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- Volume 12 (1993)
- Number 2 - Proceedings of the sixth European congr...
- Model of spatial organization of vegetation in river floodplains
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Model of spatial organization of vegetation in river floodplains
Abstract
In the framework of landscape ecology, we propose to modelize the spatial organization of vegetation in river floodplains. This model is based on the generation of non-homogeneous, anisotropic random patterns defined on a square lattice given the knowledge of the ecological functioning of these ecosystems. This model proceeds in two steps.
First, geographic information is computed (distances to the nearest dead arm and to the nearest active channel, convexity and concavity,...) using information about whole hydrographic network of channels (presently and pastly created by the fluvial dynamic). This leads to a first tesselation of the image. Then a set of probabilities of occurrence of each vegetation type is assigned to each site.
Second, a random number, weighted by the probability of the observed vegetation, is assigned to each site; then the consolidation can process. The weakest sites are eliminated while the strongest, called the survivors, extend their frontiers and incorporate the sites just deleted. The two processes, decimation and expansion, are recursive and parallel.
At every hierarchical level, islands and channels contents are updated; this allows or not the expansion of vegetation, with respect of the probabilities. Each vegetation of each element has its own expansion criteria (vegetation, geographical proximity or random choice).
The resulting patterns are not segmentations of the tessellation defined by initial geographic information. On the contrary, they present a stochastic appearance which reflects both the stochastic appearance and the spatial determinism of vegetation spatial organization in river floodplains due to the fluvial dynamic.