The Dynamics of Soil Microbial Communities on Different Timescales: A Review

Soil microbial communities are subjected to significant changes over time. The most rapid changes caused by temperature and soil moisture alternations or the by the inflow of fresh organic matter occur during the several hours or days. They are mostly related to the soil microbial activity. Seasonal dynamics are caused by annual variations in temperature and precipitation that affect the microbial community directly or indirectly through the regulation of plant life. The microbial biomass and the taxonomic composition of soil microbial communities vary significantly throughout the year, which should be taken into account when sampling for a comparative analysis of different soils. The long-term dynamics of microbial communities during primary or secondary successions lead to an increase in the total microbial biomass and the fungi/bacteria ratio, as well as to changes in the taxonomic composition of microbial communities. The main factors of the long-term dynamics are the accumulation of soil organic matter, plant successions, and changes in pH. The diversity of microbial communities during long-term dynamics can vary in different ways and does not follow a single trend. The longest dynamics of soil microbial communities are associated with changes in bioclimatic conditions. Information about soil microbial communities of the past can be obtained by studying buried and permafrost soils. The study of future changes in soil microbial communities is possible in experiments with artificial changes in climatic parameters. Plants are a significant factor in the dynamics of soil microbial communities on all timescales; in short-term periods, the major role is played by the activity of plants; in the long-term trends, the changes in the vegetation abundance and diversity are the most important factors.