årring

An årring, also known as a growth ring or annual ring, is a layer of wood produced by a tree during one growing season. In temperate climates, trees typically produce two types of wood each year. Earlywood, also called springwood, is formed in the spring when growth is rapid and is characterized by larger, thinner-walled cells. Latewood, or summerwood, is produced in late summer and autumn when growth slows, resulting in smaller, thicker-walled cells. The distinct contrast between the lighter earlywood and the darker latewood creates the visible ring.

The width of an årring can provide clues about the environmental conditions during the year of its formation. Wider rings generally indicate favorable conditions, such as ample rainfall and sunlight, leading to vigorous growth. Narrower rings suggest less favorable conditions, such as drought, cold temperatures, or competition for resources. By studying the pattern and width of årringar in a tree's trunk, scientists can reconstruct past climate conditions, a field known as dendroclimatology.

The age of a tree can be determined by counting its årringar. A cross-section of the trunk will reveal one ring for each year of the tree's life, with the youngest rings found at the center and the oldest at the bark. This method is a fundamental technique in forestry and ecological studies. The study of årringar is also used for dating historical wooden artifacts, a practice called dendrochronology.