State programs for monitoring soil microbial properties related to the carbon cycle are currently being implemented. These indices include microbial biomass carbon (Cmic) content and the rate of basal respiration (BR). The large number of sample plots and logistical difficulties limit the timely delivery of fresh soil samples to the laboratory and their analysis. In this context, it is important to understand how long and under what conditions the collected samples can be stored. The aim of this study is to compare Cmic and BR data obtained for air-dried and naturally wet soil samples stored at 22 and 4°C, respectively, over short-term (1 month) and long-term (8 months) periods. The study focuses on soil samples taken from forest, post-agricultural (abandoned lands), and urban ecosystems in the Moscow region, in the zone of soddy-podzolic soils (Albic Retisols). Soil samples were collected from a depth of 0–10 cm for the main (n = 22) and auxiliary (n = 10) experiments. The main experiment showed that short-term storage of air-dried soil samples leads to an average 15% decrease in Cmic, but a 22% increase in BR relative to those in naturally wet samples. Long-term storage of samples resulted in the loss of Cmic in both air-dried and naturally wet soil samples. The BR rate decreased consistently in naturally wet samples after eight months of storage at 4°C, while it changed unpredictably in air-dried samples. An auxiliary experiment demonstrated that air-drying of soil samples as soon as possible after sampling (within eight days) leads to a significant decrease in Cmic, but has no significant effect on the BR rate as compared with naturally wet samples. The disparity in microbial properties between air-dried and naturally wet samples intensified with longer storage periods.
Mukvich et al. (Mon,) studied this question.