B
+ Author Affiliations
- Author Affiliations

A Wildlife and Reserve Management Research Group, Department of Zoology and Entomology, PO Box 94, Rhodes University, Grahamstown 6140, Republic of South Africa.

B South African National Parks, Addo Elephant National Park, PO Box 52, Addo 6105, Republic of South Africa.

C Corresponding author. Email: d.parker@ru.ac.za

The Rangeland Journal 31(4) 395-403 https://doi.org/10.1071/RJ08039
Submitted: 5 September 2008  Accepted: 8 July 2009   Published: 27 November 2009

Abstract

The impact of elephants (Loxodonta africana) on woody plants is well known. Elephants can be regarded as drivers of ecosystem functioning by, for example, decreasing woody plant litter accumulation through defoliation. However, their influence within grassland landscapes is, by comparison, very poorly understood. We assessed the influence of elephants on grassland functionality at three separate sites (1, high elephant density, long occupation time; 2, low elephant density, short occupation time; 3, no elephants) in the Addo Elephant National Park, Eastern Cape Province, South Africa. Using landscape function analysis (LFA) we described the landscape organisation of each site, and, using visual surrogates, calculated indices of landscape stability, infiltration and nutrient cycling. The number of vegetation patches/10 m of transects surveyed was higher at sites where elephant density was high (3 elephants/km2) and where elephants had been present for a long time (>70 years). However, patch size was significantly smaller when elephant density/time of occupation increased, and the proportion of bare soil was higher where elephant density and occupation time were highest. In addition, stability, infiltration and nutrient cycling indices at a site scale were significantly lower where elephants were present at high densities and after a long occupation time. However, bare soil stability was not greatly affected by elephant grazing pressure, implying that a ‘threshold of potential concern’ has not yet arisen. We conclude that the functioning of this grassland landscape is significantly altered when elephants are present. These conclusions highlight the importance of management factors such as containment and the provision of artificial water points which may be compromising the functionality of these landscapes. We recommend ongoing assessments to inform future management decisions.

Additional keywords: landscapes, patch dynamics, rangelands, sustainability.


Acknowledgements

We gratefully acknowledge Rhodes University, the Andrew Mellon Foundation and the NRF for funding this research. Thanks also to SANPARKS (project number. 2007–03–12RBER), and Hugo Bezuidenhout in particular, for facilitating the work. Roy Lubke is thanked for his introduction to and assistance with the method, Bernard Bowles for his assistance in the field, Nicky Lunt and Christopher McQuaid for constructive comments on a previous draft and Dave Tongway for his invaluable input with the data analysis and interpretation. Thank you Dave!


References


Aguiar M. R., Sala O. E. (1999) Patch structure, dynamics and implications for the functioning of arid ecosystems. Trends in Ecology & Evolution 14, 273–277.
CrossRef | open url image1

Anderson G. D., Walker B. L. (1974) Vegetation composition and elephant damage in the Sengwa Wildlife Research Area, Rhodesia. Journal of the Southern African Wildlife Management Association 4, 1–14.
CAS |
open url image1

Ata Rezaei S., Arzani H., Tongway D. (2006) Assessing rangeland capability in Iran using landscape function indices based on soil surface attributes. Journal of Arid Environments 65, 460–473.
CrossRef | open url image1

Barnes R. F. W. (1980) The decline of the baobab tree in Ruaha National Park, Tanzania. African Journal of Ecology 18, 243–252.
CrossRef | open url image1

Britton A. J., Pearce I. S. K., Jones B. (2005) Impacts of grazing on montane heath vegetation in Wales and implications for the restoration of montane areas. Biological Conservation 125, 515–524.
CrossRef | open url image1

Carline K. A., Jones H. E., Bardgett R. D. (2005) Large herbivores affect the stoichiometry of nutrients in a regenerating woodland ecosystem. Oikos 110, 453–460.
CrossRef | CAS | open url image1

Cowling R. , and Kerley G. (2002). Impacts of elephants on the flora and vegetation of subtropical thicket in the Eastern Cape. In: ‘Elephant Conservation and Management in the Eastern Cape. Workshop Proceedings’. (Eds G. Kerley, S. Wilson and A. Massey.) pp. 55–72. (University of Port Elizabeth: Port Elizabeth, South Africa.)

