FUNGAL AND INVERTEBRATE COLONIZATION OF SALIX FRESH AND DRY LEAVES INA MOROCCAN RIVER SYSTEM

Experiments were performed on freshly shed willow leaves, some of whic h were exposed in a fresh state while others had been dried for 48 hou rs at 40-degrees-C. Their colonization by aquatic hyphomycetes and inv ertebrates was compared in the Lower Moulouya system, including the ma in river itself and its tributary, Oued Zeghzel. According to previous results, pre-dried leaves lost more weight by initial leaching than f resh leaves. Spore production and numbers of fungal species were great er on pre-dried leaves during the first two months, but no clear diffe rence in initial colonization by aquatic invertebrates was found. Late r on, hyphomycete and invertebrate colonization of fresh leaves increa sed, so that breakdown rate also increased and both leaf categories ha d lost the same weight after 4 months. Hyphomycete abundance on identi cal leaves differed according to the stations. It is concluded that au tumn-shed fresh leaves preserved anti-fungal substances that delayed f ungal conditioning for two months. These substances were rapidly leach ed in pre-dried leaves. Invertebrates used leaf packs not only for foo d, but also for support and shelter.