Tree ring (landscape feature)

A tree ring, also known as an annual ring or growth ring, is a layer of wood (xylem) grown during a single year in a tree. Tree rings are visible in a cross-section of the trunk of a tree or in a core taken from the trunk. The width, density, and other characteristics of a tree ring can provide information about past climatic conditions, forest fires, insect infestations, and other environmental factors that affected the tree's growth.

The study of tree rings for dating past events and climate is known as dendrochronology. In temperate regions, most trees produce one ring per year, making them reliable chronological markers. The lighter-colored portion of the ring typically represents earlywood, which grows quickly in the spring, while the darker, denser portion represents latewood, which grows more slowly in the late summer and fall.

The width of a tree ring is influenced by several factors. Favorable growing conditions, such as ample rainfall and sunlight, generally result in wider rings. Unfavorable conditions, such as drought, competition from other trees, or insect outbreaks, can result in narrower rings. Extremely narrow or missing rings can indicate severe stress events.

By analyzing the patterns of tree ring widths from multiple trees in a region, dendrochronologists can develop a long-term chronology that extends back hundreds or even thousands of years. This chronology can then be used to date wooden structures, reconstruct past climates, and study the history of forest ecosystems. Tree rings are a valuable tool for understanding environmental change over time.