Cumming D. H. M., Cumming G. (2003) Ungulate community structure and ecological processes: body size, hoof area and trampling in African savannas. Oecologia 134, 560–568.
PubMed |
open url image1

Cumming D. H. M., Fenton M. B., Rautenbach L., Taylor R. D., Cumming G. S., Cumming M. S., Dunlop J. M., Ford A. G., Hovorka M. D., Johnston D. S., Kalcounis M., Mahlangu Z., Portfors C. V. R. (1997) Elephants, woodlands and biodiversity in southern Africa. South African Journal of Science 93, 231–236. open url image1

Dorrough J., Ash J., McIntyre S. (2004) Plant responses to livestock grazing frequency in an Australian temperate grassland. Ecography 27, 798–810.
CrossRef | open url image1

Field C. R., Ross I. C. (1976) The savanna ecology of Kidepo National Park II. Feeding ecology of elephant and giraffe. East African Wildlife Journal 14, 10–15. open url image1

Guldemond R., Van Aarde R. (2007) The impact of elephants on plants and their community variables in South Africa’s Maputaland. African Journal of Ecology 45, 327–335.
CrossRef | open url image1

Gutzerová N., Herben T. (2001) Patch dynamics and local succession in a sandstone area with frequent disturbance. Journal of Vegetation Science 12, 533–544.
CrossRef | open url image1

Guy P. R. (1976) The feeding behaviour of elephant (Loxodonta africana) in the Sengwa area, Rhodesia. South African Journal of Wildlife Research 6, 55–63. open url image1

Hurlbert S. H. (1984) Pseudoreplication and the design of ecological field experiments. Ecological Monographs 54, 187–211.
CrossRef | open url image1

Jäkäläniemi A., Tuomi J., Siikamäki P., Kilpiä A. (2005) Colonization-extinction and patch dynamics of the perennial riparian plant Silene tatarica. Journal of Ecology 93, 670–680.
CrossRef | open url image1

Johnson B. E., Cushman J. H. (2007) Influence of a large herbivore reintroduction on plant invasions and community composition in a California grassland. Conservation Biology 21, 515–526.
CrossRef | PubMed | open url image1

Kerley G. , Wilson S. , and Massey A. (2002). Elephant conservation and management in the Eastern Cape. In ‘Workshop Proceedings’. (University of Port Elizabeth: Port Elizabeth, South Africa.)

Kerley G. I. H., Landman M. (2006) The impacts of elephants on biodiversity in the Eastern Cape Subtropical Thickets. South African Journal of Science 102, 395–402. open url image1

Kerley G. I. H. , Tongway D. , and Ludwig J. (1999). Effects of goat and elephant browsing on soil resources in succulent thicket, Eastern Cape, South Africa. In: ‘People and Rangelands: Building the Future. Proceedings of the VI International Rangeland Congress’. (Eds D. Freudenberger and D. Eldridge.) pp. 116–117. (VI International Rangeland Congress Inc.: Aitkenvale, Qld.)

Leuthold W. (1996) Recovery of woody vegetation in Tsavo National Park, Kenya, 1970–94. African Journal of Ecology 34, 101–112.
CrossRef | open url image1

Low A. B. , and Rebelo A. G. (1996). ‘Vegetation of South Africa, Lesotho and Swaziland: a Companion to the Vegetation Map of South Africa, Lesotho and Swaziland.’ (Department of Environmental Affairs and Tourism: Pretoria, South Africa.)

Ludwig J. , Tongway D. , Freudenberger D. , Noble J. , and Hodgkinson K. (2003). ‘Landscape Ecology Function and Management: Principles from Australia’s Rangelands.’ (CSIRO Publishing: Melbourne.)

