Abstract
Changes in plant community structure are identified as a result of grazing in grasslands of the flooding pampa which evolved under supposedly light grazing conditions.
The effect of excluding grazing upon total leaf area index was an increase of 30%. The largest response was observed in the distribution of leaves in the canopy. In the grazed areas, most of the green material was concentrated in the 0–5 cm layer while in the ungrazed treatments the largest portion of the leaf area was in the 10–30 cm layer. Grazing exclusion resulted in a small change in total basal area but a larger change in its distribution, from many small tussocks to less numerous large ones.
The effect of grazing upon leaf area and basal area was accounted for by changes in vigor as well as by changes in species composition. The major effect of excluding grazing upon species composition was the disappearance of some native planophile species and most of the exotics. The species composition of grazed areas of both communities was very similar while there were large differences between the ungrazed areas and between the grazed and ungrazed areas of the same community. It is suggested that there is a group of species which responds to the coarse-grained ‘signal’ of grazing and its presence can cause dissimilar communities to converge under grazing conditions. The other group of species responded to the fine-grained ‘signal’ of the environmental conditions associated with topography.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Allen, T. F. H. & Starr, T. B., 1982. Hierarchy. Perspectives for ecological complexity. The University of Chicago Press, Chicago and London, 310 pp.
Cottam, G., Glenn, F. & Whittaker, R. H., 1973. Wisconsin comparative ordination. In R. H. Whittaker (ed.), Ordination and classification of communities. Junk, The Hague, pp. 193–217.
Deregibus, V. A., Sanchez, R. A. & Casal, J. J., 1983. Effects of light quality on tiller production in Lolium spp. Plant Physiol. 72: 900–902.
Deregibus, V. A., Sanchez, R. A., Casal, J. J. & Trlica, M. J., 1985. Tillering responses to enrichment of red light beneath the canopy in a humid natural grassland. J. Appl. Ecol. 22: 199–206.
Goodall, D. W., 1973. Sample similarity and species correlation. In: R. H. Whittaker (ed.), Ordination and classification of communities. Junk, The Hague, pp. 107–149.
Greig-Smith, P., 1964. Quantitative plant ecology. Butterworths, London, 256 pp.
Joggi, D., Hofer, V. & Nösberger, J., 1983. Leaf area index, canopy structure and photosynthesis of red clover (Trifolium pratense L.). Plant Cell Environ. 6: 611–616.
Knight, D. H., 1973. Leaf area dynamics of a shortgrass prairie in Colorado. Ecology 54: 891–896.
León, R. J. C., 1975. Las comunidades herbaceas de la región Castelli-Pila. Monogr. Com. de Invest. Cient. de la Pcia. de Buenos Aires. La Plata 5: 75–107.
León, R. J. C., Rusch, G. M. & Oesterheld, M., 1984. Pastizales pampeanos, impacto agropecuario. Phytocoenologia 12: 201–218.
McNaughton, S. J., 1979. Grassland-herbivore dynamics. In: A. R. E. Sinclair & M. Norton-Griffiths (eds), Serengeti: dynamics of an ecosystem. University of Chicago Press, Chicago, pp.46–81.
McNaughton, S. J., 1983. Serengeti grassland ecology: The role of composite environmental factors and contingency in community organization. Ecol. Monogr. 53: 291–320.
McNaughton, S. J., 1984. Grazing lawns: Animal herds, plant form, and coevolution. Am. Nat. 24: 863–886.
Picket, S. T. A., 1980. Non-equilibrium coexistence of plants. Torrey Bot. Club 107: 238–248.
Sala, O. E., Soriano, A. & Perelman, S. B., 1981a. Relaciones hídricas de algunas componentes de un pastizal de la Depresión del Salado. Rev. Fac. Agron. 2: 1–10.
Sala, O. E., Deregibus, V. A., Schlichter, T. M. & Alippe, H. A., 1981b. Productivity dynamics of a native temperate grassland in Argentina. J. Range Manage. 34: 48–51.
Shannon, C. E. & Wiener, W., 1963. The mathematical theory of communication. University of Illinois Press, Urbana.
Soriano, A., 1986. Natural grasslands of South America: Temperate subhumid grasslands. In: R. T. Coupland (ed.), Natural grasslands. Elsevier Scientific Publishing Company, Amsterdam, The Netherlands (in press).
Stoddart, L. A., Smith, A. D. & Box, T. W., 1975. Range management. McGraw-Hill Book Company, New York 532 pp.
Vervoorst, F., 1967. Las comunidades vegetales de la Depresión del Salado (Prov. de Buenos Aires). INTA. La Vegetación de la República Argentina. Ser. Fitogeogr. 7: 1–262.
Webb, D. S., 1978. A history of savanna vertebrates in the New World. Part II. South America and the Great Interchange. Ann. Rev. Ecol. Syst. 9: 393–426.
Author information
Authors and Affiliations
Additional information
Nomenclature follows Cabrera (1968).
The authors thank S. B. Perelman, M. Ballester, R. A. Golluscio, and G. M. Rusch for their assistance. They also thank W. K. Lauenroth for helpful discussion. This work was supported by Consejo Nacional de Investigaciones Científicas y Técnicas and Comisión de Investigaciones Científicas de la Provincia de Buenos Aires. Preparation of the manuscript was partially supported by NSF grants INT-8414057 and BSR 81-14822.
Rights and permissions
About this article
Cite this article
Sala, O.E., Oesterheld, M., León, R.J.C. et al. Grazing effects upon plant community structure in subhumid grasslands of Argentina. Vegetatio 67, 27–32 (1986). https://doi.org/10.1007/BF00040315
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00040315