101 Questions answered
Soil Biology in Drought: Survival, Dormancy, and Recovery After Rain
No, while drought can have a major impact on soil biology, it doesn’t kill it completely. Soil organisms need water to function and sometimes to move around. As the soil dries out, soil organisms become more and more concentrated in shrinking moisture reserves, competing with one another for water and food and thereby reducing numbers through competition. Some simply die, some move in search of water, and others go into shutdown or survival mode, waiting until it rains again.
Soil microbes have evolved over a few billion years and adapted to conditions. For example:
- Bacteria form spores ready to reactivate when soil moisture increases.
- Protozoans transform into desiccation-resistant structures.
- Nematodes go into a form of suspended animation.
- Worms lay eggs then burrow deeper to hibernate.
Fungal hyphae are less bothered by drought (tillage has more of an impact) and can expand their threads to find water. Eventually though, if the soil completely dries out, they will die too.
Microbes quickly recolonise once it rains and populations bounce back providing there is sufficient food (soil organic matter), moisture and favourable soil temperatures.
