AICME II abstracts
Pattern and process in terrestrial plant communities: ...
Simulations of two-phase mosaic vegetation patterns by means of cellular automata V´ıctor Fair´en1 and Julien Esteban2 . Two-phase mosaic vegetation patterns in semi-arid environments constitute an issue of interest since [1] described the striking brousse tigr´ee vegetation bands. These vegetation bands, alternating with bands of bare soil, appear on gently sloping plateaus, along contour lines, and have been reviewed in detail by Valentin et al. [2]. Among the many mechanisms invoked to be behind the self-organization of the vegetation in bands, the runon-runoff scenario has received a considerable attention in the scientific community. According to it, water redistribution through runoff from the bare areas helps sustaining the vegetation bands. Hydrological field studies [3], [4], [5] have been carried out in order to assess this hypothesis. They have been accompanied, however, by little mathematical formalism, with cornerstones in a partial derivatives model by HilleRisLambers et al. [6] and an alternative cellular automata model developed by Dunkerley [7]. The latter approach is particularly appropriate for the description of a system dominated by the water balance. It has been outlined by Dunkerley in very simple terms and as such cannot account for the gradational zonation of the band-interband pattern, as well as for the variations in hydrologic properties along a transect. As it is inferred from field studies, the water balance in a banded vegetation pattern can be viewed as the result of an interplay between soil hydrological response, microtopography and vegetation cover, with each of these factors being strongly dependent on the others through feedback relationships. In the present contribution 1
Departamento de F´ısica Matem´ atica y Fluidos, Facultad de Ciencias, Universidad Nacional de Eduaci´ on a Distancia, Apartado 60141, 28080 Madrid, Spain (e-mail:
[email protected]). 2 IMAG-LMC, BP 53, 38041 Grenoble Cedex 9, France (e-mail:
[email protected]).
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Pattern and process in terrestrial plant communities: ...
AICME II abstracts
we move one step forward within the cellular automaton formalism by integrating all the above specificities in a model that allows for a more complete assessment of the possible feedback mechanisms leading to the specific structures in both the vegetation cover and the soil hydrologic behaviour that are reported from field work.
References [1] White, L.P., 1970, Brousse Tigr´ee patterns in southern Niger, Journal of Ecology, 58, 549-553 [2] Valentin, C., J.M. d’Herbes, J. Poesen, 1999, Soil and water components of banded vegetation patterns, Catena, 37, 1-24 [3] Seghieri, J. , S. Galle, J.L. Rajot, M. Ehrmann, 1997, Relationships between soil moisture and growth of herbaceous plants in a natural vegetation mosaic in Niger, Journal of Arid Environments, 36, 87-102 [4] Galle, S., M. Ehrmann, C. Peugeot, 1999, Water balance in a banded vegetation pattern: A case study of tiger bush in western Niger, Catena, 37, 197-216 [5] Dunkerley, D., 2002, Systematic variation of soil infiltration rates within and between the components of the vegetation mosaic in an Australian desert landscape, Hydrological Processes, 16, 119-131 [6] Hillerislambers, R., M. Rietkerk, F. Van den Bosch, H. H. T. Prins, H. de Kroon, Vegetation pattern formation in semi-arid grazing systems, Ecology, 82, 50-61. [7] Dunkerley, D. , 1999, Banded chenopod shrublands of arid Australia: modelling responses to interannual rainfall variability with cellular automata, Ecological Modelling, 121, 127-138.
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