In a detritus food chain, decomposition of detritus depends upon all, except

Options

A. Oxygen non-availability
B. Chemical composition of detritus
C. temperature and soil moisture
D. soil microbes

Answer

To solve the question regarding the factors affecting the decomposition of detritus in a detritus food chain, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding the Detritus Food Chain**:
- A detritus food chain is a type of food chain that begins with detritus, which consists of decomposing organic matter. Decomposition is a crucial process in this chain as it recycles nutrients back into the ecosystem.

2. **Analyzing the Options**:
- The options given are:
- A) Oxygen
- B) Non-availability
- C) Chemical composition of detritus
- D) Temperature and soil moisture
- E) Soil microbes

3. **Evaluating Each Option**:
- **A) Oxygen**: Oxygen is essential for aerobic decomposition. Without it, decomposition slows down significantly.
- **B) Non-availability**: This refers to the lack of oxygen. If oxygen is not available, decomposition cannot occur effectively, making this option a candidate for the exception.
- **C) Chemical composition of detritus**: The chemical makeup of detritus (e.g., nitrogen content) influences the rate of decomposition. Rich nitrogen content speeds up decomposition, while high lignin content slows it down.
- **D) Temperature and soil moisture**: Both temperature and moisture are critical for decomposition. Optimal conditions enhance microbial activity, which is necessary for breaking down detritus.
- **E) Soil microbes**: Microbes, including bacteria and fungi, are the primary decomposers. Their presence is vital for the decomposition process.

4. **Identifying the Correct Answer**:
- Since the question asks for the factor that does not affect decomposition, we see that "non-availability" of oxygen (option B) is indeed the correct answer. Decomposition requires oxygen, and without it, the process cannot occur effectively.

### Conclusion:
The correct answer is **B) Non-availability**.