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5 - Long‐term effects of herbivory on plant diversity and functional types in arid ecosystems

Published online by Cambridge University Press:  16 November 2009

By
David Ward
Edited by
Kjell Danell ,
Roger Bergström ,
Patrick Duncan  and
John Pastor
David Ward
Affiliation:
University of KwaZulu‐Natal
Kjell Danell
Affiliation:
Swedish University of Agricultural Sciences
Roger Bergström
Affiliation:
The Forestry Research Institute of Sweden
Patrick Duncan
Affiliation:
Centre National de la Recherche Scientifique (CNRS), Paris
John Pastor
Affiliation:
University of Minnesota, Duluth
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Summary

INTRODUCTION

There is a widely held belief that abiotic factors outweigh biotic factors in arid ecosystems, and that herbivory by mammals is relatively unimportant in ecosystem functioning and biodiversity maintenance (reviewed by Noy‐Meir 1973). The over‐riding importance of abiotic factors in arid regions is ascribed to the high temporal and spatial variation in rainfall. Indeed, changes in plant species composition in arid and semi‐arid regions of Africa and Asia as a consequence of grazing are positively correlated with mean annual rainfall (Milchunas & Lauenroth 1993, Ward 2004). There is a strong negative correlation between the coefficient of variation in mean annual rainfall among years and median annual rainfall of arid regions (Ward 2001, 2004). Similarly, spatial variation in rainfall is high and is not correlated with distance among stations (Ward 2001, Ward et al. 2000, 2004). This high variability in rainfall results in high spatio‐temporal variability in plant abundance and availability to herbivores. For example, Ward et al. (2000) showed that, in the Negev desert of Israel, only 1% of plant species were present in their permanent plots in all years and approximately half the plant species were found once only in ten years. Spatial variation in forage availability is also enormous (see e.g. Fig. 5.1) and most plants may be restricted to ephemeral water courses (so‐called contracted vegetation) (Whittaker 1975) in some arid regions. Furthermore, geological substrates vary considerably among arid regions, particularly in their nutrient status and distribution, as well as in their water retention capacities.

Type
Chapter
Information
Large Herbivore Ecology, Ecosystem Dynamics and Conservation , pp. 142 - 169
Publisher: Cambridge University Press
Print publication year: 2006

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References

Andersson, C. J. (1856). Lake Ngami; or Explorations and Discoveries, During Four Years' Wanderings in the Wilds of South Western Africa. London: Hurst and Blackett.CrossRefGoogle Scholar
Archer, S. (1996). Assessing and interpreting grass‐woody plant dynamics. In The Ecology and Management of Grazing Systems, ed. Hodgson, J. & Illius, A. W.. Wallingford: CAB International, pp. 101–34.Google Scholar
Archer, S., Schimel, D. S. & Holland, E. A. (1995). Mechanisms of shrubland expansion – land‐use, climate or CO2. Climatic Change, 29, 91–9.CrossRefGoogle Scholar
Behnke, R. & Abel, N. (1996). Revisited: the overstocking controversy in semiarid Africa. World Animal Review, 87, 4–27.Google Scholar
Blydenstein, J., Hungerford, C. R., Day, G. I. & Humphrey, R. (1957). Effect of domestic livestock exclusion on vegetation in the Sonoran Desert. Ecology, 38, 522–6.CrossRefGoogle Scholar
Brown, J. R. & Archer, S. (1989). Woody plant invasion of grasslands: establishment of honey mesquite (Prosopis glandulosa var. glandulosa) on sites differing in herbaceous biomass and grazing history. Oecologia, 80, 19–26.CrossRefGoogle ScholarPubMed
Brown, J. R. & Archer, S. (1999). Shrub invasion of grassland: recruitment is continuous and not regulated by herbaceous biomass or density. Ecology, 80, 2385–96.CrossRefGoogle Scholar
Cheal, D. C. (1993). Effects of stock grazing on the plants of semi‐arid woodlands and grasslands. Proceedings of the Royal Society of Victoria, 105, 57–65.Google Scholar
Clements, F. E. (1928). Plant Succession and Indicators. New York: Hafner.Google Scholar
