Gaseous nutrient cycle and sedimentary nutrient cycles have their reservoir. Name them.Why is a reservoir necessary ?

Explanation

### Step-by-Step Solution:

1. **Understanding Nutrient Cycles**:
- Nutrient cycles are processes through which nutrients move through the ecosystem. They can be classified into two main types: gaseous nutrient cycles and sedimentary nutrient cycles.

2. **Identifying Reservoirs**:
- **Gaseous Nutrient Cycle**: The reservoir for the gaseous nutrient cycle is the **atmosphere**. In this cycle, nutrients like carbon and nitrogen are present in gaseous forms (e.g., carbon dioxide and nitrogen gas).
- **Sedimentary Nutrient Cycle**: The reservoir for the sedimentary nutrient cycle is the **earth's crust**. In this cycle, nutrients such as phosphorus and iron are found in solid forms within the earth's crust.
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