Historical Drought Affects Microbial Population Dynamics and Activity During Soil Drying and Re-Wet

Area of Science:

• Soil Microbiology
• Environmental Science
• Microbial Ecology

Background:

• Drought exposure can select for drought-tolerant soil microbes, but survival mechanisms during drying and re-wetting are unclear.
• Understanding microbial responses to water stress is crucial for predicting ecosystem functions.

Purpose of the Study:

• To investigate how a history of drought affects soil microbial survival, death, and physiological potential during laboratory drying and re-wetting.
• To determine if field drought legacy influences microbial community shifts and carbon loss potential.

Main Methods:

• Soils from a 15-year field drought experiment (Altered vs. Ambient) were subjected to laboratory drying/re-wetting cycles.
• Microbial community composition was analyzed using 16S rRNA gene sequencing.
• Microbial respiration and RNA:rRNA gene ratios (protein synthesis potential) were measured.

Main Results:

• Drought-altered soils exhibited greater microbial population stability (survival) during drying/re-wetting compared to ambient soils.
• Ambient soils showed higher microbial mortality upon re-wetting.
• Altered soils had lower protein synthesis potential during dry-down, higher potential growth rates, and lower average respiration rates.

Conclusions:

• Historical drought exposure selects for soil microbial communities with enhanced survival mechanisms against water stress.
• Drought-adapted microbial communities in soils exhibit differential survival and death, leading to reduced carbon loss potential.
• These findings provide insights into the mechanisms and consequences of soil microbial adaptation to extended drought.