Soil microbial legacies differ following drying-rewetting and freezing-thawing cycles

Area of Science:

• Soil science
• Microbiology
• Climate change impacts

Background:

• Climate change is altering soil moisture dynamics through altered drying-rewetting and freezing-thawing cycles.
• Soil water availability is a key factor influencing soil microbial activity and community structure.
• The long-term effects of these cycles on soil microbiome resilience and function remain under investigation.

Purpose of the Study:

• To investigate the legacy effects of drying-rewetting and freezing-thawing cycles on soil microbial communities.
• To compare the impact of these two distinct climate-driven soil moisture fluctuations on soil respiration and microbiome structure.
• To test the hypothesis that freezing-thawing and drying-rewetting cycles have similar effects on the soil microbiome.

Main Methods:

• Microcosm experiments were designed with a two-phase approach to establish legacy effects.
• Phase 1 involved exposing soil samples to either a drying-rewetting or freezing-thawing cycle.
• Phase 2 subjected these previously treated soils to the alternative cycle, measuring soil respiration and analyzing microbiome structure.

Main Results:

• Rewetting events following drying caused larger carbon dioxide (CO2) pulses and greater shifts in microbiome structure compared to thawing events.
• A prior drying-rewetting cycle (legacy) significantly influenced the soil microbiome's response and CO2 emissions during a subsequent freezing-thawing cycle.
• Conversely, a freezing-thawing legacy did not substantially alter the microbial response to a subsequent drying-rewetting cycle.

Conclusions:

• Drying-rewetting cycles exert a stronger influence on soil microbial communities and associated CO2 production than freezing-thawing cycles.
• The observed differences are attributed to sustained alterations in soil microbiome structure induced by drying-rewetting events.
• Understanding these differential impacts is crucial for predicting soil ecosystem responses to climate change.