|The boreal forests extend the farthest north, meeting the arctic tundra at the northern end of their range. South of the boreal forests, where the climate is less harsh, are the warmer temperate forests. Some conifers grow here too, and in fact dry areas are dominated by pines. Most temperate areas, however, are occupied by the broad-leaved trees. They grow in large spreading forms in order to expose as many of their wide, paper-thin leaves as possible to direct sunlight. This is necessary for photosynthesis, the process by which all green plants manufacture oxygen and sugars from carbon dioxide, water, and the energy from sunlight. These leaves also allow huge quantities of water vapor to escape, which means that broad-leaved trees require much more precipitation and is why they are replaced by conifers in drier locations.|
Where the climate is cooler, temperate
broad-leaved trees are deciduous, meaning that each fall, nutrients from the leaves are drawn back into the branches, and the leaves
die and then fall to the ground. In the spring, new leaves are grown. Some tropical trees are also deciduous, but they shed their leaves for
the dry season instead of for winter.
The broad-leaved trees put on an impressive display of fall colors in eastern North America. Photo courtesy Naomi Woods. Vast quantities of water are needed to grow and maintain leaves. For this reason, in dry temperate areas, coniferous forests manage to take over from the broadleaf trees. Temperate rainforests are also dominated by giant coniferous trees, but very different species. The northern boreal forests consist entirely of conifers.
[boreal forests] [temperate forests] [tropical forests]
[forest walk] [diagrams]
[leaves] [water] [climate] [seasons]
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