In temperate zones trees have distinctive growing periods and periods when there is no to little growth, this effects how much growth occurs between when a ring is started and it ends. In the tropical areas of the world, trees can grow more continuously and so the rings are layed down less uniformly, because the start of a ring with uninterrupted of growth may be much longer than the temperate zones spring and summer. Since tree growth in tropics is less dependent of seasonal variations the ending the the growth period and subsequent terminus of a ring is very often less pronounced, growth may go on for longer periods of time or stop and commence a number of times with in a short period of time.