The impact of low temperatures on the structure of the microbial biomass during the soil samples storage

The assessment of the microbial biomass structure in the soil samples from A and C horizons, stored at the temperature of +5 and -70°С was conducted by a luminescence method. For the samples from the humus layer a significant decrease of biomass during the cryostorage was revealed. However, in the sample from the mineral layer at the same storage conditions such a decrease occurred in a lesser degree. The decrease of fungi mycelium length was observed in the sample, which was stored at the temperature -70°С. Also, the decrease of the number of fungi spores with large diameter ( d > 5 mkm) and the absence of the largest spores ( d > 7 mkm) was observed. The mycelium length of the pure culture of Cadophora novi-eboraci fungi was a bit decreased after the storage of samples at +5°С. Under conditions of negative temperatures (-18 and -80ºС) the mycelium length was decreased by 28% during the first days, and by 32% on the 14-th day of the incubation. The data obtained stipulate that the storage of samples under conditions of negative temperatures leads to the decrease of biomass and number of microorganisms within the soil. Therefore, it is not recommended to store soil samples under conditions of negative temperatures if it is planned to assess the structure of microbial biomass by the direct method of luminescent microscopy.