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. ED
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