DECOMPOSITION OF BEECH LEAF-LITTER BY MICROFLORA AND MESOFAUNA .1. IN-VITRO ACTION OF WHITE-ROT FUNGI ON BEECH LEAVES AND FOLIAR COMPONENTS

The decomposing capacities of three white rot fungi (Sporotrichum pulv erulentum, strain SPU, and two unidentified isolates, RM and FTS), wer e monitored in the laboratory. The fungi were grown on culture media c ontaining various leaf litter components including pectin, cellulose, lignin and phenols and gave rise to positive lysis tests with regard t o these compounds. Intact beech leaves, harvested at their shedding in the fall, were inoculated by the three fungi which caused weight loss es and a bleaching of the material with correlative degradations of ce llulose, lignin and phenolic compounds. In laboratory conditions, biod egradation of leaf constituents was particularly rapid over the first month and ceased after four months of incubation. Sporotrichum pulveru lentum was found to be the most efficient decomposer, leading to degra dation levels reaching 82%. Chemical attack of the leaves by oxidation with sodium hypochlorite, gave rise over a 16 hour period to modifica tions similar to those exhibited by biological degradations, although weight and lignin losses were more reduced than those ascribed to Spor otrichum pulverulentum.