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Rapid Recovery: How Quickly Soil Microbes Respond to Rain After Drought
Some microbes will start recovering within hours of receiving moisture from breaking rains. Soil microbes have been around for billions of years and have seen many dry periods (e.g. the late Glacial maximum, 20,000 years ago, was probably drier than the millennium drought) and soil wetting and drying is a normal part of life for soil microbes.
Soil life has a variety of adaptations to cope with the dry. Fungi form spores. Most microbes, including tardigrades and nematodes, enter a suspended animation type state without water. When water arrives, they ‘wake up’ and get back to work. In the middle of 2023, scientists revived roundworms that had been in a cryptobiotic state, 40 metres below the permafrost in Siberia for 46,000 years. All they did was ‘thaw’ the worms then add water.
The speed of recovery varies, with many soil microbes, including bacteria, doubling within 8 hours. Fungi with spores can show signs of recovery within hours, but forming complete hyphal networks might take a week or two, depending on growth speed. Nitrifying organisms may take 6-7 days to get going again.
Remember that microbes in the soil are not entirely exposed to the dry conditions to start; they live within pores inside aggregates, form biofilms on surfaces, and reside within decomposing roots and residues. Crops can’t use the water inside micro-aggregates or as small films on soil surfaces—but microbes can, and this water stays in the soil longer than water in soil pores.
Australia has been subjected to dry for a long time. A few years of dry weather won’t kill off all the microbes.
