Specific richness: a tool to take biodiversity into account in land management - Application in Haute Maurienne (Aussois, Savoie)

Abstract

Mountain landscapes worked for centuries by human activities, are endangered by agricultural abandonment (open areas become overgrown by shrub fallows or forests). Phytosociological surveys undertaken in Aussois, on 941 plots of 4 m2 each in mowed meadows and already abandoned areas (ancient mowed meadows, shrub fallows and forest edges), shows a global richness of 432 species. This paper proposes that richness should be considered as a five level concept use to compare different vegetation types or areas: species richness for a plot is the number of species per plot, local richness is the mean number of species per plot of 4 m2 for each vegetation type (mowed meadows have the highest local richness - 25 species per 4 m2), global richness is the number of different species found in at least one of the plots of a particular vegetation type (varying from 278 species in ancient mowed meadows to 232 species in forest edges), original richness is the number of species only found in one vegetation type (ancient mowed meadows have 40 original species, mowed meadows and fallows, 40), number of common species is the number of species found in all the four vegetation types (138 species). Abundance of Brachypodium pinnatum (a spreading herbaceous species) diminishes local richness and species diversity (calculated by Shannon Weaver index). It produces a quality modification of Aussois landscape which can decrease tourists attraction. Although, this initial approach could be re-evaluate according to other hierarchical levels (infraspecific, neighbouring sites, areas or regions, ...), it contributes on a conceptual and operationnal point of view to biodiversity knowledge to make the local actors of space management aware of the need to maintain biodiversity because it relates the visual perception of flora species richness and the objective assement made.