Abstract
Sustained climate warming increases the frequency and strength of soil freeze–thaw (FT) events, which strongly affect the properties of soil microbial communities. To explore the responses and mechanisms of the frequency and strength of freeze–thaw events on soil microbial communities, a lab-scale FT test was conducted on forest soil in permafrost region from the Daxing’an Mountains, China. The number of FT cycles (FTN) had a greater effect on microbial communities than FT temperature fluctuation (FTF). The FTN and FTF explained 20.9 and 10.8% of the variation in microbial community structure, respectively, and 22.9 and 11.6% of the variation in enzyme activities, respectively. The total and subgroup microbial biomass, the ratio of fungi to bacteria (F/B), and C- and N-hydrolyzing enzyme activities all decreased with an increase in FTN. Among microbial groups, arbuscular mycorrhizal fungi (AMF) were the most sensitive to FT events. Based on the changes of F/B and AMF, the reduction in soil carbon sequestration caused by frequent FT events can be explained from a perspective of microorganisms. Based on redundancy analysis and Mental Test, soil moisture, total organic carbon, and total nitrogen were the major factors affecting microorganisms in FT events. In the forest ecosystem, soil water and fertilizer were important factors to resist the damage of FT to microorganism, and sufficient water and fertilizer can lighten the damage of FT events to microorganisms. As a result of this study, the understanding of the responses of soil microorganisms to the variation in FT patterns caused by climate changes has increased, which will lead to better predictions of the effects of likely climate change on soil microorganisms.
Highlights
In 2019, a paper published in Nature Reviews Microbiology warned humanity that the effects of climate change depend heavily on the responses of microorganisms (Cavicchioli et al, 2019)
The control treatment without FT (C) was a branch, and the −4 to 4◦C (H) and −14 to 4◦C (L) FT temperature fluctuation (FTF) treatments together composed one branch. These results showed that soil microbial activities are affected by FT and that the effects of FTN are greater than those of FTF
The effects of FTN and FTF on soil microbial communities were different in the soil of a L. gmelinii forest
Summary
In 2019, a paper published in Nature Reviews Microbiology warned humanity that the effects of climate change depend heavily on the responses of microorganisms (Cavicchioli et al, 2019). Increased understanding of the microbial traits that confer ecosystem resilience to climate change will lead to better predictions and management of ecosystem responses. With the loss of the insulation provided by snow cover, minimum soil temperatures decrease, and the frequency and severity of freeze–thaw (FT) cycles increase (Sulkava and Huhta, 2003; Groffman et al, 2011; Tan et al, 2014; Boswell et al, 2020). Most studies focus only on how the number of FT cycles (FTN) or the FT temperature fluctuation (FTF) affects the microbial community, whereas the study of specific combinations of these factors often helps to increase understanding of the mechanisms of change (Rillig et al, 2019).
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