THE rapid evolution of root systems by land plants may explain a 45 per cent
drop in atmospheric carbon dioxide levels 390 million years ago.
The earliest land plants, about 410 million years ago, had roots that reached
only millimetres into the soil. But fossils from Quebec now show that just 20
million years later, some plants had roots up to a centimetre thick and half a
metre deep.
In Geology (vol 26, p 143), Jennifer Elick of the University of
Tennessee at Knoxville and her colleagues say that carbonic acid released by
roots would react with minerals, locking carbon into the soil.
