Microbial dynamics on decaying leaves in a temporary Moroccan river. I - Fungi

Monthly variations of fungal biomass and assemblages on leaves exposed to t he air and submerged, of sporulation and specific richness in the water, an d of cellulolytic activity in the leaves were investigated in a warm tempor ary river. The biomass of terrestrial fungi was relatively low in the dry a ir and cellulolytic activity also was low. During submersion, biomass and a ctivity of the aquatic hyphomycetes were greater. The fungi were most activ e in spring when the water was flowing and when breakdown was fast. Complet e exclusion of one fungal species on one leaf species, presumably by compet ition, was observed twice. From June onwards, though fungal biomass remaine d high, fungal diversity and activity decreased, and further decay was pres umably due to other microorganisms. No major difference to the same process es in temperate permanent streams appeared except that initiation of the se quence was the onset of the aquatic phase and not deciduous leaf fall.