Biologists have long debated the cause of the sharp boundary between Fynbos shrublands — with the most diverse plant ecosystem outside of the tropics — and soaring Afrotemperate forests that grow side-by-side on the same poor soil in western South Africa.
To address the mystery, the researchers conducted a four-year experiment, involving 40 plots in which they manipulated soil nutrients and the ability of forest seedlings to compete with the native Fynbos plant community.
In a recently published paper, the biologists describe how the plants of the Fynbos shrub community have remarkably thin and long roots that allow the Fynbos plants to thrive on the poorest soil in the world — an almost pure quartz sand.
“What’s novel here is that the roots — the world’s thinnest roots — actually play a central role in this game,” said Lars Hedin, Princeton’s George M. Moffett Professor of Biology. “Because if you have them and I try to invade, with my thicker roots, you will capture every nitrogen atom before I can; and there’s not many of them in this soil to start with. And it’s not just one species doing this, but the whole community has evolved with this strategy, making the soil just too miserable for anything else to survive.”