The landscape disparity index: an ecologically weigthed measure of the landscape diversity

P. Roche (1)

1 UR EMAX - Ecosystèmes méditerranéens et risques

Typically, the analysis of landscape patterns is based on a quantitative analysis of the composition or/and the spatial arrangements of categorical units mapped from aerial photographs, satellite images or land use maps using so-called landscape metrics (Gustafson, 1998). Usually in landscape studies, authors assume that different landscape habitats or elements categorised in the mapping process are well defined, and equally different from each other (Forman 1995 and references therein). But, in most cases the landscape element types are often not really distinct or at least are not equally distinct from each other and the degree of dissimilarity between the mapped landscape elements is not usually considered. I propose a new landscape diversity metric: the Landscape Disparity Index (LDI) that takes into account both the landscape elements adjacencies frequencies and the patches ecological dissimilarities. The Landscape Disparity Index appeared to belong to the group of landscape diversity metrics with some interesting properties not shared by other diversity metrics: low sensibility to thematic resolution and ecologically significant weighting. High LDI values indicate that ecologically contrasted habitats are clustered together on the analysis scale. Traditionally used landscape diversity indexes such as the Shannon Index are not as coherent, because high values can be associated with low species richness. Thus, taking into account the degree of ecological contrast between landscape elements weights the spatial heterogeneity and improves correlation with biological patterns. These preliminary results indicate that the Landscape Disparity Index could be used to identify high diversity spots at the landscape level.

Mots clés: PAYSAGE; ECOLOGIE DU PAYSAGE; INDICATEUR D'EVOLUTION DU PAYSAGE

Domaines: Sciences de l'environnement

P. Roche. The landscape disparity index: an ecologically weigthed measure of the landscape diversity. 25 Years of Landscape Ecology: Scientific principles in practice, Wageningen, NLD, 2007, Jul 2007, Wageningen, Netherlands. p. 609 - p. 610. ⟨hal-00585324⟩