Architecture sets the limit
Why should trees suffer more from cold climate than grasses, dwarf shrubs and herbaceous plants which reach 4000 m in the temperate and up to 6000 m in the subtropical zone?
The answer is simple: Trees are designed to compete for light with neighbours, not to thrive in the cold.
- With their crowns reaching into the free atmosphere they become closely coupled to the harsh alpine climate and do not profit from the warm boundary layer close to the ground.
- By shading their own root zone they prevent the sun from heating the ground. Roots stay cold because of self shading once the canopy is closed.
A cold "crown" and cold "feet" is the price to be paid for being a tree in the mountains.
Low vegetation profits from heat capture and heat storage in the soil.
Architecture determines the tree limit at high altitudes.
1 - Energy flux in forests and adjacent low stature alpine
vegetation in midsummer.