Diaz, S., Noy‐Meir, I. & Cabido, M. (2001). Can grazing response of herbaceous plants be predicted from simple vegetative traits?Journal of Applied Ecology, 38, 497–508.CrossRefGoogle Scholar
Dyksterhuis, E. J. (1949). Condition and management of range land based on quantitative ecology. Journal of Range Management, 2, 104–5.CrossRefGoogle Scholar
Ellis, J. E. & Swift, D. M. (1988). Stability of African pastoral ecosystems: alternate paradigms and implications for development. Journal of Range Management, 41, 450–9.CrossRefGoogle Scholar
Fowler, C. W. (1988). Population dynamics as related to rate of increase per generation. Evolutionary Ecology, 2, 197–204.CrossRefGoogle Scholar
Freeman, D. C. & Emlen, J. M. (1995). Assessment of interspecific interactions in plant communities: an illustration of the cold desert saltbush grasslands of North America. Journal of Arid Environments, 31, 179–98.CrossRefGoogle Scholar
Goldberg, D. & Turner, R. M. (1986). Vegetation change and plant demography in permanent plots in the Sonoran desert. Ecology, 67, 695–712.CrossRefGoogle Scholar
Hadar, L., Noy‐Meir, I. & Perevolotsky, A. (1999). The effect of shrub clearing and grazing on the composition of a Mediterranean plant community: functional groups versus species. Journal of Vegetation Science, 10, 673–82.CrossRefGoogle Scholar
Hennessey, J. T., Gibbens, R. P., Tromble, J. M. & Cardenas, M. (1983). Vegetation changes from 1935 to 1980 in mesquite dunelands and former grasslands of southern New Mexico. Journal of Range Management, 36, 370–4.CrossRefGoogle Scholar
Hesla, B. I., Tieszen, L. L. & Boutton, T. W. (1985). Seasonal water relations of savanna shrubs and grasses in Kenya. Journal of Arid Environments, 8, 15–31.Google Scholar
Higgins, S. I., Bond, W. J. & Trollope, S. W. (2000). Fire, resprouting and variability: a recipe for grass‐tree coexistence in savannna. Journal of Ecology, 88, 213–29.CrossRefGoogle Scholar
Hoffman, M. T. & Cowling, R. M. (1990). Vegetation change in the semi‐arid Karoo over the last 200 years: an expanding Karoo – fact or fiction?South African Journal of Science, 86, 286–94.Google Scholar
Idso, S. B. (1992). Shrubland expansion in the American Southwest. Climate Change, 22, 85–6.CrossRefGoogle Scholar
Illius, A. W. & O'Connor, T. G. (2000). Resource heterogeneity and ungulate population dynamics. Oikos, 89, 283–94.CrossRefGoogle Scholar
Jauffret, S. & Lavorel, S. (2003). Are plant functional types relevant to describe degradation in arid, southern Tunisian steppes?Journal of Vegetation Science, 14, 399–408.CrossRefGoogle Scholar
Jeltsch, F., Milton, S. J., Dean, W. R. J. & Rooyen, N. (1996). Tree spacing and coexistence in semiarid savannas. Journal of Ecology, 84, 583–95.CrossRefGoogle Scholar
Jeltsch, F., Milton, S. J., Dean, W. R. J. & Rooyen, N. (1997). Simulated pattern formation around artificial waterholes in the semi‐arid Kalahari. Journal of Vegetation Science, 8, 177–81.CrossRefGoogle Scholar
Jeltsch, F., Weber, G., Dean, W. R. J. & Milton, S. J. (1998). Disturbances in savanna ecosystems: modelling the impact of a key determinant. In Ecosystems and Sustainable Development, ed. Usó, J. L.Brebbia, C. A. & Power, H.. Southampton: Computational Mechanics Publications, pp. 233–42.Google Scholar
Jeltsch, F., Weber, G. E. & Grimm, V. (2000). Ecological buffering mechanisms in the savannas: a unifying theory of long‐term tree‐grass coexistence. Plant Ecology, 150, 161–71.CrossRefGoogle Scholar
Kelly, R. D. & Walker, B. H. (1977). The effects of different forms of land use on the ecology of a semi‐arid region in south‐eastern Rhodesia. Journal of Ecology, 62, 553–74.Google Scholar
Kelt, D. A. & Valone, T. J. (1995). Effects of grazing on the abundance and diversity of annual plants in Chihuahuan desert scrub habitat. Oecologia, 103, 191–5.CrossRefGoogle ScholarPubMed
Knoop, W. T. & Walker, B. H. (1985). Interactions of woody and herbaceous vegetation in a southern African savanna. Journal of Ecology, 73, 235–53.CrossRefGoogle Scholar
Kraaij, T. & Ward, D. (2005). Effects of rain, nitrogen, fire and grazing on tree recruitment and early survival in bush‐encroached savanna. Plant Ecology, in press.
