[Biology Class Notes] on Decomposition Pdf

The word decomposition refers to the process of breaking down that is, decomposing. It generally means the decomposing or breaking down of the complicated organic matter into the smaller and simpler matter, which is inorganic. It is one of the most important and significant cycles of what we know as the ecosystem. Therefore, decomposition can be said to be a metabolic process, which uses complex substances as raw materials, decomposes them to break them down, and transforms them into simple substances.

Bacteria, fungi, and a few other microorganisms are the catalysts of the process of decomposition and are given the term of decomposers. They survive by feeding on dead organisms. 

The plants and animals which are dead and decaying are seen as the raw materials which, when decomposed, creates carbon dioxide, nutrients, and water, etc. The dead plants, animals, and their leftovers, which are considered as raw materials, are known as detritus. These detritus are then converted using the microbes, which are in their entirety known as saprophytes.

Factors Affecting Decomposition

The below-mentioned factors are important factors affecting the rate of decomposition:

How quickly the raw materials react to decomposition is directly proportional to the structural and chemical properties of litter. For e.g., the litter of bryophytes takes a lot of time to decompose owing to the existence of lignin like complex chemicals within them. 

Temperature moderates the microorganisms’ growth and activity. The temperature differs in varying altitudes and elevations. The environmental changes also affect the diversity of species and the number of microorganisms present. 

The oxygen that exists in the soil’s pores affects the microorganism’ growth. When the soil is waterlogged, there is an absence of these microorganisms. In such soils, there is only the presence of anaerobic microorganism, and only they can initiate the process of decomposition. 

In soil, there exist cations and anions. Now cations and anions affect the pH of the soil. The soil’s pH, in turn, then impacts the growth of the microorganisms. 

After the decomposition process is completed, there are some elements that are released into the soil. These elements are basically potassium, sodium, calcium, and magnesium. Now some of these elements are used in the growth of the microorganism. And therefore, it impacts the speed of the decomposition. 

There is water present in the soil. Now this presence of water in the soil is responsible for several processes of microorganisms like physiological processes. These microorganisms are also present in the soil, and thus the amount of moisture present in the soil also determines the growth of the microorganisms. 

Steps To Determine Complete Decomposition

It is the initial stage of decomposition. Fragmentation means the breakdown of detritus into smaller pieces by the detritivores.

Fragmentation is the first step in the process of decomposition. Fragmentation refers to the process of breaking down the raw complex materials or the “detritus” into simpler, smaller substances with the assistance of detritivores. 

These smaller, simpler substances which were acquired in the first stage after the fragmentation of bigger complex materials may contain a huge amount of water-soluble nutrients, which are considered to be inorganic in nature. These nutrients are then dissolved in the water and get absorbed into the soil, and then through the process of leaching gets precipitated. 

Once these raw complex substances undergo the first two stages and the materials are broken down into smaller, simpler substances, and the removal of the inorganic nutrients takes place, then this process transforms the detritus into simpler substances, which are inorganic in nature. This process is completed with the aid of fungal and bacterial enzymes, and this process is known as catabolism. 

Humification is the process where a layer that is dark in colour and composed of amorphous substance is formed on the soil. This substance is known as humus. The humus is not easily susceptible to decomposition and cannot be decomposed easily. It is extremely resistant to any action on it by microbes. This layer of humus is known to be highly nutritious due to the presence of large quantities of nutrients and supplies the soil gets rich fertility through the humus. 

Last but not least comes the last stage of decomposition known as the process of mineralization. Now, mineralization is the process of breaking down the humus layer to release the inorganic nutrients present in it.