That's because old trees have gone through more cycles of dry and wet and have had time to extend their root systems. The wider the root-system, the more drought-tolerant the plant is.
A new analysis of more than 20,000 trees on five continents shows that old-growth trees are more drought tolerant than younger trees in the forest canopy and may be better able to withstand future climate extremes. The findings highlight the importance of preserving the world's remaining old-growth forests, which are biodiversity strongholds that store vast amounts of planet-warming carbon, according to forest ecologists.