Maestre F. T., Cortina J. (2004) Insights into ecosystem composition and function in a sequence of degraded semiarid steppes. Restoration Ecology 12, 494–502.
CrossRef | open url image1

Maestre F. T., Puche M. D. (2009) Indices based on surface indicators predict soil functioning in Mediterranean semi-arid steppes. Applied Soil Ecology 41, 342–350.
CrossRef | open url image1

McEvoy P. M., Flexen M., McAdam J. H. (2006) The effects of livestock grazing on ground flora in broadleaf woodlands in Northern Ireland. Forest Ecology and Management 225, 39–50.
CrossRef | open url image1

Olofsson J. (2006) Short- and long-term effects of changes in reindeer grazing pressure on tundra heath vegetation. Journal of Ecology 94, 431–440.
CrossRef | open url image1

Owen-Smith N., Kerley G. I. H., Page B., Slotow R., Van Aarde R. J. (2006) A scientific perspective on the management of elephants in the Kruger National Park and elsewhere. South African Journal of Science 102, 389–394. open url image1

Owen-Smith R. N. (1992). ‘Megaherbivores: the Influence of Very Large Body Size on Ecology.’ (Cambridge University Press: Cambridge.)

Palmer A. R., Killer F. J., Avis A. M., Tongway D. (2001) Defining function in rangelands of the Peddie district, Eastern Cape, using landscape function analysis. African Journal of Range and Forage Science 18, 53–58. open url image1

Parker D., Bernard R. (2008) Lessons from aloes in the thicket biome: reconstructing past elephant browsing to understand the present. South African Journal of Science 104, 163–164. open url image1

Rambo J. L., Faeth S. H. (1999) Effect of vertebrate grazing on plant and insect community structure. Conservation Biology 13, 1047–1054.
CrossRef | open url image1

Rao P. V. (1998). ‘Statistical Research Methods in the Life Sciences.’ (Duxbury Press: Pacific Grove, CA.)

Ruess R. W., Halter F. L. (1990) The impact of large herbivores on the Seronera woodlands, Serengeti National Park, Tanzania. African Journal of Ecology 28, 259–275.
CrossRef | open url image1

Thomson P. J. (1975) The role of elephants, fire and other agents in the decline of a Brachystegia boehmii woodland. Journal of the Southern African Wildlife Management Association 5, 11–18. open url image1

Tomlinson K. W., O’Connor T. G. (2005) The effect of defoliation environment on primary growth allocation and secondary tiller recruitment of two bunchgrasses. African Journal of Range and Forage Science 22, 29–36. open url image1

Tongway D. J. , and Hindley N. L. (2004a). ‘Landscape Function Analysis: Procedures for Monitoring and Assessing Landscapes, With Special Reference to Minesites and Rangelands.’ (CSIRO Publishing: Melbourne.)

Tongway D. J. , and Hindley N. L. (2004b). Landscape function analysis manual (Spreadsheet). Available at: www.csiro.au/services/EcosystemFunctionAnalysis.html (accessed 28 June 2009).

Van Aarde R. J., Jackson T. P., Ferreira S. M. (2006) Conservation science and elephant management in southern Africa. South African Journal of Science 102, 385–388. open url image1

van de Koppel J., Rietkerk M., Van Langevelde F., Kumar L., Klausmeier C. A., Fryxell J. M., Hearne J. W., Van Andel J., de Ridder N., Skidmore A., Stroosnijder L., Prins H. H. T. (2002) Spatial heterogeneity and irreversible vegetation change in semiarid grazing systems. American Naturalist 159, 209–218.
CrossRef | PubMed | open url image1

Western D., Maitumo D. (2004) Woodland loss and restoration in a savanna park: a 20-year experiment. African Journal of Ecology 42, 111–121.
CrossRef | open url image1








Export Citation Cited By (5)