Theory 28/Grassland & Savanna/Tree-grass balance
Savanna Is Fire Against Rain
The claim
The tree-grass balance in savanna is set by the ratio of fire frequency to rainfall, so a wet savanna with frequent fire has the same cover as a dry one without.
01Mechanism
Rain favours trees and fire kills their recruits; the ratio sets the equilibrium cover, which is why cover is not a simple function of rainfall.
02Prediction
Cover should collapse onto the ratio.
03Refutation
Cover tracking rainfall alone would remove fire.