Abstract
Two patch types were recognized in the Occidental District of the Patagonian arid steppe: i) shrubs encircled by a ring of tussock grasses, and ii) tracts of scattered tussocks. Completeness of the ring of grasses around the three dominant shrubs was a function of shrub size. Average completeness was 62, 71 and 83%, respectively for the three dominant shrubs (Senecio filaginoides, Mulinum spinosum and Adesmia campestris). A model for the cyclic dynamics of the two patch types was proposed. It includes a building phase (grass ring construction), a mature phase (maximum ring completeness) and a degenerate phase. In this last phase, triggered by shrub death, completeness of the ring progressively decreases until remnant grasses become undistinguishable from the scattered tussocks patch type. Ring formation occurred independently of shrub species. Grass species were differentially associated to the two patch types and to rings of different shrub species. Cyclical patch dynamics influenced the pattern of resource utilization, since the shrub-ring patch, with a share of only 18% of cover, contributed 44% of the total primary productivity.
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Abbreviations
- (ST):
-
Shrub-ring patch
- M:
-
asymptote, maximum completeness
- D:
-
parameter related to the initial lag
- B:
-
rate of increase in ring completeness
- z:
-
shape parameter
- r:
-
radius
References
Aguiar, M. R. 1991. Reclutamiento de pastos en la estepa patagónica: Su relación con la estructura de la vegetación. MSc Thesis, Fac. Agron., Univ. de Buenos Aires.
Aguiar, M. R., Soriano, A. & Sala, O. E., 1992. Competition and facilitation in the recruitment of seedlings in the Patagonian steppe. Func. Ecol. 6: 66–70.
Charley, J. L. & West, N. E. 1975. Plan-induced soil chemical patterns in some shrub-dominated semi-desert ecosystems in Utah. J. Ecol. 63: 945–963.
Charley, J. L. & West, N. E. 1977. Micro-patterns of nitrogen mineralization activity in soils of some shrub-dominated semi-desert ecosystems of Utah. S. Biol. & Biochem. 9: 357–365.
Connell, J. H. & Slatyer, R. O. 1977. Mechanisms of succession in natural communities and their role in community stability and organization. Amer. Nat. 111: 1119–1144.
Correa, M. N. 1971–1984. Flora Patagónica. Colecc. Cient. INTA, Buenos Aires.
Fahrig, L. & Paloheimo, J. 1988. Determinants of population size in patchy habitats. Theor. Popul. Biol. 34: 194–213.
Fernández Alduncin, R. J. & Paruelo, J. M. 1988. Root systems of two Patagonian shrubs: a quantitative description using a geometrical method. J. Range Manag. 41: 220–223.
Fernández Alduncin, R. J., Sala, O. E. & Golluscio, R. A. 1991. Woody and herbaceous aboveground production of a Patagonian steppe. J. Range Manage. 44: 434–437.
Fowler, N. L. 1984. Patchiness in patterns of growth and survival of two grasses. Oecol. 62: 424–428.
Gibson, D. J. 1988a. The relationship of sheep grazing and soil heterogeneity to plant spatial patterns in dune grassland. J. Ecol. 76: 233–252.
Gibson, D. J. 1988b. The maintenance of plant and soil heterogeneity in dune grassland. J. Ecol. 76: 497–508.
Gimingham, C. H. 1988. A reappraisal of cyclial processes in Calluna heath. Vegetatio 77: 61–64.
Goluscio, R. A., León, R. J. C. & Perelman, S. B. 1982. Caracterización de la estepa del oeste de Chubut; su relación con el gradiente ambiental. Bol. Soc. Arg. Bot., 21: 299–324.
Greig-Smith, P. 1983. Quantitative Plant Ecology. Third Edition. Blackwell, Oxford.
Jaksic, F. M. & Fuentes, E. R. 1980. Why are native herbs in the Chilean matorral more abundant beneath bushes: microclimate or grazing? J. Ecol. 68: 665–670.
Kareiva, P. 1986. Patchiness, dispersal and species interactions: consequences for communities of herbivorous insects. Community Ecology (Ed by J. Diamond & T. J. Case), pp. 196–206. Harper & Row, New York.
Legendre, L. & Legendre, P. 1983. Numerical Ecology. Developments in environmental modelling. Elsevier, Amsterdam.
Noy-Meir, I. 1979/80. Structure and function of desert ecosystems. Israel J. Bot. 28: 1–9.
Pemadasa, M. A. 1981, Cyclical change and pattern in an Arthrocnemum community in Sri Lanka. J. Ecol. 69: 565–574.
Pickett, S. T. A. & White, P. S. 1985. The ecology of natural disturbance and patch dynamics. Academic Press, New York.
Richards, F. J. 1959. A flexible growth function for empirical use. J. Exp. Bot. 10: 290–300.
Sala, O. E., Golluscio, R. A., Lauenroth, W. K. & Soriano, A. 1989. Resource partitioning between shrubs and grasses in the Patagonian steppe. Oecol. 81: 501–505.
Soriano, A. & Sala, O. E. 1983. Ecological strategies in a Patagonian arid steppe. Vegetatio 56: 9–15.
Soriano, A. & Sala, O. E. 1986. Emergence and survival of Bromus setifolius seedlings in different microsites of a Patagonian arid steppe. Israel J. Bot. 35: 91–100.
Soriano, A., Movia, C. P. & León, R. J. C. 1983. Deserts and semi-deserts of Patagonia. Temperate deserts and semideserts. (Ed by N. E. West). pp.423–457. Elsevier Scientific Publishing Company, Amsterdam.
Soriano, A., Golluscio, R. A. & Satorre, E. H. 1987. Spatial heterogeneity of root systems of grasses in the Patagonian arid steppe. Bull. Torrey Bot. Club 114: 103–108.
United Nations Edueational, Scientific and Cultural Organization 1977. World map of desertification. United Nations Conference on Desertification.
Watt, A. S. 1947. Pattern and process in the plant community. J. Ecol. 35: 1–22.
West, N. E. & Goodall, D. W. 1980. Dispersion patterns in salt desert shrub vegetation of western Utah. Bull. Ecol. Soc. Amer. 61: 131. (Abstract).
Wilkinson, L. 1986. SYSTAT: the system for statistics. Systat Inc., Evanston.
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Soriano, A., Sala, O.E. & Perelman, S.B. Patch structure and dynamics in a Patagonian arid steppe. Vegetatio 111, 127–135 (1994). https://doi.org/10.1007/BF00040332
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DOI: https://doi.org/10.1007/BF00040332