The activity of the cambium ring is influenced by the climatic changes. In woody species, the period of growth and reproduction alternate with the period of inactivity during winter. Reactivation of cambium takes place during the spring season. However, the cambium becomes more active during this season and forms plenty of xylem vessels with wider cavities called as Springwood or early wood. In winter, however, the cambial activity slows down and gives rise to narrower xylem elements. The wood thus, formed in winter is called autumn wood or latewood. As growth continues, these two types of wood are produced year after year and appear together as a concentric ring in the transverse section. This concentric ring is known as the annual ring or growth ring.  Though the activity of cambium is well seen only in places where seasonal variations are marked I.e.  Hilly areas, temperate regions. While in coastal regions there is no seasonal variation and therefore the cambium activity remains the same throughout the year and no distinction is seen in the width of the vessels. Hence annual rings are not seen.