Shifts in physiological capabilities of the microbiota during the decomposition of leaf litter in a black alder (Alnus glutinosa (Gaertn.) L.) forest

Physiological capabilities of culturable bacterial and fungal communities w ere studied over 12 months during leaf litter decomposition in a black alde r (Alnus glutinosa (Gaertn.) L.) forest at a eutric-wet and dystric-dry His tosol. Microbial biomass content, basal respiration rate, metabolic quotien t, P-glucosidase and protease activity and abiotic properties of the litter were also considered as 'integral' microbiological characteristics since b oth bacterial and fungal physiological capabilities were included. The numb er of copiotrophic and proteolytic bacteria were positively correlated whil e the numbers of cellulolytic and lipolytic bacteria were negatively correl ated. Fungal enzymatic potentials were generally positively linked with eac h other and with the corresponding physiological capabilities of bacteria. Cellulolytic bacterial numbers were positively associated with fungal polyg alacturonase and lignolytic activity. In contrast, numbers of lipolytic bac teria and the lipolytic fungal potential were negatively correlated. The fu ngal communities appeared to play a predominant role in litter breakdown at the early stages whereas bacteria completed the mineralisation. Contrary t o the integral microbiological characteristics, data on physiological capab ilities of bacteria and fungi connected with abiotic properties were poorly correlated. The connectance between bacterial and fungal capabilities, int egral microbiological characteristics and abiotic factors varied between w0 .06 and 0.51 and correlations were generally lower at the eutric-wet site. At the dystric-dry site. mineralisation rates were water-limited during the summer months. and protease and beta -glucosidase activity related to the microbial biomass were also reduced to less than 20% of the maximal values. (C) 2001 Elsevier Science Ltd. All rights reserved.