A tree ring that is consistently wide all around the stem indicates a warm summer. In high altitudes, warmth and the number of sunny days are indeed more relevant for growth than precipitation.
When the temperature at the roots reaches at least 5 to 7°C, growth can resume. The larch uses the nutrients it has stored before the winter and produces “earlywood”, the first layer of wood formed in spring.
Earlywood consists of large, thin-walled wood cells so it can ensure the efficient transport of water and nutrients to the tree crown to supply the needles. The later in the year, the flatter and more thick-walled the cells become.
This dark and dense “latewood” mainly ensures the stability of the tree.