Lamprey, H. F. (1983). Pastoralism yesterday and today: the overgrazing problem. In Tropical Savannas: Ecosystems of the World, ed. Bouliere, F.. Amsterdam: Elsevier, pp. 643–66.Google Scholar
Landsberg, J., Lavorel, S. & Stol, J. (1999). Grazing response groups among understorey plants in arid rangelands. Journal of Vegetation Science, 10, 683–96.CrossRefGoogle Scholar
Louw, G. N. & Seely, M. K. (1990). Ecology of Desert Organisms. London: Longmans.Google Scholar
Milchunas, D. G., Sala, O. E. & Lauenroth, W. K. (1988). A generalized model of the effects of grazing by large herbivores on grassland community structure. American Naturalist, 132, 87–106.CrossRefGoogle Scholar
Milchunas, D. G., Lauenroth, W. K., Chapman, P. L. & Kazempour, K. (1989). Effects of grazing, topography, and precipitation on the structure of a semi‐arid grassland. Vegetatio, 80, 11–23.CrossRefGoogle Scholar
Milchunas, D. G. & Lauenroth, W. K. (1993). Quantitative effects of grazing on vegetation and soils over a global range of environments. Ecological Monographs, 63, 327–66.CrossRefGoogle Scholar
Milton, S. J. & Dean, W. R. J. (2000). Disturbance, drought and dynamics of desert dune grassland, South Africa. Plant Ecology, 150, 37–51.CrossRefGoogle Scholar
Milton, S. J. & Hoffman, M. T. (1994). The application of state‐and‐transition models to rangeland research and management in arid succulent and semi‐arid grassy Karoo, South Africa. African Journal of Range and Forage Science, 11, 18–26.CrossRefGoogle Scholar
Milton, S. J., Dean, W. R. J., du Plessis, M. A. & Siegfried, W. R. (1994). A conceptual model of arid rangeland degradation. Bioscience, 44, 70–6.CrossRefGoogle Scholar
Noy‐Meir, I. (1973). Desert ecosystems: environment and producers. Annual Review of Ecology and Systematics, 4, 25–51.CrossRefGoogle Scholar
Noy‐Meir, I. (1982). Stability of plant‐herbivore models and possible applications to savanna. In Ecology of Tropical Savannas, ed. Huntley, B. J. & Walker, B. H.. Ecological Studies. Berlin: Springer Verlag, pp. 591–609.CrossRefGoogle Scholar
Noy‐Meir, I., Gutman, M. & Kaplan, Y. (1989). Responses of Mediterranean grassland plants to grazing and protection. Journal of Ecology, 77, 290–310.CrossRefGoogle Scholar
O'Connor, T. G. (1985). A Synthesis of Field Experiments Concerning the Grass Layer in the Savanna Regions of Southern Africa. South African National Scientific Programmes Report 114. CSIR, Pretoria.
O'Connor, T. G. (1991). Local extinction in perennial grasslands: a life‐history approach. American Naturalist, 137, 753–73.CrossRefGoogle Scholar
Perkins, J. S. & Thomas, D. S. G. (1993). Spreading deserts or spatially confined environmental impacts? Land degradation and cattle ranching in the Kalahari desert of Botswana. Land Degradation and Rehabilitation, 4, 179–94.CrossRefGoogle Scholar
Pickup, G. & Chewings, V. H. (1994). A grazing gradient approach to land degradation assessment in arid areas from remotely‐sensed data. International Journal of Remote Sensing, 15, 597–617.CrossRefGoogle Scholar
Reid, R. S. & Ellis, J. E. (1995). Impacts of pastoralists on woodlands in south Turkana, Kenya: livestock‐mediated tree recruitment. Ecological Applications, 5, 978–92.CrossRefGoogle Scholar
Ruiz, N., Ward, D. & Saltz, D. (2002a). Crystals of calcium oxalate in leaves: constitutive or induced defence?Functional Ecology, 16, 99–105.CrossRefGoogle Scholar
Ruiz, N., Ward, D. & Saltz, D. (2002b). Responses of Pancratium sickenbergeri to simulated bulb herbivory: combining defense and tolerance strategies. Journal of Ecology, 90, 472–9.CrossRefGoogle Scholar
Saltz, D. (2001). Ungulates of Makhtesh Ramon: dynamics, behaviour, and their conservation implications. In The Makhteshim Country: a Laboratory of Nature, ed. Krasnov, B. & Mazor, E.. Sofia, Bulgaria: Pensoft, pp. 273–87.Google Scholar
Saltz, D. & Ward, D. (2000). Responding to a three‐pronged attack: desert lilies subject to herbivory by dorcas gazelles. Plant Ecology, 148, 127–38.CrossRefGoogle Scholar
