What is Decomposition?
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.
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Factors Affecting Decomposition
The below-mentioned factors are important factors affecting the rate of decomposition:
Litter Quality
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
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.
Aeration
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.
Soil pH
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.
Inorganic Chemicals
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.
Moisture
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
Fragmentation
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.
Leaching
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.
Catabolism
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
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.
Mineralization
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.
FAQs on Decomposition
1. What is decomposition in biology, and what are decomposers?
In biology, decomposition is the natural process of breaking down complex organic matter (like dead plants and animals) into simpler inorganic substances such as carbon dioxide, water, and nutrients. The microorganisms that carry out this process, primarily bacteria and fungi, are known as decomposers. They play a vital role in the ecosystem's nutrient cycle.
2. What are the five main steps in the process of decomposition?
The decomposition process in an ecosystem occurs in five distinct steps as per the CBSE Class 12 syllabus for the academic year 2025-26:
- Fragmentation: The breakdown of detritus (dead organic matter) into smaller particles by organisms called detritivores, like earthworms.
- Leaching: Water-soluble inorganic nutrients seep down into the soil horizons and get precipitated as unavailable salts.
- Catabolism: The enzymatic conversion of degraded detritus into simpler inorganic substances by bacteria and fungi.
- Humification: The accumulation of a dark-coloured, amorphous, nutrient-rich substance called humus, which is highly resistant to microbial action.
- Mineralization: The final release of inorganic nutrients (like Ca²⁺, Mg²⁺, K⁺) into the soil as the humus is further degraded by microbes.
3. What is detritus, and what is the function of detritivores?
Detritus is the term for all non-living organic material, including fallen leaves, dead wood, animal remains, and faecal matter. Detritivores, such as earthworms, mites, and millipedes, are organisms that feed on this detritus. Their primary function is to perform fragmentation, breaking the detritus into much smaller pieces, which increases the surface area for subsequent microbial action and speeds up the overall decomposition process.
4. What are the key factors that affect the rate of decomposition?
The rate of decomposition is controlled by several key environmental and chemical factors. The most important ones include:
- Litter Quality: The chemical composition of the detritus. Materials rich in lignin and chitin decompose slowly, while those rich in nitrogen and water-soluble substances decompose faster.
- Temperature: Warm temperatures (around 25°C) favour the growth and activity of decomposer microbes, accelerating the process.
- Moisture: Optimal soil moisture is essential for microbial activity. Extreme dryness or waterlogging can slow down or inhibit decomposition.
- Aeration (Oxygen): Most decomposers are aerobic, meaning they require oxygen. Poor aeration, such as in waterlogged soil, slows decomposition significantly.
- Soil pH: The acidity or alkalinity of the soil affects the population and activity of different microbial species.
5. How would the rate of decomposition differ between a tropical rainforest and the arctic tundra?
The rate of decomposition would be significantly faster in a tropical rainforest than in the arctic tundra. This is because the warm temperatures and high moisture levels in the rainforest create ideal conditions for decomposer organisms like bacteria and fungi to thrive year-round. In contrast, the arctic tundra has extremely low temperatures for most of the year, which severely inhibits microbial activity, causing dead organic matter to accumulate for long periods with very slow decomposition.
6. What is the difference between humification and mineralization?
Humification and mineralization are two sequential stages in decomposition. Humification is the process where decomposed organic matter is transformed into humus—a stable, dark, amorphous substance that is resistant to further decay and enriches the soil. Mineralization is the subsequent process where this humus is slowly broken down by other microbes to release the locked-in inorganic nutrients (like nitrates and phosphates) back into the soil, making them available for plants.
7. Why is humus considered so valuable for soil fertility?
Humus is extremely valuable for soil fertility for two main reasons. First, it acts as a reservoir of essential nutrients. Due to its slow rate of decomposition, it releases nutrients gradually, ensuring a steady supply for plants. Second, its colloidal nature helps improve soil structure, increases its water-holding capacity, and enhances aeration, creating a healthier environment for plant roots and beneficial soil organisms.
8. What is the difference between decomposition and putrefaction?
Decomposition is a broad term for the breakdown of any organic matter. Putrefaction is a specific type of decomposition that refers to the anaerobic breakdown of proteins, primarily by bacteria and fungi. This process is often associated with the production of foul-smelling gases like hydrogen sulphide and ammonia, which is why it is commonly linked to the decay of animal carcasses. Essentially, all putrefaction is a form of decomposition, but not all decomposition is putrefaction.
