Why trees cannot grow taller than about 130 meters

Settled in 2004 by George W. Koch, Stephen C. Sillett, Gregory M. Jennings, Stephen D. Davis.

Since Leonardo da Vinci's early studies of how sap rises through plants, botanists debated what ultimately caps tree height, with candidate limits including mechanical stability, nutrient transport, and hydraulic constraints. Koch, Sillett, Jennings and Davis climbed and sampled the tallest known coast redwoods (Sequoia sempervirens) in northern California, measuring how leaf water potential, photosynthetic capacity and structural traits change with height. They found water transport becomes so constrained near the treetop that leaf expansion and photosynthesis approach zero, and xylem pressure approaches the threshold for irreversible embolism (air bubble blockage), predicting a maximum height of roughly 122-130 meters, matching the height of the tallest living trees. Their 2004 Nature paper is now the standard reference for the physiological limit to tree height.

The world's tallest living things are limited not by strength but by how hard gravity makes it to pull water up a thin tube against its own weight, a limit trees are already bumping up against today.

Explanations that circulated

• Assuming trees are limited mainly by mechanical strength (buckling under their own weight or wind load) rather than by the hydraulic physics of pulling water up against gravity and increasing xylem tension with height

References

• The limits to tree height, George W. Koch, Stephen C. Sillett, Gregory M. Jennings, Stephen D. Davis, Nature, 2004