Decomposers play a very important role in keeping our environment clean. They break down complex organic matter and convert it into simple inorganic substances like water, carbon dioxide and nutrients. This natural process is known as decomposition. The raw material for decomposition is the detritus, which comprises dead and decaying plant remains such as leaves, branches, flowers, roots and dead animal remains, including faecal matter.
Decomposition involves a series of important steps, namely fragmentation, leaching, catabolism, humification and mineralisation. Of these steps, fragmentation, leaching and catabolism occur simultaneously on the detritus. During fragmentation, the detritus is broken down into smaller particles by detritivores, which are organisms that feed on and break down dead plant or animal matter while returning essential nutrients to the environment. During leaching, inorganic nutrients that are soluble in water drain into the soil and get precipitated as unavailable salts. While during catabolism, the detritus is further acted upon by bacteria and fungi and is degraded into simpler inorganic substances by the action of their enzymes.
The next step of decomposition is humification, where the detritus gets converted into a dark, amorphous substance called humus. Humus is extremely resistant to microbial action and thus has a very slow rate of decomposition. Finally during mineralisation, the last step of decomposition, certain microbes act on the humus, degrade it and release inorganic nutrients into the soil. Both humification and mineralisation occur inside the soil. However, the process of decomposition is affected by several factors. It is primarily an oxygen-requiring process and the chemical composition of the detritus along with climatic factors such as temperature and soil moisture affect the rate of decomposition. For a particular temperature, the rate of decomposition is slower if the detritus is rich in substances like lignin and chitin and is faster if the detritus is rich in nitrogen and water-soluble substances like sugars. Climatic conditions such as temperature and soil moisture affect the activity of microbes, thus affecting the rate of decomposition. That is, the rate of decomposition is faster when the temperature is warm and the environment is moist, whereas low temperature and lack of oxygen favours anaerobiosis, which slows the process of decomposition and leads to a build-up of organic materials. Therefore, the process of decomposition helps to recycle the nutrients required for the very existence of life.