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Difficulty: MediumEcological Functions, Nutrient Cycles and Ecological Succession

Consider the following statements regarding the process of decomposition in an ecosystem and its role in nutrient cycling:

1. Decomposition rate is significantly slower if detritus is rich in lignin and chitin, whereas it is faster if detritus is rich in nitrogen and water-soluble substances like sugars.
2. Warm and moist environmental conditions severely inhibit microbial activity, leading to slow decomposition and the accumulation of organic matter.
3. Mineralization is the step in decomposition where microbes further degrade humus to release inorganic nutrients into the soil.

Which of the statements given above are correct?

  1. A
    1 and 2 only
  2. 1 and 3 onlyAnswer
  3. C
    2 and 3 only
  4. D
    1, 2 and 3

Answer

The statement combination '1 and 3 only' is correct.
Decomposition is a foundational ecological function that recycles nutrients bound in dead organic matter back into abiotic pools. Statement 1 accurately states chemical substrate controls: detritus rich in chitin and lignin decomposes slowly due to complex chemical bonds, while nitrogen and water-soluble sugars decay rapidly. Statement 3 correctly defines mineralization as the final microbial breakdown of humus releasing inorganic plant nutrients. Statement 2 is false because warm and moist climates accelerate microbial respiration and decay; cold and anaerobic environments are what inhibit decomposition.

Step-by-Step Solution

1
Evaluate Statement 1 regarding chemical composition of detritus
Statement 1 is correct
Structural polymers like lignin and chitin are resistant to enzymatic degradation, slowing decomposition, while nitrogenous compounds and soluble sugars are easily metabolized by decomposers.
2
Evaluate Statement 2 regarding climatic factors influencing decomposition
Statement 2 is incorrect
Warm temperatures and high moisture favor microbial metabolism and oxygen diffusion, thereby accelerating decomposition. Low temperatures and anaerobic conditions inhibit decomposition.
3
Evaluate Statement 3 regarding the definition of mineralization
Statement 3 is correct
Humification forms dark colloidal humus, which is subsequently mineralized by specific soil microbes to yield inorganic minerals (NH4+NH_4^+, PO43−PO_4^{3-}, Ca2+Ca^{2+}, etc.).

Key Concept

Factors regulating ecosystem decomposition rate and steps of nutrient mineralization
Estimated Time:1m 0s
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Topics

Ecological Functions, Nutrient Cycles and Ecological Succession