These rings can tell us how old the tree is, and what the weather was like during each year of the trees life. The light-colored rings represent wood that grew in the spring and early summer, while the dark rings represent wood that grew in the late summer and fall.
The science of tree-ring analysis is called dendrochronology. Examining the rings in tree cross-sections from cookies or sample cores (which are used more often) can tell you a lot about a tree, its history and the environmental conditions it grew under.
What could affect tree growth?
Independent variables could include sunlight, rainfall, soil nutrients, and topographic location. Competition among trees could also be considered an independent variable. Environmental disturbances such as construction, fire, insects, weather patterns, and storms can also greatly influence tree growth.