Extreme effects of drought on composition of the soil bacterial community and decomposition of plant tissue

Summary The decomposition of soil organic matter, as an essential part of nutrient cycling, has a crucial role in maintaining soil fertility and the regulation of climate. This function of the soil is likely to be affected by extreme weather events that are expected to be more frequent and severe in the future. We conducted an experiment from M arch 2014 to M arch 2015 to test the effects of extreme drought on composition of the bacterial community and decomposition of plant tissue with soil microclimate variables such as soil temperature and moisture. Precipitation was excluded for a 5‐month period by transparent roofs. To follow organic matter decomposition, we used the tea bag method. Soil samples were taken to determine the effects of extreme drought on the bacterial community 6 months after the dry period (mid‐term). Drought plots were drier ( P < 0.001) and warmer ( P < 0.001) than control plots as a consequence of the extreme drought treatment. The permanova test showed that the dry period altered soil bacterial communities accordingly ( F permanova = 10.36, P = 0.002). However, there was no significant difference between the control and drought‐treated plots 6 months after the dry period in terms of bacterial alpha diversity. Furthermore, rates of organic matter decomposition in the control plots were significantly larger by an average of 93.7% than in the drought plots. The results also indicated that soil temperature and moisture had significant effects on decomposition. Overall, the findings demonstrate clearly the response of soil bacteria and soil function to experimental drought. The strong effect of changes in precipitation and increasing temperature on mass loss suggests that extreme weather events, such as extreme droughts, can markedly change the composition of soil bacterial communities and processes of decomposition. This effect is expected to be more pronounced during dry periods of increasing severity and frequency. Highlights We studied the effects of extreme drought on plant tissue decay and soil bacterial diversity. Microbial degradation of organic matter was followed by the novel tea bag method. Changes in soil microclimate altered bacterial community structure and decomposition. Microbiota and soil function were markedly affected by extreme weather events like droughts.