# A dead tree falls in a woodland. Over several years, decomposers break down the wood, returning nutrients to the soil. Explain how the rate of decomposition of the fallen tree would change if the woodland experienced a prolonged period of cold, dry weather. Give three reasons for your answer.

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 5.5 Decomposition and decay · Explain · 5 marks

> A dead tree falls in a woodland. Decomposers begin to break down the wood over several years, returning nutrients to the soil. A prolonged period of cold, dry weather then affects the woodland.

## Mark scheme (5 marks)

1. Low temperature reduces the rate of decomposition because enzyme activity in decomposers is reduced / enzymes work more slowly at low temperatures
2. Dry conditions reduce water availability, which is needed for the metabolic reactions of decomposers / for decomposers to survive and function
3. The combination of cold and dry conditions reduces the growth and reproduction of decomposers (bacteria and fungi), so fewer decomposers are present to break down the wood
4. Overall, the rate of decomposition decreases / the fallen tree takes longer to fully decompose

## Key terms

- [decomposers](https://www.gradenine.co.uk/glossary/decomposers)
- [decomposition](https://www.gradenine.co.uk/glossary/decomposition)

## Related

- [Revision notes for Edexcel A-Level Biology A: Salters-Nuffield (9BN0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-dead-tree-falls-in-a-3691ddb8) · Published by Druglandscape Ltd.