Theory 10/Boreal Forest/Treeline
Treeline Is a Degree-to-Frost Ratio
The claim
The boreal treeline is set by the ratio of growing degree days to frost damage rather than by temperature alone.
01Mechanism
Trees establish where warmth permits growth and frost does not kill seedlings; the ratio determines the establishment niche.
02Prediction
Treeline position should track the ratio.
03Refutation
Treeline tracking mean temperature would remove frost.