Theory 39/Geometry & Scale/Forest ecology
Trees Stop at a Hydraulic Limit
The claim
Maximum tree height is set by the ratio of water potential gradient to path length, so taller trees need disproportionately safer xylem.
01Mechanism
Water must be lifted against gravity and resistance; the taller the tree, the closer the leaf water potential sits to the cavitation threshold.
02Prediction
Maximum height should track the safety margin.
03Refutation
Height limited by mechanical support alone would remove the hydraulic term.