How Drought Affects Trees
Scientists who study forests say they’ve discovered something disturbing about the way prolonged drought affects trees, having to do with the way trees drink. They don’t ‘drink’ the way we do — they suck water up from the ground all the way to their leaves, through a bundle of channels in a part of the trunk called the xylem. The bundles are like blood vessels.
When drought dries out the soil, a tree has to suck harder. And that can actually be dangerous, because sucking harder increases the risk of drawing air bubbles into the tree’s plumbing.
Drought stress increases the likelihood of embolism, reduces photosynthesis and may eventually lead to plant death.
Plant scientist Brendan Choat explains: “As drought stress increases, you have more and more gas accumulating in the plumbing system, until they can’t get any water up into the leaves. This is really bad news for the plant because this is like having an embolism in a human blood vessel.”
Like a human embolism, the gas bubbles stop the flow of fluid. If that persists, it means thirst, starvation and eventually death.
Choat is from the University of Western Sydney in Australia, a region that has seen years of record-breaking drought. He wondered: How much drought does it take before trees start choking on air bubbles?