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 were studied over 12 months during leaf litter decomposition in a black alder (Alnus glutinosa (Gaertn.) L.) forest at a eutric-wet and dystric-dry Histosol. Microbial biomass content, basal respiration rate, metabolic quotient, β-glucosidase and protease activity and abiotic properties of the litter were also considered as ‘integral’ microbiological characteristics since both bacterial and fungal physiological capabilities were included. The number of copiotrophic and proteolytic bacteria were positively correlated while the numbers of cellulolytic and lipolytic bacteria were negatively correlated. Fungal enzymatic potentials were generally positively linked with each other and with the corresponding physiological capabilities of bacteria. Cellulolytic bacterial numbers were positively associated with fungal polygalacturonase and lignolytic activity. In contrast, numbers of lipolytic bacteria and the lipolytic fungal potential were negatively correlated. The fungal communities appeared to play a predominant role in litter breakdown at the early stages whereas bacteria completed the mineralisation. Contrary to the integral microbiological characteristics, data on physiological capabilities of bacteria and fungi connected with abiotic properties were poorly correlated. The connectance between bacterial and fungal capabilities, integral microbiological characteristics and abiotic factors varied between 0.06 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 β-glucosidase activity related to the microbial biomass were also reduced to less than 20% of the maximal values.