Theory 46/New analysis/Dendrochronology
Tree Rings Record Dry Air
The claim
Tree-ring isotopes track vapour pressure deficit more than precipitation, because stomatal closure responds to atmospheric demand.
01Mechanism
Isotopic discrimination depends on transpiration, which is driven by dryness of air.
02Prediction
Isotopes should track VPD.
03Refutation
Isotopes tracking rainfall would remove demand.