FUNGAL SUCCESSION AND CHANGES IN THE FUNGAL DEGRADATION POTENTIAL DURING THE INITIAL-STAGE OF LITTER DECOMPOSITION IN A BLACK-ALDER FOREST [ALNUS-GLUTINOSA (L) GAERTN]

The succession of fungal decomposers over the first year of Litter bre akdown at two sites (wet and moist) of a black alder forest in Norther n Germany was investigated. The active fungi were isolated after separ ation from dormant propagules by a litter washing method. Their decomp osition potential was determined in vitro by investigating the amylase , protease, lipase, xylanase, polygalacturonase, pectin lyase, cellula se and laccase activities. Based upon the observed frequency and enzym atic potential of the isolates, the total fungal degradation potential was determined. In the initial phase of the decomposition a zymogenic microflora of the genera Mucor, Alternaria and Epicoccum colonized th e litter. This flora was progressively replaced by autochthonous speci es, principally of the genus Fusarium. With only few exceptions, the f ungal succession was similar on the litter of both sites. The amylase potential was consistently large during the whole investigation, where as the laccase potential remained small with no significant variations . On the contrary, all other enzymatic potentials underwent complex va riations, that were related to the fungal succession. These variations were similar at both sites and were in accordance with results of sim ilar studies. Nevertheless, the interest and importance of such variat ions in enzymatic potentials has to be verified by chemical analysis o f litter decomposition.