Saltz, D., Schmidt, H., Rowen, M.et al. (1999). Assessing grazing impacts by remote sensing in hyper‐arid environments. Journal of Range Management, 52, 500–7.CrossRefGoogle Scholar
Schlesinger, W., Reynolds, J. F., Cunningham, G. L.et al. (1990). Biological feedbacks in global desertification. Science, 247, 1043–8.CrossRefGoogle ScholarPubMed
Scholes, R. J. & Archer, S. R. (1997). Tree‐grass interactions in savannas. Annual Review of Ecology and Systematics, 28, 545–70.CrossRefGoogle Scholar
Scholes, R. J. & Walker, B. H. (1993). An African Savanna: Synthesis of the Nylsvley Study. Cambridge: Cambridge University Press.CrossRefGoogle Scholar
Sinclair, A. R. E. & Fryxell, J. M. (1985). The Sahel of Africa: ecology of a disaster. Canadian Journal of Zoology, 63, 987–94.CrossRefGoogle Scholar
Skarpe, C. (1990a). Shrub layer dynamics under different herbivore densities in an arid savanna, Botswana. Journal of Applied Ecology, 27, 873–85.CrossRefGoogle Scholar
Skarpe, C. (1990b). Structure of the woody vegetation in disturbed and undisturbed arid savanna. Vegetatio, 87, 11–18.CrossRefGoogle Scholar
Smit, G. N., Rethman, N. F. G. & Moore, A. (1996). Review article: vegetative growth, reproduction, browse production and response to tree clearing of woody plants in African savanna. African Journal of Range and Forage Science, 13, 78–88.CrossRefGoogle Scholar
Smith, C. C. (1940). The effect of overgrazing and erosion upon the biota of the mixed‐grass prairie of Oklahoma. Ecology, 21, 381–97.CrossRefGoogle Scholar
Smith, Stafford D. M. & Morton, S. R. (1990). A framework for the ecology of arid Australia. Journal of Arid Environments, 18, 255–78.Google Scholar
Teague, W. R. & Smit, G. N. (1992). Relations between woody and herbaceaous components and the effects of bush‐clearing in southern African savannas. Journal of the Grassland Society of South Africa, 9, 60–71.CrossRefGoogle Scholar
Rooyen, N., Bredenkamp, G. J. & Theron, G. K. (1991). Kalahari vegetation: veld condition trends and ecological status of species. Koedoe, 34, 61–72.Google Scholar
Vegten, J. A. (1983). Thornbush invasion in eastern Botswana. Vegetatio, 56, 3–7.CrossRefGoogle Scholar
Venter, J., Liggitt, B., Tainton, N. M. & Clarke, G. P. M. (1989). The influence of different land use practices on soil erosion, herbage production, and grass species richness and diversity. Journal of the Grassland Society of Southern Africa, 6, 89–98.Google Scholar
Vesk, P. A., Leishman, M. R. & Westoby, M. (2004). Simple traits do not predict grazing response in Australian shrublands and woodlands. Journal of Applied Ecology, 41, 22–31.CrossRefGoogle Scholar
Walker, B. H. & Noy‐Meir, I. (1982). Aspects of the stability and resilience of savanna ecosystems. In Ecology of Tropical Savannas, ed. Huntley, B. J. & Walker, B. H.. Berlin: Springer Verlag, pp. 556–90.CrossRefGoogle Scholar
Walker, B. H., Ludwig, D., Holling, C. S. & Peterman, R. M. (1981). Stability of semi‐arid savanna grazing systems. Journal of Ecology, 69, 473–98.CrossRefGoogle Scholar
Walter, H. (1939). Grassland, Savanne und Busch der ariden Teile Afrikas in ihrer oekologischen Bedingheit. Jaarboek wissenschaftelike Botaniek, 87, 750–860.Google Scholar
Walter, H. (1954). Die Verbuschung, eine Erscheinung der subtropischen Savannengebiete, und ihre ökologischen Ursachen. Vegetatio, 5/6, 6–10.CrossRefGoogle Scholar
Walter, H. (1971). Ecology of Tropical and Subtropical Vegetation. Edinburgh: Oliver & Boyd.Google Scholar
Ward, D. (2001). Plant species diversity and population dynamics in Makhtesh Ramon. In The Makhteshim Country: a Laboratory of Nature, ed. Krasnov, B. & Mazor, E.. Sofia, Bulgaria: Pensoft, pp. 171–86.Google Scholar
Ward, D. (2002). Do we understand the causes of bush encroachment? In Multiple Use Management of Natural Forests and Woodlands: Policy Refinements and Scientific Progress, ed. Seydack, A. W., Vorster, T., Vermeulen, W. J. & Merwe, I. J.. Pretoria: DWAF, pp. 189–201.Google Scholar
