Decomposition

Decomposition is the process where dead plants and animals break down into simpler materials with the help of bacteria, fungi, and microorganisms. This process is important for recycling nutrients in the soil and supporting life in ecosystems. It is part of the Class 12 Ecosystem chapter in Biology. This article includes the decomposition process, factors affecting decomposition, catabolism in decomposition etc.

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This Story also Contains

1. What is Decomposition?
2. Process of Decomposition
3. Ecological Impact of Decomposition
4. Practical Applications of Decomposition

What is Decomposition?

Decomposition is a naturally occurring process that degrades organic substances into simpler organic or inorganic matter, such as carbon dioxide, water, and eventually, nutrient-rich soil. This process is very important and helps in nutrient cycling within an ecosystem by returning the important elements to the environment.

Importance of Decomposition in Ecosystems: Decomposition is an essential process for the health and balance of ecosystems. It aids in:

• Recycling nutrients, making them available for plant use.

• Decomposition of dead organic matter, preventing the accumulation of dead material.

• Maintaining the food web by providing energy and nutrient supply to decomposers and detritivores.

• Soil formation and fertility.

Factors Affecting Decomposition

It is influenced by various environmental and biological factors. Understanding those factors is important to studying ecological cycles and properly managing waste. The major factors affecting decomposition are:

Temperature

The temperature in the habitat influences the metabolic rate of microorganisms responsible for the decomposition process.

Microbial activity

• In general, high temperatures increase the activity of most microbes, hence decomposition. The optimum for most microbial activity falls between 25°C to 35°C.
• Extremely high temperatures denature microbial enzymes involved in decomposition, slowing down the process.
• Very low temperatures depress microbial metabolism, and decomposition slows down drastically. Under freezing conditions, decomposition can almost grind to a halt.

Moisture

Water is a prerequisite of any microbial activity and, as such, predominantly determines the speed of decomposition.

Role in Decomposition Rate

• Sufficient moisture allows for the diffusion of enzymes and nutrients for microbial activity.
• Excessive moisture creates anaerobic conditions, under these conditions, the rate of aerobic microbial activity is very slow and often accompanied by foul odours.
• Insufficient moisture strips microbes of activity and enzyme function, reducing decomposition rates.

Oxygen Availability

Oxygen is a very essential factor that determines whether it is an aerobic or anaerobic decomposition process.

Aerobic vs. Anaerobic Decomposition

• Aerobic decomposition goes on in the presence of oxygen, it is therefore usually faster and more efficient. Carbon dioxide, water, and heat form as by-products.
• Anaerobic Decomposition takes place in an oxygen-deficient environment.
• It is slower, leading to the formation of methane a very potent greenhouse gas along with other gases that may be foul-smelling.

pH Levels

It is the acidity or alkalinity of their medium that influences their growth or activity as decomposers.

Optimum Conditions for Decomposers

• Most decomposers, especially bacteria, favour a slightly acid-to-neutral medium with a pH range of 6-7.
• Inhibitive factors include very acidic or alkaline conditions since, under such conditions, microbial activity is impaired and decomposition is slowed due to the failure of enzymatic action.

Presence of Decomposers

The types and quantity of decomposers significantly come into the decomposition process.

Types and their role

• Bacteria: bacteria form primary decomposers for most environments, particularly during the initial stages of decomposition.

• Fungi: Fungi, mainly in the form of moulds and yeasts, are also an important component for decaying tough organic material such as wood lignin.

• Invertebrates: Earthworms, insects, and other invertebrates physically break down organic matter, increasing the surface area available for microbial action.

• Protozoa and Nematodes: These regulate the populations of bacteria and fungi to maintain a balanced populace for decomposition in the ecosystem.

Also Read:

• Practice MCQ on Decomposition
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Process of Decomposition

Decomposition, therefore, is a complicated process that comprises many stages, whose major feature includes some specific physical and biochemical changes that the body undergoes while breaking down.

Steps of decomposition include:

Fragmentation

• The physical breaking down of dead organic matter into smaller pieces.
• Examples of Detritivores include earthworms, beetles, and other soil organisms
• Has the effect of increasing the surface area for the action of microbes.

Leaching

• Leaching is the process by which soluble substances are washed out from decomposing matter.
• Water percolates in the soil and sweeps with it the soluble compounds. It leaches easily dissolved substances and minerals from decomposing material.

Catabolism

• The breakdown of complex organic molecules into simple compounds.
• Microorganisms such as bacteria and fungi secrete enzymes to digest organic matter.
• Conversion of large organic molecules into simpler compounds such as amino acids, sugars, and fatty acids.

Humification

• The process of forming humus, a stable, dark organic material.
• Products of catabolism are further broken down by continued microbial activity.
• Soil enrichment by humus improves its structure and fertility.

Mineralisation

• The final stage at when organic matter is converted to inorganic substances.
• Microorganisms further process the humus and release the nutrients.
• Mobilisation of inorganic nutrients such as nitrogen, phosphorus, and potassium into the soil and their availability to plants for uptake.

Ecological Impact of Decomposition

Decomposition is one of the major ecological processes and hence plays a very significant role in the health and sustainability of an ecosystem. Decomposers, through the decomposition of organic matter, contribute to several important ecological processes:

Nutrient Cycling

Decomposition is the critical component of nutrient cycling, returning the essential elements to the environment.

• During decomposition, decomposers release nutrients like nitrogen, phosphorus, and potassium into the soil.
• These, in turn, are available to plants for uptake, promoting growth and productivity.
• It involves the breakdown of complex organic molecules into simple inorganic compounds, making them readily available to plants and other organisms.

Soil Formation

Decomposition builds up and enhances soils, acting on their structure and fertility.

• Humus is the stable, organic component of soils, resulting from the decomposition of plant and animal remains.
• Humus enhances the soil texture, water-holding capacity, and nutrient retention.
• Any decomposition organisms, like bacteria, fungi, or even earthworms, boost the fertility of the soil through metabolic processes.
• Such organisms decompose organic matter and mix it with the soil, enriching its quality.

Impact on Plant Growth

The decomposition products are such that they feed the plants by providing them with the nutrients for proper growth and development.

• Nutrients released in decomposition get absorbed by the roots of plants and support their growth.
• This provides a constant supply of decomposed material hence the constant source of nutrients required for healthy development in plants.
• In decomposition, organic matter improves the aeration of the soil aside from improving its water-holding capacity to attain optimal growth for the roots.

Role in Food Webs

Decomposition is integral in food webs, as it supports a diverse array of organisms while keeping the ecosystem balanced.

• The process of decomposition is initiated by bacteria and fungi, which start decomposing dead organic matter.
• These major decomposers, in turn, become food for minor decomposers, such as protozoa and nematodes.
• Organisms like earthworms and insects, together with scavengers, consume decaying organic material and break it down further to recycle the nutrient content.
• Detritivores break down organic matter into smaller pieces, increasing the surface area for microbial action.

Practical Applications of Decomposition

Decomposition has practical applications in sustainable practices like composting and vermiculture, tending to the benefit of soil health.

Composting

• It refers to the aerobic decomposition of organic matter to obtain nutrient-rich compost.
• Aerobic and anaerobic methods of composting, with aerobic composting being the prevalent and more efficient approach.
• It improves soil fertility, enhances structure, and increases microbial activity.

Vermiculture

• It is the process of using earthworms to decompose organic matter, resulting in nutrient-rich worm castings.
• These efficiently digest organic waste into the appearance of valuable worm castings.
• It improves soil fertility, enhances the structure, and is low maintenance.

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