Rainforests are the most complex and species-rich environments on earth. Their great diversity is due to the humid warm climate, the many different types of habitats, the many roles which organisms can play in forests, and the amazing specializations in reproductive strategies and other mechanisms to reduce competition within the forest. In rainforests, woody plants predominate to a much greater extent than in temperate forests. Between 45% and 53% of all rainforest plants are woody. Some of these trees are so immense, one wonders if they are as old as temperate trees, some of which have been dated to 1000 years of age or more. It is very difficult to estimate the age of tropical trees, since they do not form annual growth rings, due to the absence of seasonal growth periods. Some of the large trees (such as the dipterocarps, the dominant trees of Southeast Asian rainforests) mature at approximately 50 to 60 years of age, but they may live for hundreds of years beyond maturity. Although the potential age span may be great, few trees will attain maximum age because most will die before adulthood, succumbing to competition, parasites, strangler vines, and damage from natural catastrophes such as storms. Thus, among woody rainforest trees, a few will be of a great diameter, but most will be relatively small.