Theory 47/Tropical Rainforest/Carbon sink
The Sink Tips on Dry Air
The claim
The tropical forest carbon sink turns to a source above a vapour pressure deficit threshold, even at high soil moisture.
01Mechanism
Dry air closes stomata, which reduces photosynthesis while respiration continues; the deficit sets the crossover.
02Prediction
The sink should flip at a VPD threshold.
03Refutation
The sink tracking soil moisture would remove atmospheric demand.