London, August 28 : A new study has determined that after mountain glaciers melt, primitive bacteria start to invade the soil immediately, enriching it with nutrients, cementing the ground, and preventing landslides.
Researchers, who have studied the process in the Peruvian Andes, carried out the study.
A few studies have looked at the types of plants that colonize mountain valleys that were previously covered in ice.
But, before plants move in, there is usually a period, which at high latitudes and altitudes can last several years, during which the newly uncovered soil appears totally barren.
According to a report in New Scientist, to investigate what is happening during this period, Steve Schmidt of the University of Colorado, US, and colleagues examined the soil at the retreating edge of the Puca glacier in the Peruvian Andes.
Between 2000 and 2005, they sampled the top 10 centimetres of ground that was revealed as the glacier moved uphill at a rate of 20 metres per year.
They analyzed the chemical structure of the samples and screened for bacteria.
They found that over the years, the "oldest" soil - the dirt taken from the point that was revealed at the glacier edge in 2000 - changed rapidly.
The first organisms to appear in the soil were cyanobacteria.
These primitive bacteria are found in many marine ecosystems and some land-based ecosystems. It is these bacteria that have pumped oxygen into Earth's atmosphere 3.4 billion years ago, allowing land life to evolve.
By running DNA analyses on the soil, Schmidt and his colleagues show how the bacteria population changed over the first five years.
Whereas "young" soil contained just three distinct genetic strains of cyanobacteria, four-year-old soil harboured up to 20.
The cyanobacteria increased the amount of carbon available in the soil, through photosynthesis and, along with other types of bacteria; they also boosted nitrogen levels in the soil, an essential nutrient for plant life.
Another, perhaps more surprising, function of the cyanobacteria seems to be to hold the ground together.
Previous studies have shown that they secrete sugary chemicals that help hold the soil particles together and prevent erosion.
At Puca glacier, the researchers found that soil shear strength was nearly double in the oldest soil relative to the youngest.
According to Schmidt and colleagues, "An important role of cyanobacteria in extreme environments may be to hold the soil in place."