The correct option is (c).
Explanation
Nutrient cycling involves the movement and exchange of organic and inorganic matter within an ecosystem. In forest ecosystems, decomposition is the primary mechanism that converts dead organic matter (detritus) into inorganic substances, ensuring the continuity of nutrient availability for producers.
Statement-wise Analysis:
- Statement 1 is Correct: Decomposition is the process by which decomposers, such as bacteria and fungi, break down complex organic matter from dead plants and animals. This process converts organic compounds into simpler inorganic substances (nutrients), which are cycled back into the soil.
- Statement 2 is Incorrect: Humus is a dark, amorphous substance formed during decomposition that is highly resistant to microbial action. While it decomposes very slowly, it serves as a reservoir of nutrients rather than preventing their release. Through a process called mineralization, humus is further degraded by microbes to slowly release inorganic nutrients into the soil, making them available to plants.
- Statement 3 is Correct: Once decomposers and mineralization processes release inorganic nutrients (such as nitrogen, phosphorus, and potassium) into the soil solution, these nutrients are absorbed by the roots of living plants. The plants use these nutrients for growth and metabolism, thereby re-entering the food chain.
Key Takeaway:
The nutrient cycle relies on decomposition to convert detritus into humus and inorganic minerals. Humus acts as a slow-release nutrient bank, and plant roots absorb the mineralized nutrients to sustain the ecosystem's productivity.