Tree roots need access to water and oxygen held in underground pockets called soil pores. With ideal soil and moisture conditions, trees can send roots down to great depths. But conditions are often less than ideal, with stones, bedrock or compact soil physically halting them in their downward path as well as reducing oxygen levels.
When life gets tough, the roots take the easy option, staying close to the surface and spreading out a long way from the tree. Drought conditions can also cause some trees to have shallow root systems so that they can maximise rainfall collection by being nearer to the surface.
- How do trees grow straight up, even on a slope?
- Why don’t plants get sunburn?
- When trees grow, where does the matter come from?
- Where does soil come from?
Asked by: Ray Smith, via email
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Dr Emma Davies is a science writer and editor with a PhD in food chemistry from the University of Leeds. She writes about all aspects of chemistry, from food and the environment to toxicology and regulatory science.