The diagram below shows a simplified representation of the nitrogen cycle in an agroforestry ecosystem, where alder trees (Alnus glutinosa) are grown alongside a food crop.
Complete the table below by matching each biological process to the correct letter (AAA, BBB, CCC, DDD, EEE, or FFF) from the diagram.
| Process | Letter |
|---|---|
| Assimilation | |
| Decomposition (Ammonification) | |
| Denitrification | |
| Nitrification | |
| Nitrogen fixation (by mutualistic root bacteria) |
The absorption of nitrate ions by the root hair cells of the crop plant relies on active transport.
(i) Describe the mechanism of active transport.
Explain why waterlogged soil (which lacks oxygen) significantly reduces the rate of active transport in root hair cells.
In this agroforestry system, a large volume of leaves falls from the alder trees each autumn and is incorporated into the soil. Explain how this practice increases soil fertility and enhances subsequent crop yield without the addition of synthetic chemical fertilisers.
