Theory 13/Boreal Forest/Insect outbreaks
Outbreaks Need Stressed Hosts
The claim
Boreal insect outbreaks occur when the ratio of drought stress to host defence exceeds a threshold, not when insect populations are large.
01Mechanism
Defence depends on resin and carbon reserves, which drought depletes; outbreaks begin when defences fail, and populations follow.
02Prediction
Outbreaks should track the ratio.
03Refutation
Outbreaks tracking insect counts would remove the defence term.