Biodiversity and ecosystem functioning

The link between vegetation and soil at a few meter-scale was studied in an old physiognomically homogeneous fallow-land (over 30 years) of anthropic Sudanian savanna with poor tree cover. Sampling was conducted systematically on a 60 m x 60 m surface, following a five-metre grid. Floristic releves were made in quadrats (1 m x 1 m), in each corner of which infiltrability was measured by a method derived from the single-ring infiltrometer. Seventy four herbaceous species are present ; the 156 releves could be classified in seven floristic units, which have a clear link with the soil hydropedological characteristics at a few meter-scale. Among the 18 main species (present in at least 10% of the 156 releves) only four could be considered as indifferent to infiltrability, another eight preferred relatively high infiltrability microsites, and the last six preferred poor infiltrability microsites. The relatively high floristic richness of the site can be partly explained by the aptitude of various species to exploit one or another of the different microsites available. The results also suggest a certain structural and functional redundancy between species. (Résumé d'auteur