In seasonal climates, trees preserve a continuous record of annual events, in particular, climate.
Dendrochronology, the study of the annual growth in trees, is the only method of paleoenvironmental research that produces proxy data of consistently annual resolution. Initially the cells are thin walled to conduct the abundant spring soil moisture.
Dendrochronology has three main uses: , -logia) was developed during the first half of the 20th century originally by the astronomer A. Douglass, who founded the Laboratory of Tree-Ring Research at the University of Arizona. He expected changes in solar activity would affect climate patterns on Earth.
The climate would be recorded by tree-ring growth patterns.
Adequate moisture and a long growing season result in a wide ring. Alternating poor and favorable conditions, such as mid summer droughts, can result in several rings forming in a given year.
Each ring is one of the many concentric bands surrounding the pith and all are more or less distinguishable from each other.
As soil water declines through the summer, the cells become thicker-walled and more dense.
Thus each annual ring consists of early (light) and late (dark) wood. Douglass, the 'father' of dendrochronology was interested in the affect of sunspots on the earths climate.
Many trees in temperate zones make one growth ring each year, with the newest adjacent to the bark.
Through a tree's life, a year-by-year ring pattern is formed which reflects the climatic conditions in which the tree grew.