The soil contains more species than any other environment on Earth. Knowing what happens to these organisms during winter can help us understand why our relationship with the soil matters.
Millions of Microbes
The two most abundant members of the soil community are fungi and bacteria. Both of these act as primary decomposers in the soil and are very necessary to soil health, affecting the availability of plant nutrients and thus plant health. Microbes can degrade virtually all plant-derived compounds which have first been fragmented by larger soil organisms. In the soil ecosystem then, microbes have a really important role. They are essential to the process of decomposition and mineralisation, and these activities can determine the availability to plants.
Their extreme diversity also means that they can co-exist as a soil community without too much competition. There is a species for every niche! Many of these can survive unfavourably cold conditions through their ability to remain inactive. Some bacteria can even withstand being frozen as their membranes don’t burst as do those of multi-cellular animals. But of all the myriad of soil organisms, the earthworm has the most admirable survival strategy.
“The Intestines of the Earth” was Aristotle’s incredibly apposite description of earthworms. Charles Darwin examined their effects for many years and also seen earthworms highly. These cold-blooded prehistoric creatures are really astonishing. They are most active in spring and autumn and make up most of the animal biomass in soil. Feeding on organic matter and converting it into rich humus is realised by the worms’ actions of pulling down below any suitable material eg leaves, manure and after that shredding and somewhat digesting it.
Stuff which has passed through the earthworm’s intestine has 1000 times more soil-benevolent bacteria acting as a strong biocide and helps to eliminate ground disorders. It also contains high concentrations of nitrogen, sulphur, potash, phosphorus, calcium, magnesium, growth hormones and vitamins. They are essential to a wholesome ‘living’ ground and composting – soils with lots of worms are the best.
Harsh winters can wipe out earthworms but as cold weather causes the soil to harden and cool some species make cocoons of eggs which can survive freezing temperatures while others will burrow deeper into the ground. There they curl up in a burrow pocket, produce anti-freeze mucus which surrounds their bodies and begin a type of hibernation called estivation. Their reduced metabolic rate keeps them ticking over so that when warmth returns to the soil in spring they will have survived long enough to continue reproduction. This incidentally can happen frequently; worm populations can double every 60 days! They can also live for two to three years given the right conditions, and eat more than their own body weight every day. It would seem that they are so abundant we should hardly ever need to worry about them. However, vegetable growing will deplete the soil of its nutrients. Without a replenished organic layer, the soil will become barren and lifeless. While earthworms are practically working miracles and can even break down certain soil chemicals which are harmful to humans into harmless residues – they are sensitive to others. Pesticides can kill earthworms as can fluctuations of pH and oxygen levels in soil and the overuse of fertilisers.