Changes in Labile and Microbial Pools of Carbon and Nitrogen in Forest Litter Samples under Different Methods of Storage

Resumo

The influence of conservation procedures (drying, freezing, and storage at low positive temperatures) and preliminary aerobic incubation on the result of determination of labile and microbial pools of carbon and nitrogen has been analyzed using forest litter samples from the northern, middle, and southern taiga spruce forests. It was established that drying of litter samples and their subsequent moistening before analyzing them resulted in a decrease of microbial carbon and nitrogen concentrations against the background of increasing concentrations of elements of the labile pool. Freezing of the samples had similar effect on the labile pool, but it did not lead to a statistically significant change in concentrations of C and N in microbial biomass. Storage at low positive temperatures resulted in decrease of microbial pool, but its on the labile forms of carbon and nitrogen effect was ambiguous, and this was associated with the growth and death cycles of microbial biomass. Preliminary aerobic incubation of litter samples did not lead to restoration of carbon and nitrogen concentrations typical for fresh samples. The main direction of nitrogen compounds transformation was determined by the C : N ratio in labile organic matter and microbial biomass, and depended on the storage method: the processes of net mineralization predominate when drying, while the processes of net immobilization dominated during freezing and storage at low positive temperatures.