Malam Issa O. auteur aut IRD Trichet J. auteur aut IRD Défarge C. auteur aut IRD Couté A. auteur aut IRD Valentin Christian auteur aut IRD text journalArticle eng text/pdf reformatted digital access Microbiotic crusts resulting from the colonization of soil surfaces by communities of microorganisms dominated by cyanobacteria, eucaryotic algae or lichens are widespread in arid and semi-arid regions. In the 'tiger bush' of Niger (Sahel) microbiotic crusts occur in bare bands between densely vegetated bands. The tiger bush soils are sandy loams with pH 4.7-6.5. Three different microbiotic crusts are recognised, forming strips parallel to the vegetation banding. They are all formed mainly by filamentous cyanobacteria dominated by Schizothrix. Other important genera are Scytonema, Lyngbya, Nostoc, and Phormidium. The filamentous microorganisms trap sand particles and finer particles stick on the filament surfaces. These effects enhance coil cohesion and resistance to erosion. Soil porosity is also increased by the microbial cover, with additinal pores delineated by filaments on the surfaces of crusts and porous organic bodies derived from microbial remains at depth. The microbiotic crusts are essential components of the tiger bush ecosystem. Water leaving the lower sides of vegetated bands results inplant decay, and on the upslope sides vegetation grows because of increased water supply. Microbial covers help resist erosion, and increase water and nutrient retention, thus providing substrates for the expansion of plants form adjacent vegetated bands. (Résumé d'auteur) specialized FORMATION VEGETALE DYNAMIQUE DE VEGETATION SURFACE DU SOL CROUTE MICROBIOLOGIE DU SOL MICROORGANISME MICROMORPHOLOGIE POROSITE ANALYSE PHYSICOCHIMIQUE CARACTERISTIQUE HYDRIQUE BROUSSE TIGREE 082VEGET02 Valentin Christian ed. edt IRD Poesen J. ed. edt IRD 37 1-2 175-196 1999 0341-8162 https://www.documentation.ird.fr/hor/fdi:010018927 10.1016/S0341-8162(99)00052-1 0341-8162 [F A010018923] https://www.documentation.ird.fr/hor/fdi:010018927 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/2021-05/010018927.pdf IRD - Base Horizon / Pleins textes 1999-09-08 2021-05-27 fdi:010018927 fre