Ward, D. (2004). The effects of grazing on plant biodiversity in arid ecosystems. In Biodiversity in Drylands: Towards a Unified Framework, ed. Shachak, M., Pickett, S. T. A., Gosz, J. R. & Perevolotsky, A.. Oxford: Oxford University Press, pp. 233–49.Google Scholar
Ward, D. & Ngairorue, B. T. (2000). Are Namibia's grasslands desertifying?Journal of Range Management, 53, 138–44.CrossRefGoogle Scholar
Ward, D. & Olsvig‐Whittaker, L. (1993). Plant species diversity at the junction of two desert biogeographic zones. Biodiversity Letters, 1, 172–85.CrossRefGoogle Scholar
Ward, D. & Rohner, C. (1997). Anthropogenic causes of high mortality and low recruitment in three Acacia tree taxa in the Negev desert, Israel. Biodiversity and Conservation, 6, 877–93.CrossRefGoogle Scholar
Ward, D. & Saltz, D. (1994). Foraging at different spatial scales: dorcas gazelles foraging for lilies in the Negev desert. Ecology, 75, 48–58.CrossRefGoogle Scholar
Ward, D., Olsvig‐Whittaker, L. & Lawes, M. J. (1993). Vegetation‐environment relationships in a Negev desert erosion cirque. Journal of Vegetation Science, 4, 83–94.CrossRefGoogle Scholar
Ward, D., Spiegel, M. & Saltz, D. (1997). Gazelle herbivory and interpopulation differences in calcium oxalate content of leaves of a desert lily. Journal of Chemical Ecology, 23, 333–46.CrossRefGoogle Scholar
Ward, D., Saltz, D., Rowen, M. & Schmidt, I. (1998a). Effects of grazing by re‐introduced Equus hemionus on the vegetation in a Negev desert erosion cirque. Journal of Vegetation Science, 10, 579–86.CrossRefGoogle Scholar
Ward, D., Ngairorue, B. T., Kathena, J., Samuels, R. & Ofran, Y. (1998b). Land degradation is not a necessary outcome of communal pastoralism in arid Namibia. Journal of Arid Environments, 40, 357–71.CrossRefGoogle Scholar
Ward, D., Saltz, D. & Olsvig‐Whittaker, L. (2000). Distinguishing signal from noise: long‐term studies of vegetation in Makhtesh Ramon erosion cirque, Negev desert, Israel. Plant Ecology, 150, 27–36.CrossRefGoogle Scholar
Ward, D., Saltz, D. & Ngairorue, B. T. (2004). Spatio‐temporal rainfall variation and stock management in arid Namibia. Journal of Range Management, 57, 130–40.CrossRefGoogle Scholar
Weber, G. E., Moloney, K. & Jeltsch, F. (2003). Simulated long‐term vegetation response to alternative stocking strategies in savanna rangelands. Plant Ecology, 150, 77–96.CrossRefGoogle Scholar
Weltzin, J. F. & McPherson, G. R. (1997). Spatial and temporal soil moisture partitioning by trees and grasses in a temperate savanna, Arizona, USA. Oecologia, 112, 156–64.CrossRefGoogle Scholar
Westoby, M. (1980). Elements of a theory of vegetation dynamics in arid rangelands. Israel Journal of Botany, 28, 169–94.Google Scholar
Westoby, M. (1999). The LHS strategy scheme in relation to grazing and fire. In Sixth International Rangeland Congress Vol. 2, ed. Eldridge, D. & Freudenberger, D.. Townsville, Australia: International Rangeland Congress, pp. 893–6.Google Scholar
Westoby, M., Walker, B. & Noy‐Meir, I. (1989). Opportunistic management for rangelands not at equilibrium. Journal of Range Management, 42, 266–74.CrossRefGoogle Scholar
Whittaker, R. H. (1975). Communities and Ecosystems. New York: MacMillan.Google Scholar
Wiegand, T. & Milton, S. J. (1996) Vegetation change in semiarid communities: simulating probabilities and time scales. Vegetatio, 125, 169–83.CrossRefGoogle Scholar
Wiegand, K., Jeltsch, F. & Ward, D. (1999). Analysis of the population dynamics of Acacia trees in the Negev desert, Israel with a spatially explicit computer simulation model. Ecological Modeling, 117, 203–24.CrossRefGoogle Scholar
Wiegand, K., Ward, D. & Saltz, D. (2005). Multi‐scale patterns encroachment in an arid savanna with a shallow soil layer. Journal of Vegetation Science, 16, 311–20.CrossRefGoogle Scholar

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