Why dwarfism is an advantage above treeline

In the cold, being small has an advantage: dwarfs capture warmth, roots under trees stay cold.

Meristems (the tissues which develop new cells) of small alpine plants are close to or under the ground and experience warmer temperatures than meristems of trees.

1 - Alpine grasses and sedges live in a warmer world than treeline trees. The orange zone highlights the difference between ground temperature under grassland and treeline trees.